JP3899952B2 - Optical signal processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical signal processing device, and more specifically, can be used as an optical switch, an optical gate device, a separation device that separates time-division multiplexed optical signals, a wavelength conversion device, and an optical logic operation device. The present invention relates to an optical signal processing device capable of operating at a speed higher than s.
[0002]
[Prior art]
Various systems have been proposed as all-optical switches that perform wavelength conversion or optical regeneration at a bit rate of 40 Gbit / s or higher. As an optical switch capable of high-speed operation exceeding 40 Gbps, a configuration in which a semiconductor optical amplifier (SOA) and an optical interferometer are combined has been reported (for example, Y. Ueno, et al., “Ultra high-speed all-optical”). data regeneration and wave conversion for OTDM system ", in the processing of European Conference on Optical Communication 2002, (2002) Th. F. 2.1. In this configuration, the operating speed exceeding the response speed of the SOA alone is realized by differentially operating the Mach-Zehnder type or Michelson type interferometer using the cross phase modulation (XPM) of the SOA.
[0003]
Among them, an optical switch that combines a polarization separation type interference system that performs polarization multiplexing / demultiplexing by polarization mode dispersion (PMD) of two birefringence media and SOA is called UNI (Ultrafast Nonlinear Interferometer) (for example, K. L. Hall, et al., “100 Gbit / s bit with logic”, Optics Letters, vol. 23, pp. 1271, (1998)). This optical switch has been demonstrated to operate with a PRBS2 ³¹ −1 modulation signal at a repetition rate of 100 Gbps, which is one digit or more shorter than the SOA gain recovery time, and is very promising as an optical switch for ultra 40 Gbps operation.
[0004]
[Problems to be solved by the invention]
In the case of the UNI configuration, two elements, a separation element and a multiplexing element, are required as the birefringence medium element (HiBi element) constituting the optical interferometer. It is physically impossible to prepare two HiBi elements having the same PMD amount, and it is necessary to separately prepare a Babinet-Soleil phase compensation element for the correction. In addition, a configuration in which HiBi elements are combined has been proposed (for example, C. Schubert, et al., “160-Gb / s All-Optical Demultiplexing a Gain-Transparent Ultrafast-NonlinearIterTraUFerN). ", IEEE Photonics Technology Letters, vol. 13, No. 5 pp. 475 (2001)).
[0005]
In any case, since the HiBi element having a fixed PMD amount is used, the width of the optical pulse to be wavelength-converted is theoretically limited. As a result, the configuration of the optical switch corresponding to the optical pulse width should be determined in advance. There was a restriction that it had to be.
[0006]
For these reasons, the conventional configuration has some practical problems such as the complexity of the device and the flexibility of the device configuration.
[0007]
This type of optical switch is also used as a wavelength converter that changes the optical carrier of a signal, as an optical gate device that extracts a signal in a specific time slot, as a separation device that separates time-division multiplexed optical signals, It also functions as a logical operation device between pulses, and simplification of the configuration is also desired when used as such a device.
[0008]
An object of the present invention is to solve such problems and to provide an optical signal processing apparatus that operates at a high speed with a simpler configuration.
[0009]
It is another object of the present invention to provide an optical signal processing device with less restrictions on the optical pulse width.
[0010]
[Means for Solving the Problems]
An optical signal processing apparatus according to the present invention is an optical pulse separation / synthesis apparatus including a first input terminal for first pulse light, a second input terminal for second pulse light, and first and second input / output ports. And generating a preceding light pulse from a light pulse input to the first input / output port and a subsequent light pulse delayed by a predetermined time from the preceding light pulse, and outputting the generated light pulse from the first input / output port. An optical pulse separating / combining device for synthesizing two optical pulses input to the second input / output port separated by the predetermined time at the same time position and outputting the combined pulse from the second input / output port; A first optical circulator having two and third ports, wherein the first port is connected to the first input terminal, and the second port is the first input / output port of the optical pulse separation / synthesis device 1st optical circular connected to An optical combiner that combines the second pulse light from the second input terminal with the output light of the third port of the first optical circulator, and the output light of the optical combiner A phase modulator that modulates the phase of the subsequent optical pulse contained in the output light of the third port of the first optical circulator by the second pulsed light, and the latter is determined by the presence or absence of the second pulsed light. A phase modulator having a phase modulation amount of the row optical pulse different by π, and a second optical circulator having first, second, and third ports, which are output from the phase modulator and input to the first port The preceding optical pulse and the subsequent optical pulse to be supplied from the second port to the second input / output port of the optical pulse separating / combining device, and from the second input / output port of the optical pulse separating / combining device Input to the second port A second optical circulator that outputs the light to be output from the third port, and a polarization separation device that extracts a predetermined polarization component from the output of the third port of the second optical circulator. .
[0011]
Preferably, the polarization separation device extracts the predetermined polarization component and a polarization component orthogonal to the predetermined polarization component from the output of the third port of the second optical circulator.
[0012]
Preferably, the optical pulse separating / combining device includes first and second reflectors and a polarizing beam splitter. The polarization beam splitter separates input light of the first input / output port into polarized waves orthogonal to each other, supplies one polarization component to the first reflector, and reflects the reflected light from the first reflector. Light is supplied to the first input / output port as the preceding light pulse, the other polarization component is supplied to the second reflector, and the reflected light of the second reflector is supplied to the subsequent light pulse. Is supplied to the first input / output port. The polarization beam splitter further supplies a preceding optical pulse of the input light of the second input / output port to the second reflector, and reflects the reflected light of the second reflector to the second input beam. In addition to being supplied to the output port, a subsequent light pulse is supplied to the first reflector, and the reflected light of the first reflector is supplied to the second input / output port.
[0013]
Preferably, the optical signal processing device according to the present invention further includes an adjusting device for adjusting an optical path length between the first reflector and the polarizing beam splitter. Preferably, the optical signal processing device according to the present invention further includes an adjusting device for adjusting an optical path length between the second reflector and the polarizing beam splitter. Thereby, the two optical paths in the optical pulse separation / synthesis apparatus can be adjusted independently.
[0014]
Preferably, the phase modulator is a semiconductor optical amplifier.
[0015]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention. FIG. 2 shows a timing chart of the present embodiment.
[0017]
An RZ pulse signal light as indicated by reference numeral 50 in FIG. 2 is input to the input terminal 10, and a switch control signal (control light pulse) 54 synchronized with the signal light pulse 50 is input to the input terminal 12 (FIG. 2). Enter. The optical circulator 14 includes three ports A, B, and C, and is an optical device that outputs the input light of the port A from the port B and outputs the input light of the port B from the port C. The signal light 50 (FIG. 2) input to the input terminal 10 is input to the port A of the optical circulator 14 and input from the port B to the input / output port 16 a of the PMD (polarization mode dispersion) generator 16.
[0018]
The PMD generator 16 generates a preceding light pulse from a light pulse input to the input / output port 16a and a subsequent light pulse delayed by a predetermined time from the preceding light pulse, and outputs the generated light pulse from the first input / output port 16a. It functions as an optical pulse separation / synthesis device that combines two optical pulses that are input to the input / output port 16b at a predetermined time, at the same time position, and outputs the combined pulse from the input / output port 16b.
[0019]
Specifically, the PMD generator 16 includes, as basic optical elements, a polarizing beam splitter 18, a mirror 20 that reflects one of the S wave and the P wave separated by the polarizing beam splitter 18, and a mirror 22 that reflects the other. And half-wave plates 24 and 26 for adjusting the power distribution of the separation into the S wave and the P wave in the polarization beam splitter 18. A mirror 20 and a half-wave plate 24 are arranged on one straight line intersecting at 90 with the polarizing beam splitter 18 at the center, with the polarizing beam splitter 18 in between, and a mirror 22 with the polarizing beam splitter 18 in between on the other straight line. A half-wave plate 26 is disposed. The distance between the mirror 20 and the polarization beam splitter 18 can be adjusted by a motor 28, and the distance between the mirror 22 and the polarization beam splitter 18 can be adjusted by a motor 29. The control circuit 30 supplies drive control signals to the motors 28 and 29 to control the distances of the mirrors 20 and 22 from the polarization beam splitter 18.
[0020]
The adjustment of the optical path length by the motors 28 and 29 may be only one, for example, the adjustment of the timing position of the subsequent light pulse. Needless to say, by making both adjustable, it becomes possible to deal with a wide bit rate, and the applicable range is expanded.
[0021]
As will be described in detail later, the PMD generator 16 is an apparatus that can set an arbitrary delay time according to the polarization. In this embodiment, each optical pulse of the signal light 50 is divided into two optical pulses on the time axis. And two optical pulses that are separated in time are combined into one optical pulse on the same time. Here, it is assumed that the optical path A between the polarizing beam splitter 18 and the mirror 20 is shorter than the optical path B between the polarizing beam splitter 18 and the mirror 22, and the propagation time difference between the optical paths A and B is τ / 2.
[0022]
The signal light output from the port B of the optical circulator 14 enters the polarization beam splitter 18 with a polarization direction of 45 ° via the input / output port 16a and the half-wave plate 24 as a polarization control element.
[0023]
The polarization beam splitter 18 separates the signal light from the half-wave plate 24 into P waves and S waves having polarization directions orthogonal to each other, and supplies the P waves to the mirror 20 and the S waves to the mirror 22. Both mirrors 20 and 22 totally reflect incident light. The lights reflected by the mirrors 20 and 22 are combined by the polarization beam splitter 18 and enter the port B of the optical circulator 14 through the half-wave plate 24 and the input / output port 16a. The P wave reciprocates in the optical path A, and the S wave reciprocates in the optical path B. Therefore, at the port B of the optical circulator 14, the S wave is delayed by τ with respect to the P wave, as indicated by reference numeral 52 in FIG. That is, the PMD generator 16 temporally separates each optical pulse of the signal light 50 into a preceding optical pulse 52P composed of P waves and a subsequent optical pulse 52S composed of S waves.
[0024]
The optical pulses 52P and 52S thus separated in time are applied to the optical coupler 32 from the port C of the optical circulator 14. Further, a control light pulse is input from the input terminal 12 to the optical coupler 32 at a timing indicated by reference numeral 54 in FIG. The optical coupler 32 combines both input lights and enters the semiconductor optical amplifier (SOA) 34. The delay times of the optical paths A and B of the PMD generator 16 are set so that the control light pulse 54 is positioned between the preceding light pulse 52P and the following light pulse 52S in the SOA 34. In other words, the optical path A is such that the control light pulse 54 consumes the carriers present in the SOA 34 and the trailing light pulse 52S passes through the SOA 34 before the carrier density is completely restored to the steady value by current injection. , B delay times are set.
[0025]
The SOA 34 is forward-biased by a DC power source (not shown). The SOA 34 is made of, for example, a buried waveguide type element using an InGaAsP / InP system as an active layer material, and antireflection coating is applied to both ends thereof. Since the trailing light pulse 52S passes through the SOA 34 before the density of carriers consumed by the control light pulse 54 is completely restored to the steady value by current injection, the trailing light pulse 52S is different from the preceding light pulse 52P. Pass through the SOA 34 with different refractive index values. In other words, the trailing light pulse 52S is subjected to cross phase modulation (XPM) by the control light pulse 54 in the SOA 34. As a result, the preceding light pulse 52P and the following light pulse 52S propagate through optical paths having different effective lengths while passing through the same SOA 34, resulting in a phase difference therebetween.
[0026]
The light intensity of the control light pulse 54, the length of the SOA 34, and the current value are set so that the phase change of the subsequent light pulse 52S due to the presence or absence of the control light pulse 54 becomes π. As a result, the phase of the subsequent optical pulse 56S output from the SOA 34 differs by π as shown by reference numeral 56 in FIG. 2 depending on the presence or absence of the control light pulse. 56P represents a preceding light pulse, and 56S represents a following light pulse.
[0027]
The optical bandpass filter (BPF) 35 extracts the wavelength component of the signal light 50 from the output light of the SOA 34. The output light of the optical BPF 35 is input to the port A of the optical circulator 36 and applied from the port B to another input / output port 16 b of the PBS generator 16. Of the output light of the SOA 34, necessary light is the preceding light pulse 56 </ b> P and the following light pulse 56 </ b> S generated from the signal light 50. Since the wavelengths of the control light pulse 54 and the signal light 50 can be made different, an optical bandpass filter 35 that extracts only the preceding light pulse 56P and the following light pulse 56S of the signal light is provided between the SOA 34 and the port A of the optical circulator 36. To place. Of course, a similar optical bandpass filter may be disposed at another appropriate location in the subsequent stage.
[0028]
Similar to the optical circulator 14, the optical circulator 36 is an optical device that includes three ports A, B, and C, outputs the input light of the port A from the port B, and outputs the input light of the port B from the port C. .
[0029]
The preceding light pulse 56P and the following light pulse 56S output from the port B of the optical circulator 36 are respectively transferred to the optical path B through the input / output port 16b and the half-wave plate 26 as a polarization control element. Then, the light beam 56S enters the polarization beam splitter 18 in a polarization direction such that the following light pulse 56S goes to the optical path A. Since the polarization directions of the preceding light pulse 56P and the following light pulse 56S are orthogonal, the arrangement angle between the half-wave plate 26 and the polarization beam splitter 18 may be simply adjusted.
[0030]
The polarization beam splitter 18 supplies the preceding light pulse 56P from the half-wave plate 24 to the mirror 22 and supplies the following light pulse 56S to the mirror 20. The light pulses reflected by the mirrors 20 and 22 are combined by the polarization beam splitter 18 and enter the port B of the optical circulator 36 through the half-wave plate 26 and the input / output port 16b. In the PMD generator 16, the preceding light pulse 56P and the following light pulse 56S pass through the opposite optical paths when the respective pulses of the signal light 50 are first separated into the preceding light pulse 52P and the following light pulse 52S. As a result, the preceding light pulse 56P is delayed by τ relative to the following light pulse 56S, and both light pulses 56P and 56S are located at the same position in time as indicated by reference numerals 58P and 58S in FIG. It becomes like this. However, since the phase of the subsequent light pulse 58S differs by π depending on the presence or absence of the control light pulse 54, the polarization direction of the combined light pulse also differs by 90 ° depending on the presence or absence of the control light pulse.
[0031]
The optical circulator 36 supplies the light incident on the port B from the PMD generator 16 to the polarization beam splitter 38 from the port C. The polarization beam splitter 38 is arranged in a polarization direction that passes the output light from the port C of the optical circulator 36 when a control light pulse is present. Therefore, the polarization beam splitter 38 supplies the signal light when the control light pulse 54 is present to the output port 40 as indicated by reference numeral 60 in FIG. 2, and the signal light when the control light pulse 54 is not present is shown in FIG. Is supplied to the output port 42 as indicated by reference numeral 62.
[0032]
Thus, in this embodiment, the signal light 50 input to the input terminal 10 can be switched to the output terminal 40 or 42 depending on the presence or absence of the pulse of the control signal light 54. This means that the present embodiment functions as a TDM separation device that separates signal light into two channels on the time axis. For this purpose, for example, the control light 54 may be synchronized with the signal light 50 and may be a clock pulse having a frequency corresponding to ½ of the bit rate of the signal light 50.
[0033]
If attention is paid to the output terminal 40, this embodiment functions as an optical gate device that gates the signal light input to the input terminal 10 according to the presence or absence of a pulse of the control signal light 50.
[0034]
In the present embodiment, the PMD generator 16 is used before and after the SOA 34, and the temporally separated preceding optical pulse and subsequent optical pulse included in the output light of the SOA 34 are converted into the preceding optical pulse and the subsequent optical pulse within the PMD generator 16. An optical path opposite to that at the time of generation of the row light pulse is passed. Thus, in the conventional example in which the PMD generator such as a birefringent medium is disposed before and after the SOA, the PMD amount must be adjusted respectively. In the present embodiment, the PMD of the PMD generator 16 is used. You just need to adjust the amount, ie the delay time.
[0035]
Although the embodiment using the SOA 34 has been described, a phase modulation element that can deviate the phase depending on the presence or absence of an optical pulse positioned immediately before in time, for example, a nonlinear medium such as a semiconductor waveguide or a nonlinear crystal is used instead of the SOA 34. Can do.
[0036]
This embodiment can also be used as a wavelength conversion device or a waveform shaping device. In this case, all 1 optical clock pulses are input to the input terminal 10, and pulse signal light whose wavelength is to be converted is input to the input terminal 12. In the embodiment shown in FIG. 1, the output signal waveform basically depends on the pulse waveform of the signal light 50 input to the input terminal 10. Therefore, by using the signal light 50 as a clock pulse light having a clean waveform, the pulse waveform can be shaped while converting the wavelength.
[0037]
In this embodiment, the input light of the PMD generator 16 needs to be linearly polarized in a predetermined polarization direction. When there is a possibility that an optical signal that does not satisfy this requirement may be input, a polarization control device that controls the polarization of the input light to a linear polarization in the predetermined polarization direction is provided immediately before the input terminals 16a and 16b. Just place it.
[0038]
【The invention's effect】
As can be easily understood from the above description, according to the present invention, downsizing is possible and adjustment is also facilitated. Furthermore, a wider range of data rates can be easily accommodated.
[0039]
Since the gate width can be changed depending on the relative position of the two reflectors, the pulse width of the input signal light can be flexibly handled.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an embodiment of the present invention.
FIG. 2 is a timing chart of the present embodiment.
[Explanation of symbols]
10: input terminal 12: input terminal 14: optical circulator 16: PMD generator 16a, 16b: input / output port 18: polarization beam splitter 20, 22: mirror 24, 26: half-wave plate 28, 29: motor 30: control circuit 32: Optical coupler 34: Semiconductor optical amplifier (SOA)
35: Optical bandpass filter 36: Optical circulator 38: Polarizing beam splitter 40, 42: Output terminal

Claims (6)

A first input terminal (10) of the first pulsed light (50);
A second input terminal (12) of the second pulsed light (54);
An optical pulse separating / synthesizing device having first and second input / output ports, which is delayed by a predetermined time from a preceding light pulse and a preceding light pulse from the light pulse input to the first input / output port (16a). A trailing optical pulse is generated and output from the first input / output port (16a), and two optical pulses separated by the predetermined time input to the second input / output port (16b) are placed at the same time position. An optical pulse separation / synthesis device (16) for synthesizing and outputting the synthesized pulse from the second input / output port (16b);
A first optical circulator (14) having first, second and third ports, wherein the first port is connected to the first input terminal (10), and the second port is the optical pulse separation A first optical circulator (14) connected to the first input / output port (16a) of the synthesizer;
An optical multiplexer (32) for multiplexing the second pulsed light (54) from the second input terminal (12) to the output light of the third port of the first optical circulator (14);
A phase in which the output light of the optical multiplexer (32) is input and the phase of the subsequent optical pulse included in the output light of the third port of the first optical circulator (14) is modulated by the second pulse light. A phase modulator (34), wherein the phase modulation amount of the subsequent optical pulse differs by π depending on the presence or absence of the second pulse light;
A second optical circulator (36) having first, second and third ports, the preceding optical pulse and the following light output from the phase modulator (34) and input to the first port A pulse is supplied from the second port to the second input / output port (16b) of the optical pulse separation / synthesis device (16), and the second input / output port (16b) of the optical pulse separation / synthesis device (16) is supplied. ) From the third port, the second optical circulator (36) for outputting the light input to the second port from the third port;
Polarization separator (38) for extracting a predetermined polarization component from the output of the third port of the second optical circulator (36)
An optical signal processing device comprising: The polarization polarization device (38) extracts the predetermined polarization component and a polarization component orthogonal to the predetermined polarization component from the output of the third port of the second optical circulator (36). Optical signal processing device. The optical pulse separation / synthesis device (16)
First and second reflectors (20, 22);
The input light of the first input / output port (16a) is separated into mutually orthogonal polarized waves, one polarization component is supplied to the first reflector (20), and the first reflector (20 ) Is supplied to the first input / output port (16a) as the preceding light pulse, and the other polarization component is supplied to the second reflector (22). The reflected light of (22) is supplied as the subsequent light pulse to the first input / output port (16a), and the preceding light pulse in the input light of the second input / output port (16b) The second reflector (22) is supplied, the reflected light of the second reflector (22) is supplied to the second input / output port (16b), and a subsequent light pulse is supplied to the first reflector (22). And the reflected light of the first reflector (20) is reflected to the second input / output port. Supplied to preparative polarization beam splitter (18)
The optical signal processing apparatus according to claim 1, comprising: The optical signal processing according to claim 1, further comprising a first adjusting device (28, 30) for adjusting an optical path length between the first reflector (20) and the polarizing beam splitter (18). apparatus. The optical signal processing according to claim 1, further comprising a second adjusting device (29, 30) for adjusting an optical path length between the second reflector (22) and the polarizing beam splitter (18). apparatus. The optical signal processing apparatus according to claim 1, wherein said phase modulator (34) comprises a semiconductor optical amplifier.

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