JP3909656B2 - Multiple wavelength batch wavelength converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an effective technique for a multiple wavelength batch wavelength conversion device applied to an optical transmission system such as optical communication, optical switching, and optical information processing using wavelength multiplexing.
[0002]
[Prior art]
FIG. 7 illustrates an arrayed waveguide type diffraction grating as a normal wavelength demultiplexer. For the sake of simplicity, an array waveguide type diffraction grating having 1 input and 16 outputs used in an optical transmission system in which 16 wavelengths are multiplexed will be described as an example. The material is a silica-based waveguide, a polymer waveguide, or a semiconductor waveguide. In FIG. 7, 1001 is an input waveguide, 1002 is an input slab waveguide, 1003 is an array waveguide, 1004 is an output slab waveguide, and 1005 to 1020 are output waveguides.
[0003]
In FIG. 7, when wavelength multiplexed light S <b> 1 to S <b> 16 (wavelengths λ <b> 1 to λ <b> 16) is input to the input waveguide 1001, it is distributed by the input slab waveguide 1002 and distributed with equal intensity to the arrayed waveguide 1003. . Each distributed wavelength multiplexed light has a delay difference according to the optical path length of the arrayed waveguide 1003 and is input to the output slab waveguide 1004 to converge. At this time, since the phase condition differs depending on the wavelength, an arrayed waveguide type diffraction grating is used as an optical spectrometer by utilizing the phenomenon that different wavelengths are concentrated in the output waveguides 1005 to 1020. That is, the signal light S1 (wavelength λ1) is output to the output waveguide 1005, the signal light S2 (wavelength λ2) is output to the output waveguide 1006, the signal light S3 (wavelength λ3) is output to the output waveguide 1007, and so on. The signal lights S4 to S16 (wavelengths λ4 to λ16) are output to the output waveguides 1008 to 1020, respectively.
[0004]
Although FIG. 7 shows an example of 1 input and 16 outputs, it can be used as an optical spectrometer with 16 inputs and 16 outputs, for example, by increasing the number of input waveguides. The input / output characteristics of the arrayed waveguide grating in this case are as shown in FIG. 8, for example. In FIG. 8, the vertical axis is the input port of the arrayed waveguide grating, and the horizontal axis is the output port. The numbers in the table, for example, “1” means “signal light of wavelength λ1”.
[0005]
Here, in FIG. 8, the wavelength intervals of the signal lights S1 to S30 are set to an equal interval, for example, 1 nm. The wavelength λ1 of the signal light S1 is 1531 nm, and the wavelength λ30 of the signal light S30 is 1560 nm. For example, when λ17 = 1557 nm, λ18 = 1558 nm, or the like is input, λ17 obtains an output result equivalent to λ1, and λ18 obtains an output result equivalent to λ2. The free spectral range at this time is λ17−λ1 = 16 nm.
[0006]
Next, a conventional multiple wavelength batch wavelength conversion system will be described. FIG. 9 is a diagram for explaining a conventional multiple wavelength collective wavelength conversion system. References include, for example, “multi-wavelength converters” Kikuchi, Shibata, and Ito (Japanese Patent Application No. 11-65036). In the figure, 1201 is an input port for wavelength multiplexed signal light S1 to S16, 1202 is an input port for pump light P2 to P17, 1203 is a 16-output arrayed waveguide grating, 1204 to 1220 are wavelength conversion elements, and 1221 is 16-input arrayed waveguide gratings 1222-1224 are output waveguides.
[0007]
In FIG. 9, when wavelength multiplexed signal lights S1 to S16 having 16 wavelengths (wavelengths λ1 to λ16) are input from the input port 1201, the signal lights S1 to S16 are output to the output ports due to the characteristics of the arrayed waveguide grating 1203. Demultiplexed and output. On the other hand, when pump lights (continuous lights) P2 to P17 having wavelengths of λ2 to λ17 are input to the input port 1202, they are similarly demultiplexed, so that each wavelength conversion element 1204 to 1220 has one wavelength of signal light S and One wavelength of pump light P is input.
[0008]
The wavelength conversion elements 1204 to 1220 are made of, for example, a semiconductor amplifier, and when the signal light S and the pump light P are input, wavelength conversion light is generated by four-wave mixing (see FIG. 10). For example, when the wavelength of the signal light S is λ1 and the wavelength of the pump light P is λ2, the wavelength of the wavelength-converted light H is λ3 (λ1-λ2 = λ2-λ3). The port 1224 combines the wavelength-converted lights H3 to H18 thus obtained by the wavelength conversion elements 1204 to 1220 by the arrayed waveguide diffraction grating 1221. In FIG. 9, an output waveguide 1222 is a combination of the original signal lights S1 to S16, and is used for monitoring an input signal. The output waveguide 1223 is a combination of pump lights P2 to P176.
[0009]
In FIG. 9, when the port 1201 is an input and the port 1224 is an output, it can be seen that wavelength-multiplexed signal light of 16 wavelengths is collectively converted. However, this method has the following drawbacks.
[0010]
As shown in FIG. 9, the conventional example requires 16 wavelength conversion elements 1204 to 1220 for 16 wavelength multiple wavelength batch wavelength conversion. However, there is a technical limitation to increase the scale of the arrayed waveguide diffraction grating or increase the number of wavelength conversion elements. Currently, in the configuration that combines the arrayed waveguide diffraction grating for input and the wavelength conversion element, The maximum is 16 channels for semiconductor monolithic integrated devices and 32 channels for hybrid integrated circuits of semiconductor and PLC (reference: M.Zirngibl et al., IEEE Photon.Technol.Lett., Vol.6, pp.513). -515,1994 or F.Ebisawa et al., Proc. OFC'99, ThB1, 1999). That is, if the transmission bit rate per wavelength is 10 Gb / s, the total throughput is 320 Gb / s.
[0011]
Here, only the multi-wavelength batch conversion between adjacent wavelengths (wavelength conversion from 1551 to 1554 nm signal light to 1557 to 1566 nm) has been described, but by changing the wavelength of the pump light, multiple wavelengths to farther wavelengths Multiple wavelength batch wavelength conversion from batch conversion (for example, 1.55 μm band to 1.58 μm band) is also possible.
[0012]
[Problems to be solved by the invention]
As described above, in FIG. 9, the conventional example requires 16 wavelength conversion elements for batch wavelength conversion of a plurality of 16 wavelengths. However, there are technical limitations in increasing the scale of the arrayed waveguide diffraction grating and increasing the number of wavelength conversion elements. Currently, a semiconductor monolithic integrated circuit uses a 16-channel semiconductor / PLC hybrid integrated circuit. As for what is currently obtained, the one with 32 channels is the largest. That is, if the transmission bit rate per wavelength is 10 Gb / s, the total throughput is 320 Gb / s. Therefore, there has been a demand for the emergence of a multi-wavelength collective wavelength conversion device that collectively converts more wavelengths to increase the total throughput.
[0013]
[Means for Solving the Problems]
In order to achieve such an object, the configuration of the present invention is a wavelength conversion device that collectively transfers wavelength multiplexed signal light within a certain wavelength band to another wavelength band,
An input waveguide for inputting wavelength multiplexed signal light (wavelength interval f, number of wavelengths n) and a wavelength of 2 input m outputs for branching the wavelength multiplexed signal light into m (m = n / i, i is an integer) A demultiplexer, m waveguides each guiding the branched wavelength multiplexed light, m wavelength conversion elements connected to each of the waveguides, and wavelengths generated by the wavelength conversion elements A wavelength multiplexer for multiplexing the converted light,
The wavelength multiplexed signal light is input to one input port of the wavelength demultiplexer, and the pump light having the number of wavelengths m and the wavelength interval i × f is wavelength multiplexed and input to the other input port,
The wavelength demultiplexer is composed of an arrayed waveguide type diffraction grating with reduced demultiplexing sensitivity, and has a wavelength band for demultiplexing of i × f and includes at least m output ports, so that wavelength multiplexing of n wavelengths is achieved. The signal light is demultiplexed into m sets of wavelength multiplexed signal lights each having a wavelength of i waves, and then output to each output port. The wavelength multiplexed signal lights that have been demultiplexed into the m sets are transmitted through the same waveguide. Propagated and input to the same wavelength conversion element,
In addition to the wavelength multiplexed signal light consisting of i-wave wavelengths, one pump light is input to the wavelength conversion element,
The wavelength conversion element simultaneously converts wavelength-multiplexed signal light composed of i-wave wavelengths,
The wavelength multiplexer multiplexes the wavelength-converted light that has been wavelength-converted by the wavelength conversion elements.
[0015]
Here, the input means for the pump light described above has a 2-input m-output as a wavelength demultiplexer, and wavelength multiplexed signal light is input to one input port of the wavelength demultiplexer, and the number of wavelengths. It is effective to reduce the number of ports of the system if the pump light with m · wavelength interval i × f (nm) is wavelength-multiplexed and input to the other input port of the wavelength demultiplexer. is there.
[0016]
Here, if the polarization state of the pump light is characterized by the fact that the TE polarized light intensity and the TM polarized light intensity are equal as the pump light input means, it is effective because the polarization dependence of the system is canceled.
[0017]
In order to cancel the wavelength dependence of the system, the wavelength demultiplexer has a characteristic that the insertion loss of the signal light having a wavelength close to that of the pump light is larger than the insertion loss of the signal light having a wavelength far from the pump light. Or, as a characteristic of the wavelength multiplexer, the insertion loss of wavelength converted light having a wavelength close to that of the pump light is larger than the insertion loss of wavelength converted light having a wavelength far from the pump light. Then it is effective.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a reference example of the present invention. Here, assuming a WDM system using 16 wavelengths, signal lights having wavelengths λ1 to λ16 are used as the wavelength multiplexed signal lights S1 to S16. In FIG. 1, reference numeral 101 denotes a wavelength multiplexed signal light input waveguide, 102 denotes an arrayed waveguide type diffraction grating with one input and four outputs, 103 to 106 denote input couplers, 107 to 110 denote wavelength conversion elements, and 111 denotes an array waveguide. A diffraction grating 112 is an output port. Further, continuous light having wavelengths λ5, λ9, λ13, and λ17 is used as the pump lights P5, P9, P13, and P17.
[0019]
What is characteristic here is that the wavelength interval at which the arrayed waveguide type diffraction grating 102 demultiplexes is changed. When signal light S1 to S16 having wavelengths λ1 to λ16 are input by reducing the demultiplexing sensitivity of the arrayed waveguide grating 102, the signal light S1 to S4 having wavelengths λ1 to λ4 is input to the top port. In addition, the signal lights S5 to S8 having wavelengths λ5 to λ8 are set to the second port, the signal lights S9 to S12 having wavelengths λ9 to λ12 are set to the third port, and the signal lights S13 to S16 having wavelengths λ13 to λ16 are set. Can be demultiplexed to the fourth port.
[0020]
Furthermore, when the input couplers 103 to 106 are used to input pump lights P5, P9, P13, and P17, which are continuous lights having wavelengths λ5, λ9, λ13, and λ17,
(1) Four wavelength signal lights S1, S2, S3, S4 (wavelengths λ1, λ2, λ3, λ4) and one wavelength pump light P5 having a wavelength of λ5 are input to the wavelength converter 107,
(2) Four wavelength signal lights S5, S6, S7, and S8 (wavelengths are λ5, λ6, λ7, and λ8) and one wavelength pump light P9 having a wavelength of λ9 are input to the wavelength converter 108,
(3) Four wavelength signal lights S9, S10, S11, S12 (wavelengths are λ9, λ10, λ11, λ12) and one wavelength pump light P13 having a wavelength of λ13 are input to the wavelength converter 109,
{Circle around (4)} Four wavelength signal lights S13, S14, S15, S16 (wavelengths are λ13, λ14, λ15, λ16) and one wavelength pump light P17 having a wavelength of λ17 are input to the wavelength converter 110.
[0021]
Assuming four-wave mixing using a semiconductor amplifier as the wavelength conversion elements 107 to 110, as shown in FIG.
(1) In the wavelength conversion element 107, the wavelength of the signal light S1 (wavelength λ1) is λ9, the wavelength of the signal light S2 (wavelength λ2) is λ8, the wavelength of the signal light S3 (wavelength λ3) is λ7, and the signal light The wavelength of S4 (wavelength λ4) is converted to λ6,
(2) In the wavelength conversion element 108, the wavelength of the signal light S5 (wavelength λ5) is λ13, the wavelength of the signal light S6 (wavelength λ6) is λ12, and the wavelength of the signal light S7 (wavelength λ7) is λ11. The wavelength of S8 (wavelength λ8) is converted to λ10,
(3) In the wavelength conversion element 109, the wavelength of the signal light S9 (wavelength λ9) is λ17, the wavelength of the signal light S10 (wavelength λ10) is λ16, the wavelength of the signal light S11 (wavelength λ11) is λ15, and the signal light The wavelength of S12 (wavelength λ12) is converted to λ14,
(4) In the wavelength conversion element 110, the wavelength of the signal light S13 (wavelength λ13) is λ21, the wavelength of the signal light S14 (wavelength λ14) is λ20, and the wavelength of the signal light S15 (wavelength λ15) is λ19. The wavelength of S16 (wavelength λ16) is converted to λ18.
[0022]
Furthermore, of the arrayed waveguide grating 111,
(1) At the input port connected to the wavelength conversion element 107, only wavelength-converted light with wavelengths λ6 to λ9 is multiplexed.
(2) At the input port connected to the wavelength conversion element 108, only wavelength-converted light with wavelengths λ10 to λ13 is multiplexed,
(3) At the input port connected to the wavelength conversion element 109, only wavelength-converted light having a wavelength of λ14 to λ17 is multiplexed.
{Circle around (4)} By combining only wavelength-converted lights having wavelengths of λ18 to λ21 at the input port connected to the wavelength conversion element 110, batch wavelength conversion of a plurality of wavelengths becomes possible. That is, the wavelength conversion of the signal lights S1 to S16 having the wavelengths λ1 to λ16 into the wavelength converted lights H1 to H16 having the wavelengths λ6 to λ21 is possible.
[0023]
In general, in four-wave mixing, batch conversion of about 8 wavelengths can be performed by one semiconductor amplifier. As described above, since a system having 32 semiconductor amplifiers can be configured, a total throughput of 32 ports × 8 wavelengths × 10 Gb / s = 2, 560 Gb / s can be realized.
[0024]
The configuration of the example of FIG. 1 requires the optical couplers 103 to 106, which causes insertion loss of the optical coupler and increases the number of input ports. However, in the system having four semiconductor amplifiers, the problem is so much Don't be. However, increasing the semiconductor amplifier Furthermore, for example, when set to 32, the above problems, that is, preferably better to eliminate the increase in the insertion loss of the optical coupler with increasing input port, if so, the next first The embodiment may be adopted.
[0025]
First Embodiment
FIG. 3 is a diagram for explaining the first embodiment of the present invention, which eliminates the drawbacks of the reference example (FIG. 1). In FIG. 3, reference numerals 201 and 202 denote wavelength multiplexed light input waveguides, 203 denotes a two-input four-output arrayed waveguide type diffraction grating, 204 to 207 denote wavelength conversion elements, 208 denotes an arrayed waveguide type diffraction grating, and 209 denotes an output. Port.
[0026]
When the signal light S1 to S16 having wavelengths λ1 to λ16 is input to the arrayed waveguide grating 203, the signal light S1 to S4 having wavelengths λ1 to λ4 is used as the top port, and the wavelengths are λ5 to λ8. Signal lights S5 to S8 to the second port, signal lights S9 to S12 having wavelengths λ9 to λ12 to the third port, and signal lights S13 to S16 having wavelengths λ13 to λ16 to the fourth port. Can be demultiplexed. Further, the pump light P5 having the wavelength λ5 is used as the top port, the pump light P9 having the wavelength λ9 is used as the second port, the pump light P13 having the wavelength λ13 is used as the third port, and the pump having the wavelength λ17 is used. The light P17 can be demultiplexed to the fourth port. That is, the difference from FIG. 1 is that the input waveguide 202 of the arrayed waveguide type diffraction grating 203 is used without using a coupler to input pump light.
[0027]
By adopting the configuration of FIG. 3, an optical coupler is not necessary, and the number of input ports can be reduced.
[0028]
Second Embodiment
Become the most problems in the first embodiment (FIG. 3) is a polarization dependence in four-wave mixing. In general, four-wave mixing does not occur unless the polarization planes of the signal light and the pump light match. However, it is not realistic to always align the polarization of the signal light in a certain direction (the direction of the pump light). Therefore, a circuit configuration as shown in FIG. 4 is adopted as the pump light input 202.
[0029]
In FIG. 4, 301, 302, 303, and 304 are semiconductor lasers corresponding to wavelengths λ5, λ9, λ12, and λ17, 305 to 308 are polarization-maintaining optical fibers, 309 is an optical coupler, and 312 is a quarter-wave plate 310. And a half-wave plate 311. The output end (right end in FIG. 4) of the polarization controller 312 is connected to the input waveguide 202 shown in FIG. 3, and the wavelength-multiplexed pump lights P5 to P17 (wavelengths λ5 to λ17) are supplied.
[0030]
By adopting the configuration of FIG. 4, the polarization direction of the pump lights P5 to P17 having wavelengths λ5 to λ17 can be adjusted using the polarization controller 312 so that the TE polarization and the TM polarization are the same. it can. By adjusting in this way, it is possible to obtain four-wave mixing that does not depend on the polarization direction of the input signal light.
[0031]
[ Third Embodiment]
FIG. 5 illustrates a third embodiment. Four-wave mixing generally has high conversion efficiency at wavelengths close to that of pump light, and low conversion efficiency at far wavelengths (FIG. 5A). In order to solve this problem, the arrayed waveguide grating 203 of FIG. 3 is configured such that the insertion loss at a wavelength near the pump light is larger than the insertion loss at a wavelength far from the pump light. By doing so, uniform wavelength-converted light can be obtained regardless of the conversion efficiency (FIG. 5B).
[0032]
The realization method of FIG. 5 is demonstrated using FIG. The arrayed waveguide type diffraction grating can be regarded as a wavelength filter when attention is paid only to a specific output port. That is, as shown in FIG. 6, when the optical loss of a certain output port is graphed with respect to the wavelength of the input light, the transmission band has a low optical loss (about 5 dB) and the optical loss is high in other wavelength bands (about 45 dB). Usually, the input light is arranged near the center of the transmission band, in the “normal wavelength arrangement region” in the figure. That is, since all four wavelengths of the signal light are arranged in this region, there is no significant difference in the optical loss of the four wavelengths. This result is shown in FIG. However, if four wavelengths are arranged in the “wavelength arrangement region in the present invention” in FIG. 6, the optical loss with respect to the wavelength changes greatly, so that FIG. 5B can be realized.
[0033]
[ Fourth Embodiment]
In the third embodiment, the difference in conversion efficiency is compensated by the array waveguide type diffraction grating 203 on the input side, but it can also be compensated by the array waveguide type diffraction grating 208 on the output side. The insertion loss of the wavelength close to the pump light of the arrayed waveguide grating 208 is made larger than the insertion loss of the wavelength far from the pump light. By doing so, uniform wavelength-converted light can be obtained regardless of the conversion efficiency.
[0034]
【The invention's effect】
As described above, according to the present invention, a plurality of wavelengths capable of performing wavelength conversion of a larger number of wavelengths at one time and increasing the total throughput even though fewer wavelength conversion elements are used than in the prior art. A collective wavelength converter can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a reference example of the present invention.
FIG. 2 is an explanatory diagram showing a signal conversion state in a reference example .
FIG. 3 is a block diagram showing a first embodiment of the present invention.
FIG. 4 is a configuration diagram showing a second embodiment of the present invention.
FIG. 5 is an explanatory diagram for explaining a third embodiment of the present invention.
FIG. 6 is an explanatory diagram illustrating a method of realizing the third embodiment.
FIG. 7 is a configuration diagram showing an arrayed waveguide type diffraction grating.
FIG. 8 is an explanatory diagram showing an input / output state of an arrayed waveguide type diffraction grating.
FIG. 9 is a block diagram showing an example of a conventional multiple wavelength batch wavelength conversion device.
FIG. 10 is an explanatory diagram showing an example of four-wave mixing as wavelength conversion.
[Explanation of symbols]
101 Wavelength multiplexed signal light input waveguide 102 Array waveguide type diffraction grating 103-106 Input coupler 107-110 Wavelength conversion element 111 Array waveguide type diffraction grating 112 Output port 201, 202 Input waveguide 203 Array waveguide type Diffraction gratings 204 to 207 Wavelength conversion element 208 Array waveguide type diffraction grating 209 Output ports 301 to 304 Semiconductor lasers 305 to 308 Polarization plane preserving optical fiber 309 Optical coupler 310 1/4 wavelength plate 311 1/2 wavelength plate 312 Polarization controller

Claims (4)

A wavelength conversion device that collectively transfers wavelength multiplexed signal light within a certain wavelength band to another wavelength band,
An input waveguide for inputting wavelength multiplexed signal light (wavelength interval f, number of wavelengths n) and a wavelength of 2 input m outputs for branching the wavelength multiplexed signal light into m (m = n / i, i is an integer) A demultiplexer, m waveguides each guiding the branched wavelength multiplexed light, m wavelength conversion elements connected to each of the waveguides, and wavelengths generated by the wavelength conversion elements A wavelength multiplexer for multiplexing the converted light,
The wavelength multiplexed signal light is input to one input port of the wavelength demultiplexer, and the pump light having the number of wavelengths m and the wavelength interval i × f is wavelength multiplexed and input to the other input port,
The wavelength demultiplexer is composed of an arrayed waveguide type diffraction grating with reduced demultiplexing sensitivity, and has a wavelength band for demultiplexing of i × f and includes at least m output ports, so that wavelength multiplexing of n wavelengths is achieved. The signal light is demultiplexed into m sets of wavelength multiplexed signal lights each having a wavelength of i waves, and then output to each output port. The wavelength multiplexed signal lights that have been demultiplexed into the m sets are transmitted through the same waveguide. Propagated and input to the same wavelength conversion element,
In addition to the wavelength multiplexed signal light consisting of i-wave wavelengths, one pump light is input to the wavelength conversion element,
The wavelength conversion element simultaneously converts wavelength-multiplexed signal light composed of i-wave wavelengths,
The wavelength multiplexer combines the wavelength-converted lights wavelength-converted by the wavelength conversion elements.   The multi-wavelength batch wavelength conversion device according to claim 1, wherein the polarization state of the pump light is such that the TE polarized light intensity and the TM polarized light intensity are equal.   The multiple wavelength batch wavelength conversion device according to claim 1, wherein the wavelength demultiplexer has a characteristic that the insertion loss of the signal light having a wavelength close to the pump light is larger than the insertion loss of the signal light having a wavelength far from the pump light. Multiple wavelength batch wavelength converter characterized by being large and large.   The multi-wavelength batch wavelength conversion device according to claim 1, wherein the wavelength multiplexer has a characteristic that an insertion loss of wavelength converted light having a wavelength close to that of pump light is an insertion loss of wavelength converted light having a wavelength far from the pump light. Multiple wavelength batch wavelength conversion device characterized in that it is larger than.

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