Optical signal processing device, tap coefficient update method, program, and optical signal processing system

Abstract

An optical signal processing device (1) comprises: a polarization separator (11) for separating an input polarization multiplexed signal; an optical coupler (12x) for branching one polarization component; an optical coupler (12y) for branching the other polarization component; optical filters (2a, 2b) to which the polarization component branched by the optical coupler (12x) is input; optical filters (2c, 2d) to which the polarization component branched by the optical coupler (12y) is input; an optical coupler (13x) for multiplexing the outputs of the optical filters (2a, 2c); an optical coupler (13y) for multiplexing the outputs of the optical filters (2b, 2d); and a tap coefficient updating unit (10) for separating a polarization multiplexed signal by adaptively setting tap coefficients of the optical filters (2a to 2d).

Description

[Technical Field]

[0001] The present invention relates to an optical transmission system, and more particularly to an optical signal processing system that demultiplexes a polarization multiplexed signal using optical signal processing in transmitting and receiving an optical polarization multiplexed signal. [Background technology]

[0002] The rapid increase in traffic in data centers has led to progress in the standardization of 100 Gigabit Ethernet® and the development of optical modules. The mainstream optical module for 100 Gigabit Ethernet® is composed of a 4-wavelength x 25 Gbit / s Intensity Modulation-Direct Detection (IM-DD) transceiver, and development is progressing on smaller, more energy-efficient modules such as CFP4 (Centum gigabit Form factor Pluggable 4) and QSFP28 (Quad Form Factor Pluggable 28) as optical interfaces within data centers.

[0003] Meanwhile, in order to directly connect data centers, the development of optical modules that output any optical signal on a wavelength division multiplexing (WDM) grid is progressing. For example, small modules such as XFP and SFP+, which are standards for 10 gigabits, have begun to be sold commercially, and Non-Patent Document 1 states that the use of these optical modules will enable the construction of low-cost WDM systems.

[0004] On the other hand, in the case of a WDM system using optical signals of 100 Gbps or more, it is common to use polarization multiplexed signals to reduce the baud rate of the signals in order to relax the requirements for the electrical characteristics of the receiver. Non-Patent Document 2 describes that optical transceivers that transmit and receive these polarization multiplexed signals use internal digital signal processing to demultiplex the polarization multiplexed signals. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Toshiya Matsuda et al., "Study on Direct Interconnection between Remote Memories Using Pluggable Wavelength Tunable Optical Modules and Error Correcting Coded Memory," IEICE Technical Report Vol. 119, No. 442, BPN2019-54, pp. 7-11, published February 24, 2020 [Non-patent document 2] Kazuaki Kikuchi, "Adaptive Equalization Techniques for Digital Coherent Optical Receivers", IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J96-B, No. 3, pp. 212-219, March 1, 2013 Summary of the Invention [Problem to be solved by the invention]

[0006] The DSP (Digital Signal Processor) that performs the aforementioned digital signal processing is usually configured as an ASIC (Application Specific Integrated Circuit), but its power consumption still accounts for a large proportion of the overall power consumption of an optical transceiver. The power consumption of this DSP makes it difficult to miniaturize optical transceivers that support polarization multiplexed signals. Furthermore, when regenerative repeaters are used in long-distance transmissions, the power consumption of the DSP is added for each repeater, resulting in an increase in the power consumption of the entire system. Therefore, an object of the present invention is to reduce the power consumption of a signal processing device that demultiplexes a polarization multiplexed signal, or a signal processing system that uses a signal processing device. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the optical signal processing device of the present invention is characterized by comprising: a polarization separator that separates an input polarization multiplexed signal into two polarization components; a first optical coupler that branches one of the polarization components separated by the polarization separator; a second optical coupler that branches the other polarization component separated by the polarization separator; first and second optical filters to which the polarization component branched by the first optical coupler is input; third and fourth optical filters to which the polarization component branched by the second optical coupler is input; a third optical coupler that combines outputs of the first and third optical filters; a fourth optical coupler that combines outputs of the second and fourth optical filters; and a tap coefficient update unit that separates the polarization multiplexed signal by adaptively setting tap coefficients of the first to fourth optical filters. Other means will be described in the detailed description of the invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the power consumption of a signal processing device that demultiplexes a polarization multiplexed signal, or a signal processing system that uses a signal processing device. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram of an optical signal processing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of an optical filter. [Figure 3] 1 is a configuration diagram of an optical signal processing system according to a first embodiment. [Figure 4] FIG. 10 is a configuration diagram of an optical signal processing system according to a second embodiment. [Figure 5] FIG. 2 is a diagram illustrating the operation of each part of the optical signal processing device. [Figure 6] 10 is a flowchart of a tap coefficient update process. [Figure 7] 10 is a graph showing power consumption in a comparative example and the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and equations. Optical Signal Processing Device of This Embodiment FIG. 1 is a configuration diagram of an optical signal processing device 1 according to this embodiment. The optical signal processing device 1 includes a tap coefficient updating unit 10, a polarization separator 11, optical couplers 12x and 12y, optical filters 2a to 2d, optical couplers 13x and 13y, and a polarization combiner 19.

[0011] Polarization separator 11 separates the input polarization multiplexed signal into two polarization components. The optical coupler 12x is a first optical coupler that branches one of the polarized components separated by the polarization separator 11. The polarized component Ex i is input to the optical filters 2a and 2b. The optical coupler 12y is a second optical coupler that branches the other polarized component split by the polarization separator 11. The other polarized component Ey split by the optical coupler 12y i is input to optical filters 2c and 2d.

[0012] The optical filters 2a to 2d are controlled by the tap coefficient update unit 10 to adjust the amount of attenuation of each phase of the input optical signal. The optical filters 2a to 2d correspond to the first to fourth optical filters. Details of the optical filters 2a to 2d will be described later with reference to FIG. 2.

[0013] The optical coupler 13x is a third optical coupler that combines the light output from the optical filters 2a and 2c. The optical coupler 13x outputs a polarization-separated optical signal Ex o is. The optical coupler 13y is a fourth optical coupler that combines the light output from the optical filters 2b and 2d. The optical coupler 13y outputs a polarization split optical signal Ey o is.

[0014] The polarization combiner 19 receives the polarization-separated optical signal Ex output from the optical coupler 13x. o and the polarization split optical signal Ey output from the optical coupler 13y.o and are synthesized.

[0015] The tap coefficient update unit 10 is a computer including a program 101, a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, and a RAM (Random Access Memory) 104.

[0016] The CPU 102 is a control unit, and updates the control coefficients of the optical filters 2a to 2d by executing the program 101. The ROM 103 is a non-volatile memory, and stores data and programs. The RAM 104 is a volatile memory, and stores variables and the like that are temporarily saved by the program. The program 101 is interpreted and executed by the CPU 102, and thereby the processing shown in FIG. 6 is performed.

[0017] The CPU 102 calculates the difference between a predetermined amplitude and the output signal obtained by combining the output signals of the optical filters 2a to 2d as an error signal. The CPU 102 further calculates tap coefficients for each of the optical filters 2a to 2d based on the error signal, the output signal of the polarization separator 11, and the output signal obtained by combining the output signals of the optical filters 2a to 2d.

[0018] Generally, polarization separation in DSP is performed by adjusting the tap coefficients h of an FIR (Finite Impulse Response) filter connected in a butterfly configuration. k (k=0,...,n). This FIR filter is a moving average filter. The output of the FIR filter, u o (t) is the input signal u i Using (t), it is expressed as the following equation (1).

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[0019] To simply configure equation (1) for an input optical signal, an optical coupler with a very large number of branches must be used, which leads to a degradation of signal quality due to a large loss of optical signal power. Here, when equation (1) is Fourier transformed and rewritten in the frequency domain, it becomes the following equation (2).

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[0020] Here, the center frequency of the optical signal is ω0, and the frequency interval is sufficiently small relative to the signal band is Δω. The optical signal processing device 1 that demultiplexes such a polarization multiplexed signal can reduce its own power consumption.

[0021] Several algorithms have been proposed for adaptively updating the tap coefficients of an FIR filter. For example, the tap coefficient update unit 10 updates the tap coefficients according to the following equation (3), similar to the CMA (Constant Modulus Algorithm) described in Non-Patent Document 2.

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[0022] where H is the tap coefficient, μ is the step size, ε is the error signal, the asterisk in the upper right corner of the variable denotes the complex conjugate, and m is the amplitude.

[0023] FIG. 2 is a diagram showing the configuration of the optical filters 2a to 2d. Each of the optical filters 2a to 2d includes an optical demultiplexer 21, a plurality of optical phase shifters 22a to 22n, optical attenuators 23a to 23n, and an optical multiplexer 24. The optical demultiplexer 21 demultiplexes the optical signal at predetermined phase intervals (Δω intervals). The demultiplexed optical signals are input to a plurality of optical phase shifters 22a to 22n, respectively.

[0024] Optical phase shifters 22a to 22n control the phase of each frequency component. Optical attenuators 23a to 23n control the amplitude of each frequency component. Optical multiplexer 24 multiplexes each frequency component. This makes it possible to realize equation (2) in the frequency domain.

[0025] Here, the tap coefficients of the optical attenuators 23a to 23n in the optical filter 2a are F11=(f110, f111, f112, ..., f11 n ) The tap coefficients of the optical attenuators 23a to 23n in the optical filter 2b are F12=(f120, f121, f122, ..., f12 n ) The tap coefficients of the optical attenuators 23a to 23n in the optical filter 2c are F21=(f210, f211, f212, ..., f21 n ) The tap coefficients of the optical attenuators 23a to 23n in the optical filter 2d are F22=(f220, f221, f222, ..., f22 n )

[0026] The output of optical demultiplexer 21 in optical filter 2 corresponds to U(ω0+jΔω). The attenuation amount of optical attenuators 23a to 23n is calculated from the absolute value of the coefficient of each frequency component. The phase change amount of optical phase shifters 22a to 22n is calculated from the argument of the coefficient of each frequency component.

[0027] FIG. 3 is a configuration diagram of an optical signal processing system S according to the first embodiment. The optical signal processing system S includes a polarization multiplexed signal transmitter 3, a wavelength multiplexer 5, a wavelength demultiplexer 7, an optical signal processing device 1, and a polarization multiplexed signal receiver 9.

[0028] The polarization multiplexed signal transmitter 3 transmits a polarization multiplexed signal. The polarization multiplexed signal output from the polarization multiplexed signal transmitter 3 is input to a wavelength multiplexer 5 via an optical patch cord 4. The wavelength multiplexer 5 wavelength-multiplexes the polarization multiplexed signal. The polarization multiplexed signal wavelength-multiplexed by the wavelength multiplexer 5 is input to the wavelength demultiplexer 7 via the optical transmission line 6.

[0029] The wavelength demultiplexer 7 demultiplexes the wavelength multiplexed signal. The wavelength multiplexed signal demultiplexed by the wavelength demultiplexer 7 is input to the optical signal processing device 1. The optical signal processing device 1 outputs a polarization multiplexed signal with orthogonal linearly polarized light. The polarization multiplexed signal with orthogonal linearly polarized light output from the optical signal processing device 1 is input to a polarization multiplexed signal receiver 9 via a polarization-maintaining optical patch cord 8. The polarization-maintaining optical patch cord 8 maintains the polarization state of the polarization multiplexed signal. This allows the optical signal processing system S, which uses the optical signal processing device 1 that separates the polarization multiplexed signal, to perform polarization separation without using a DSP, thereby reducing its own power consumption.

[0030] FIG. 4 is a configuration diagram of an optical signal processing system S according to the second embodiment. The optical signal processing system S includes a polarization multiplexed signal transmitter 3, a wavelength multiplexer 5, a wavelength demultiplexer 7, an optical patch cord 8A, and a polarization multiplexed signal receiver 91. The polarization multiplexed signal receiver 91 includes an optical signal processing device 1.

[0031] The polarization multiplexed signal transmitter 3 transmits a polarization multiplexed signal. The polarization multiplexed signal output from the polarization multiplexed signal transmitter 3 is input to a wavelength multiplexer 5 via an optical patch cord 4. The wavelength multiplexer 5 wavelength-multiplexes the polarization multiplexed signal. The polarization multiplexed signal wavelength-multiplexed by the wavelength multiplexer 5 is input to the wavelength demultiplexer 7 via the optical transmission line 6.

[0032] The wavelength demultiplexer 7 demultiplexes the wavelength multiplexed signal. The wavelength multiplexed signal demultiplexed by the wavelength demultiplexer 7 is input to the optical signal processing device 1 included in the polarization multiplexed signal receiver 91. The optical signal processing device 1 outputs a polarization multiplexed signal of orthogonal linearly polarized light. The polarization multiplexed signal of orthogonal linearly polarized light output from the optical signal processing device 1 is processed by other parts of the polarization multiplexed signal receiver 91. As a result, the optical signal processing system S using the optical signal processing device 1 that separates the polarization multiplexed signal can perform polarization separation without using a DSP, and therefore can reduce its own power consumption.

[0033] FIG. 5 is a diagram illustrating the operation of each part of the optical signal processing device 1. The optical signal processing device 1 includes the tap coefficient update unit 10, polarization separator 11, optical couplers 12x and 12y, optical filters 2a to 2d, optical couplers 13x and 13y, and polarization combiner 19 shown in FIG. 1. The optical signal processing device 1 further includes optical couplers 14x and 14y, optical couplers 151 to 160, quarter-wave plates 161 to 164, optical couplers 171 to 178, and photodetectors 181 to 192. The photodetectors 181 to 192 are, for example, photodiodes, and are detectors that detect light. These photodetectors 181 to 192 detect an output signal obtained by combining output signals from the optical filters 2a to 2d connected in a butterfly configuration. In the drawings, the photodetector is abbreviated to PD (Photo Detector), and the quarter-wave plates 161 to 164 are abbreviated to 90°PS. Also, the optical couplers 12x and 12y, the optical couplers 14x and 14y, and the optical couplers 151 to 160 are abbreviated to optical branching in the drawings.

[0034] Polarization separator 11 separates the input polarization multiplexed signal into two polarization components. The optical coupler 12x splits one of the polarized components split by the polarization splitter 11. The polarized component is Ex i Polarization component Ex i is input to the optical filters 2a and 2b, the photodetector 181, and the optical couplers 151 and 155. i is shown in equation (4).

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[0035] The optical coupler 12y branches the other polarized component separated by the polarization separator 11. The other polarized component is i Polarization component Ey i is input to the optical filters 2c and 2d, the optical couplers 156 and 160, and the photodetector 192. i is shown in equation (5).

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[0036] The optical filters 2a to 2d are controlled by the tap coefficient update unit 10 to adjust the amount of attenuation of each phase of the input optical signal. The tap coefficient of the optical filter 2a is F11, the tap coefficient of the optical filter 2b is F12, the tap coefficient of the optical filter 2c is F21, and the tap coefficient of the optical filter 2d is F22.

[0037] The optical coupler 13x combines the light output from the optical filters 2a and 2c. The optical coupler 13x outputs a polarization-separated optical signal Ex o The polarization split optical signal Ex o is branched by the optical coupler 14x and output to the optical couplers 152 to 154. o is shown in equation (6).

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[0038] The optical coupler 13y combines the light output from the optical filters 2b and 2d. The optical coupler 13y outputs a polarization split optical signal Ey o The polarization split optical signal Ey o is branched by the optical coupler 14y and output to the optical couplers 157 to 159. o is shown in equation (7).

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[0039] The optical coupler 151 receives the polarized component Ex output from the optical coupler 12x. i is input from the optical coupler 151. i The branched signals are output to optical couplers 171 and 172. The optical coupler 152 receives the polarization-separated optical signal Ex o is input from the optical coupler 152. oThe branched signals are output to the optical coupler 171 and the quarter wave plate 161. The signal output from the quarter wave plate 161 is output to the optical coupler 172.

[0040] The optical coupler 153 receives the polarization-separated optical signal Ex o is input from the optical coupler 153. The polarization split optical signal Ex o The branched signals are output to the photodetector 184 and the polarization combiner 19 in FIG. The optical coupler 154 receives the polarization-separated optical signal Ex o is input from the optical coupler 154. The polarization demultiplexed optical signal Ex o The branched signal is output to the optical coupler 173 and the quarter wave plate 162. The signal output from the quarter wave plate 162 is output to the optical coupler 175.

[0041] The optical coupler 155 receives the polarized component Ex output from the optical coupler 12x. i is input from the optical coupler 155. i The branched signals are output to optical couplers 174 and 176. The optical coupler 156 receives the polarized component Ey output from the optical coupler 12y. i is input from the optical coupler 156. i The branched signals are output to optical couplers 173 and 175.

[0042] The optical coupler 157 receives the polarization split optical signal Ey output from the optical coupler 14y. o is input from the optical coupler 157. o The branched signal is output to the quarter wave plate 163 and the optical coupler 176. The signal output from the quarter wave plate 163 is output to the optical coupler 174. The optical coupler 158 receives the polarization split optical signal Ey output from the optical coupler 14y. o is input from the optical coupler 158. The polarization split optical signal Ey o The branched signals are output to a photodetector 189 and the polarization combiner 19 in FIG.

[0043] The optical coupler 159 receives the polarization split optical signal Ey output from the optical coupler 14y. o is input from the optical coupler 159. o The branched signal is output to the quarter wave plate 164 and the optical coupler 178. The signal output from the quarter wave plate 164 is output to the optical coupler 177. The optical coupler 160 receives the polarized component Ey output from the optical coupler 12y. i is input from the optical coupler 160. i The branched signals are output to optical couplers 177 and 178.

[0044] The optical coupler 171 receives the polarized component Ex i and the polarization split optical signal Ex output from the optical coupler 152. o and are input. Polarization component Ex i and Ex o The combined signal is output to the photodetector 182. The optical coupler 172 receives the polarized component Ex i and the polarization separated optical signal Ex emitted from the quarter wave plate 161. o * and are input. Polarization component Ey i and Ex o * The combined signal is output to the photodetector 183.

[0045] The optical coupler 173 receives the polarized component Ex output from the optical coupler 154. i and the polarization component Ey output from the optical coupler 156 i and are input. Polarization component Ex i and Ey i The combined signal is output to the photodetector 185. The optical coupler 174 receives the polarized component Ex i and the polarization split optical signal Ey output from the quarter wave plate 163. o * and are input. Polarization component Ex iand Ey o * The combined signal is output to the photodetector 186.

[0046] The optical coupler 175 receives the polarization-separated optical signal Ex o * and the polarization component Ey output from the optical coupler 156 i and are input. Polarization component Ey i and Ex o * The combined signal is output to the photodetector 187. The optical coupler 176 receives the polarized component Ex i and the polarization split optical signal Ey output from the optical coupler 157. o and are input. Polarization component Ex i and Ey o The combined signal is output to the photodetector 188.

[0047] The optical coupler 177 receives the polarization-separated optical signal Ey output from the quarter-wave plate 164. o * and the polarization component Ey output from the optical coupler 160. i and are input. Polarization component Ey i and Ey o * The combined signal is output to the photodetector 190. The optical coupler 178 receives the polarized component Ex i and the polarization split optical signal Ex output from the optical coupler 152. o and are input. Polarization component Ex i and Ex o The combined signal is output to the photodetector 191.

[0048] The output powers of the optical couplers 12x and 12y are adjusted to be equal, and the input powers to the photodetectors 181 to 182 are adjusted to be equal. If the coefficients are omitted, the photodetector 181 is a square-law detector, and therefore its detection output v1 is expressed by equation (8).

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[0049] The detection output v2 of the photodetector 182 is expressed by equation (9).

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[0050] The detection output v3 of the photodetector 183 is expressed by equation (10).

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[0051] The detection output v4 of the photodetector 184 is expressed by equation (11).

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[0052] The detection output v5 of the photodetector 185 is expressed by equation (12).

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[0053] The detection output v6 of the photodetector 186 is expressed by equation (13).

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[0054] The detection output v7 of the photodetector 187 is expressed by equation (14).

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[0055] The detection output v8 of the photodetector 188 is expressed by equation (15).

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[0056] The detection output v9 of the photodetector 189 is expressed by equation (16).

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[0057] Photodetector 190 detection output v 10 is expressed by equation (17).

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[0058] Photodetector 191 detection output v 11 is expressed by equation (18).

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[0059] Photodetector 192 detection output v 12 is expressed by equation (19).

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[0060] In this case, using equation (20) using v1 to v4, Ex i Ex o * can be calculated.

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[0061] According to equation (21), Ey i Ex o * can be calculated.

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[0062] According to equation (22), Ex i Eye o * can be calculated.

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[0063] According to equation (23), Ey i Eye o * can be calculated.

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[0064] And Ex i Ex o * Therefore, the coefficients of F11 can be updated using equation (3). F11=(f110, f111, ... , f11 n ) is the (h0, h1, ..., h n ) is equivalent to Ey i Ex o * Therefore, the coefficients of F12 can be updated using equation (3). F12=(f120, f121, ... , f12 n ) is the (h0, h1, ..., h n ) is equivalent to

[0065] Ex i Eye o * Therefore, the coefficients of F21 can be updated using equation (3). F21=(f210, f211, ... , f21 n ) is the (h0, h1, ..., h n ) is equivalent to Ey i Eye o * Therefore, the coefficients of F22 can be updated using equation (3). F22 = (f220, f221, ... , f22 n) is the (h0, h1, ..., h n ) is equivalent to

[0066] FIG. 6 is a flowchart of the tap coefficient update process. The CPU 102 detects the output from the polarization separator 11 and the output from the optical signal processing device 1 with a photodetector (step S10). Next, the CPU 102 determines the difference between the predetermined amplitude m and the output from the optical signal processing device 1 as an error signal ε (step S11). After updating the tap coefficients based on the error signal ε, the output from the optical signal processing device 1, and the output from the polarization separator 11 (step S12), the CPU 102 returns to the process of step S10 and repeats it.

[0067] We evaluated the power consumption of an optical signal processing circuit that uses the present invention to demultiplex a polarization multiplexed signal. Generally, the power consumption of optical devices is much smaller than that of electrical circuits. In the case of an example of a tunable chromatic dispersion compensator with a configuration equivalent to the optical filter of the present invention, the power consumption is 0.24 W, and the power consumption of the present invention equipped with four optical filters can be estimated at 0.96 W. We also assumed that the power consumption of the photodetector and control circuit is negligibly small. On the other hand, in a comparative example of the power consumption of a DSP that separates a polarization multiplexed signal, which is a prior art, the power consumption is 0.1 W / Gbps, depending on the signal bit rate.

[0068] FIG. 7 is a graph showing the power consumption of the comparative example and the present invention. While the power consumption of the comparative example increases as the bit rate increases, the power consumption of the present invention maintains a predetermined value regardless of the bit rate. For example, when compared at a bit rate of 800 Gbps, the power consumption of the present invention can be reduced to about 1 / 100 of that of the prior art.

[0069] As described above, by using the present invention, it is possible to significantly reduce the power consumption of a signal processing circuit that separates a polarization multiplexed signal, and to reduce the size of an optical module that can transmit and receive a polarization multiplexed signal.

[0070] "effect" The effects of the optical signal processing device and the like according to the present invention will be described below. 《Claim 1》 a polarization separator that separates an input polarization multiplexed signal into two polarization components; a first optical coupler that branches one of the polarized components separated by the polarization separator; a second optical coupler that branches the other polarized component separated by the polarization separator; first and second optical filters to which the polarized wave components branched by the first optical coupler are input; third and fourth optical filters to which the polarized wave components branched by the second optical coupler are input; a third optical coupler that combines the outputs of the first and third optical filters; a fourth optical coupler that combines the outputs of the second and fourth optical filters; a tap coefficient update unit that demultiplexes a polarization multiplexed signal by adaptively setting tap coefficients of the first to fourth optical filters; An optical signal processing device comprising:

[0071] This makes it possible to reduce the power consumption of the signal processing device that separates the polarization multiplexed signal.Furthermore, the first to fourth optical filters can be connected in a butterfly configuration.

[0072] 《Claim 2》 The first to fourth optical filters are an optical demultiplexer that demultiplexes an optical signal in predetermined phase increments; a plurality of optical phase shifters for controlling the phases of the respective frequency components of the optical signals demultiplexed by the optical demultiplexer; a plurality of optical attenuators for controlling the amplitude of the optical signal whose phase has been controlled by each of the optical phase shifters; an optical multiplexer that multiplexes the optical signals output from the plurality of optical attenuators; 2. The optical signal processing device according to claim 1, comprising:

[0073] This makes it possible to set the tap coefficients of the optical filters connected in a butterfly configuration.

[0074] 《Claim 3》 The tap coefficient update unit adaptively setting coefficients of the first to fourth optical filters so that a signal obtained by applying a moving average filter to the input polarization multiplexed signal is output. 2. The optical signal processing device according to claim 1, wherein:

[0075] This makes it possible to realize a moving average filter using an optical filter without using a DSP.

[0076] 《Claim 4》 a step of detecting an output signal of a polarization separator that separates an input polarization multiplexed signal into two polarization components by a detector; a step of detecting an output signal obtained by multiplexing output signals of optical filters connected in a butterfly configuration with the polarization separator by a detector; a control unit calculating, as an error signal, a difference between a predetermined amplitude and an output signal obtained by multiplexing output signals of the optical filters; the control unit calculating tap coefficients of the optical filter based on an output signal obtained by combining the error signal, the output signal of the polarization separator, and the output signal of the optical filter; 2. A tap coefficient updating method comprising:

[0077] This makes it possible to demultiplex a polarization multiplexed signal while suppressing power consumption.

[0078] 《Claim 5》 On the computer, a step of detecting an output signal of a polarization separator that separates an input polarization multiplexed signal into two polarization components; a step of detecting an output signal obtained by multiplexing output signals of optical filters connected in a butterfly configuration to the polarization separator; a step of calculating, as an error signal, a difference between a predetermined amplitude and an output signal obtained by multiplexing the output signals of the optical filters; calculating tap coefficients of the optical filter based on an output signal obtained by combining the error signal, the output signal of the polarization separator, and the output signal of the optical filter; A program to execute.

[0079] This makes it possible to demultiplex a polarization multiplexed signal while suppressing power consumption.

[0080] 《Claim 6》 a polarization multiplexed signal transmitter for transmitting a polarization multiplexed signal; a wavelength multiplexer connected by an optical patch cord and wavelength-multiplexing the polarization multiplexed signal; a wavelength demultiplexer connected to the wavelength multiplexer via an optical transmission line, for demultiplexing the signal wavelength-multiplexed by the wavelength multiplexer; an optical signal processing device according to claim 1, which outputs a polarization multiplexed signal of orthogonal linearly polarized light after polarization separation of the polarization multiplexed signal demultiplexed by the wavelength demultiplexer; a polarization multiplexed signal receiver connected by a polarization-maintaining optical patch cord that maintains the polarization state of the polarization multiplexed signal output from the optical signal processing device; An optical signal processing system comprising:

[0081] This makes it possible to reduce the power consumption of a signal processing system that uses a signal processing device that separates a polarization multiplexed signal.

[0082] 《Claim 7》 a polarization multiplexed signal transmitter for transmitting a polarization multiplexed signal; a wavelength multiplexer connected by an optical patch cord and wavelength-multiplexing the polarization multiplexed signal; a wavelength demultiplexer connected to the wavelength multiplexer via an optical transmission line, for demultiplexing a wavelength multiplexed signal; a polarization multiplexed signal receiver incorporating the optical signal processing device according to claim 1, which is connected to the wavelength demultiplexer by an optical patch cord and which depolarizes the polarization multiplexed signal demultiplexed by the wavelength demultiplexer; An optical signal processing system comprising:

[0083] This makes it possible to reduce the power consumption of a signal processing system that uses a signal processing device that separates a polarization multiplexed signal. [Explanation of symbols]

[0084] 1 Optical signal processing device 10 Tap coefficient update unit 101 Program 102 CPU 103 ROM 104 RAM 11 Polarization separator 12x optical coupler (first optical coupler) 12y Optical Coupler (Second Optical Coupler) 13x optical coupler (third optical coupler) 13y Optical Coupler (4th Optical Coupler) 14x, 14y optical coupler 151~160 Optical coupler 161~164 1 / 4 wavelength plate 171~178 Optical coupler 181~191 Photodetector (detector) 19 Polarization combiner 2a Optical filter (first optical filter) 2b Optical filter (second optical filter) 2c Optical filter (third optical filter) 2d Optical Filter (4th Optical Filter) 21 Optical demultiplexer 22a~22n Optical phase shifter 23a~23n Optical attenuator 24 Optical multiplexer 3 Polarization multiplexed signal transmitter 4 Optical Patch Cords 5 wavelength multiplexer 6 Optical transmission line 7 wavelength demultiplexer 8,8A Polarization-Maintaining Optical Patch Cord 9,91 Polarization multiplexed signal receiver

Claims

1. a polarization separator that separates an input polarization multiplexed signal into two polarization components; a first optical coupler that branches one of the polarized components separated by the polarization separator; a second optical coupler that branches the other polarized component separated by the polarization separator; first and second optical filters to which the polarized wave components branched by the first optical coupler are input; third and fourth optical filters to which the polarized wave components branched by the second optical coupler are input; a third optical coupler that combines outputs of the first and third optical filters; a fourth optical coupler that combines outputs of the second and fourth optical filters; a tap coefficient update unit that demultiplexes a polarization multiplexed signal by adaptively setting tap coefficients of the first to fourth optical filters; An optical signal processing device comprising:

2. The first to fourth optical filters are an optical demultiplexer that demultiplexes an optical signal in predetermined phase increments; a plurality of optical phase shifters for controlling the phases of the respective frequency components of the optical signals demultiplexed by the optical demultiplexer; a plurality of optical attenuators for controlling the amplitude of the optical signal whose phase has been controlled by each of the optical phase shifters; an optical multiplexer that multiplexes the optical signals output from the plurality of optical attenuators; 2. The optical signal processing device according to claim 1, comprising:

3. The tap coefficient update unit adaptively setting coefficients of the first to fourth optical filters so that a signal obtained by applying a moving average filter to the input polarization multiplexed signal is output.

2. The optical signal processing device according to claim 1.

4. A tap coefficient updating method executed by an optical signal processing device according to any one of claims 1 to 3, comprising: a step of detecting an output signal of a polarization separator that separates an input polarization multiplexed signal into two polarization components by a detector; a detector detecting a first polarization split signal output from the third optical coupler and / or a second polarization split signal output from the fourth optical coupler; a control unit calculating an error signal based on a difference between a predetermined amplitude and a signal obtained by combining the first polarization separation signal and the second polarization separation signal; the control unit calculating tap coefficients of the first to fourth optical filters based on the error signal, the output signal of the polarization separator, and the first and second polarization separation signals; 2. A tap coefficient updating method comprising:

5. A computer that controls the optical signal processing device according to any one of claims 1 to 3, a step of detecting an output signal of a polarization separator that separates an input polarization multiplexed signal into two polarization components; detecting, by a detector, the first polarization split signal output from the third optical coupler and / or the second polarization split signal output from the fourth optical coupler; a step of calculating an error signal based on a difference between a predetermined amplitude and a signal obtained by combining the first polarization separation signal and the second polarization separation signal; calculating tap coefficients of the first to fourth optical filters based on the error signal, the output signal of the polarization separator, and the first and second polarization separation signals; A program to execute.

6. a polarization multiplexed signal transmitter for transmitting a polarization multiplexed signal; a wavelength multiplexer connected by an optical patch cord and wavelength-multiplexing the polarization multiplexed signal; a wavelength demultiplexer connected to the wavelength multiplexer via an optical transmission line, for demultiplexing the signal wavelength-multiplexed by the wavelength multiplexer; an optical signal processing device according to claim 1, wherein the polarization multiplexed signal demultiplexed by the wavelength demultiplexer is depolarized and then a polarization multiplexed signal of orthogonal linearly polarized light is output; a polarization multiplexed signal receiver connected by a polarization-maintaining optical patch cord that maintains the polarization state of the polarization multiplexed signal output from the optical signal processing device; An optical signal processing system comprising:

7. a polarization multiplexed signal transmitter for transmitting a polarization multiplexed signal; a wavelength multiplexer connected by an optical patch cord and wavelength-multiplexing the polarization multiplexed signal; a wavelength demultiplexer connected to the wavelength multiplexer via an optical transmission line, for demultiplexing a wavelength multiplexed signal; a polarization multiplexed signal receiver incorporating the optical signal processing device according to claim 1, which is connected to the wavelength demultiplexer by an optical patch cord and which depolarizes the polarization multiplexed signal demultiplexed by the wavelength demultiplexer; An optical signal processing system comprising:

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