JP7801564B2 - Optical demultiplexer and transmission device - Google Patents

Description

This case relates to an optical demultiplexing device and a transmission device.

For example, Patent Document 1 discloses an optical demultiplexer in which asymmetric Mach-Zehnder interferometers (AMZ), each having a pair of arms of different lengths, are connected in multiple stages in a tree configuration as an optical integrated circuit. This type of optical demultiplexer is used, for example, in a wavelength division multiplexing optical transmission device, as a means for demultiplexing signal light for each wavelength from wavelength division multiplexed signal light input from a transmission line, and as a means for demultiplexing transmission light for each wavelength to be optically modulated from multi-wavelength light.
It is used for this purpose.

Japanese Patent Application Laid-Open No. 2019-135524

The signal light or transmission light (hereinafter referred to as wavelength light) for each wavelength branched by the above-mentioned optical demultiplexer is output from the rearmost AMZ, but the output port is determined randomly by the initial optical phase within the pair of arms of each AMZ. As a result, each wavelength light cannot be output to an arbitrary output destination, making it difficult to perform appropriate signal processing for each wavelength of each wavelength light. This problem is not limited to the optical demultiplexer disclosed in Patent Document 1, but also exists in other optical demultiplexers that use AMZs in which the optical output port is determined randomly.

The present invention aims to provide an optical demultiplexing device and transmission device that can perform appropriate signal processing for each wavelength.

In one aspect, an optical demultiplexing device includes a first light source that outputs a plurality of wavelength lights having a constant wavelength interval; a first demultiplexing unit that demultiplexes the plurality of wavelength lights and outputs the demultiplexed light at random from one of a plurality of output ports ; a plurality of conversion units that convert the plurality of wavelength lights output from the first demultiplexing unit into a plurality of electrical signals; a first detection unit that detects the plurality of electrical signals output from the plurality of conversion units; a first switch unit that selects an output destination for each of the plurality of electrical signals from a plurality of output destinations; and a first control unit that controls the first light source and the first switch unit. the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light input from the first light source is demultiplexed and output to different ones of the plurality of conversion units, respectively; the first control unit controls the first light source so that the plurality of wavelength light is input to the first demultiplexing unit one by one in sequence, and controls the first switch unit so that an electrical signal detected by the first detection unit among the plurality of electrical signals is output to one of the plurality of output destinations corresponding to the wavelength light from which the electrical signal was converted.

In one aspect, an optical demultiplexing device includes a second light source that outputs a plurality of wavelength lights having a constant wavelength interval; a second demultiplexing unit that demultiplexes the plurality of wavelength lights and outputs the demultiplexed light at random from one of a plurality of output ports ; a plurality of optical modulators that optically modulate the plurality of wavelength lights output from the second demultiplexing unit based on a plurality of data signals; a second detection unit that detects the plurality of wavelength lights input to the plurality of optical modulators; a second switch unit that selects input sources of the plurality of data signals for the plurality of optical modulators from a plurality of input sources; and a second control unit that controls the second light source and the second switch unit. each of the plurality of asymmetric Mach-Zehnder interferometers has a pair of arms with different lengths, and the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light input from the second light source is demultiplexed and output to mutually different optical modulators among the plurality of optical modulators, and the second control unit controls the second light source so that the plurality of wavelength light is input to the second demultiplexing unit one by one in sequence, and controls the second switch unit so that a data signal is input from an input source corresponding to the wavelength light among the plurality of input sources to an optical modulator to which a wavelength light detected by the second detection unit is input from among the plurality of wavelength light.

In one aspect, the transmission device includes a light source that outputs a plurality of wavelength lights having a constant wavelength interval; first and second demultiplexing units that demultiplex the plurality of wavelength lights and output the demultiplexed light at random from one of a plurality of output ports ; an optical switch that selects an output destination of the plurality of wavelength lights from the first demultiplexing unit or the second demultiplexing unit; a plurality of conversion units that convert the plurality of wavelength lights output from the first demultiplexing unit into a plurality of electrical signals; a first detection unit that detects the plurality of electrical signals output from the plurality of conversion units; a first switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations; a second detection unit that detects wavelength light of the plurality of wavelengths input to each of the plurality of optical modulators; a second switch unit that selects an input source of the plurality of data signals to each of the plurality of optical modulators from a plurality of input sources; and a third control unit that controls the light source, the optical switch, the first switch unit, and the second switch unit, wherein the first demultiplexing unit has a plurality of first asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths, and the second demultiplexing unit has a plurality of second asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths, and the plurality of second asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength lights input from the light source are demultiplexed and output to mutually different conversion units among the plurality of conversion units, and the plurality of second asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength lights input from the light source are demultiplexed and output to mutually different optical modulators among the plurality of optical modulators, and the third control unit has a first control mode for controlling the first switch unit and a second control mode for controlling the second switch unit, and in the first control mode, controls the optical switch so that the plurality of wavelength lights are input to the first demultiplexing unit, and and controls the light source so that the wavelengths of the light beams are sequentially input to the first demultiplexing unit, controls the first switch unit so that the electrical signal detected by the first detection unit is output to one of the plurality of output destinations corresponding to the wavelength light from which the electrical signal was converted, and in the second control mode, controls the optical switch so that the plurality of wavelengths of the light beams are input to the second demultiplexing unit, controls the light source so that the plurality of wavelengths of the light beams are sequentially input to the second demultiplexing unit one by one, and controls the second switch unit so that a data signal is input from one of the plurality of input sources corresponding to the wavelength light to an optical modulator to which the wavelength light detected by the second detection unit is input.

In one aspect, an optical demultiplexing device includes a plurality of third light sources each outputting one of a plurality of wavelength light beams having a constant wavelength interval; a third demultiplexing unit demultiplexing input light by wavelength and outputting the demultiplexed input light beams at random from one of a plurality of output ports ; a selector selecting the input light beam from one of the plurality of wavelength light beams and a wavelength-multiplexed signal light beam of a plurality of signal light beams each having a wavelength common to that of the plurality of wavelength light beams; a plurality of detectors detecting the plurality of demultiplexed light beams output from the third demultiplexing unit using the plurality of wavelength light beams output from the plurality of third light sources; a plurality of converters converting the detected plurality of demultiplexed light beams into a plurality of electrical signals; a third switch unit selecting an output destination for each of the plurality of electrical signals from a plurality of output destinations; a detector detecting the wavelengths of the plurality of demultiplexed light beams; and a third control unit controlling the selector, the plurality of third light sources, and the third switch unit, the plurality of asymmetric Mach-Zehnder interferometers are connected to each other such that the plurality of demultiplexed light beams are output to different detecting sections among the plurality of detecting sections, respectively; the third control section controls the selection section to switch the input light from the wavelength multiplexed signal light to one of the plurality of wavelength light beams, controls one of the plurality of third light sources so that the plurality of wavelength light beams are input to the third demultiplexing section one by one in sequence, controls the third switch section based on the wavelength detected by the detection section so that each of the plurality of electrical signals is output to one of the plurality of output destinations corresponding to the wavelength of the demultiplexed light beam from which it was converted, and controls the wavelengths of the plurality of wavelength light beams output by the plurality of third light sources based on the wavelength detected by the detection section so that the plurality of demultiplexed light beams are detected by wavelength light corresponding to each wavelength among the plurality of wavelength light beams.

One aspect is that appropriate signal processing can be performed for each wavelength.

FIG. 1 is a configuration diagram illustrating an example of an optical demultiplexer. FIG. 10 is a diagram illustrating an example of a technique for allocating wavelength light to output ports of an optical demultiplexer. 1 is a configuration diagram showing an optical demultiplexing device according to a first embodiment; 1A and 1B are diagrams illustrating an example of wavelength-multiplexed signal light and wavelength optical spectrum; 10 is a flowchart illustrating an example of the operation of a control unit. FIG. 10 is a diagram illustrating an example of a state in which all wavelength light is input to an optical demultiplexer. 10 is a diagram illustrating an example of a state in which wavelength light having a center wavelength being selected is input to an optical demultiplexer. FIG. FIG. 10 is a diagram illustrating an example of a setting table in a memory. 1 is a diagram illustrating an example of a state in which wavelength-multiplexed signal light is input to an optical demultiplexer. FIG. 1 is a configuration diagram illustrating an example of a digital signal processing unit including a cross-connect switch. 2 is a configuration diagram showing an example of an analog signal processing unit 2 including a cross-connect switch. FIG. 1 is a configuration diagram illustrating an example of an optical demultiplexing device including a control unit, an input signal detection unit, and a digital signal processing unit including a cross-connect switch. FIG. 10 is a configuration diagram showing another example of an optical demultiplexing device including a control unit, an input signal detection unit, and a digital signal processing unit including a cross-connect switch. FIG. 10 is a configuration diagram showing an optical demultiplexing device according to a second embodiment. 10 is a flowchart illustrating an example of the operation of a control unit. FIG. 10 is a diagram illustrating an example of a state in which all wavelength light is input to an optical demultiplexer. 10 is a diagram illustrating an example of a state in which wavelength light having a center wavelength being selected is input to an optical demultiplexer. FIG. FIG. 10 is a diagram illustrating an example of a setting table in a memory. 1 is a configuration diagram illustrating an example of an optical demultiplexing device equipped with a digital signal processing unit including a cross-connect switch. 1 is a configuration diagram illustrating an example of an optical demultiplexing device equipped with an analog signal processing unit including a cross-connect switch. FIG. 1 is a configuration diagram illustrating an example of a transmission device. 10 is a flowchart illustrating an example of the operation of a control unit. FIG. 10 is a configuration diagram illustrating an example of a cross-connect switch used when the number of wavelengths of wavelength light from a light source is eight. 10 is a diagram illustrating an example of a change in power consumption of a phase shifter with respect to the number of wavelengths to be demultiplexed by an optical demultiplexer. FIG. 10 is a configuration diagram showing an optical demultiplexing device according to a fourth embodiment. 10 is a diagram illustrating an example of a state in which wavelength light having a center wavelength being selected is input to an optical demultiplexer. FIG. 10 is a diagram illustrating another example of a state in which wavelength light having a center wavelength being selected is input to the optical demultiplexer. FIG. 1 is a diagram illustrating an example of a state in which wavelength-multiplexed signal light is input to an optical demultiplexer. FIG. 10 is a diagram illustrating an example of a setting table in a memory. 10 is a flowchart illustrating an example of the operation of a control unit. FIG. 10 is a diagram illustrating an example of a state in which wavelength light having a selected center wavelength is input to an optical demultiplexer, and wavelength light having an unselected center wavelength is input to an optical-electrical converter.

(Configuration of optical demultiplexer)
FIG. 1 is a configuration diagram showing an example of an optical demultiplexer 1. The optical demultiplexer 1 has a front-stage demultiplexing circuit 11 and rear-stage demultiplexing circuits 12 and 13 optically connected to the rear of the front-stage demultiplexing circuit 11. As an example, the optical demultiplexer 1 demultiplexes wavelength light having center wavelengths λa to λd spaced at regular wavelength intervals from a wavelength-multiplexed signal light having four wavelengths. The optical demultiplexer 1 performs demultiplexing processing using each of the front-stage demultiplexing circuit 11 and the rear-stage demultiplexing circuits 12 and 13 as a unit. The optical demultiplexer 1 is an example of a first and second demultiplexing section.

Optical demultiplexer 1 has asymmetric Mach-Zehnder interferometers (hereinafter referred to as AMZs) 1a-1i connected in multiple stages in a tree configuration. Pre-demultiplexing circuit 11 has AMZs 1a-1c, post-demultiplexing circuit 12 has AMZs 1d-1f, and post-demultiplexing circuit 13 has AMZs 1g-1i.

Each of the AMZs 1a to 1i has a pair of arms Au and Ad with different lengths (waveguide lengths), an input coupler Ca, and an output coupler Cb. The input coupler Ca and output coupler Cb are each 2x2 couplers with two input ports and two output ports.

The input ends of the pair of arms Au and Ad are optically connected to the two output ports of the input coupler Ca, and the output ends of the pair of arms Au and Ad are optically connected to the two input ports of the output coupler Cb. The signal light Sa to Sd input to the input coupler Ca is input to the pair of arms Au and Ad.

A phase shifter Hu is provided in the upper arm Au, and a phase shifter Hd is provided in the lower arm Ad. The phase shifters Hu and Hd adjust the optical phase within each pair of arms Au and Ad of AMZ1a-1i, respectively. This compensates for optical phase shifts due to manufacturing variations, etc.

The phase shifters Hu and Hd are heaters formed from a thin film of metal (resistive material) such as tungsten, titanium, or platinum, and change the temperature of the waveguides in the arms Au and Ad. This changes the refractive index in the arms Au and Ad, thereby adjusting the optical phase in the arms Au and Ad. Note that the configuration of the phase shifters Hu and Hd is not limited to this, and they may also be means for electrically changing the carrier density in the waveguides of each arm Au and Ad using the carrier plasma effect.

In order to control the phase shifters Hu and Hd of the AMZs 1a to 1i, the optical demultiplexer 1 also includes monitor circuits Mon#1 to #12 that monitor the output light power of the AMZs 1a to 1i, compensation circuits Dec#1 to #6 that reduce the power in response to the monitored output light power, and compensation circuits Inc#1 to #3 that increase the power in response to the monitored output light power. The monitor circuits Mon#1 to #12 are implemented, for example, using photodiodes, while the compensation circuits Dec#1 to #3 and Inc#1 to #3 are implemented, for example, using FPGAs (Field Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits).

Monitor circuits Mon#1-#12 monitor the output optical power of AMZs 1b, 1c, 1e, 1f, 1h, and 1i, respectively. Compensation circuits Dec#1-#6 and Inc#1-#3 compensate for optical phase shifts by controlling the amount of optical phase adjustment within a pair of arms Au and Ad for phase shifters Hu and Hd according to the output optical power. For example, compensation circuits Dec#1-#6 and Inc#1-#3 control the heater power supplied to phase shifters Hu and Hd.

The pre-demultiplexing circuit 11 includes AMZs 1a-1c, compensation circuits Inc#1, Dec#2, #3, and monitor circuits Mon#1-#4. AMZs 1b and 1c are optically connected downstream of AMZ 1a. AMZs 1d and 1g are optically connected downstream of AMZs 1b and 1c. The input end of AMZ 1a has an input port Pin, which receives wavelength light or wavelength-multiplexed signal light.

Monitor circuits Mon#1 and #3 are optically connected to one output port of output coupler Cb of AMZ1b and AMZ1c, respectively, via branch coupler CP. Monitor circuit Mon#1 monitors the power of the output light output from AMZ1b to AMZ1d. Monitor circuit Mon#1 notifies compensation circuit Inc#1 of the monitored power. Monitor circuit Mon#3 monitors the power of the output light output from AMZ1c to AMZ1g. Monitor circuit Mon#3 notifies compensation circuit Inc#1 of the monitored power.

Monitor circuits Mon#2 and #4 are optically connected to the other output port of output coupler Cb of AMZ1b and AMZ1c, respectively. Monitor circuits Mon#2 and #4 monitor the power of the output light output from the other output port of output coupler Cb. Monitor circuit Mon#2 notifies compensation circuit Dec#1 of the monitored power. Monitor circuit Mon#4 notifies compensation circuit Dec#2 of the monitored power.

Compensation circuit Inc#1 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1a in accordance with the results of monitoring the output light by monitor circuits Mon#1 and Mon#3. Compensation circuit Dec#1 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1b in accordance with the results of monitoring the output light by monitor circuit Mon#2. Compensation circuit Dec#2 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1c in accordance with the results of monitoring the output light by monitor circuit Mon#4.

With the above configuration, the power of the output light output from one output port of the output coupler Cb of AMZ1b and AMZ1c to the subsequent AMZ1d and AMZ1g increases, and the power of the output light output from the other output port of the output coupler Cb of AMZ1b and AMZ1c to the monitor circuits Mon#2 and Mon#4 decreases.

The post-stage demultiplexing circuit 12 includes AMZs 1d-1f, compensation circuits Inc#2, Dec#3, #4, and monitor circuits Mon#5-#8. AMZs 1e and 1f are optically connected downstream of AMZ 1d. One output port of the output coupler Cb of AMZs 1e and 1f is provided with output ports P#1 and P#2, respectively, from which the branched light is output.

Monitor circuits Mon#5 and #7 are optically connected to one output port of output coupler Cb of AMZ1e and AMZ1f, respectively, via branch coupler CP. Monitor circuit Mon#5 monitors the power of the output light output from AMZ1e to output port P#1. Monitor circuit Mon#5 notifies compensation circuit Inc#2 of the monitored power. Monitor circuit Mon#7 monitors the power of the output light output from AMZ1f to output port P#2. Monitor circuit Mon#7 notifies compensation circuit Inc#2 of the monitored power.

Monitor circuits Mon#6 and #8 are optically connected to the other output port of output coupler Cb of AMZ1e and AMZ1f, respectively. Monitor circuits Mon#6 and #8 monitor the power of the output light output from the other output port of output coupler Cb. Monitor circuit Mon#6 notifies compensation circuit Dec#3 of the monitored power. Monitor circuit Mon#8 notifies compensation circuit Dec#4 of the monitored power.

Compensation circuit Inc#2 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1d in accordance with the results of monitoring the output light by monitor circuits Mon#5 and Mon#7. Compensation circuit Dec#3 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1e in accordance with the results of monitoring the output light by monitor circuit Mon#6. Compensation circuit Dec#4 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1f in accordance with the results of monitoring the output light by monitor circuit Mon#8.

With the above configuration, the power of the output light output from one output port of the output coupler Cb of AMZ1e and 1f to the subsequent output ports P#1 and #2 increases, and the power of the output light output from the other output port of the output coupler Cb of AMZ1e and 1f to the monitor circuits Mon#6 and #8 decreases.

The post-stage demultiplexing circuit 13 includes AMZs 1g-1i, compensation circuits Inc#3, Dec#5, #6, and monitor circuits Mon#9-#12. AMZs 1h and 1i are optically connected downstream of AMZ 1g. One output port of the output coupler Cb of AMZs 1h and 1i is provided with output ports P#3 and P#4, respectively, from which the branched light is output.

Monitor circuits Mon#9 and #11 are optically connected to one output port of output coupler Cb of AMZ1h and AMZ1i via branch coupler CP. Monitor circuit Mon#9 monitors the power of the output light output from AMZ1h to output port P#3. Monitor circuit Mon#9 notifies compensation circuit Inc#3 of the monitored power. Monitor circuit Mon#12 monitors the power of the output light output from AMZ1i to output port P#4. Monitor circuit Mon#11 notifies compensation circuit Inc#3 of the monitored power.

Monitor circuits Mon#10 and #12 are optically connected to the other output port of output coupler Cb of AMZ1h and AMZ1i, respectively. Monitor circuits Mon#10 and #12 monitor the power of the output light output from the other output port of output coupler Cb. Monitor circuit Mon#10 notifies compensation circuit Dec#5 of the monitored power. Monitor circuit Mon#12 notifies compensation circuit Dec#6 of the monitored power.

Compensation circuit Inc#3 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1g in accordance with the results of monitoring the output light by monitor circuits Mon#9 and #11. Compensation circuit Dec#5 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1h in accordance with the results of monitoring the output light by monitor circuit Mon#10. Compensation circuit Dec#6 controls the amount of optical phase adjustment for phase shifters Hu and Hd of AMZ1i in accordance with the results of monitoring the output light by monitor circuit Mon#12.

With the above configuration, the power of the output light output from one output port of the output coupler Cb of AMZ1h and 1i to the subsequent output ports P#3 and #4 increases, and the power of the output light output from the other output port of the output coupler Cb of AMZ1h and 1i to the monitor circuits Mon#10 and #12 decreases.

In this way, the front-stage demultiplexing circuit 11 and rear-stage demultiplexing circuits 12 and 13 are connected in multiple stages in a tree configuration so that wavelength light with center wavelengths λa to λd is input from AMZ1a to AMZ1b and 1c, respectively, and then input from AMZ1b and 1c to the subsequent separate AMZs 1d and 1g, respectively. The wavelength spacing of the transmission bands of AMZ1a to 1i is determined according to the arm length difference. More specifically, the wavelength spacing of the transmission bands of AMZ1a to 1i is essentially inversely proportional to the arm length difference.

The arm length difference between AMZ1a-1c is set so that the wavelength spacing of the transmission band is the wavelength spacing Δλ between the center wavelengths λa-λd. The arm length difference between AMZ1d-1f and AMZ1g-1i is set to 1/2 the arm length difference between AMZ1a-1c so that the wavelength spacing of the transmission band is twice the center wavelength spacing Δλ (2 x Δλ).

As a result, the front-stage demultiplexing circuit 11 demultiplexes the combined light of each wavelength light with center wavelengths λa to λd into combined light of wavelength light with center wavelengths λa and λc and combined light of wavelength light with center wavelengths λb and λd, and the rear-stage demultiplexing circuits 12 and 13 demultiplex each combined light into wavelength light with center wavelengths λa to λd.

At this time, the output ports P#1 to P#4 for wavelength light with center wavelengths λa to λd are randomly determined by the initial optical phase within the pair of arms Au and Ad of each AMZ 1a to 1i. For example, wavelength light with center wavelength λa may be output from output port P#1, wavelength light with center wavelength λc may be output from output port P#2, wavelength light with center wavelength λb may be output from output port P#3, and wavelength light with center wavelength λd may be output from output port P#4. However, the combination of wavelength light with center wavelengths λa to λd and output ports P#1 to P#4 is not constant. As shown in parentheses, there are also cases where wavelength light with center wavelength λd is output from output port P#1, wavelength light with center wavelength λb is output from output port P#2, wavelength light with center wavelength λc is output from output port P#3, and wavelength light with center wavelength λa is output from output port P#4.

As a result, it is not possible to output light with center wavelengths λa to λd to any desired destination, making it difficult to perform appropriate signal processing for each light wavelength.

In contrast, as shown below, it is possible to input light with a specific center wavelength from the center wavelengths λa to λd into optical demultiplexer 1 and assign the light with the specific center wavelength to any of output ports P#1 to P#4 by operating only compensation circuits Inc#1 to #3 and Dec#1 to #6 on the path from input port Pin to any of output ports P#1 to P#4.

Figure 2 shows an example of a method for assigning wavelength light to output ports P#1 to P#4 of the optical demultiplexer 1. In Figure 2, components that are common to Figure 1 are assigned the same reference numerals, and their description will be omitted.

This example demonstrates a method of assigning output port P#1 to wavelength light with a center wavelength λa. Of the wavelengths λa to λd, only wavelength light with a center wavelength λa is input to input port Pin. To ensure that wavelength light with a center wavelength λa is output from output port P#1, compensation circuits Inc#1, Dec#1, and #3 on path K connecting input port Pin and output port P#1 operate, while the other compensation circuits Inc#3, Dec#2, and #4-#6 stop operating. Additionally, the connection between monitor circuits Mon#3 and #7 on parts other than path K is severed so that the monitoring results of the two do not affect the control of compensation circuits Inc#1 and #2.

By controlling the optical phase along path K in this way, it is possible to intentionally direct wavelength light with center wavelength λa to output port P#1. Furthermore, by controlling the optical phase of each of the other wavelengths with center wavelengths λb to λd in the same manner as above, it is possible to assign them to any of output ports P#2 to P#4.

However, adding a circuit to implement the above method to the optical demultiplexer 1 would increase the size and cost. Therefore, in the following embodiment, the wavelength light output from each output port P#1 to #4 is detected, and based on the detection results, an electrical cross-connect switch is switched to select the output destination of the wavelength light or the input source of the data signal modulated by the wavelength light. This allows appropriate signal processing to be performed for each wavelength light according to the center wavelengths λa to λd.

(First Example)
3 is a configuration diagram showing an optical demultiplexing device 90 of the first embodiment. The optical demultiplexing device 90 is mounted on, for example, a transmission device, and performs signal processing by demultiplexing the signal light Sa to Sd input from the transmitting device 80 via a transmission path (not shown) such as an optical fiber into signal light having center wavelengths λa to λd.

The optical demultiplexing device 90 includes a light source 20, an optical switch 21, an optical demultiplexer 1, photodiodes (PD) 22a-22d, an analog signal processing unit 23, analog-to-digital converters (AD) 24a-24d, a cross-connect switch (SW) 25, and a digital signal processing unit 26. The optical demultiplexing device 90 also includes a control unit 50, a light emission driver 51, a compensation circuit driver 52, an input signal detector 53, and a memory 54. The light emission driver 51, the compensation circuit driver 52, the input signal detector 53, the analog signal processing unit 23, and the digital signal processing unit 26 are implemented, for example, by an FPGA or an ASIC. The control unit 50 is implemented by a circuit including a processor such as a CPU (Central Processing Unit).

The optical switch 21 has two input ports and two output ports Pa and Pb. One input port receives wavelength-multiplexed signal light of multiple signal lights Sa-Sd from the transmitter 80, and the other input port receives wavelength light La-Ld from the light source 20.

Light source 20 is a multi-wavelength light source and is an example of a first light source that outputs wavelength light La to Ld. Light emission driver 51 drives light source 20 in accordance with a wavelength instruction signal input from controller 50. Light source 20 outputs wavelength light La to Ld with center wavelengths λa to λd specified by the wavelength instruction signal. Controller 50 is an example of a first controller that controls light source 20 and cross-connect switch 25.

Figure 4 shows an example of the spectrum of wavelength-multiplexed signal light and wavelength light La to Ld. The horizontal axis in Figure 4 represents wavelength.

Wavelength-multiplexed signal light includes signal light Sa-Sd whose center wavelengths λa-λd match those of wavelength light La-Ld. In other words, the center wavelengths λa of signal light Sa and wavelength light La match each other, the center wavelengths λb of signal light Sb and wavelength light Lb match each other, the center wavelengths λc of signal light Sc and wavelength light Lc match each other, and the center wavelengths λd of signal light Sd and wavelength light Ld match each other. The interval Δλ between the center wavelengths λa-λd is constant.

The signal light Sa-Sd is assigned to, for example, wavelength-multiplexed transmission channels CH1-CH4, respectively. The transmitter 80 generates wavelength-multiplexed signal light by optically modulating the light with center wavelengths λa-λd using the main signal of each channel CH1-CH4 and wavelength-multiplexing it.

Referring again to FIG. 3, the optical switch 21 switches between output ports Pa and Pb, which output the wavelength-multiplexed signal light and wavelength light La to Ld, in accordance with a switching signal input from the control unit 50. One output port, Pa, is optically connected to the input port Pin of the optical demultiplexer 1, while the other output port, Pb, is open. When setting up the cross-connect switch 25, the control unit 50 switches the optical switch 21 so that wavelength light La to Ld is output from output port Pa.

Wavelength light La-Ld is input from light source 20 to optical demultiplexer 1 and demultiplexed. AMZs 1a-1i of optical demultiplexer 1 are connected to each other so that wavelength light La-Lb is output to different PDs 22a-22d, respectively. For convenience, illustration of AMZs 1a-1i of optical demultiplexer 1 is omitted in Figure 3 and subsequent figures.

The compensation circuit drive unit 52 starts or stops the operation of the compensation circuits Inc#i and Dec#j (i = 1 to 3, j = 1 to 6) according to the on/off instruction signal input from the control unit 50. When the on/off instruction signal indicates on, the compensation circuit drive unit 52 starts the operation of the compensation circuits Inc#i and Dec#j, and when the on/off instruction signal indicates off, the compensation circuit drive unit 52 stops the operation of the compensation circuits Inc#i and Dec#j.

Prior to setting the cross-connect switch 25, the control unit 50 causes the light source 20 to output all wavelengths La-Ld to the optical demultiplexer 1 and then starts the operation of all compensation circuits Inc#i and Dec#j. The output wavelengths La-Ld input to the demultiplexer 1 have their optical phases compensated by the compensation circuits Inc#i and Dec#j, and are output randomly from one of the output ports P#1-#4. This assigns an output port P#1-#4 to each wavelength La-Ld.

In this example, it is assumed that wavelength light Ld is output from output port P#1, wavelength light Lb is output from output port P#2, wavelength light Lc is output from output port P#3, and wavelength light La is output from output port P#4. After output ports P#1-#4 are assigned to each wavelength light La-Ld, the control unit 50 stops the operation of all compensation circuits Inc#i and Dec#j and causes the light source 20 to output each wavelength light La-Ld one by one to the optical demultiplexer 1. Wavelength light La-Ld is input from the optical demultiplexer 1 to PDs 22a-22d.

PD22a converts wavelength light Ld into an electrical signal Ed, and PD22b converts wavelength light Lb into an electrical signal Eb. PD22c converts wavelength light Lc into an electrical signal Ec, and PD22a converts wavelength light La into an electrical signal Ea. PD22a-22d are an example of multiple conversion units. Wavelength light La-Ld are input from PD22a-22d to analog signal processing unit 23.

The analog signal processing unit 23 has analog circuits AP#1 to AP#4 that perform analog signal processing on the electrical signals Ea to Ed. Examples of analog circuits AP#1 to AP#4 include, but are not limited to, clock extraction circuits.

Electrical signal Ed is input to analog circuit AP#1, and electrical signal Eb is input to analog circuit AP#2. Electrical signal Ec is input to analog circuit AP#3, and electrical signal Ea is input to analog circuit AP#4. Analog circuits AP#1-#4 notify input signal detection unit 53 of the presence or absence of input of electrical signals Ed, Eb, Ec, and Ea. Wavelength light La-Ld is input from analog signal processing unit 23 to ADs 24a-24d.

ADs 24a-24d convert the electrical signals Ed, Eb, Ec, and Ea from analog to digital signals. The electrical signals Ed, Eb, Ec, and Ea are input from ADs 24a-24d to the cross-connect switch 25.

The cross-connect switch 25 is an example of a first switch unit, and selects the output destination of each of the electrical signals Ea to Ed from multiple output destinations. The digital signal processing unit 26 is connected downstream of the cross-connect switch 25, and the digital signal processing unit 26 includes digital circuits DPr_a to DPr_b that perform digital signal processing on the electrical signals Ea to Ed, respectively. The cross-connect switch 25 selects one of the digital circuits DPr_a to DPr_d as the output destination for each of the electrical signals Ea to Ed in accordance with a selection signal input from the control unit 50.

The cross-connect switch 25, for example, has 2x2 switches SW#1 to #4. Switches SW#1 to #4 are, for example, Banyan switches. Switch SW#1 has input ports P11 and P12 and output ports P13 and P14, switch SW#2 has input ports P21 and P22 and output ports P23 and P24, switch SW#3 has input ports P31 and P32 and output ports P33 and P34, and switch SW#4 has input ports P41 and P42 and output ports P43 and P44.

Switches SW#3 and #4 are connected after switches SW#1 and #2. Input ports P11 and P12 of switch SW#1 are connected to ADs 24a and 24b, respectively, and output ports P13 and P14 of switch SW#1 are connected to input port P31 of switch SW#3 and input port P41 of switch SW#4, respectively. Input ports P21 and P22 of switch SW#2 are connected to ADs 24c and 24d, respectively, and output ports P23 and P24 of switch SW#2 are connected to input port P32 of switch SW#3 and input port P42 of switch SW#4, respectively.

Furthermore, output ports P33 and P34 of switch SW#3 are connected to digital circuits DPr_a and DPr_b, respectively. Output ports P43 and P44 of switch SW#4 are connected to digital circuits DPr_c and DPr_d, respectively.

Each switch SW#1-#4 can switch the connection between input ports P11, P12, P21, P22, P31, P32, P41, and P42 and output ports P13, P14, P23, P24, P33, P34, P43, and P44 in accordance with a selection signal. Therefore, the cross-connect switch 25 can output the electrical signals Ed, Eb, Ec, and Ea input from ADs 24a-24d to any of the digital circuits DPr_a-DPr_d in accordance with the selection signal.

Digital circuits DPr_a-DPr_d are, for example, digital filter circuits that perform digital signal processing to compensate for degradation that occurs along the transmission path for each wavelength light La-Ld. Digital circuits DPr_a-DPr_d perform digital signal processing according to the center wavelengths λa-λd. For this reason, digital circuit DPr_a is a circuit dedicated to the electrical signal Ea converted from wavelength light La, digital circuit DPr_b is a circuit dedicated to the electrical signal Eb converted from wavelength light Lb, digital circuit DPr_c is a circuit dedicated to the electrical signal Ec converted from wavelength light La, and digital circuit DPr_d is a circuit dedicated to the electrical signal Ea converted from wavelength light La.

The input signal detector 53 is an example of a first detector and detects the electrical signals Ed, Eb, Ec, and Ea output from the PDs 22a-22d, respectively. The controller 50 controls the cross-connect switch 25 so that the electrical signals Ea-Ed detected by the input signal detector 53 are output to the output destinations of the digital circuits DPr_a-DPr_d corresponding to the wavelengths La-Ld from which the electrical signals Ea-Ed were converted.

For example, the input signal detection unit 53 detects the electrical signals Ed, Eb, Ec, and Ea based on notifications from the analog circuits AP#1 to AP#4. The input signal detection unit 53 transmits a detection signal to the control unit 50 indicating the analog circuits AP#1 to AP#4 that have notified the control unit 50 of the input of the electrical signals Ed, Eb, Ec, and Ea.

The control unit 50 identifies the output ports P#1-#4 of the optical demultiplexer 1 to which the analog circuits AP#1-#4 indicated by the detection signal are connected. The control unit 50 registers the correspondence between the center wavelengths λa-λd of the output wavelength light La-Ld, the output ports P#1-#4 corresponding to the detection signal, the input ports P11, P12, P21, P22 of the cross-connect switch 25 to which the output ports P#1-#4 are connected, and the output ports P33, P34, P43, P44 in the cross-connect switch 25 setting table in memory 54.

After compensating for the optical phase shift of AMZ1a-1i, the control unit 50 configures each switch SW#1-#4 in the cross-connect switch 25 according to the configuration table. In other words, the control unit 50 configures the connections between the input ports P11, P12, P21, P22, P31, P32, P41, and P42 of each switch SW#1-#4 and the output ports P13, P14, P23, P24, P33, P34, P43, and P44.

For example, the control unit 50 connects the input port P11 and output port P14 of switch SW#1 and connects the input port P41 and output port P44 of switch SW#4 so that the electrical signal Ed input from the output port P#1 of the optical demultiplexer 1 to the input port P11 of switch SW#1 is output to the digital circuit DPr_d. The control unit 50 also connects the input port P22 and output port P23 of switch SW#2 and connects the input port P32 and output port P33 of switch SW#3 so that the electrical signal Ea input from the output port P#4 of the optical demultiplexer 1 to the input port P22 of switch SW#2 is output to the digital circuit DPr_a.

The control unit 50 also connects the input port P12 and output port P13 of switch SW#1 and connects the input port P31 and output port P34 of switch SW#3 so that the electrical signal Eb input from the output port P#2 of the optical demultiplexer 1 to the input port P12 of switch SW#1 is output to the digital circuit DPr_b. The control unit 50 also connects the input port P21 and output port P24 of switch SW#2 and connects the input port P42 and output port P43 of switch SW#4 so that the electrical signal Ec input from the output port P#3 of the optical demultiplexer 1 to the input port P21 of switch SW#2 is output to the digital circuit DPr_c.

As a result, each wavelength of light La-Ld is converted into an electrical signal Ea-Ed, and then input via the cross-connect switch 25 to the appropriate digital circuit DPr_a-DPr_d corresponding to the center wavelength λa-λd. Therefore, the optical demultiplexing device 90 can perform appropriate signal processing for each center wavelength λa-λd.

(Operation of the control unit)
5 is a flowchart showing an example of the operation of the control unit 50. The control unit 50 executes this operation every time the cross-connect switch 25 is configured.

First, the control unit 50 switches the optical switch 21 so that wavelength light La to Ld is input to the optical demultiplexer 1 (step St1). As a result, the optical switch 21 selects wavelength light La to Ld as output light from the output port Pa.

Next, the control unit 50 controls the light emission driver 51 so that all wavelengths of light La to Ld are output from the light source 20 (step St2). As a result, all wavelengths of light La to Ld are simultaneously input to the optical demultiplexer 1, and wavelengths of light La to Ld are output randomly from the output ports P#1 to P#4.

Next, the control unit 50 causes the compensation circuits Inc#1-#3 and Dec#1-#6 to start controlling the phase shifters Hu and Hd of each AMZ 1a-1i so that they begin adjusting the optical phase (step St3). This compensates for the optical phase shifts of each wavelength light La-Ld.

After compensating for the optical phase shift, the control unit 50 instructs the compensation circuits Inc#1-#3 and Dec#1-#6 to stop controlling the phase shifters Hu and Hd of the AMZs 1a-1i so that the phase shifters Hu and Hd stop adjusting the optical phase (step St4). Therefore, before outputting the wavelength light beams La-Ld one by one, each wavelength light beam La-Ld is associated with an output port P#1-#4 of the optical demultiplexer 1.

Figure 6 shows an example of a state in which all wavelength light La-Ld is input to the optical demultiplexer 1. As an example, wavelength light La-Ld is demultiplexed by the optical demultiplexer 1, with wavelength light Ld being output from output port P#1 and wavelength light Lb being output from output port P#2. Furthermore, wavelength light Lc is output from output port P#3 and wavelength light La is output from output port P#4. At this time, compensation circuits Inc#1-#3 and Dec#1-#6 control the phase shifters Hu and Hd. Therefore, within the optical demultiplexer 1, the optical phase shift of wavelength light La-Ld is compensated for by the phase shifters Hu and Hd.

Referring again to FIG. 5, after the operation of step St4, the control unit 50 selects one wavelength from the center wavelengths λa to λd of the wavelength light La to Ld (step St5). Note that the order in which the center wavelengths λa to λd are selected is not limited. Next, the control unit 50 controls the light emission drive unit 51 so that only the wavelength light La to Ld with the selected center wavelengths λa to λd is output from the light source 20 (step St6). As a result, only the wavelength light La to Ld with the selected center wavelengths λa to λd is input to the optical demultiplexer 1, and the wavelength light La to Ld is output from the pre-assigned output port out of the output ports P#1 to #4.

Next, the control unit 50 determines whether the input signal detection unit 53 has detected the electrical signals Ea-Ed (step St7). The control unit 50 determines whether the electrical signals Ea-Ed have been detected by receiving a detection signal from the input signal detection unit 53. If the electrical signals Ea-Ed have not been detected (No in step St7), the process of step St7 is executed again.

Furthermore, if the electrical signals Ea-Ed are detected (Yes in step St7), the control unit 50 registers the output ports P#1-#4 of the wavelength light La-Ld from which the electrical signals Ea-Ed are converted, and the input ports P11, P12, P21, and P22 of the cross-connect switch 25 corresponding to these output ports P#1-#4, in the setting table in the memory 54 based on the detection signal (step St8).

Next, the control unit 50 determines whether any unselected center wavelengths λa to λd exist (step St9). If any unselected center wavelengths λa to λd exist (No in step St9), the control unit 50 selects another center wavelength λa to λd (step St5) and performs the operations from step St6 onwards again.

Figure 7 shows an example of a state in which wavelength light La with a selected center wavelength λa is input to the optical demultiplexer 1. The control unit 50 instructs the light emission driver 51 to output wavelength light La by sending a wavelength instruction signal indicating the center wavelength λa. This causes the light source 20 to output only wavelength light La. Wavelength light La is output from the associated output port P#4 of the optical demultiplexer 1 when compensating for the optical phase shift, and is converted into an electrical signal Ea by the PD 22d.

The electrical signal Ea is input to analog circuit AP#4 of the analog signal processing unit 23. Analog circuit AP#4 notifies the input signal detection unit 53 of the input of the electrical signal Ea. The input signal detection unit 53 detects the electrical signal Ea and transmits a detection signal indicating the analog circuit AP#4 that sent the notification to the control unit 50.

Figure 8 shows an example of a setting table in memory 54. The setting table registers the center wavelengths λa to λd of wavelength light La to Ld, the output port IDs (P#1 to #4) of the optical demultiplexer 1, and the input port IDs (P11, P12, P21, P22) and output port IDs (P33, P34, P43, P44) of the cross-connect switch 25.

The center wavelengths λa to λd and the output port IDs of the cross-connect switch 25 are pre-registered in a settings table. Because output ports P33, P34, P43, and P44 are connected to digital circuits DPr_a to DPr_d in a one-to-one relationship, there is also a one-to-one correspondence between center wavelengths λa to λd and output ports P33, P34, P43, and P44.

The control unit 50 uses the detection signal to identify the output ports P#1-P#4 of the optical demultiplexer 1 that output the wavelength light La-Ld from which the electrical signals Ea-Ed were converted. Because the analog circuits AP#1-#4 are connected to the output ports P#1-#4 in a one-to-one relationship, the control unit 50 can identify the output ports P#1-#4 that correspond to the analog circuits AP#1-#4 indicated by the detection signal.

The control unit 50 also identifies the input ports P11, P12, P21, and P22 of the cross-connect switch 25 that correspond to the identified output ports P#1 to #4. Because the output ports P#1 to #4 are connected to the input ports P11, P12, P21, and P22 in a one-to-one relationship, the control unit 50 can identify the input ports P11, P12, P21, and P22 that correspond to the output ports P#1 to #4.

For example, if the control unit 50 selects center wavelength λa in step St5, it receives a detection signal indicating electrical signal Ea to analog circuit AP#4. Therefore, the control unit 50 identifies output port P#4 connected to analog circuit AP#4 and registers it in the setting table. Furthermore, the control unit 50 identifies input port P22 of the cross-connect switch 25 corresponding to output port P#4 and registers it in the setting table. Note that the output port ID of the optical demultiplexer 1 and the input port ID of the cross-connect switch 25 are identified for the other center wavelengths λb to λd using a similar method.

Referring again to FIG. 5, the control unit 50 determines the cross-connection of the cross-connect switch 25 based on the setting table (step St10) and sets the cross-connection to the cross-connect switch 25 using a selection signal indicating the connection relationship (step St11). For example, the control unit 50 performs connection settings for switches SW#2 and #3 between input port P22 and output port P33 for electrical signal Ea so that electrical signal Ea is output from output port P33 of the cross-connect switch 25. The control unit 50 also performs connection settings for switches SW#1 and #4 between input port P11 and output port P44 for electrical signal Ed so that electrical signal Ed is output from output port P44 of the cross-connect switch 25.

As a result, the electrical signals Ea-Ed are input to digital circuits DPr_a-DPr_d, respectively, which correspond to the center wavelengths λa-λd of the original wavelength light La-Ld.

Next, the control unit 50 switches the optical switch 21 so that the wavelength-multiplexed signal light including the signal lights Sa to Sd is input to the optical demultiplexer 1 (step St12). That is, the control unit 50 switches the output destination of the wavelength-multiplexed signal light from output port Pb to output port Pb.

Figure 9 shows an example of the state in which wavelength-multiplexed signal light is input to the optical demultiplexer 1. The wavelength-multiplexed signal light is demultiplexed into signal lights Sa-Sd by the optical demultiplexer 1 and converted into electrical signals Ea'-Ed' by PDs 22a-22d. The electrical signals Ea'-Ed' are input to digital circuits DPr_a-DPr_d, respectively, via the cross-connect switch 25 configured as described above. As a result, appropriate signal processing is performed on the electrical signals Ea'-Ed' according to the center wavelengths λa-λd of the original signal lights Sa-Sd.

(Modification of the first embodiment)
10 is a block diagram showing an example of a digital signal processing unit 26r including a cross-connect switch 25r. In FIG. 10, components common to those in FIG. 3 are given the same reference numerals, and descriptions thereof will be omitted.

Digital signal processing unit 26r is provided in optical demultiplexing device 90 in place of digital signal processing unit 26, and includes a cross-connect switch 25r similar to cross-connect switch 25. Digital signal processing unit 26r also includes digital circuits DPr_a to DPr_d. Cross-connect switch 25r is connected to the preceding ADs 24a to 24d.

In this example, the control unit 50 can also input the electrical signals Ea-Ed to the digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd by configuring the cross-connect switch 25r using the same method as above.

Figure 11 is a configuration diagram showing an example of an analog signal processing unit 23s including a cross-connect switch 25s. In Figure 11, components that are common to Figure 3 are assigned the same reference numerals, and their description will be omitted.

The analog signal processing unit 23s is provided in the optical demultiplexing device 90 in place of the analog signal processing unit 23, and includes a cross-connect switch 25s similar to the cross-connect switch 25. The analog signal processing unit 23s also includes analog circuits AP#1 to AP#4. The analog circuits AP#1 to AP#4 are connected upstream of the cross-connect switch 25s.

In this example, the control unit 50 can also input the electrical signals Ea-Ed to the digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd by configuring the cross-connect switch 25s using the same method as above.

Figure 12 is a configuration diagram showing an example of an optical demultiplexing device 90a equipped with a control unit 50a, an input signal detection unit 53a, and a digital signal processing unit 26a including a cross-connect switch 25a. In Figure 12, components common to those in Figure 3 are designated by the same reference numerals, and their description will be omitted.

The digital signal processing unit 26a is provided in the optical demultiplexing device 90a in place of the digital signal processing unit 26. The control unit 50a, input signal detection unit 53a, and cross-connect switch 25a have the same functions as the control unit 50, input signal detection unit 53, and cross-connect switch 25, respectively.

The cross-connect switch 25a is connected between the input signal detection unit 53a and the digital circuits DPr_a-DPr_d. The input signal detection unit 53a detects the electrical signals Ea-Ed for each of the lanes Wa-Wd to which the electrical signals Ea-Ed are transmitted from the ADs 24a-24d. The input signal detection unit 53a sends a detection signal indicating the analog circuits AP#1-#4 corresponding to the lanes Wa-Wd to the control unit 50a.

In this example, the control unit 50a can also input the electrical signals Ea-Ed to the digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd by configuring the cross-connect switch 25a using the same method as above.

Figure 13 is a configuration diagram showing another example of an optical demultiplexing device 90b equipped with a control unit 50b, an input signal detection unit 53b, and a digital signal processing unit 26b including a cross-connect switch 25b. In Figure 13, components common to those in Figure 3 are designated by the same reference numerals, and their description will be omitted.

Digital signal processing unit 26b is provided in optical demultiplexing device 90b in place of digital signal processing unit 26. Control unit 50b, input signal detection unit 53b, and cross-connect switch 25b have the same functions as control unit 50, input signal detection unit 53, and cross-connect switch 25, respectively.

The input signal detection unit 53b is connected between the cross-connect switch 25b and the digital circuits DPr_a-DPr_d. The input signal detection unit 53b detects the electrical signals Ea-Ed for each of the lanes Wa-Wd through which the electrical signals Ea-Ed are transmitted from the cross-connect switch 25b. The input signal detection unit 53b transmits a detection signal to the control unit 50b indicating the lane Wa-Wd on which the electrical signal Ea-Ed was detected.

The control unit 50b identifies the output ports P33, P34, P43, and P44 of the cross-connect switch 25b that are connected to the lanes Wa to Wd indicated by the detection signal. Based on the initial cross-connect connection settings of the cross-connect switch 25b, the control unit 50b identifies the input ports P11, P12, P21, and P22 and output ports P#1 to #4 that are connected to the identified output ports P33, P34, P43, and P44.

In this example, the control unit 50b can also input the electrical signals Ea-Ed to the digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd by configuring the cross-connect switch 25b using the same method as above.

However, in this example, the input ports P11, P12, P21, and P22 and output ports P#1 to #4 are identified from the lanes Wa to Wd indicated by the detection signals based on the initial cross-connect connection settings of the cross-connect switch 25b, so the identification process takes more effort than in the example of Figure 12. Therefore, as in the example of Figure 12, when the input signal detection unit 53a connected upstream of the cross-connect switch 25a detects the electrical signals Ea to Ed input to the cross-connect switch 25 from the PDs 22a to 22d, it is easier to identify the input ports P11, P12, P21, and P22 and output ports P#1 to #4 than in this example.

(Second Example)
Fig. 14 is a configuration diagram showing an optical demultiplexing device 91 of the second embodiment. In Fig. 14, components common to those in Fig. 3 are assigned the same reference numerals, and their description will be omitted. The optical demultiplexing device 90 is mounted on, for example, a transmission device, and generates wavelength-multiplexed signal light by wavelength-multiplexing signal light Sa to Sd, whose center wavelengths λa to λd are spaced at regular intervals, and transmits the wavelength-multiplexed signal light to a transmission path (not shown).

The optical demultiplexing device 91 includes a light source 20, an optical switch 21, an optical demultiplexer 1, optical modulators (MD) 30a-30d, an analog signal processing unit 31, digital-to-analog converters (DA) 32a-32d, a cross-connect switch (SW) 33, a digital signal processing unit 34, and a multiplexing unit (MUX) 37. The optical demultiplexing device 91 also includes a control unit 56, a light emission driver 51, a compensation circuit driver 52, an input signal detector 55, and a memory 57. The input signal detector 55, the analog signal processing unit 31, and the digital signal processing unit 34 are implemented, for example, by an FPGA or ASIC. The control unit 56 is implemented by a circuit including a processor such as a CPU.

Light source 20 is an example of a second light source and outputs wavelength light La-Ld as transmission light for generating signal light Sa-Sb. Control unit 56 uses a wavelength instruction signal to instruct light emission driver 51 on the center wavelengths λa-λd of the wavelength light La-Ld to be output. Wavelength light La-Ld is input to optical demultiplexer 1. Optical demultiplexer 1 is an example of a second demultiplexing unit and demultiplexes wavelength light La-Ld. AMZs 1a-1i of optical demultiplexer 1 are connected to each other so that wavelength light La-Ld is demultiplexed and output to different MDs 30a-30d, respectively.

The compensation circuit driver 52 starts or stops the operation of the compensation circuits Inc#i and Dec#j (i = 1 to 3, j = 1 to 6) in accordance with the on/off instruction signal input from the controller 56. The on/off instruction signal is as described above. Prior to setting the cross-connect switch 33, the controller 56 assigns output ports P#1 to P#4 to each of the wavelengths La to Ld, causing the light source 20 to output all wavelengths La to Ld to the optical demultiplexer 1, and then starts the operation of all compensation circuits Inc#i and Dec#j.

Each wavelength light La-Ld is output randomly from one of the output ports P#1-#4 of the optical demultiplexer 1. In this example, as in the first embodiment, it is assumed that wavelength light Ld is output from output port P#1, wavelength light Lb is output from output port P#2, wavelength light Lc is output from output port P#3, and wavelength light La is output from output port P#4. Wavelength light La-Ld is input to MDs 30d, 30b, 30c, and 30a from output ports P#4, #2, #3, and #4, respectively.

MDs 30a-30d optically modulate wavelength light Ld, Lb, Lc, and La based on data signals Dd, Db, Dc, and Dd, respectively. The optically modulated wavelength light La-Ld is input to multiplexer 37 as signal light Sa-Sd. Multiplexer 37 is, for example, an optical coupler, and multiplexes wavelength light La-Ld to generate wavelength-multiplexed signal light Smux. Wavelength-multiplexed signal light Smux is output from multiplexer 37 to a transmission path (not shown).

In addition, data signals Dd, Db, Dc, and Dd are input from the digital signal processing unit 34 to MDs 30a to 30d, respectively, via the cross-connect switch 33.

The digital signal processing unit 34 generates electrical data signals Da-Dd by, for example, performing frame conversion processing on an externally input Ethernet (registered trademark; the same applies below). The digital signal processing unit 34 has digital circuits DPs_a-DPs_d.

Digital circuits DPs_a to DPs_d generate data signals Da to Dd. Digital circuit DPs_a generates data signal Da from an Ethernet signal corresponding to channel CH1 (see Figure 4) with a center wavelength λa. Data signal Da is used for optical modulation of wavelength light La. Digital circuit DPs_b generates data signal Db from an Ethernet signal corresponding to channel CH2 with a center wavelength λb. Data signal Db is used for optical modulation of wavelength light Lb.

Data signal Dc is used for optical modulation of wavelength light Lc. Digital circuit DPs_c generates data signal Dc from an Ethernet signal corresponding to channel CH3 with a center wavelength λc. Data signal Dc is used for optical modulation of wavelength light Lc. Digital circuit DPs_d generates data signal Dd from an Ethernet signal corresponding to channel CH4 with a center wavelength λd. Data signal Dd is used for optical modulation of wavelength light Ld.

Digital circuits DPs_a to DPs_d are connected to input ports P11, P12, P21, and P22, respectively, of the cross-connect switch 33. Data signals Da to Dd are input to the cross-connect switch 33 from input ports P11, P12, P21, and P22, respectively.

The cross-connect switch 33 is an example of a second switch unit, and selects the digital circuit from which the data signals Da-Dd are input to MDs 30a-30d from among the digital circuits DPs_a-DPs_d that are the input sources of the data signals Da-Dd. The cross-connect switch 33 has switches SW#1-#4 connected to each other, similar to the cross-connect switch 25.

The output ports P33, P34, P43, and P44 of the cross-connect switch 33 are connected to DAs 32a to 32d, respectively. The cross-connect switch 33 selects the input ports from input ports P11, P12, P21, and P22 to be connected to each of the output ports P33, P34, P43, and P44 in accordance with a selection signal input from the control unit 56.

DAs 32a-32d convert data signals Da-Dd input from output ports P33, P34, P43, and P44 from digital to analog signals and output them to analog signal processing unit 31. Analog signal processing unit 31 is, for example, a drive circuit for MDs 30a-30d. Data signals Da-Dd are input to MDs 30a-30d via the analog signal processing unit.

The input signal detector 55 is an example of a second detector and detects the wavelength light Ld, Lb, Lc, and La input to MDs 30a-30d, respectively. For example, the input signal detector 55 detects the output ports P#1-#4 of the optical demultiplexer 1 from which the wavelength light Ld, Lb, Lc, and La are output based on the monitoring results of monitor circuits Mon#5, #7, #9, and #11. The monitor circuits Mon#5, #7, #9, and #11 notify the input signal detector 55 of the monitoring results of the power of the output light output from AMZs 1e, 1f, 1h, and 1i to output ports P#1-#4.

The input signal detection unit 55 transmits a detection signal to the control unit 56 indicating, for example, which of the output ports P#1 to P#4 corresponds to the monitor circuits Mon#5, #7, #9, and #11 for which the power of the monitoring result is above a predetermined threshold. For example, if the power of the monitoring result of monitor circuit Mon#5 is above a predetermined threshold, the detection signal indicates that wavelength light Ld is being output from output port P#1, and if the power of the monitoring result of monitor circuit Mon#11 is above a predetermined threshold, the detection signal indicates that wavelength light La is being output from output port P#4.

The control unit 56 controls the light source 20 so that the wavelength light beams La-Ld are input sequentially to the demultiplexer 1 one by one. At this time, the control unit 56 identifies the output ports P33, P34, P43, and P44 of the cross-connect switch 33 that output the data signals Da-Dd to the MDs 30a-30d connected to the output ports P#1-#4 of the optical demultiplexer 1 indicated by the detection signal. Here, the control unit 56 performs the identification using, for example, information on the correspondence between the output ports P#1-#4 and the output ports P33, P34, P43, and P44 that is stored in advance in the memory 54.

The control unit 56 registers the correspondence between the center wavelengths λa to λd of the output wavelength light La to Ld, the output ports P#1 to #4 indicated by the detection signal, the input ports P11, P12, P21, and P22 of the cross-connect switch 33, and the output ports P33, P34, P43, and P44 in the setting table of the cross-connect switch 33 in the memory 57. After compensating for the optical phase shift of AMZ1a to 1i, the control unit 56 sets each switch SW#1 to #4 in the cross-connect switch 33 according to the setting table. In other words, the control unit 56 sets the connections between the input ports P11, P12, P21, P22, P31, P32, P41, and P42 of each switch SW#1 to #4 and the output ports P13, P14, P23, P24, P33, P34, P43, and P44.

For example, the control unit 56 connects the input port P22 and output port P23 of switch SW#2 and connects the input port P32 and output port P33 of switch SW#3 so that wavelength light Ld input from output port P#1 of optical demultiplexer 1 to MD30a is optically modulated by the data signal Dd input from digital circuit DPs_d to MD30a. The control unit 56 also connects the input port P11 and output port P14 of switch SW#1 and connects the input port P41 and output port P44 of switch SW#4 so that wavelength light La input from output port P#4 of optical demultiplexer 1 to MD30d is optically modulated by the data signal Da input from digital circuit DPs_a to MD30d.

In this way, while one of the wavelength light beams La-Ld is being input to the optical demultiplexer 1, the control unit 56 controls the cross-connect switch 33 so that data signals Da-Dd are input from one of the digital circuits DPs_a-DPs_d that corresponds to the detected wavelength light beam to the modulator MD30d, 30b, 30c, 30a to which the wavelength light beam La-Ld detected by the input signal detection unit 55 is input. The control unit 56 is an example of a second control unit that controls the light source 20 and the cross-connect switch 33.

As a result, data signals Dd, Db, Dc, and Da are input to each of MDs 30a-30d from digital circuits DPs_d, DPs_b, DPs_c, and DPs_a corresponding to wavelength light Ld, Lb, Lc, and La input from optical demultiplexer 1. Therefore, wavelength light Ld, Lb, Lc, and La are optically modulated based on data signals Dd, Db, Dc, and Da corresponding to center wavelengths λa-λd. This allows optical demultiplexing device 91 to perform appropriate optical modulation processing for each center wavelength λa-λd.

(Operation of the control unit)
15 is a flowchart showing an example of the operation of the control unit 56. The control unit 56 executes this operation every time the cross-connect switch 33 is set.

First, the control unit 56 controls the light emission driver 51 so that all wavelengths of light La to Ld are output from the light source 20 (step St21). As a result, all wavelengths of light La to Ld are simultaneously input to the optical demultiplexer 1, and wavelengths of light La to Ld are output randomly from the output ports P#1 to P#4.

Next, the control unit 56 causes the compensation circuits Inc#1-#3 and Dec#1-#6 to start controlling the phase shifters Hu and Hd of each AMZ 1a-1i so that the phase shifters Hu and Hd begin adjusting the optical phase (step St22). This compensates for the optical phase shifts of each wavelength light La-Ld.

After compensating for the optical phase shift, the control unit 56 instructs the compensation circuits Inc#1-#3 and Dec#1-#6 to stop controlling the phase shifters Hu and Hd of the AMZs 1a-1i so that the phase shifters Hu and Hd stop adjusting the optical phase (step St23). Therefore, before outputting the wavelength light beams La-Ld one by one, each wavelength light beam La-Ld is associated with an output port P#1-#4 of the optical demultiplexer 1.

Figure 16 shows an example of a state in which all wavelength light La-Ld is input to the optical demultiplexer 1. As an example, wavelength light La-Ld is demultiplexed by the optical demultiplexer 1, with wavelength light Ld being output from output port P#1 and wavelength light Lb being output from output port P#2. Furthermore, wavelength light Lc is output from output port P#3 and wavelength light La is output from output port P#4. At this time, compensation circuits Inc#1-#3 and Dec#1-#6 control the phase shifters Hu and Hd. Therefore, within the optical demultiplexer 1, the optical phase shift of wavelength light La-Ld is compensated for by the phase shifters Hu and Hd.

Referring again to FIG. 15, after the operation of step St23, the control unit 56 selects one wavelength from the center wavelengths λa to λd of the wavelength light La to Ld (step St25). Note that the order in which the center wavelengths λa to λd are selected is not limited. Next, the control unit 56 controls the light emission drive unit 51 so that only the wavelength light La to Ld with the selected center wavelengths λa to λd is output from the light source 20 (step St26). As a result, only the wavelength light La to Ld with the selected center wavelengths λa to λd is input to the optical demultiplexer 1, and the wavelength light La to Ld is output from the pre-assigned output port out of the output ports P#1 to #4.

Next, the control unit 56 determines whether or not the wavelength light La-Ld has been detected by the input signal detection unit 55 (step St26). The control unit 56 determines whether or not the wavelength light La-Ld has been detected by receiving a detection signal from the input signal detection unit 55. If the wavelength light La-Ld has not been detected (No in step St26), the process of step St26 is executed again.

Furthermore, if wavelength light La-Ld is detected (Yes in step St26), the control unit 56 registers the output ports P#1-#4 of wavelength light La-Ld and the output ports P33, P34, P43, and P44 of the cross-connect switch 33 corresponding to these output ports P#1-#4 in the setting table in the memory 54 based on the detection signal (step St27).

Next, the control unit 56 determines whether any unselected center wavelengths λa to λd exist (step St28). If any unselected center wavelengths λa to λd exist (No in step St28), the control unit 56 selects another center wavelength λa to λd (step St24) and performs the operations from step St25 onwards again.

Figure 17 shows an example of a state in which wavelength light La with a selected center wavelength λa is input to the optical demultiplexer 1. The control unit 56 instructs the light emission driver 51 to output wavelength light La by sending a wavelength instruction signal indicating the center wavelength λa. This causes the light source 20 to output only wavelength light La. Wavelength light La is input to MD30d from output port P#4 of the optical demultiplexer 1, which is associated with the compensation for the optical phase shift.

At this time, the cross-connect connection of the cross-connect switch 33 is in the initial setting state, so a data signal Dd is input to MD30d from a digital circuit DPs_d that does not correspond to wavelength light La. As a result, wavelength light La is optically modulated by a data signal Dd that does not correspond to its center wavelength λa.

Figure 18 shows an example of a settings table in memory 57. The settings table registers the center wavelengths λa to λd of wavelength light La to Ld, the output port IDs (P#1 to #4) of the optical demultiplexer 1, and the input port IDs (P11, P12, P21, P22) and output port IDs (P33, P34, P43, P44) of the cross-connect switch 25.

The center wavelengths λa to λd and the input port IDs of the cross-connect switch 33 are pre-registered in a settings table. Since input ports P11, P12, P21, and P22 are connected to digital circuits DPs_a to DPs_d in a one-to-one relationship, there is also a one-to-one correspondence between center wavelengths λa to λd and input ports P11, P12, P21, and P22.

The control unit 50 uses the detection signal to identify the output ports P#1 to P#4 of the optical demultiplexer 1 that output the wavelength light La to Ld. The output ports P#1 to P#4 are connected to MDs 30a to 30d, respectively, and the output ports P33, P34, P43, and P44 of the cross-connect switch 33 are connected to MDs 30a to 30d, respectively. Therefore, there is a one-to-one correspondence between the output ports P#1 to P#4 and the output ports P33, P34, P43, and P44.

For this reason, the control unit 56 can identify the output ports P33, P34, P43, and P44 of the cross-connect switch 33 that correspond to the output ports P#1 to P#4 indicated by the detection signal, for example, from the above-mentioned correspondence information stored in advance in memory 57.

For example, if the control unit 56 selects the center wavelength λa in step St24, it receives a detection signal indicating wavelength light La from output port P#4. Therefore, the control unit 56 registers P#4 in the setting table as the output port ID of the optical demultiplexer 1 corresponding to the center wavelength λa.

Furthermore, the control unit 56 identifies output port P44 of the cross-connect switch 33 corresponding to output port P#4 and registers the output port ID P44 in the setting table. Note that the output port IDs of the cross-connect switch 25 of the optical demultiplexer 1 are identified for the other center wavelengths λb to λd using a similar method.

Referring again to FIG. 15, the control unit 56 determines the cross-connection of the cross-connect switch 33 based on the setting table (step St29) and sets the cross-connection to the cross-connect switch 33 using a selection signal indicating the connection relationship (step St30).

For example, the control unit 56 performs connection settings for switches SW#1 and SW#4 between output port P44 of the data signal Da and input port P11 so that the data signal Da is output from output port P44 of the cross-connect switch 33. The control unit 56 also performs connection settings for switches SW#2 and SW#3 between output port P33 of the data signal Dd and input port P22 so that the data signal Dd is output from output port P33 of the cross-connect switch 33.

As a result, data signals Da-Dd are input to MDs 30a-30d, which optically modulate wavelength light La-Ld corresponding to data signals Da-Dd. Therefore, appropriate optical modulation processing is performed on wavelength light La-Ld according to the center wavelengths λa-λd.

(Modification of the second embodiment)
19 is a diagram showing an example of an optical demultiplexing device 91a equipped with a digital signal processing unit 34a including a cross-connect switch 33a. In FIG. 19, components common to those in FIG. 14 are designated by the same reference numerals, and description thereof will be omitted.

The digital signal processing unit 34a is provided in the optical demultiplexing device 91a in place of the digital signal processing unit 34 and includes a cross-connect switch 33a similar to the cross-connect switch 33. The digital signal processing unit 34a also includes digital circuits DPr_a to DPr_d. The cross-connect switch 33a is connected downstream of the digital circuits DPr_a to DPr_d.

In this example, the control unit 56 configures the cross-connect switch 33a in the same manner as above, allowing MDs 30d, 30b, 30c, and 30a to optically modulate wavelength light La-Ld using data signals Da-Dd input from digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd.

Figure 20 is a configuration diagram showing an example of an optical demultiplexing device 91b equipped with an analog signal processing unit 31b including a cross-connect switch 33b. In Figure 20, components that are common to Figure 14 are assigned the same reference numerals, and their description will be omitted.

The analog signal processing unit 31b is provided in the optical demultiplexing device 91b in place of the analog signal processing unit 31, and includes a cross-connect switch 33b similar to the cross-connect switch 33.

In this example, the control unit 56 configures the cross-connect switch 33a in the same manner as above, allowing MDs 30d, 30b, 30c, and 30a to optically modulate wavelength light La-Ld using data signals Da-Dd input from digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd.

(Third Example)
Fig. 21 is a configuration diagram showing an example of a transmission device 9. In Fig. 21, components common to Fig. 3 and Fig. 14 are given the same reference numerals, and descriptions thereof will be omitted.

Transmission device 9 includes the configuration of the optical demultiplexers 90 and 91 described above. Note that transmission device 9 may include the configuration of modified optical demultiplexers 90a and 90b instead of optical demultiplexer 90, and may further include the configuration of modified optical demultiplexers 91a and 91b instead of optical demultiplexer 91.

The transmission device 9 has a control unit 58, a memory 59, a transmitter 91c that transmits wavelength-multiplexed signal light, and a receiver 90c that receives other wavelength-multiplexed signal light. The transmitter 91c has the same functions as the optical demultiplexer 91, and the receiver 90c has the same functions as the optical demultiplexer 90.

The receiver 90c includes a light source 20, an optical switch 21, an optical demultiplexer 1, photodiodes 22a-22d, an analog signal processor 23, analog-to-digital converters 24a-24d, a cross-connect switch 25, a digital signal processor 26, a light emission driver 51, a compensation circuit driver 52a, and an input signal detector 53. The optical demultiplexer 1r includes AMZs 1a-1i, similar to the optical demultiplexer 1. The AMZs 1a-1i of the optical demultiplexer 1r are connected to each other so that wavelength light La-Lb is output to the different photodiodes 22a-22d, respectively. The AMZs 1a-1i of the optical demultiplexer 1r are examples of multiple first asymmetric Mach-Zehnder interferometers. The compensation circuit driver 52a has the same function as the compensation circuit driver 52.

The transmitter 91c includes an optical demultiplexer 1s, MDs 30a-30d, an analog signal processor 31, DAs 32a-32d, a cross-connect switch 33, a digital signal processor 34, a multiplexer 37, a compensation circuit driver 52b, and an input signal detector 55. The optical demultiplexer 1s includes AMZs 1a-1i, similar to the optical demultiplexer 1. The AMZs 1a-1i of the optical demultiplexer 1s are connected to each other so that wavelength light La-Ld is demultiplexed and output to different MDs 30a-30d, respectively. The AMZs 1a-1i of the optical demultiplexer 1s are an example of a plurality of second asymmetric Mach-Zehnder interferometers. The compensation circuit driver 52b has the same function as the compensation circuit driver 52.

The transmitter 91c and receiver 90c share the light source 20 for wavelengths La to Ld. Therefore, one output port Pa of the optical switch 21 is optically connected to the optical demultiplexer 1r of the receiver 90c, and the other output port Pb is connected to the optical demultiplexer 1s of the transmitter 91c, as indicated by the reference numeral 210.

The optical switch 21 switches between output ports Pa and Pb for wavelength light La-Ld from the light source 20 in accordance with a switching signal from the control unit 58. When wavelength light La-Ld is input to the optical demultiplexer 1s of the transmitter 91c, the transmitter 91c uses wavelength light La-Ld as the transmission light for data signals Da-Dd. In this case, the MDs 30a-30d set the cross-connect switch 33 in response to the detection of wavelength light La-Ld as described above, and then optically modulate the wavelength light La-Ld based on the data signals Da-Dd to generate signal light Sa'-Sd', respectively. The signal light Sa'-Sd' is multiplexed into wavelength-multiplexed signal light Smux by the multiplexer 37 and transmitted to the receiver.

Furthermore, when wavelength light La-Ld is input to the optical demultiplexer 1r of the receiving unit 90c, the cross-connect switch 25 is set based on the detection results of the electrical signals Ea-Ed converted from wavelength light La-Ld as described above.

The control unit 58 is realized by a circuit including a processor such as a CPU. The control unit 58 is an example of a third control unit that controls the light source 20, the optical switch 21, and the cross-connect switches 25 and 33. The memory 57 also stores the setting tables shown in Figures 8 and 18.

The control unit 58 has a reception setting mode in which the cross-connect switch 25 of the receiving unit 90c is set using a method similar to that of the control unit 50, and a transmission setting mode in which the cross-connect switch 33 of the transmitting unit 91c is set using a method similar to that of the control unit 56. The reception setting mode is an example of a first control mode for controlling the cross-connect switch 25, and the transmission setting mode is an example of a second control mode for controlling the cross-connect switch 33. The control unit 58 can switch its operating mode between the reception setting mode and the transmission setting mode, for example, by a network monitoring control device (not shown).

Figure 22 is a flowchart showing an example of the operation of the control unit 56. This operation is executed, for example, when the transmission device 9 is started up.

The control unit 56 determines whether the operating mode is the transmission setting mode (step St41). If the operating mode is the transmission setting mode (Yes in step St41), the control unit 56 controls the optical switch 21 to switch so that the wavelength light La to Ld is input to the optical demultiplexer 1s of the transmitter 91c (step St42). Next, the control unit 56 sets the cross-connect switch 33 of the transmitter 91c using a method similar to that shown in FIG. 15 (step St43).

Also, if the operating mode is not the transmission setting mode (No in step St41), the control unit 56 determines whether the operating mode is the reception setting mode (step St44). If the operating mode is not the reception setting mode (No in step St44), the control unit 56 ends operation.

Also, if the operating mode is the reception setting mode (No in step St44), the control unit 56 controls the optical switch 21 to switch so that the wavelength light La to Ld is input to the optical demultiplexer 1r of the receiving unit 90c (step St45). Next, the control unit 56 sets the cross-connect switch 25 of the receiving unit 90c using a method similar to that shown in FIG. 5 (step St46).

Therefore, transmission device 9 can perform appropriate signal processing on wavelengths La to Ld, similar to optical demultiplexing devices 90 and 91.

(Another example of a cross-connect switch)
23 is a configuration diagram showing an example of a cross-connect switch 25n used when the number of wavelengths of wavelength light from the light source 20 is eight. The cross-connect switch 25n has 2×2 switches SW#1 to #12 connected in multiple stages. Each of the switches SW#1 to #12 is, for example, a Banyan switch.

The cross-connect switch 25n has eight input ports Pin and eight output ports Pout, the same number as the number of wavelengths. When used in the optical demultiplexing device 90, the cross-connect switch 25n inputs and outputs eight electrical signals and selects the output destination of each electrical signal. When used in the optical demultiplexing device 91, the cross-connect switch 25n inputs and outputs eight data signals and selects the input source of the data signals for each of the MDs 30a to 30d. This allows the optical demultiplexing devices 90 and 91 to handle eight wavelengths of light. When the number of wavelengths is N, the number of stages of switches SW#1 to #12 in the cross-connect switch 25n is log ₂ N.

(Comparison of power consumption)
24 is a diagram showing an example of changes in power consumption of the phase shifters Hu, Hd with respect to the number of wavelengths to be demultiplexed by the optical demultiplexer 1. Circles indicate the total power consumption of the phase shifters Hu, Hd of each AMZ 1a to 1i of the optical demultiplexer 1 when used in the optical demultiplexing devices 90 and 91. Crosses indicate the total power consumption of the phase shifters Hu, Hd of each AMZ 1a to 1i of the optical demultiplexer 1 when used in the method shown in FIG. 2 (hereinafter referred to as the comparative method).

In the comparative method, output ports P#1-#4 are fixedly assigned to wavelengths La-Ld. Therefore, compensation circuits Inc#1-#3 and Dec#1-#12 control phase shifters Hu and Hd along the path K for each wavelength La-Ld so that the peak of the transmission band coincides with the center wavelengths λa-λd of that wavelength La-Ld.

In contrast, in optical demultiplexers 90 and 91, output ports P#1 to P#4 can be freely assigned to wavelengths La to Ld. Therefore, each compensation circuit Inc#1 to #3 and Dec#1 to #12 can control phase shifters Hu and Hd so that the peak of the transmission band coincides with the center wavelengths λa to λd of wavelengths La to Ld, minimizing power consumption. Therefore, optical demultiplexers 90 and 91 consume less power than the comparative method.

(Fourth Example)
Fig. 25 is a block diagram showing an optical demultiplexing device 90 of the fourth embodiment. In Fig. 25, the same components as those of the optical demultiplexing device 90 of the first embodiment described with reference to Fig. 3 are denoted by the same reference numerals, and detailed description thereof will basically be omitted.

The optical demultiplexing device 90 of the fourth embodiment includes multiple wavelength-tunable light sources 28, a first optical switch 21a, a second optical switch 21b, an optical demultiplexer 1, and optical-to-electrical converters (O/E) 27a-27d. The O/Es 27a-27d include a 90-degree optical hybrid circuit and a BPD (balanced photodiode). The optical demultiplexing device 90 also includes an analog signal processing unit 23, ADs 24a-24d, a cross-connect switch 25, and a digital signal processing unit 26. The optical demultiplexing device 90 also includes a control unit 50, a light emission driver 51, a compensation circuit driver 52, a memory 54, and an output light detector 60. The light emission driver 51, the compensation circuit driver 52, the output light detector 60, the analog signal processing unit 23, and the digital signal processing unit 26 are implemented, for example, by an FPGA or ASIC. The control unit 50 is implemented by a circuit including a processor such as a CPU. The optical demultiplexer 1 of the fourth embodiment is an example of a third demultiplexing section.

The first optical switch 21a has two input ports and one output port Pa. Multiple wavelength-multiplexed signal light beams Sa-Sd are input to one input port from the transmitter 80, and one of the wavelength light beams La-Ld is selectively input to the other input port from the second optical switch 21b. The second optical switch 21b has one input port and two output ports. One of the wavelength light beams La-Ld is selectively input to the input port from one of the multiple wavelength-tunable light sources 28.

The multiple wavelength-tunable light sources 28 are an example of a third light source that switches between and outputs one of multiple wavelength light beams La-Ld with constant wavelength intervals. One of the multiple wavelength-tunable light sources 28 is optically connected to the input port of the second optical switch 21b. All but one of the multiple wavelength-tunable light sources 28, the remaining three, are optically connected to the 90-degree optical hybrid circuits of the O/Es 27b-27d. The light emission driver 51 drives the multiple wavelength-tunable light sources 28 in accordance with a wavelength instruction signal input from the controller 50. The multiple wavelength-tunable light sources 28 each output wavelength light beams La-Ld with center wavelengths λa-λd specified by the wavelength instruction signal. The controller 50 is an example of a third controller that controls the multiple wavelength-tunable light sources 28 and the cross-connect switch 25.

The first optical switch 21a switches the input source of the input light between the second optical switch 21b and the transmitter 80 in accordance with a switching signal input from the control unit 50. In other words, the first optical switch 21a is an example of a selector that selects the input light from one of the wavelengths La to Ld and wavelength-multiplexed signal light that shares the same center wavelengths λa to λd as the wavelengths La to Ld. The output port Pa is optically connected to the input port Pin of the optical demultiplexer 1. The second optical switch 21b switches the output port that outputs the wavelengths La to Ld in accordance with a switching signal input from the control unit 50. One of the output ports is optically connected to the input port of the first optical switch 21a. The other output port is optically connected to the 90-degree optical hybrid circuit of the O/E 27a. When configuring the cross-connect switch 25, the control unit 50 switches the first optical switch 21a and the second optical switch 21b so that the wavelengths La to Ld are output from the output port Pa.

Wavelength light La-Ld is input to the optical demultiplexer 1 from one of multiple wavelength-tunable light sources 28 and separated into wavelengths. The AMZs 1a-1i of the optical demultiplexer 1 are connected to each other so that wavelength light La-Ld is output to different 90-degree optical hybrid circuits, O/Es 27a-27d, respectively.

Prior to setting the cross-connect switch 25, the control unit 50 controls the first optical switch 21a to output the wavelength-multiplexed signal light to the optical demultiplexer 1 and also starts the operation of all compensation circuits Inc#i and Dec#j. The wavelength-multiplexed signal light input to the optical demultiplexer 1 has its optical phase compensated by the compensation circuits Inc#i and Dec#j, is demultiplexed into signal lights Sa-Sd, and is output randomly from output ports P#1-#4. By inputting the wavelength-multiplexed signal light to the optical demultiplexer 1 in advance, noise can be suppressed when detecting the wavelength lights La-Ld that are later output as output light from output ports P#1-#4.

In this example, it is assumed that signal light Sd is output from output port P#1, signal light Sb is output from output port P#2, signal light Sc is output from output port P#3, and signal light Sa is output from output port P#4. After each of the signal lights Sa-Sd has been output from output ports P#1-#4, the control unit 50 stops the operation of all compensation circuits Inc#i and Dec#j, and switches each of the wavelength lights La-Ld to one of the multiple wavelength-tunable light sources 28 one by one and outputs them to the optical demultiplexer 1.

For example, as shown in FIG. 26, the control unit 50 causes one of the multiple wavelength-tunable light sources 28 to output wavelength light La to the optical demultiplexer 1. Wavelength light La is input from the optical demultiplexer 1 to the O/E 27d. Similarly, the control unit 50 switches one of the multiple wavelength-tunable light sources 28 to output wavelength light Lb to Ld one by one to the optical demultiplexer 1, whereby wavelength light Lb to Ld is input from the optical demultiplexer 1 to one of the O/Es 27a to 27c. For example, as shown in FIG. 27, when the control unit 50 causes one of the multiple wavelength-tunable light sources 28 to output wavelength light Ld to the optical demultiplexer 1, wavelength light Ld is input from the optical demultiplexer 1 to the O/E 27a. The output ports P#1 to P#4 notify the output light detection unit 60 of the presence or absence of input of wavelength light La to Ld.

As shown in Figure 28, the 90-degree optical hybrid circuit of O/E 27a uses wavelength light Ld as local light and detects signal light Sd as demultiplexed light, while the 90-degree optical hybrid circuit of O/E 27b uses wavelength light Lb as local light and detects signal light Sb as demultiplexed light. As shown in Figure 28, the 90-degree optical hybrid circuit of O/E 27c uses wavelength light Lc as local light and detects signal light Sc as demultiplexed light, while the 90-degree optical hybrid circuit of O/E 27d uses wavelength light La as local light and detects signal light Sa as demultiplexed light. Multiple 90-degree optical hybrid circuits are an example of multiple detection units. The demultiplexed signal light Sa-Sd is each input from the 90-degree optical hybrid circuit to the BPD.

As shown in FIG. 28, the BPD of O/E 27a converts signal light Sd into an electrical signal Ed', and the BPD of O/E 27b converts signal light Lb into an electrical signal Eb'. As shown in FIG. 28, the BPD of O/E 27c converts signal light Sc into an electrical signal Ec', and the BPD of O/E 27d converts signal light Sa into an electrical signal Ea'. The BPDs are an example of multiple conversion units. The electrical signals Ea' to Ed' are input from the BPDs to the analog signal processing unit 23.

The analog signal processing unit 23 has analog circuits AP#1 to AP#4 that perform analog signal processing on the electrical signals Ea' to Ed'. The electrical signal Ed' is input to analog circuit AP#1, and the electrical signal Eb' is input to analog circuit AP#2. The electrical signal Ec' is input to analog circuit AP#3, and the electrical signal Ea' is input to analog circuit AP#4. The electrical signals Ea' to Ed' are input from the analog signal processing unit 23 to AD 24a to AD 24d.

ADs 24a to 24d convert the electrical signals Ed', Eb', Ec', and Ea' from analog to digital signals. The electrical signals Ed', Eb', Ec', and Ea' are input from ADs 24a to 24d to the cross-connect switch 25.

The cross-connect switch 25 is an example of a third switch unit, and selects the output destination of each of the electrical signals Ea' to Ed' from multiple output destinations. The digital signal processing unit 26 is connected downstream of the cross-connect switch 25. The digital signal processing unit 26 includes digital circuits DPr_a to DPr_b that perform digital signal processing on the electrical signals Ea' to Ed', respectively. The cross-connect switch 25 selects one of the digital circuits DPr_a to DPr_d as the output destination for each of the electrical signals Ea' to Ed' in accordance with a selection signal input from the control unit 50.

Each switch SW#1-#4 can switch the connection between input ports P11, P12, P21, P22, P31, P32, P41, and P42 and output ports P13, P14, P23, P24, P33, P34, P43, and P44 in accordance with a selection signal. Therefore, the cross-connect switch 25 can output the electrical signals Ed', Eb', Ec', and Ea' input from ADs 24a-24d to any of the digital circuits DPr_a-DPr_d in accordance with the selection signal.

Digital circuits DPr_a to DPr_d perform digital signal processing on each electrical signal Ea' to Ed' to compensate for degradation that occurs in each signal light Sa to Sd along the transmission path. Digital circuits DPr_a to DPr_d perform digital signal processing according to the center wavelengths λa to λd. For this reason, digital circuit DPr_a is a circuit dedicated to the electrical signal Ea' converted from signal light Sa. Digital circuit DPr_b is a circuit dedicated to the electrical signal Eb' converted from signal light Sb. Digital circuit DPr_c is a circuit dedicated to the electrical signal Ec' converted from signal light Sc. Digital circuit DPr_d is a circuit dedicated to the electrical signal Ed' converted from signal light Sd.

The output light detector 60 is an example of a third detector and detects the wavelengths λa to λd of the wavelength light La to Ld as demultiplexed light output from the output ports P#1 to P#4, respectively. The control unit 50 controls the cross-connect switch 25 so that the signal light Sa to Sd with wavelengths λa to λd detected by the output light detector 60 is output to the output destination of the digital circuits DPr_a to DPr_d that corresponds to the signal light Sa to Sd from which the electrical signals Ea' to Ed' were converted.

For example, the output light detector 60 detects the wavelengths λa to λd of the wavelength light Ld, Lb, Lc, and La based on notifications from output ports P#1 to P#4. The output light detector 60 sends a detection signal to the controller 50 indicating the output ports P#1 to P#4 from which the input of wavelength light Ld, Lb, Lc, and La was notified.

The control unit 50 registers the wavelengths λa to λd of the wavelength light La to Ld being output, the output ports P#1 to #4 corresponding to the detection signal, the input ports P11, P12, P21, and P22 of the cross-connect switch 25 to which the output ports P#1 to #4 are connected, the output ports P33, P34, P43, and P44, and the correspondence between one channel of each of the multiple wavelength-tunable light sources 28 in a setting table for the cross-connect switch 25 in the memory 54, as shown in FIG. 29.

After compensating for the optical phase shift of AMZ1a-1i, the control unit 50 configures each switch SW#1-#4 in the cross-connect switch 25 according to the configuration table. In other words, the control unit 50 configures the connections between the input ports P11, P12, P21, P22, P31, P32, P41, and P42 of each switch SW#1-#4 and the output ports P13, P14, P23, P24, P33, P34, P43, and P44.

For example, as shown in FIG. 28, the control unit 50 connects the input port P11 and output port P14 of switch SW#1 and connects the input port P41 and output port P44 of switch SW#4 so that the electrical signal Ed' input from the output port P#1 of the optical demultiplexer 1 to the input port P11 of switch SW#1 is output to the digital circuit DPr_d. The control unit 50 also connects the input port P22 and output port P23 of switch SW#2 and connects the input port P32 and output port P33 of switch SW#3 so that the electrical signal Ea' input from the output port P#4 of the optical demultiplexer 1 to the input port P22 of switch SW#2 is output to the digital circuit DPr_a.

The control unit 50 also connects the input port P12 and output port P13 of switch SW#1 and connects the input port P31 and output port P34 of switch SW#3 so that the electrical signal Eb' input from output port P#2 of optical demultiplexer 1 to input port P12 of switch SW#1 is output to digital circuit DPr_b. The control unit 50 also connects the input port P21 and output port P24 of switch SW#2 and connects the input port P42 and output port P43 of switch SW#4 so that the electrical signal Ec' input from output port P#3 of optical demultiplexer 1 to input port P21 of switch SW#2 is output to digital circuit DPr_c.

As a result, each signal light Sa-Sd is converted into an electrical signal Ea'-Ed', and then input via the cross-connect switch 25 to the appropriate digital circuit DPr_a-DPr_d corresponding to the center wavelength λa-λd. Therefore, the optical demultiplexing device 90 can perform appropriate signal processing for each center wavelength λa-λd.

(Operation of the control unit)
30 is a flowchart showing an example of the operation of the control unit 50. The control unit 50 executes this operation every time the cross-connect switch 25 is set.

First, the control unit 50 switches the first optical switch 21a and the second optical switch 21b so that the wavelength-multiplexed signal light is input to the optical demultiplexer 1 (step St61). As a result, the first optical switch 21a selects the input port connected to the transmitter 80 as the input source (see Figure 25). The second optical switch 21b selects the output port connected to the O/E 27a as the output destination (see Figure 25).

Next, the control unit 50 causes the compensation circuits Inc#1-#3 and Dec#1-#6 to start controlling the phase shifters Hu, Hd of each AMZ 1a-1i so that they begin adjusting the optical phase (step St62). As a result, the wavelength-multiplexed signal light output from the transmitter 80 is input to the optical demultiplexer 1, and the optical phase shift of each signal light Sa-Sd is compensated for.

After compensating for the optical phase shift, the control unit 50 instructs the compensation circuits Inc#1-#3 and Dec#1-#6 to stop controlling the phase shifters Hu and Hd of the AMZs 1a-1i so that the phase shifters Hu and Hd stop adjusting the optical phase (step St63). This reduces noise when detecting the wavelength light La-Ld that is later output as output light from the output ports P#1-#4.

After the operation of step St63, the control unit 50 switches the first optical switch 21a and the second optical switch 21b so that the wavelength light La to Ld is input to the optical demultiplexer 1 (step St64). As a result, the first optical switch 21a selects the input port connected to the second optical switch 21b as the input source (see Figure 26). The second optical switch 21b selects the output port connected to the first optical switch 21a as the output destination (see Figure 26).

Next, the control unit 50 selects one center wavelength λa from the center wavelengths λa to λd of the wavelength light beams La to Ld (step St65). Next, the control unit 50 controls the light emission driver 51 so that only the wavelength light beam La with the selected center wavelength λa is output from one of the multiple wavelength-tunable light sources 28 (step St66). As a result, only the wavelength light beam La with the selected center wavelength λa is input to the optical demultiplexer 1, and the wavelength light beam La is output as demultiplexed light from one of the output ports P#1 to P#4. In this embodiment, the wavelength light beam La is output from output port P#4 (see Figure 26).

Next, the control unit 50 determines whether the wavelength λa of the wavelength light La is detected by the output light detection unit 60 (step St67). The control unit 50 determines whether the wavelength λa is detected by receiving a detection signal from the output light detection unit 60. If the wavelength λa is not detected (No in step St67), the process of step St67 is executed again.

Furthermore, if wavelength λa is detected (Yes in step St67), the control unit 50 registers the correspondence between the center wavelength λa of the wavelength light La being output, the output port P#4 corresponding to the detection signal, the input port P22 of the cross-connect switch 25 to which output port P##4 is connected, the output port P44, and channel #1 of one of the multiple wavelength-tunable light sources 28 in the cross-connect switch 25 setting table in memory 54 (step St68).

Next, the control unit 50 determines whether any unselected center wavelengths λa to λd exist (step St69). If any unselected center wavelengths λa to λd exist (Yes in step St69), the control unit 50 selects the next center wavelength λb (step St65) and performs the operations from step St66 onwards again. By repeating steps St65 to St69, registration of center wavelengths λa to λd in the setting table is completed (see Figure 29).

Next, the control unit 50 controls the light emission driver 51 based on the setting registration table so that unselected wavelength light beams La-Lc with center wavelengths λa-λc are output from the remaining of the multiple wavelength-tunable light sources 28 (step St70). As a result, as shown in FIG. 31, wavelength light beam Ld with center wavelength λd is input to O/E 27a via the first optical switch 21a and the second optical switch 21b, and wavelength light beam La with center wavelength λa is input to O/E 27d. Similarly, wavelength light beam Lb with center wavelength λb is input to O/E 27b, and wavelength light beam La with center wavelength λc is input to O/E 27c.

Next, the control unit 50 determines the cross-connection of the cross-connect switch 25 based on the setting table (step St71) and sets the cross-connect switch 25 using a selection signal indicating the connection relationship (step St72). For example, the control unit 50 performs connection settings for switches SW#2 and #3 between input port P22 and output port P33 of the electrical signal Ea so that the electrical signal Ea' is output from output port P33 of the cross-connect switch 25 (see FIG. 28). The control unit 50 also performs connection settings for switches SW#1 and #4 between input port P11 and output port P44 of the electrical signal Ed so that the electrical signal Ed' is output from output port P44 of the cross-connect switch 25 (see FIG. 28).

As a result, the electrical signals Ea' to Ed' are input to digital circuits DPr_a to DPr_d, which correspond to the center wavelengths λa to λd of the wavelength light La to Ld, respectively.

Next, the control unit 50 switches the first optical switch 21a so that the wavelength-multiplexed signal light including the signal lights Sa to Sd is input to the optical demultiplexer 1, and switches the second optical switch 21b so that the wavelength light La is directly input to the O/E 27a (step St73). That is, the control unit 50 switches the input source of the first optical switch 21a from the second optical switch 21b to the transmitting device 80. The control unit 50 also switches the output destination of the second optical switch 21b from the first optical switch 21a to the O/E 27a.

As a result, when wavelength-multiplexed signal light is input to the optical demultiplexer 1, the wavelength-multiplexed signal light is demultiplexed by the optical demultiplexer 1, and signal light Sa-Sd as demultiplexed light is input to the O/Es 27d-27a. Furthermore, wavelength light La-Ld is input to the O/Es 27d-27a as local light. The 90° hybrid optical circuits of the O/Es 27d-27a each detect the signal light Sa-Sd based on the local light and output electrical signals Ea'-Ed'. The electrical signals Ea'-Ed' are input to the cross-connect switch 27 via the BPDs of the O/Es 27d-27a, the analog signal processing unit 23, and the A/Ds 24d-24a. Then, by setting step St72, the electrical signals Ea'-Ed' are input to digital circuits DPr_a-DPr_d corresponding to the center wavelengths λa-λd, respectively, where digital signal processing is performed and the signals are output (see FIG. 28). In this way, the optical demultiplexing device 90 can perform appropriate signal processing for each of the center wavelengths λa-λd.

In each embodiment, the optical demultiplexers 1, 1r, and 1s are configured as shown in FIG. 1, with the front-stage demultiplexing circuit 11 and rear-stage demultiplexing circuits 12 and 13 each including three AMZs 1a to 1i, connected in multiple stages in a tree configuration. However, the configuration of the optical demultiplexers 1, 1r, and 1s is not limited to the above example, as long as wavelength light La to Ld is demultiplexed by multiple AMZs and output from mutually different output ports P#1 to P#4.

The above-described embodiment is a preferred example of the present invention. However, it is not limited to this and various modifications can be made without departing from the spirit of the present invention.

In addition, the following supplementary notes are provided in relation to the above description.
(Supplementary Note 1) A first light source that outputs light of a plurality of wavelengths with a constant wavelength interval;
a first demultiplexing unit that demultiplexes the plurality of wavelength lights;
a plurality of conversion units that convert the plurality of wavelength lights into a plurality of electrical signals, respectively;
a first detector that detects the plurality of electrical signals output from the plurality of converters;
a first switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a first control unit that controls the first light source and the first switch unit,
the first demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the first light source are demultiplexed and output to different conversion units among the plurality of conversion units, respectively;
The first control unit
controlling the first light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit one by one in sequence;
An optical demultiplexing device characterized by controlling the first switch unit so that an electrical signal detected by the first detection unit among the plurality of electrical signals is output to one of the plurality of output destinations corresponding to the wavelength light from which the electrical signal was converted.
(Supplementary Note 2) The optical demultiplexing device according to Supplementary Note 1, wherein the first detector detects the plurality of electrical signals input from the plurality of converters to the first switch unit.
(Supplementary Note 3) The optical demultiplexing device according to Supplementary Note 1 or 2, characterized in that the pair of arms of the plurality of asymmetric Mach-Zehnder interferometers are provided with phase shifters that adjust the optical phases in the pair of arms, respectively.
(Supplementary Note 4) The first control unit
controlling the first light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit;
adjusting the optical phase of each of the phase shifters of the plurality of asymmetric Mach-Zehnder interferometers when the plurality of wavelength lights are input to the first demultiplexing unit;
4. The optical demultiplexing device according to claim 3, wherein when the plurality of wavelength lights are input sequentially one by one to the first demultiplexing unit, the phase shifter of each of the plurality of asymmetric Mach-Zehnder interferometers is caused to stop adjusting the optical phase.
(Supplementary Note 5) An optical switch that selects light to be input to the first demultiplexing unit from wavelength-multiplexed signal light including a plurality of signal lights each having a central wavelength that matches the plurality of wavelength lights, and the plurality of wavelength lights,
The optical demultiplexing device described in any one of Supplementary Notes 1 to 4, characterized in that the first control unit controls the optical switch to control the first switch unit so that the multiple wavelength lights are input from the optical switch to the first demultiplexing unit, and after control of the first switch unit is completed, controls the optical switch so that the wavelength-multiplexed signal light is input from the optical switch to the first demultiplexing unit.
(Supplementary Note 6) A second light source that outputs a plurality of wavelength lights having a constant wavelength interval;
a second demultiplexing unit that demultiplexes the plurality of wavelength lights;
a plurality of optical modulators that optically modulate the plurality of wavelength lights demultiplexed by the second demultiplexing unit based on a plurality of data signals;
a second detector that detects the plurality of wavelength light beams input to the plurality of optical modulators;
a second switch unit that selects an input source of the plurality of data signals for each of the plurality of optical modulators from a plurality of input sources;
a second control unit that controls the second light source and the second switch unit,
the second demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the second light source are demultiplexed and output to different modulators among the plurality of modulators, respectively;
The second control unit is
controlling the second light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit one by one in sequence;
an optical demultiplexing device characterized in that the second switch unit is controlled so that a data signal is input from an input source corresponding to the wavelength light among the plurality of input sources to a modulator to which the wavelength light detected by the second detection unit is input among the plurality of wavelength light.
(Supplementary Note 7) The optical demultiplexing device according to Supplementary Note 6, wherein the pair of arms of the plurality of asymmetric Mach-Zehnder interferometers are provided with phase shifters that adjust optical phases in the pair of arms, respectively.
(Supplementary Note 8) The second control unit
controlling the second light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit;
adjusting the optical phase of each of the phase shifters of the plurality of asymmetric Mach-Zehnder interferometers when the plurality of wavelength lights are input to the second demultiplexing unit;
8. The optical demultiplexing device according to claim 7, wherein when the plurality of wavelength lights are input sequentially one by one to the second demultiplexing section, the phase shifter of each of the plurality of asymmetric Mach-Zehnder interferometers is caused to stop adjusting the optical phase.
(Supplementary Note 9) A light source that outputs a plurality of wavelength lights with a constant wavelength interval;
first and second demultiplexing units that demultiplex the plurality of wavelength lights;
an optical switch that selects an output destination of the plurality of wavelength lights from the first demultiplexing unit or the second demultiplexing unit;
a plurality of conversion units that convert the plurality of wavelength lights demultiplexed by the first demultiplexing unit into a plurality of electrical signals, respectively;
a first detector that detects the plurality of electrical signals output from the plurality of converters;
a first switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a plurality of optical modulators that optically modulate the plurality of wavelength lights demultiplexed by the second demultiplexing unit based on a plurality of data signals;
a second detector that detects wavelength light beams input to the plurality of optical modulators from among the plurality of wavelength light beams;
a second switch unit that selects an input source of the plurality of data signals for each of the plurality of optical modulators from a plurality of input sources;
a third control unit that controls the light source, the optical switch, the first switch unit, and the second switch unit;
the first demultiplexing unit includes a plurality of first asymmetric Mach-Zehnder interferometers, each having a pair of arms with different lengths;
the second demultiplexing unit includes a plurality of second asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of first asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the light source are demultiplexed and output to different conversion units among the plurality of conversion units, respectively;
the plurality of second asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the light source are demultiplexed and output to different modulators among the plurality of modulators, respectively;
The third control unit is
a first control mode for controlling the first switch unit and a second control mode for controlling the second switch unit,
In the first control mode,
controlling the optical switch so that the plurality of wavelength lights are input to the first demultiplexing unit;
controlling the light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit one by one in sequence;
controlling the first switch unit so that the electrical signal detected by the first detector is output to an output destination corresponding to the wavelength light from which the electrical signal is converted, among the plurality of output destinations;
In the second control mode,
controlling the optical switch so that the plurality of wavelength lights are input to the second demultiplexing unit;
controlling the light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit one by one in sequence;
a transmission device that controls the second switch unit so that a data signal is input from an input source corresponding to the wavelength light among the plurality of input sources to a modulator to which the wavelength light detected by the second detection unit is input among the plurality of wavelength light.
(Supplementary Note 10) The optical demultiplexing device according to Supplementary Note 1, wherein the first detector detects the plurality of electrical signals input from the plurality of converters to the first switch unit.
(Supplementary Note 11) The optical demultiplexing device according to Supplementary Note 9 or 10, characterized in that the pair of arms of the plurality of first and second asymmetric Mach-Zehnder interferometers are provided with phase shifters that adjust the optical phases in the pair of arms, respectively.
(Supplementary Note 12) In the first control mode, the third control unit
controlling the light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit;
adjusting the optical phase of each of the phase shifters of the first asymmetric Mach-Zehnder interferometers when the plurality of wavelength lights are input to the first demultiplexing unit;
12. The transmission device according to claim 11, wherein when the plurality of wavelength lights are input sequentially one by one to the first demultiplexing unit, the phase shifter of each of the plurality of first asymmetric Mach-Zehnder interferometers is caused to stop adjusting the optical phase.
(Supplementary Note 13) In the second control mode, the third control unit
controlling the light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit;
adjusting the optical phase of each of the phase shifters of the second asymmetric Mach-Zehnder interferometers when the plurality of wavelength lights are input to the second demultiplexing unit;
13. The transmission device according to claim 11, wherein when the plurality of wavelength lights are input sequentially one by one to the second demultiplexing unit, the phase shifter of each of the plurality of second asymmetric Mach-Zehnder interferometers is caused to stop adjusting the optical phase.
(Supplementary Note 14) A plurality of third light sources each outputting one of a plurality of wavelength lights having a constant wavelength interval;
a third demultiplexing unit that demultiplexes the input light into wavelengths;
a selector that selects the input light from one of the plurality of wavelength lights and a wavelength-multiplexed signal light of a plurality of signal lights each having a wavelength common to that of the plurality of wavelength lights;
a plurality of detecting units that detect the plurality of demultiplexed light beams demultiplexed by the third demultiplexing unit using the plurality of wavelength light beams output from the plurality of third light sources, respectively;
a plurality of conversion units that convert the detected demultiplexed light beams into a plurality of electrical signals, respectively;
a third switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a detection unit that detects the wavelengths of the plurality of demultiplexed lights;
a third control unit that controls the selection unit, the plurality of third light sources, and the third switch unit,
the third demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of demultiplexed lights are output to different detecting units among the plurality of detecting units, respectively;
The third control unit is
controlling the selector so that the input light is switched from the wavelength multiplexed signal light to one of the plurality of wavelength lights;
controlling one of the plurality of third light sources so that the plurality of wavelength light beams are input one by one sequentially to the third demultiplexing unit;
controlling the third switch unit based on the wavelength detected by the detection unit so that each of the plurality of electrical signals is output to an output destination, among the plurality of output destinations, that corresponds to the wavelength of the demultiplexed light from which the signal is converted;
an optical demultiplexing device characterized in that the wavelengths of the plurality of wavelength lights output from the plurality of third light sources are controlled based on the wavelengths detected by the detection unit so that the plurality of demultiplexed light lights are detected by wavelength lights corresponding to each of the plurality of wavelength lights.

1, 1r, 1s Optical demultiplexer 1a to 1i Asymmetric Mach-Zehnder interferometer 9 Transmission device 20 Light source 21 Optical switch 21a First optical switch 21b Second optical switch 22a to 22d Photodiodes 25, 25s, 25r, 25n Cross connect switches 27a to 27d Optical-electrical converter 28 Tunable wavelength light source 33, 33a, 33b Cross connect switches 30a to 30d Optical modulator 50, 56, 58 Control unit 53, 55 Input signal detection unit 60 Output light detection unit 90, 90a, 90b Optical demultiplexer 91, 91a, 91b Optical demultiplexer Inc#i (i: positive integer) Compensation circuit Dec#j (j: positive integer) Compensation circuit Mon#m (m: positive integer) Monitor circuit Au, Ad Arm Hu, Hd Phase shifter

Claims (8)

a first light source that outputs a plurality of wavelength lights having uniform wavelength intervals;
a first demultiplexing unit that demultiplexes the plurality of wavelength lights and outputs the demultiplexed lights at random from one of a plurality of output ports ;
a plurality of conversion units that convert the plurality of wavelength lights output from the first demultiplexing unit into a plurality of electrical signals, respectively;
a first detector that detects the plurality of electrical signals output from the plurality of converters;
a first switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a first control unit that controls the first light source and the first switch unit,
the first demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the first light source are demultiplexed and output to different conversion units among the plurality of conversion units, respectively;
The first control unit
controlling the first light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit one by one in sequence;
An optical demultiplexing device characterized by controlling the first switch unit so that an electrical signal detected by the first detection unit among the plurality of electrical signals is output to one of the plurality of output destinations corresponding to the wavelength light from which the electrical signal was converted. The optical demultiplexing device according to claim 1, characterized in that the first detection unit detects the multiple electrical signals input from the multiple conversion units to the first switch unit. An optical demultiplexing device according to claim 1 or 2, characterized in that each pair of arms of the plurality of asymmetric Mach-Zehnder interferometers is provided with a phase shifter that adjusts the optical phase within each pair of arms. The first control unit
controlling the first light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit;
adjusting the optical phase of each of the phase shifters of the plurality of asymmetric Mach-Zehnder interferometers when the plurality of wavelength lights are input to the first demultiplexing unit;
4. The optical demultiplexing device according to claim 3, wherein when the plurality of wavelength lights are input sequentially one by one to the first demultiplexing section, the phase shifter of each of the plurality of asymmetric Mach-Zehnder interferometers is caused to stop adjusting the optical phase. an optical switch for selecting light to be input to the first demultiplexing unit from wavelength-multiplexed signal light including a plurality of signal lights each having a central wavelength that matches the plurality of wavelength lights, and the plurality of wavelength lights;
The optical demultiplexing device according to any one of claims 1 to 4, characterized in that the first control unit controls the optical switch to control the first switch unit so that the plurality of wavelength lights are input from the optical switch to the first demultiplexing unit, and after control of the first switch unit is completed, controls the optical switch so that the wavelength-multiplexed signal light is input from the optical switch to the first demultiplexing unit. a second light source that outputs light of a plurality of wavelengths at regular wavelength intervals;
a second demultiplexing unit that demultiplexes the plurality of wavelength lights and outputs the demultiplexed lights at random from one of a plurality of output ports ;
a plurality of optical modulators that optically modulate the plurality of wavelength lights output from the second demultiplexing unit based on a plurality of data signals;
a second detector that detects the plurality of wavelength light beams input to the plurality of optical modulators;
a second switch unit that selects an input source of the plurality of data signals for each of the plurality of optical modulators from a plurality of input sources;
a second control unit that controls the second light source and the second switch unit,
the second demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the second light source are demultiplexed and output to different optical modulators among the plurality of optical modulators, respectively;
The second control unit is
controlling the second light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit one by one in sequence;
an optical demultiplexing device that controls the second switch unit so that a data signal is input from an input source corresponding to the wavelength light among the plurality of input sources to an optical modulator to which the wavelength light detected by the second detection unit is input among the plurality of wavelength light. a light source that outputs a plurality of wavelength lights having a constant wavelength interval;
first and second demultiplexing units that demultiplex the plurality of wavelength lights and output the demultiplexed lights at random from one of a plurality of output ports ;
an optical switch that selects an output destination of the plurality of wavelength lights from the first demultiplexing unit or the second demultiplexing unit;
a plurality of conversion units that convert the plurality of wavelength lights output from the first demultiplexing unit into a plurality of electrical signals, respectively;
a first detector that detects the plurality of electrical signals output from the plurality of converters;
a first switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a plurality of optical modulators that optically modulate the plurality of wavelength lights demultiplexed by the second demultiplexing unit based on a plurality of data signals;
a second detector that detects wavelength light beams input to the plurality of optical modulators from among the plurality of wavelength light beams;
a second switch unit that selects an input source of the plurality of data signals for each of the plurality of optical modulators from a plurality of input sources;
a third control unit that controls the light source, the optical switch, the first switch unit, and the second switch unit;
the first demultiplexing unit includes a plurality of first asymmetric Mach-Zehnder interferometers, each having a pair of arms with different lengths;
the second demultiplexing unit includes a plurality of second asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of first asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the light source are demultiplexed and output to different conversion units among the plurality of conversion units, respectively;
the plurality of second asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of wavelength light beams input from the light source are demultiplexed and output to different optical modulators among the plurality of optical modulators, respectively;
The third control unit is
a first control mode for controlling the first switch unit and a second control mode for controlling the second switch unit,
In the first control mode,
controlling the optical switch so that the plurality of wavelength lights are input to the first demultiplexing unit;
controlling the light source so that the light beams of the plurality of wavelengths are input to the first demultiplexing unit one by one in sequence;
controlling the first switch unit so that the electrical signal detected by the first detector is output to one of the plurality of output destinations corresponding to the wavelength light from which the electrical signal is converted;
In the second control mode,
controlling the optical switch so that the plurality of wavelength lights are input to the second demultiplexing unit;
controlling the light source so that the light beams of the plurality of wavelengths are input to the second demultiplexing unit one by one in sequence;
a transmission device characterized in that the second switch unit is controlled so that a data signal is input from an input source corresponding to the wavelength light among the plurality of input sources to an optical modulator to which the wavelength light detected by the second detection unit is input among the plurality of wavelength light. a plurality of third light sources each outputting one of a plurality of wavelength lights having a constant wavelength interval;
a third demultiplexing unit that demultiplexes the input light into wavelengths and outputs the demultiplexed light randomly from one of a plurality of output ports ;
a selector that selects the input light from one of the plurality of wavelength lights and a wavelength-multiplexed signal light of a plurality of signal lights each having a wavelength common to that of the plurality of wavelength lights;
a plurality of detecting units configured to detect the plurality of demultiplexed light beams output from the third demultiplexing unit using the plurality of wavelength light beams output from the plurality of third light sources;
a plurality of conversion units that convert the detected demultiplexed light beams into a plurality of electrical signals, respectively;
a third switch unit that selects an output destination of each of the plurality of electrical signals from a plurality of output destinations;
a detection unit that detects the wavelengths of the plurality of demultiplexed lights;
a third control unit that controls the selection unit, the plurality of third light sources, and the third switch unit,
the third demultiplexing unit includes a plurality of asymmetric Mach-Zehnder interferometers each having a pair of arms with different lengths,
the plurality of asymmetric Mach-Zehnder interferometers are connected to each other so that the plurality of demultiplexed lights are output to different detecting units among the plurality of detecting units, respectively;
The third control unit is
controlling the selector so that the input light is switched from the wavelength multiplexed signal light to one of the plurality of wavelength lights;
controlling one of the plurality of third light sources so that the plurality of wavelength light beams are input one by one sequentially to the third demultiplexing unit;
controlling the third switch unit based on the wavelength detected by the detection unit so that each of the plurality of electrical signals is output to an output destination, among the plurality of output destinations, that corresponds to the wavelength of the demultiplexed light from which the signal is converted;
an optical demultiplexing device characterized in that the wavelengths of the plurality of wavelength lights output from the plurality of third light sources are controlled based on the wavelengths detected by the detection unit so that the plurality of demultiplexed light lights are detected by wavelength lights corresponding to each of the plurality of wavelength lights.