WO2021070790A1 - 光信号処理回路、光受信装置及び光信号処理方法 - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6164—Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/04—Control of transmission; Equalising
- H04B3/06—Control of transmission; Equalising by the transmitted signal
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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Definitions
- the present invention relates to an optical signal processing circuit, an optical receiving device, and an optical signal processing method.
- a digital coherent method has been used in a large-capacity backbone optical communication system exceeding 100 Gbps (Gigabit per second). Further, in such an optical communication system, communication by a multi-level modulation method such as QPSK (Quadrature Phase Shift Keying) method or 16QAM (Quadrature Amplitude Modulation) has been put into practical use. Further, higher-order multi-level modulation methods such as 32QAM and 64QAM are being developed with the aim of further increasing the capacity.
- QPSK Quadrature Phase Shift Keying
- 16QAM Quadrature Amplitude Modulation
- a subcarrier multiplexing method that realizes 1 Tbps transmission by wavelength division multiplexing of a plurality of subcarriers is effective in consideration of feasibility.
- the subcarrier interval becomes denser, the frequency utilization efficiency improves, so that a technique for transmitting by narrowing the subcarrier multiplex interval becomes important. Therefore, the development of a technique for performing wavelength division multiplexing transmission with a close subcarrier interval is being actively carried out.
- a technique for performing wavelength division multiplexing transmission with such a close subcarrier interval for example, a technique such as Non-Patent Document 1 is disclosed.
- the optical transmission system of Non-Patent Document 1 is a communication system that transmits a polarized multiplex multi-valued optical signal of a digital coherent method.
- NRZ subcarrier signals are wavelength-multiplexed at intervals equal to or less than the baud rate and transmitted, and on the receiving side, linearity by MIMO (Multi Input Multi Output) processing with signals between adjacent subcarriers
- MIMO Multi Input Multi Output
- Non-Patent Document 1 In an optical transmission system that exceeds 1 Tbps as in Non-Patent Document 1, the crosstalk of the subcarrier signal is suppressed by performing MIMO processing on the receiving side.
- the circuit scale on the receiving side may increase when the number of multiplexed subcarrier signals increases.
- an object of the present disclosure to provide an optical signal processing circuit, an optical receiving device, and an optical signal processing method capable of suppressing an increase in circuit scale.
- the optical signal processing circuit is a frequency that generates the continuous subcarrier signal after frequency domain MIMO equalization processing based on the continuous subcarrier signal including the target subcarrier signal in the received optical multicarrier signal.
- a region MIMO equalizer and a time domain MIMO equalizer that generates the target subcarrier signal after the time domain MIMO equalization process based on the continuous subcarrier signal after the frequency domain MIMO equalization process.
- the optical receiver includes an optical receiver for receiving an optical multicarrier signal, a plurality of frequency domain MIMO equalizers, and a plurality of time domain MIMO equalizers, and the plurality of frequency domain MIMOs.
- each of the equalizers is based on the continuous subcarrier signal including the target subcarrier signal selected for each frequency domain MIMO equalizer in the received optical multicarrier signal.
- Each of the plurality of time domain MIMO equalizers generates the continuous subcarrier signal of the above, and each of the plurality of time domain MIMO equalizers after the time domain MIMO equalization process is based on the continuous subcarrier signal after the frequency domain MIMO equalization process. It generates a target subcarrier signal.
- the optical signal processing method generates the continuous subcarrier signal after frequency domain MIMO equalization processing based on the continuous subcarrier signal including the target subcarrier signal in the received optical multicarrier signal. Based on the continuous subcarrier signal after the frequency domain MIMO equalization process, the target subcarrier signal after the time domain MIMO equalization process is generated.
- an optical signal processing circuit capable of suppressing an increase in circuit scale.
- FIG. 1 It is a block diagram which shows the structure of the FDE-MIMO equalizer which concerns on Embodiment 1.
- FIG. 2 It is a block diagram which shows the structure of the TDE-MIMO equalizer of the comparative example. It is a block diagram which shows the structure of the TDE-MIMO equalizer which concerns on Embodiment 1.
- FIG. It is a graph for demonstrating the effect of Embodiment 1.
- FIG. It is a block diagram which shows the structure of the FDE-MIMO equalizer which concerns on Embodiment 2.
- FIG. It is a block diagram which shows the structure of the FDE-MIMO equalizer which concerns on Embodiment 2.
- FIG. It is a block diagram which shows the structure of the TDE-MIMO equalizer which concerns on Embodiment 2.
- FIG. It is a block diagram which shows the structure of the TDE-MIMO equalizer which
- Non-Patent Document 1 Example 1
- an optical transmission system that enables flexible transmission path selection such as a transmission system using a ROADM (Reconfigurable Optical Add / Drop Multiplexer) device
- a signal composed of multiple subcarriers is combined into one signal. It is generally defined as a channel and route control is performed on a channel-by-channel basis.
- the signal spectrum is cut by the characteristics of an optical switch such as WSS (Wavelength Selective Switch) mounted on the ROADM device, and the signal band is narrowed.
- WSS Widelength Selective Switch
- the signal band is narrowed.
- it is also affected by the limitation of the analog front-end band of the transmitter / receiver and the asymmetric spectral narrowing due to the light source frequency offset.
- Non-Patent Document 1 discloses a MIMO equalization method in which NRZ type subcarrier signals having a wide signal band are wavelength-multiplexed, but such a wide band NRZ type subcarrier signal is a ROADM device. It is greatly affected by band narrowing associated with passage. When such narrowing of the signal spectrum or asymmetric band narrowing occurs, the band narrowing is performed while effectively canceling the crosstalk between overlapping subcarriers, which is the original purpose of the MIMO equalizer. In order to compensate for the waveform distortion caused by the conversion with high accuracy, the filter characteristics required for the MIMO equalizer become very steep.
- Non-Patent Document 1 not only the number of taps of the FIR (Finite Impulse Response) filter constituting the MIMO equalizer increases and the circuit scale increases, but also CMA (Constant Modulus Algorithm) or the like is used. There is a problem that the convergence of the coefficient optimization of the MIMO equalizer is deteriorated and the characteristics are greatly deteriorated.
- FIR Finite Impulse Response
- CMA Constant Modulus Algorithm
- FIG. 1 shows the configuration of the wavelength division multiplexing optical transmission system of the comparative example
- FIG. 2 shows the configuration of the subcarrier multiplexing signal transmitted and received by the wavelength division multiplexing optical transmission system of the comparative example.
- the wavelength division multiplexing optical transmission system 9 of the comparative example includes an optical transmission device 10 and an optical reception device 90 that perform optical communication via an optical fiber transmission line 31.
- a ROADM device 32 is arranged on the optical fiber transmission line 31.
- the optical transmitter 10 includes a plurality of optical transmitters 11 (11-1 to 11-5 in this example) that convert a plurality of subcarrier signals (SUBs) into optical signals to be transmitted, and a plurality of generated optical signals. It is provided with a combiner 12 that combines the two.
- the optical receiver 90 includes a demultiplexer 21 that separates the received optical signal into a plurality of subcarrier signals, and a plurality of optical receivers 22 that convert the plurality of subcarrier signals that are optical signals into signals that can be processed. (22-1 to 22-5 in this example) and a hybrid MIMO equalizer 900 that performs MIMO equalization processing by two methods are provided.
- subcarrier signals SUB1 to SUB5 are wavelength-multiplexed to generate one channel signal (Ch), and a subcarrier multiplexing signal including a plurality of channel signals is transmitted and received.
- Subcarrier signals SUB1 ⁇ SUB5 are subcarrier signal of the NRZ type, are wavelength-multiplexed at intervals of a frequency f 0.
- the subcarrier signals SUB1 to SUB5 are converted into optical signals by optical transmitters 11-1 to 11-5 each composed of a digital / analog converter, a light source, an optical modulator, and the like. Further, the optical signals from the optical transmitters 11-1 to 11-5 are wavelength-multiplexed by the combiner 12 to generate one channel signal.
- the channel signal wavelength-multiplexed in this way is further wavelength-multiplexed together with other channel signals, passes through the optical fiber transmission line 31 and the ROADM device 32, and is transmitted to the optical receiver 90.
- the optical receiver 90 separates the received channel signal into a plurality of subcarrier signals by the duplexer 21.
- the separated subcarrier signal is transmitted to the hybrid MIMO equalizer 900 via optical receivers 22-1 to 22-5 composed of a coherent mixer, an optical / electric converter, an analog / digital converter, and the like.
- a crosstalk component between a plurality of subcarriers remains in the subcarrier signal separated by the demultiplexer 21.
- a crosstalk component between two or three subcarriers may remain. Therefore, each subcarrier signal cannot be demodulated as it is. Therefore, by performing MIMO equalization processing, the crosstalk component can be canceled and the subcarrier signal can be demodulated. That is, in this example, as shown in FIG. 2, since the broadband NRZ type subcarrier signals SUB1 to SUB5 are wavelength-multiplexed, the spectra of the subcarrier signals overlap on the frequency axis and the crosstalk shown by the diagonal line is generated. Occurs. For the subcarrier signal in this crosstalk region, the crosstalk can be suppressed and the subcarrier signal can be separated by performing MIMO equalization processing of each subcarrier signal on the receiving side.
- the outermost side of the spectrum of the plurality of overlapping NRZ subcarrier signals is sharply cut off. And lose information.
- the MIMO equalizer on the receiving side suppresses crosstalk between subcarriers, which is the original purpose, and high waveform distortion due to band narrowing, etc.
- the characteristics of each FIR filter required for the MIMO equalizer become steep, and the number of taps increases significantly.
- Non-Patent Document 1 the circuit scale is increased, and even if the number of taps can be increased, the convergence of the blind equalization algorithm represented by CMA deteriorates. As a result, the signal quality is deteriorated.
- the MIMO equalizer (hereinafter referred to as FDE-MIMO equalizer) 910 and the time domain MIMO equalizer by the FDE (Frequency-Domain Equalizer) which is the frequency domain MIMO equalizer are used.
- the MIMO equalization process is performed by a hybrid MIMO equalizer 900 having a MIMO equalizer (hereinafter referred to as TDE-MIMO equalizer) 920 by a TDE (Time-Domain Equalizer) which is a vessel.
- the FDE has a filter configuration in which a received signal sequence is once converted into a frequency domain by FFT (Fast Fourier Transform) processing, multiplied by a filter shape, and returned to the time domain by IFFT (Inverse Fast Fourier Transform).
- FFT Fast Fourier Transform
- IFFT Inverse Fast Fourier Transform
- the number of frequency domain filter coefficients of FDE is equivalent to the size of FFT / IFFT, and is one digit or more larger than the number of time domain tap coefficients of TDE.
- FDE is not suitable for equalizers that compensate for waveform distortion with dynamic fluctuations, but it is very effective for compensating for static or very slow fluctuation waveform distortion with high accuracy.
- the circuit scale can be suppressed and the TDE can cope with dynamic fluctuations.
- TDE is not suitable for realizing highly accurate and steep filter characteristics due to the problem of circuit scale due to the increase in the number of taps.
- FIG. 3 shows an outline of the MIMO equalization process of the comparative example.
- the received subcarrier signals SUB1 to SUB5 are subjected to FDE-MIMO equalization processing by the FDE-MIMO equalizer 910, and the subcarriers after the FDE-MIMO equalization processing are performed.
- Generate signals SUB1 to SUB5 S901.
- the subcarrier signals SUB1 to SUB5 after the FDE-MIMO equalization process are subjected to the TDE-MIMO equalization process by the TDE-MIMO equalizer 920, and the demodulatorable subcarrier signals SUB1 to SUB1 to the TDE-MIMO process are performed.
- Generate SUB5 (S902).
- the FDE-MIMO equalizer 910 becomes a 10 ⁇ 10 MIMO equalizer
- the TDE-MIMO equalizer 920 becomes a 10 ⁇ 10 MIMO equalizer. It becomes a 10 ⁇ 10 MIMO equalizer.
- the N ⁇ N MIMO equalizer is a MIMO equalizer in which the input signal ⁇ output signal is N ⁇ N, and the number of FIR filters (or filter coefficient multipliers) constituting the equalizer is N. ⁇ N MIMO equalizers.
- the FDE-MIMO equalizer has the feature that a steep and highly accurate filter can be realized with high circuit mounting efficiency, and the TDE-MIMO equalizer has the feature that crosstalk compensation can be performed dynamically and adaptively. There is.
- the circuit scale It is possible to suppress the increase as much as possible and to compensate for the crosstalk between the subcarriers while suppressing the deterioration of the characteristics of the MIMO equalizer.
- the MIMO equalizers are 10 ⁇ 10 FDE-MIMO equalizer and 10 ⁇ 10 TDE-MIMO equalizer. It becomes a vessel.
- each equalizer is composed of 100 FIR filters (or filter coefficient multipliers). Then, when the number of subcarrier signals to be multiplexed or the number of polarization multiplex increases, the number of FIR filters (or filter coefficient multipliers) of the MIMO equalizer increases in proportion to the increase, so that the circuit scale increases. There's a problem.
- FIG. 4 shows an outline of the optical signal processing circuit 1 according to the embodiment
- FIG. 5 shows an outline of the optical receiving device according to the embodiment.
- the optical signal processing circuit 1 includes an FDE-MIMO equalizer (frequency domain MIMO equalizer) 2 and a TDE-MIMO equalizer (time domain MIMO equalizer) 3.
- the FDE-MIMO equalizer 2 generates a continuous subcarrier signal after frequency domain MIMO equalization processing based on a continuous subcarrier signal including a target subcarrier signal in the received channel signal (optical multicarrier signal).
- the TDE-MIMO equalizer 3 generates a target subcarrier signal after the time domain MIMO equalization process based on the continuous subcarrier signal after the frequency domain MIMO equalization process.
- the FDE-MIMO equalizer 2 has (2N + 1) ⁇ ( 2N + 1) FDE-MIMO equalizer
- TDE-MIMO equalizer 3 is (2N + 1) ⁇ 1 TDE-MIMO equalizer.
- the number of inputs and the number of outputs of each equalizer are proportional to the number of polarization multiplexes. For example, when the channel signal is 3 subcarriers and 2 polarization multiplexing, it becomes a 6 ⁇ 6 FDE-MIMO equalizer and a 6 ⁇ 2 TDE-MIMO equalizer.
- the optical receiver 5 includes an optical receiver 4 and a plurality of optical signal processing circuits 1.
- the optical receiver 4 receives a channel signal in which a plurality of subcarrier signals are multiplexed.
- Each of the plurality of optical signal processing circuits 1 performs FDE-MIMO equalization processing and TDE-MIMO for continuous subcarrier signals including the target subcarrier signal selected for each optical signal processing circuit 1 in the received channel signal.
- the optical signal processing circuit 1a (first optical signal processing circuit) among the plurality of optical signal processing circuits 1 includes an FDE-MIMO equalizer 2a (first FDE-MIMO equalizer) and a TDE-MIMO.
- the FDE-MIMO equalizer 2a is based on the first continuous subcarrier signal including the first target subcarrier signal in the received channel signal, and the first continuous subcarrier after the frequency domain MIMO equalization process.
- a signal is generated, and the TDE-MIMO equalizer 3a generates a first target subcarrier signal after the time domain MIMO equalization process based on the first continuous subcarrier signal after the frequency domain MIMO equalization process.
- the optical signal processing circuit 1b among the plurality of optical signal processing circuits 1 includes an FDE-MIMO equalizer 2b (second FDE-MIMO equalizer) and a TDE-MIMO. It is equipped with an equalizer 3b (second TDE-MIMO equalizer).
- the FDE-MIMO equalizer 2b is based on the second continuous subcarrier signal including the second target subcarrier signal in the received channel signal, and the second continuous subcarrier after the frequency domain MIMO equalization process.
- a signal is generated, and the TDE-MIMO equalizer 3b generates a second target subcarrier signal after the time domain MIMO equalization process based on the second continuous subcarrier signal after the frequency domain MIMO equalization process.
- crosstalk between subcarriers is performed by equalizing the continuous subcarrier signal including the target subcarrier signal with the FDE-MIMO equalizer and the TDE-MIMO equalizer as the processing unit. While suppressing the circuit scale, the circuit scale can be further reduced as compared with the comparative example.
- FIG. 6 shows the configuration of the wavelength division multiplexing optical transmission system according to the present embodiment.
- the wavelength division multiplexing optical transmission system 6 according to the present embodiment includes an optical transmission device 10 and an optical reception device 20 that perform optical communication via an optical fiber transmission line 31 as in a comparative example. ing.
- the comparative example as described with reference to FIG. 2, five subcarrier signals are wavelength-multiplexed to generate one channel signal, and the subcarrier multiplexed signal is transmitted and received.
- the configuration of the hybrid MIMO equalizer on the receiving side is mainly different from that of the comparative example of FIG. 1 described above, and the other parts are the same as those of the comparative example.
- the hybrid MIMO equalizer 100 includes a plurality of FDE-MIMO equalizers 110 and a plurality of TDE-MIMO equalizers 120.
- FDE-MIMO equalizers 110-1 to 110-5 and TDE-MIMO equalizers 120-1 to 120-5 are provided.
- the optical receivers 22-1 to 22-5 input the subcarrier signals required by the FDE-MIMO equalizers 110-1 to 110-5 to the FDE-MIMO equalizers 110 to 110-5, respectively.
- the optical receivers 22-1 to 22-5 may be one optical receiver or an arbitrary number of optical receivers.
- the basic functions of the FDE-MIMO equalizer 110 and the TDE-MIMO equalizer 120 are the same as in the comparative example. That is, the FDE-MIMO equalizer 110 can compensate for the waveform distortion of static fluctuations with high accuracy, and can efficiently implement a steep filter characteristic in a circuit. Such an FDE-MIMO equalizer 110 has almost no fluctuation once the transmission path is determined, such as the influence of band narrowing due to the passage of the ROADM device 32, temperature fluctuations such as light source frequency offset, and aging deterioration. It is possible to highly accurately equalize asymmetric spectral stenosis and the like caused by very slow fluctuations, and effectively cancel static crosstalk between subcarriers.
- the FDE-MIMO equalizer 110 It is not possible to completely compensate for crosstalk between subcarriers only by static equalization by the FDE-MIMO equalizer 110 with a predetermined filter coefficient, and crosstalk fluctuations, waveform distortions, etc. due to polarization fluctuations, etc. Residual crosstalk and residual waveform distortion components due to various causes remain. Therefore, next, the output of the FDE-MIMO equalizer 110 is equalized using the TDE-MIMO equalizer 120.
- the TDE-MIMO equalizer 120 compensates for the residual dynamic variation waveform distortion. Since the TDE-MIMO equalizer 120 updates the tap coefficient in real time using an algorithm such as CMA, it is possible to adaptively equalize crosstalk and waveform distortion accompanied by fluctuations, and FDE. -Residual crosstalk and waveform distortion that could not be suppressed by the MIMO equalizer 110 alone are appropriately compensated, and the subcarrier signal can be suitably demodulated.
- the subcarrier signal group SUBG includes a target subcarrier signal and a subcarrier signal that causes crosstalk with respect to the target subcarrier signal.
- the subcarrier signal (crosstalk induced signal) that causes crosstalk is a signal that overlaps with the target subcarrier signal in the frequency domain, and is, for example, an adjacent subcarrier signal adjacent to the target subcarrier signal in the frequency domain.
- the subcarrier signal that causes crosstalk is not limited to the adjacent subcarrier signal, and may include a plurality of subcarrier signals.
- the subcarrier signal SUB3 is used as the target subcarrier signal among the subcarrier signals SUB1 to SUB5, the subcarrier signal SUB3 and the adjacent subcarrier signals SUB2 and SUB4 in the frequency domain overlap with each other. Crosstalk occurs.
- the subcarrier signals SUB1 and SUB5 further separated from the subcarrier signal SUB3 do not overlap with the subcarrier signal SUB3 in the frequency domain, crosstalk does not occur.
- the subcarrier signals SUB2 to SUB4 including the target subcarrier signal SUB3 and the adjacent subcarrier signals SUB2 and SUB4 can cause crosstalk.
- MIMO equalization processing is performed as SUBG.
- the target subcarrier signal is the subcarrier signal SUB1
- the subcarrier signals SUB1 and SUB2 including the target subcarrier signal SUB1 and the adjacent subcarrier signal SUB2 are designated as the subcarrier signal group SUBG in which crosstalk can occur, such as MIMO.
- the number of subcarrier signals included in the channel signal is not limited to 5, and may be any number, and the number of subcarrier signals of the subcarrier signal group SUBG is not limited to 3, and may be any number.
- the FDE-MIMO equalizers 110-1 to 110-5 and the TDE-MIMO equalizers 120-1 to 120-5 are intended for the subcarrier signals SUB1 to SUB5, respectively.
- MIMO processing is performed by using a subcarrier signal and a 3 subcarrier signal (or 2 subcarrier signals) including each subcarrier signal as a subcarrier signal group SUBG.
- the FDE-MIMO equalizer 110-1 and the TDE-MIMO equalizer 120-1 use the subcarrier signal SUB1 as the target subcarrier signal and the subcarrier signals SUB1 and SUB2 as the subcarrier signal group SUBG.
- the FDE-MIMO equalizer 110-2 and the TDE-MIMO equalizer 120-2 use the subcarrier signal SUB2 as the target subcarrier signal and the subcarrier signals SUB1 to SUB3 as the subcarrier signal group SUBG. The same applies to the FDE-MIMO equalizers 110-3 to 110-5 and the TDE-MIMO equalizers 120-1 to 120-5.
- FIG. 7 shows an outline of the MIMO equalization process according to the present embodiment.
- the subcarrier signal group SUBGs selected for the received subcarrier signals SUB1 to SUB5 are subjected to FDE by the FDE-MIMO equalizers 110-1 to 110-5.
- -MIMO equalization processing is performed to generate a subcarrier signal group SUBG after FDE-MIMO equalization processing (S101).
- the subcarrier signal group SUBG after the FDE-MIMO equalization process is subjected to the TDE-MIMO equalization process with the TDE-MIMO equalizers 120-1 to 120-5, respectively, and can be demodulated after the TDE-MIMO process.
- Subcarrier signals SUB1 to SUB5 are generated (S102).
- the FDE-MIMO equalizer 110-1 inputs the subcarrier signals SUB1 and SUB2 to perform the FDE-MIMO equalization process, and performs the FDE-MIMO equalization process to obtain the subcarrier signals SUB1 and SUB2 after the FDE-MIMO equalization process.
- the TDE-MIMO equalizer 120-1 inputs the subcarrier signals SUB1 and SUB2 after the FDE-MIMO equalization process, performs the TDE-MIMO equalization process, and outputs the subcarrier signal SUB1 after the TDE-MIMO process. To do.
- the FDE-MIMO equalizer 110-2 inputs the subcarrier signals SUB1 to SUB3, performs FDE-MIMO equalization processing, and outputs the subcarrier signals SUB1 to SUB3 after the FDE-MIMO equalization processing.
- the TDE-MIMO equalizer 120-2 inputs the subcarrier signals SUB1 to SUB3 after the FDE-MIMO equalization process, performs the TDE-MIMO equalization process, and outputs the subcarrier signal SUB2 after the TDE-MIMO process. To do. The same applies to the FDE-MIMO equalizers 110-3 to 110-5 and the TDE-MIMO equalizers 120-1 to 120-5.
- the FDE-MIMO equalizer 110 becomes a 6 ⁇ 6 MIMO equalizer
- the TDE-MIMO equalizer 120 Is a 6 ⁇ 2 MIMO equalizer.
- the polarization multiplex number of the subcarrier signal is not limited to 2, and may be any number.
- FIG. 8 shows a specific configuration of the FDE-MIMO equalizer of the comparative example.
- the FDE-MIMO equalizer 910 includes an FFT circuit 111, an FDE-MIMO core circuit 912, an IFFT circuit 113, and a filter coefficient multiplier 114.
- the FDE-MIMO equalizer 910 inputs the received subcarrier signal SUB [N] and the adjacent subcarrier signals SUB [N + 1] and SUB [N-1].
- the FDE-MIMO equalized subcarrier signal SUB [N] and the adjacent subcarrier signals SUB [N + 1] and SUB [N-1] are output.
- each subcarrier signal includes an X polarization component / Y polarization component.
- the FFT circuit 111 is provided with each subcarrier signal in the input time domain (Stinx [n + 1], Stiny [n + 1], Stinx [n], Stiny [n], Stinx [n-1], Stiny [n-1]). Is converted into a subcarrier signal in the frequency domain (Sfinx [n + 1], Sfiny [n + 1], Sfinx [n], Sfiny [n], Sfinx [n-1], Sfiny [n-1]), and the converted frequency.
- the subcarrier signal of the domain is output to the FDE-MIMO core circuit 912.
- the FDE-MIMO core circuit 912 performs FDE-MIMO equalization processing on each subcarrier signal in the frequency domain, and subcarrier signals in the frequency domain after crosstalk and band narrowing are compensated (FDE-MIMO equalization processing).
- Sfoutx [n + 1], Sfouty [n + 1], Sfoutx [n], Sfouty [n], Sfoutx [n-1], Sfouty [n-1]) are output to the IFFT circuit 113.
- the FDE-MIMO core circuit 912 compensates for waveform distortion due to crosstalk components and band narrowing with a 6 ⁇ 6 filter configuration. While TDE is composed of an FIR filter that realizes a convolution operation, FDE can be realized by a filter coefficient multiplier 114 that only multiplies filter characteristics (filter coefficients H11 to H66). That is, the FDE-MIMO equalizer 910 is a 6 ⁇ 6 FDE-MIMO equalizer composed of 6 ⁇ 6 filter coefficient multipliers 114. That is, the FDE-MIMO equalizer 910 includes 36 filter coefficient multipliers 114 with filter coefficients H11 to H66. As a result, the FDE-MIMO core circuit 912 with steep and highly accurate filter characteristics can be efficiently mounted.
- the filter coefficient multiplier 114 is arranged in a matrix of 6 rows ⁇ 6 columns.
- Filter coefficient multipliers 114 with filter coefficients H11 to H16 for inputting Sfinx [n + 1] are arranged in the first line (input line of Sfinx [n + 1]), and in the second line (input line of Sfiny [n + 1]).
- Filter coefficient multipliers 114 with filter coefficients H21 to H26 for inputting Sfiny [n + 1] are arranged. That is, the filter coefficient multiplier 114 of the filter coefficients H11 to H16 and H21 to H26 is a circuit for inputting the subcarrier signal SUB [N + 1].
- the filter coefficient multiplier 114 of the filter coefficients H31 to H36 and H41 to H46 is a circuit for inputting the subcarrier signal SUB [N].
- the filter coefficient multiplier 114 of the filter coefficients H51 to H56 and H61 to H66 is a circuit for inputting the subcarrier signal SUB [N-1].
- the filter coefficient multipliers 114 of the filter coefficients H11, H21, H31, H41, H51, and H61 for outputting Sfoutx [n + 1] are arranged, and the second column ( In the output sequence of Sfouty [n + 1]), filter coefficient multipliers 114 having filter coefficients H12, H22, H32, H42, H52, and H62 for outputting Sfouty [n + 1] are arranged.
- the filter coefficient multiplier 114 of the filter coefficients H11 to H12, H21 to H22, H31 to H32, H41 to H42, H51 to H52, and H61 to H62 is a circuit that outputs the subcarrier signal SUB [N + 1].
- the filter coefficient multipliers 114 of the filter coefficients H11 to H12, H21 to H22, H31 to H32, H41 to H42, H51 to H52, and H61 to H62 are subcarrier signals SUB [N + 1], SUB [N], and SUB. This is a circuit that inputs [N-1] and outputs a subcarrier signal SUB [N + 1].
- the filter coefficient multipliers 114 of the filter coefficients H13 to H14, H23 to H24, H33 to H34, H43 to H44, H53 to H54, and H63 to H64 have subcarrier signals SUB [N + 1], SUB [N], and SUB.
- This is a circuit that inputs [N-1] and outputs a subcarrier signal SUB [N].
- the filter coefficient multipliers 114 of the filter coefficients H15 to H16, H25 to H26, H35 to H36, H45 to H46, H55 to H56, and H65 to H66 are subcarrier signals SUB [N + 1], SUB [N], and SUB [N-. 1] is input, and the subcarrier signal SUB [N-1] is output.
- the subcarrier signals SUB [N] and SUB [N-1] are used, and the subcarrier after FDE-MIMO processing is used.
- the subcarrier signals SUB [N + 1] and SUB [N-1] are used to generate the subcarrier signal SUB [N] after FDE-MIMO processing. ..
- Sfoutx [n] Sfinx [n + 1] multiplied by the filter coefficient H13 of frequency + f 0 (the subcarrier adjacent to the positive side) and Sfiny [n + 1] multiplied by the filter coefficient H23 of frequency + f 0.
- the subcarrier signals SUB [N + 1] and SUB [N] are used to generate the subcarrier signal SUB [N-1] after FDE-MIMO processing. To do. For example, when Sfoutx [n-1] is generated, Sfinx [n + 1] multiplied by the filter coefficient H15 of the frequency + 2f 0 (two subcarriers adjacent to the positive side) is multiplied by the filter coefficient H25 of the frequency + 2f 0.
- each subcarrier signal that has been subjected to FDE-MIMO equalization processing by the FDE-MIMO core circuit 912 is again subjected to time domain subcarrier signals (Stoutx [n + 1], Stouty [n + 1], Stoutx [n], Stouty. It is converted into [n], Stoutx [n-1], Stouty [n-1]), and the subcarrier signal in the converted time domain is output to the subsequent TDE-MIMO equalizer 920.
- FIG. 9 shows a specific configuration of the FDE-MIMO equalizer according to the present embodiment.
- the FDE-MIMO equalizer 110 includes an FFT circuit 111, an FDE-MIMO core circuit 112, an IFFT circuit 113, and a filter coefficient multiplier 114, as in the comparative example.
- the subcarrier signal SUB [N] and the target subcarrier signal are used, and the subcarrier signals SUB [N-1], SUB [N] and SUB [N + 1] are used as the subcarrier signal SUBG.
- the FDE-MIMO equalizer 110 inputs the received subcarrier signal SUB [N] and the adjacent subcarrier signals SUB [N + 1] and SUB [N-1], and the FDE-MIMO equalized subcarrier signal SUB. [N] and adjacent subcarrier signals SUB [N + 1] and SUB [N-1] are output. Further, each subcarrier signal includes an X polarization component / Y polarization component.
- the configuration of the FDE-MIMO core circuit is different from that of the comparative example. That is, the FDE-MIMO core circuit 112 has a 6 ⁇ 6 filter configuration similar to that of the comparative example, and the FDE-MIMO equalizer 110 is a 6 ⁇ 6 FDE-MIMO equalizer, but in the present embodiment. , A part of the filter coefficient multiplier 114 constituting the FDE-MIMO equalizer is deleted with respect to the comparative example.
- the filter coefficient multiplier 114 that is not used in the calculation is deleted. Thereby, in this example, eight filter coefficient multipliers 114 can be reduced as compared with the comparative example.
- the FDE-MIMO core circuit 112 includes only 28 filter coefficient multipliers H11 to H14, H21 to H24, H31 to H36, H41 to H46, H53 to H56, and H63 to H66. ..
- the filter coefficient multiplier 114 of the filter coefficients H11 to H14 and H21 to H24 becomes a circuit for inputting the subcarrier signal SUB [N + 1].
- the filter coefficient multiplier 114 of the filter coefficients H31 to H36 and H41 to H46 is a circuit for inputting the subcarrier signal SUB [N] as in the comparative example.
- the filter coefficient multiplier 114 of the filter coefficients H53 to H56 and H63 to H66 serves as a circuit for inputting the subcarrier signal SUB [N-1].
- the filter coefficient multipliers 114 having filter coefficients H11 to H12, H21 to H22, H31 to H32, and H41 to H42 are subcarrier signal SUB [N + 1] (first subcarrier signal) and subcarrier signal SUB [N]. It is a circuit (first FDE-MIMO equalization circuit) that inputs (second subcarrier signal) and outputs subcarrier signal SUB [N + 1].
- the filter coefficient multipliers 114 of the filter coefficients H13 to H14, H23 to H24, H33 to H34, H43 to H44, H53 to H54, and H63 to H64 are subcarrier signals SUB [N + 1] (first), as in the comparative example.
- Subcarrier signal), subcarrier signal SUB [N] (second subcarrier signal) and subcarrier signal SUB [N-1] (third subcarrier signal) are input, and the subcarrier signal SUB [N] is input. It becomes an output circuit (second FDE-MIMO equalization circuit).
- the filter coefficient multipliers 114 having filter coefficients H35 to H36, H45 to H46, H55 to H56, and H65 to H66 are subcarrier signal SUB [N] (second subcarrier signal) and subcarrier signal SUB [N-1]. It is a circuit (second FDE-MIMO equalization circuit) that inputs (third subcarrier signal) and outputs subcarrier signal SUB [N-1].
- the filter coefficient multiplier 114 (filter coefficients H13, H14, H23, H24, H33, H34, H43, H44, H53, H54, H63, H64) used for the calculation of the subcarrier signal SUB [N] is not deleted. .. That is, as in the comparative example, by adding the subcarrier signals SUB [N + 1] and SUB [N-1] to the subcarrier signal SUB [N], the subcarrier signal SUB [N] after FDE-MIMO processing can be obtained. Generate. As a result, MIMO equalization processing can be performed using the subcarrier signals SUB [N + 1] and SUB [N-1] that are vertically adjacent to the subcarrier signal SUB [N] in the frequency domain.
- the filter coefficient multiplier 114 (filter coefficients H11, H12, H21, H22, H31, H32, H41, H42) used for the calculation of the subcarrier signal SUB [N + 1] is left, and the subcarrier signal shown in the region A1 is left.
- the filter coefficient multiplier 114 (filter coefficients H51, H52, H61, H62) that is not used in the calculation of SUB [N + 1] is deleted.
- the subcarrier signal SUB [N + 1] after the FDE-MIMO processing is generated by adding the subcarrier signal SUB [N] to the subcarrier signal SUB [N + 1].
- MIMO equalization processing can be performed using only the subcarrier signal SUB [N] adjacent to the lower side in the frequency domain with respect to the subcarrier signal SUB [N + 1].
- the filter coefficient multiplier 114 (filter coefficients H35, H36, H45, H46, H55, H56, H65, H66) used for the calculation of the subcarrier signal SUB [N-1] is left, and the sub shown in the area A2 is left.
- the filter coefficient multiplier 114 (filter coefficients H15, H16, H25, H26) that is not used in the calculation of the carrier signal SUB [N-1] is deleted.
- the subcarrier signal SUB [N-1] after the FDE-MIMO processing is generated by adding the subcarrier signal SUB [N] to the subcarrier signal SUB [N-1].
- MIMO equalization processing can be performed using only the subcarrier signal SUB [N] adjacent to the upper side of the subcarrier signal SUB [N-1] in the frequency domain.
- Each filter coefficient of the filter coefficient multiplier 114 differs depending on the transmission path and the characteristics of the system, but since it is static, the method of training at system startup and the characteristics of each transmission path / system in advance are determined. A method of evaluating and pre-calculating the optimum filter coefficient can be considered.
- the actual filter coefficient may be updated.
- a known pilot tone or training pattern may be embedded in the signal itself to determine the filter coefficient, including static and quasi-static fluctuations.
- FIG. 10 shows a specific configuration of the TDE-MIMO equalizer of the comparative example.
- the TDE-MIMO equalizer 920 includes a TDE-MIMO core equalizer 921, a filter coefficient update unit 122, and an FIR filter 123.
- the TDE-MIMO equalizer 920 includes a subcarrier signal SUB [N] and an adjacent subcarrier signal SUB that have been subjected to FDE-MIMO equalization processing by the FDE-MIMO equalizer 910.
- each subcarrier signal includes an X polarization component / Y polarization component.
- each subcarrier signal in the input time domain (Stinx [n + 1], Stiny [n + 1], Stinx [n], Stiny [n], Stinx [n-1], Stiny [ TDE-MIMO equalization processing is performed on n-1]), and subcarrier signals (Sfoutx [n + 1], Sfouty [n + 1], Sfoutx [n], Sfouty [n] in the time domain after the TDE-MIMO equalization processing are performed. ], Sfoutx [n-1], Sfouty [n-1]).
- the TDE-MIMO core equalizer 921 is provided with 6 ⁇ 6 time domain FIR filters 123 in order to suitably separate the six time domain signals. That is, the TDE-MIMO equalizer 920 is a 6 ⁇ 6 TDE-MIMO equalizer composed of 6 ⁇ 6 FIR filters 123. That is, the TDE-MIMO core equalizer 921 includes an FIR filter 123 having 36 tap coefficients W11 to W66.
- the TDE-MIMO equalizer 920 outputs weighted additions of components between subcarriers.
- the tap coefficients (W11 to W66) of each FIR filter 123 are set to tap coefficients of about 10 to 20 taps, respectively, from the viewpoint of circuit scale and dynamic coefficient update.
- the FIR filters 123 are arranged in a matrix of 6 rows ⁇ 6 columns.
- FIR filters 123 with tap coefficients W11 to W16 for inputting Stinx [n + 1] are arranged in the first line (input line of Stinx [n + 1]), and Stiny [is input in the second line (input line of Stiny [n + 1]).
- FIR filters 123 having tap coefficients W21 to W26 for inputting [n + 1] are arranged. That is, the FIR filters 123 having tap coefficients W11 to W16 and W21 to W26 are circuits for inputting the subcarrier signal SUB [N + 1].
- the FIR filters 123 having tap coefficients W31 to W36 and W41 to W46 are circuits for inputting the subcarrier signal SUB [N].
- the FIR filters 123 having tap coefficients W51 to H56 and W61 to H66 are circuits for inputting the subcarrier signal SUB [N-1].
- FIR filters 123 having tap coefficients W11, W21, W31, W41, W51, and W61 for outputting Stoutx [n + 1] are arranged, and the FIR filters 123 of the tap coefficients W11, W21, W31, W41, W51, and W61 are arranged, and the FIR filters 123 are arranged in the second column (Stouty [n + 1]
- An FIR filter 123 having tap coefficients W12, W22, W32, W42, W52, and W62 for outputting Stouty [n + 1] is arranged in the output string of n + 1].
- the FIR filters 123 having tap coefficients W11 to W12, W21 to W22, W31 to W32, W41 to W42, W51 to W52, and W61 to W62 are circuits that output the subcarrier signal SUB [N + 1].
- the FIR filters 123 having tap coefficients W11 to W12, W21 to W22, W31 to W32, W41 to W42, W51 to W52, and W61 to W62 have subcarrier signals SUB [N + 1], SUB [N], and SUB [N]. -1] is input and the subcarrier signal SUB [N + 1] is output.
- the FIR filters 123 having tap coefficients W13 to W14, W23 to W24, W33 to W34, W43 to W44, W53 to W54, and W63 to W64 have subcarrier signals SUB [N + 1], SUB [N], and SUB [N]. -1] is input, and the subcarrier signal SUB [N] is output.
- the FIR filters 123 having tap coefficients W15 to W16, W25 to W26, W35 to W36, W45 to W46, W55 to W56, and W65 to W66 are subcarrier signals SUB [N + 1], SUB [N], and SUB [N-1]. Is a circuit that inputs and outputs a subcarrier signal SUB [N-1].
- the subcarrier signals SUB [N] and SUB [N-1] are used, and the subcarrier after TDE-MIMO processing is used.
- Stinx [n] FIR-filtered with a tap coefficient W31 of the carrier
- Stiny [n] FIR-filtered with a tap coefficient W41 of frequency -f 0
- frequency -2f 0 two subcarriers next to each other on the negative side.
- the FIR-filtered Stinx [n-1] with the tap coefficient W51 and the FIR-filtered Stiny [n-1] with the tap coefficient W61 of frequency -2f 0 are added.
- the subcarrier signals SUB [N + 1] and SUB [N-1] are used to generate the subcarrier signal SUB [N] after TDE-MIMO processing. ..
- FIR filter processing is performed with Tinx [n + 1] that has been FIR-filtered with a tap coefficient W13 of frequency + f 0 (the subcarrier adjacent to the positive side) and Stinx [n + 1] that has been FIR filtered with a tap coefficient W23 of frequency + f 0.
- Stiny [n + 1] FIR-filtered Stinx [n] with tap coefficient W33, FIR-filtered Stiny [n] with tap coefficient W43, and tap coefficient of frequency -f 0 (subcarrier next to the negative side). and Stinx [n-1] that FIR filtering with W53, adding the Stiny [n-1] that FIR filter with tap coefficients W63 frequency -f 0.
- the subcarrier signals SUB [N + 1] and SUB [N] are used to generate the subcarrier signal SUB [N-1] after TDE-MIMO processing.
- the tap coefficient W25 of frequency + 2f 0 (subcarriers adjacent to the two on the positive side) is used for FIR-filtered Stinx [n + 1] and the tap coefficient W25 of frequency + 2f 0.
- FIR-filtered Stiny [n + 1] FIR-filtered Stinx [n] with a tap coefficient W35 of frequency + f 0 (subcarrier next to the positive side), and FIR-filtered Stiny with a tap coefficient W45 of frequency + f 0. [N]
- Stinx [n-1] that has been FIR-filtered with the tap coefficient W55, and Stiny [n-1] that has been FIR-filtered with the tap coefficient W65 are added.
- FIG. 11 shows a specific configuration of the TDE-MIMO equalizer according to the present embodiment.
- the TDE-MIMO equalizer 120 includes a TDE-MIMO core equalizer 121, a filter coefficient update unit 122, and an FIR filter 123, as in the comparative example.
- the subcarrier signal SUB [N] and the target subcarrier signal are used, and the subcarrier signals SUB [N-1], SUB [N] and SUB [N + 1] are used. Let it be a subcarrier signal SUBG.
- the TDE-MIMO equalizer 120 inputs the subcarrier signal SUB [N] processed by the FDE-MIMO equalizer 110 and the adjacent subcarrier signals SUB [N + 1] and SUB [N-1]. Then, the FDE-MIMO equalized subcarrier signal SUB [N] is output. Further, each subcarrier signal includes an X polarization component / Y polarization component.
- the configuration of the TDE-MIMO core equalizer is different from that of the comparative example. That is, the TDE-MIMO core equalizer 121 has a 6 ⁇ 2 filter configuration unlike the comparative example, and the TDE-MIMO equalizer 120 is a 6 ⁇ 2 FDE-MIMO equalizer.
- each subcarrier signal in the input time domain (Stinx [n + 1], Stiny [n + 1], Stinx [n], Stiny [n], Stinx [n-1], TDE-MIMO equalization processing is performed on Stiny [n-1]), and subcarrier signals (Sfoutx [n], Sfouty [n]) in the time domain after the TDE-MIMO equalization processing are output. Therefore, in the present embodiment, some FIR filters 123 constituting the TDE-MIMO equalizer are deleted from the comparative example.
- each subcarrier signal is processed in parallel by the FDE-MIMO equalizer and the TDE-MIMO equalizer. Then, since the output of the TDE-MIMO equalizer 120 is only the target subcarrier signal, in this example, the FIR filter 123 other than that used for the output of the central subcarrier signal is deleted. Thereby, in this example, 24 FIR filters 123 can be reduced as compared with the comparative example.
- the TDE-MIMO core equalizer 121 includes only the FIR filters 123 having 12 tap coefficients W13 to W14, W23 to W24, W33 to W34, W43 to W44, W53 to W54, and W63 to W64. ..
- the FIR filters 123 having tap coefficients W13 to W14 and H23 to H24 serve as a circuit for inputting the subcarrier signal SUB [N + 1].
- the FIR filters 123 having tap coefficients W33 to H34 and H43 to H44 serve as a circuit for inputting the subcarrier signal SUB [N].
- the FIR filter 123 having tap coefficients W53 to H54 and H63 to H64 serves as a circuit for inputting the subcarrier signal SUB [N-1].
- the FIR filters 123 having tap coefficients W13 to W14, W23 to W24, W33 to W34, W43 to W44, W53 to W54, and W63 to W64 are subcarrier signals SUB [N + 1] (first), as in the comparative example.
- Subcarrier signal), subcarrier signal SUB [N] (second subcarrier signal) and subcarrier signal SUB [N-1] (third subcarrier signal) are input, and the subcarrier signal SUB [N] is input. It becomes an output circuit (TDE-MIMO equalization circuit).
- the FIR filters 123 (tap coefficients W13, W14, W23, W24, W33, W34, W43, W44, W53, W54, W63, W64) used for the calculation of the subcarrier signal SUB [N] are not deleted. That is, by adding the subcarrier signals SUB [N + 1] and SUB [N-1] to the subcarrier signal SUB [N], the subcarrier signal SUB [N] after the TDE-MIMO processing is generated.
- the FIR filters (tap coefficients W11, W12, W21, W22, W31, W32, W41, W42, W51, W52, W61, W62), which are not used in the calculation of the subcarrier signal SUB [N], are shown in the area A3.
- the FIR filters (tap coefficients W15, W16, W25, W26, W35, W36, W45, W46, W55, W56, W65, W66) shown in region A4 are deleted.
- MIMO equalization processing can be performed using the subcarrier signals SUB [N + 1] and SUB [N-1] that are vertically adjacent to the subcarrier signal SUB [N] in the frequency domain. it can.
- each FIR filter 123 is sequentially updated by the filter coefficient updating unit 122 so as to be the optimum coefficient while calculating the error using a blind equalization algorithm such as CMA.
- the tap coefficients are optimized so that the crosstalk generated between the subcarriers is canceled with each other, so that the original subcarrier signals can be demodulated from the overlapping subcarrier signals on the frequency axis. ..
- the present embodiment paying attention to the fact that the adjacent subcarriers dominate the influence of crosstalk in the optical receiving device of the optical transmission system that performs optical transmission by wavelength division multiplexing of the subcarrier signals.
- MIMO equalization processing for each target subcarrier signal it is possible to reduce the circuit scale of the MIMO equalizer.
- the plurality of FDE-MIMO equalizers and the plurality of TDE-MIMO equalizers of the hybrid MIMO equalizer receive each subcarrier signal group including the target subcarrier signal and the adjacent subcarrier signal as an input for each subcarrier signal group. Perform MIMO equalization processing.
- the FDE-MIMO equalizer is, for example, a 6 ⁇ 6 FDE-MIMO equalizer, but the circuit scale can be reduced by deleting the linear equalization process between subcarriers to which the influence of crosstalk is small.
- the TDE-MIMO equalizer inputs a subcarrier signal group including the target subcarrier and the adjacent subcarrier and outputs only the target subcarrier, for example, a 6 ⁇ 2 TDE-MIMO equalizer performs linear equalization processing. Can be performed, and the circuit scale can be reduced.
- FIG. 12 is a graph showing a comparative example and the circuit scale of the MIMO equalizer of the present embodiment.
- the required number of filters (number of filter coefficient multipliers) of the FDE-MIMO equalizer is (2N) 2 in the comparative example, and N ⁇ 28 in the present embodiment.
- the required number of filters for the TDE-MIMO equalizer is (2N) 2 in the comparative example, and N ⁇ 12 in the present embodiment.
- the number of filters increases exponentially as the number of subcarriers increases, but in the present embodiment, the number of filters increases only at a constant rate even if the number of subcarriers increases. Does not increase. Therefore, as the number of subcarriers increases, the number of filters can be reduced as compared with the comparative example. In this example, the number of filters can be reduced by 37.5% in the case of 8 subcarriers.
- the number of filters increases with the square of the number of subcarriers as described above. Therefore, the wiring inside the circuit increases as the number of subcarriers increases. As the circuit becomes complicated, the circuit scale further increases as the circuit is mounted.
- the number of filters increases in proportion to the number of subcarriers, even if the number of subcarriers increases, the number of independent circuits for each subcarrier simply increases, so that the circuit is mounted.
- the circuit scale that increases with this is fixed. That is, in the present embodiment, since it can be realized only by arranging a plurality of MIMO equalizers for each subcarrier, the constraint condition of circuit mounting can be relaxed (so-called scale-out).
- 13 and 14 show a specific configuration of the FDE-MIMO equalizer according to the present embodiment.
- 13 and 14 are, for example, configuration examples of the FDE-MIMO equalizer 110-1 or 110-5.
- the basic configuration is the same as the FDE-MIMO equalizer 110 described in the first embodiment.
- the FDE-MIMO equalizer 110-1 or 110-5 processes the subcarrier signal at the frequency end of the channel signal, it has 2 subcarrier inputs x 2 subcarrier outputs.
- the FDE-MIMO equalizer 110-1 inputs the subcarrier signals SUB1 and SUB2, and outputs the subcarrier signals SUB1 and SUB2 after the FDE-MIMO equalization process.
- the FDE-MIMO equalizer 110-5 inputs the subcarrier signals SUB4 and SUB5, and outputs the subcarrier signals SUB4 and SUB5 after the FDE-MIMO equalization process.
- the filter coefficient multiplier 114 of the unused subcarrier signal is controlled (set) so as not to operate. For example, the circuit operation of the corresponding filter coefficient multiplier 114 may be stopped, or the filter coefficient of the filter coefficient multiplier 114 may be set to zero.
- the calculation of the subcarrier signal SUB [N-1] shown in the area A5 is performed. Stop the circuit of the filter coefficient multiplier 114 (filter coefficients H53, H54, H55, H56, H63, H64, H65, H66), or set the filter coefficient to zero. Further, the circuit of the filter coefficient multiplier 114 (filter coefficients H35, H36, H45, H46) into which the subcarrier signal SUB [N] is input may be stopped, or the filter coefficient may be set to zero.
- circuit stop and the zero setting of the filter coefficient may be fixed in advance or dynamically set according to the subcarrier signal.
- a monitor circuit for monitoring the input signal of the FDE-MIMO equalizer may be provided to control the circuit operation of the subcarrier in which the signal is not detected according to the spectrum of the monitored input signal.
- the circuit operation may be controlled as shown in FIG. 13, or the unused circuit may be deleted as shown in FIG.
- the filter coefficient multiplier 114 (filter coefficients H53, H54, H55, H56, H63, H64, H65, H66) of the unused subcarrier signal shown in the area A5 is deleted. That is, the FDE-MIMO core circuit 112 may include only 20 filter coefficient multipliers 114 with filter coefficients H11 to H14, H21 to H24, H31 to H36, and H41 to H46. Further, the filter coefficient multiplier 114 (filter coefficients H35, H36, H45, H46) into which the subcarrier signal SUB [N] is input may be deleted. That is, the FDE-MIMO core circuit 112 may include only 16 filter coefficient multipliers 114 with filter coefficients H11 to H14, H21 to H24, H31 to H34, and H41 to H44.
- 15 and 16 show a specific configuration of the TDE-MIMO equalizer according to the present embodiment.
- 15 and 16 are, for example, configuration examples of the TDE-MIMO equalizer 120-1 or 120-5.
- the basic configuration is the same as the TDE-MIMO equalizer 120 described in the first embodiment.
- the TDE-MIMO equalizer 120-1 or 120-5 processes the subcarrier signal at the frequency end of the channel signal, it has 2 subcarrier inputs x 1 subcarrier output.
- the TDE-MIMO equalizer 120-1 inputs the subcarrier signals SUB1 and SUB2, and outputs the subcarrier signal SUB1 after the TDE-MIMO equalization process.
- the TDE-MIMO equalizer 120-5 inputs the subcarrier signals SUB4 and SUB5, and outputs the subcarrier signal SUB5 after the TDE-MIMO equalization process.
- the output of the TDE-MIMO equalizer becomes an unstable signal. Therefore, in the example of FIG. 15, when there is an unused subcarrier signal (when a certain subcarrier signal is not input), the FIR filter 123 of the unused subcarrier signal is controlled (set) so as not to operate. For example, the circuit operation of the corresponding FIR filter 123 may be stopped, or the tap coefficient of the FIR filter 123 may be set to zero.
- the calculation of the subcarrier signal SUB [N-1] shown in the region A6 is performed. Stop the circuit of the FIR filter 123 (tap coefficient W53, W54, W63, W64), or set the tap coefficient to zero.
- the circuit stop and the zero setting of the tap coefficient may be fixed in advance and dynamically set according to the subcarrier signal, as in the case of the FDE-MIMO equalizer of the present embodiment. May be good.
- the circuit operation may be controlled as shown in FIG. 15, or the unused circuit may be deleted as shown in FIG. That is, in the example of FIG. 16, the FIR filter 123 (tap coefficients W53, W54, W63, W64) of the unused subcarrier signal shown in the area A6 is deleted. That is, the TDE-MIMO core equalizer 121 may include only the FIR filters 123 having eight tap coefficients W13 to W14, W23 to W24, W33 to W34, and W43 to W44.
- the operation of the unused circuit may be controlled. This makes it possible to stabilize the circuit operation while using the same circuit configuration as other FDE-MIMO equalizers and TDE-MIMO equalizers. Further, in the FDE-MIMO equalizer and the TDE-MIMO equalizer, unused circuits may be further deleted. As a result, the circuit scale can be further reduced.
- circuit described as a comparative example and the circuit described as an embodiment may be combined.
- the FDE-MIMO equalizer of the comparative example and the TDE-MIMO equalizer according to the embodiment may be combined.
- Appendix A2 A wavelength division multiplexing optical transmission method characterized in that a subcarrier signal is used as a polarization multiplexing signal in Appendix A1 and the order of MIMO equalization is doubled by the number of polarization multiplexing.
- Appendix A3 A wavelength division multiplexing transmission method characterized in that the number N of subcarrier signals to be multiplexed in Appendix A1 or Appendix A2 is 1.
- N is a natural number
- (Appendix B1) A frequency domain MIMO equalizer that generates the continuous subcarrier signal after frequency domain MIMO equalization processing based on a continuous subcarrier signal including a target subcarrier signal in the received optical multicarrier signal.
- a time domain MIMO equalizer that generates the target subcarrier signal after the time domain MIMO equalization process based on the continuous subcarrier signal after the frequency domain MIMO equalization process.
- An optical signal processing circuit (Appendix B2)
- the continuous subcarrier signal includes N (N is a natural number) subcarrier signals that are continuously multiplexed with frequencies above and below the target subcarrier signal.
- the input x output of the frequency domain MIMO equalizer is (2N + 1) x (2N + 1).
- the input ⁇ output of the time domain MIMO equalizer is (2N + 1) ⁇ 1.
- the optical signal processing circuit according to Appendix B1. (Appendix B3) The N subcarrier signals are polarized and multiplexed with M polarized signals, respectively.
- the input ⁇ output of the frequency domain MIMO equalizer is M (2N + 1) ⁇ M (2N + 1).
- the input ⁇ output of the time domain MIMO equalizer is M (2N + 1) ⁇ M.
- the N is 1.
- the continuous subcarrier signal includes a subcarrier signal that causes crosstalk with respect to the target subcarrier signal.
- the optical signal processing circuit includes any one of Appendix B1 to B4.
- the continuous subcarrier signal includes a subcarrier signal that overlaps with the target subcarrier signal in the frequency domain.
- the optical signal processing circuit according to any one of Appendix B1 to B5.
- the continuous subcarrier signal includes a subcarrier signal adjacent to the target subcarrier signal in the frequency domain.
- the optical signal processing circuit according to any one of Appendix B1 to B6.
- the continuous subcarrier signal includes first to third subcarrier signals that are continuous on the frequency axis.
- the frequency domain MIMO equalizer is A first frequency domain processing circuit that generates the first subcarrier signal after frequency domain MIMO equalization processing based on the first subcarrier signal and the second subcarrier signal.
- a second frequency that generates the second subcarrier signal after frequency domain MIMO equalization processing based on the first subcarrier signal, the second subcarrier signal, and the third subcarrier signal.
- Domain processing circuit and A third frequency domain processing circuit that generates the third subcarrier signal after frequency domain MIMO equalization processing based on the second subcarrier signal and the third subcarrier signal.
- the optical signal processing circuit according to any one of Appendix B1 to B7.
- the frequency domain MIMO equalizer controls the third frequency domain processing circuit so that it does not operate when the third subcarrier signal is not input.
- the optical signal processing circuit according to Appendix B8. (Appendix B10)
- the frequency domain MIMO equalizer stops the operation of the third frequency domain processing circuit, or sets the arithmetic coefficient of the third frequency domain processing circuit to zero.
- the optical signal processing circuit according to Appendix B9. (Appendix B11)
- the continuous subcarrier signal includes first to third subcarrier signals that are continuous on the frequency axis.
- the time domain MIMO equalizer is based on the first subcarrier signal, the second subcarrier signal, and the third subcarrier signal, and the second sub carrier after the time domain MIMO equalization process.
- a time domain processing circuit that generates a carrier signal is provided.
- the optical signal processing circuit according to any one of Appendix B1 to B7. (Appendix B12)
- the time domain MIMO equalizer controls the time domain processing circuit that calculates the third subcarrier signal so as not to operate when the third subcarrier signal is not input.
- the optical signal processing circuit according to Appendix B11.
- the frequency domain MIMO equalizer stops the operation of the circuit that calculates the third subcarrier signal, or calculates the third subcarrier signal.
- the optical signal processing circuit according to Appendix B12. (Appendix B14) It is provided with an optical receiver that receives an optical multicarrier signal, a plurality of frequency domain MIMO equalizers, and a plurality of time domain MIMO equalizers. Each of the plurality of frequency domain MIMO equalizers has a frequency based on a continuous subcarrier signal including a target subcarrier signal selected for each frequency domain MIMO equalizer in the received optical multicarrier signal.
- the above-mentioned continuous subcarrier signal after the region MIMO equalization processing is generated, and Each of the plurality of time domain MIMO equalizers generates the target subcarrier signal after the time domain MIMO equalization process based on the continuous subcarrier signal after the frequency domain MIMO equalization process.
- Optical receiver. (Appendix B15)
- the continuous subcarrier signal includes N (N is a natural number) subcarrier signals that are continuously multiplexed with frequencies above and below the target subcarrier signal.
- the input ⁇ output of the plurality of frequency domain MIMO equalizers is (2N + 1) ⁇ (2N + 1).
- the input ⁇ output of the plurality of time domain MIMO equalizers is (2N + 1) ⁇ 1.
- the continuous subcarrier signal includes N (N is a natural number) subcarrier signals that are continuously multiplexed with frequencies above and below the target subcarrier signal.
- the input x output of the frequency domain MIMO equalization process is (2N + 1) x (2N + 1).
- the input ⁇ output of the time domain MIMO equalization processing is (2N + 1) ⁇ 1.
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Abstract
Description
まず、非特許文献1の技術について検討したところ、発明者らは、非特許文献1では次のような点で十分ではないことを見出した。例えば、ROADM(Reconfigurable Optical Add/Drop Multiplexer)機器を用いた伝送システムのようにフレキシブルな伝送経路選択を可能とする光伝送システムにおいては、複数のサブキャリアを多重して構成された信号を一つのチャネルとして定義し、チャネル単位で経路制御するのが一般的である。
次に、上記非特許文献1の課題を解決するための比較例について検討する。図1は、比較例の波長多重光伝送システムの構成を示しており、図2は、比較例の波長多重光伝送システムで送受信するサブキャリア多重信号の構成を示している。
図4は、実施の形態に係る光信号処理回路1の概要を示し、図5は、実施の形態に係る光受信装置の概要を示している。
以下、図面を参照して実施の形態1について説明する。図6は、本実施の形態に係る波長多重光伝送システムの構成を示している。図6に示すように、本実施の形態に係る波長多重光伝送システム6は、比較例と同様に、光ファイバ伝送路31を介して光通信を行う光送信装置10と光受信装置20を備えている。また、ここでは、比較例と同様、図2で説明したように、5つのサブキャリア信号を波長多重して1つのチャネル信号を生成し、サブキャリア多重信号を送受信する。
図8は、比較例のFDE-MIMO等化器の具体的な構成を示している。図8に示すように、FDE-MIMO等化器910は、FFT回路111、FDE-MIMOコア回路912、IFFT回路113、フィルタ係数乗算器114を含む。ここでは、本実施の形態と比較するため、FDE-MIMO等化器910は、受信したサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を入力し、FDE-MIMO等化処理されたサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を出力する。また、各サブキャリア信号は、X偏波成分/Y偏波成分を含んでいる。
図9は、本実施の形態に係るFDE-MIMO等化器の具体的な構成を示している。図9に示すように、FDE-MIMO等化器110は、比較例と同様に、FFT回路111、FDE-MIMOコア回路112、IFFT回路113、フィルタ係数乗算器114を含む。この例では、サブキャリア信号SUB[N]と対象サブキャリア信号とし、サブキャリア信号SUB[N-1]、SUB[N]及びSUB[N+1]をサブキャリア信号SUBGとする。FDE-MIMO等化器110は、受信したサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を入力し、FDE-MIMO等化処理されたサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を出力する。また、各サブキャリア信号は、X偏波成分/Y偏波成分を含んでいる。
図10は、比較例のTDE-MIMO等化器の具体的な構成を示している。図10に示すように、TDE-MIMO等化器920は、TDE-MIMOコア等化器921、フィルタ係数更新部122、FIRフィルタ123を含む。ここでは、本実施の形態と比較するため、TDE-MIMO等化器920は、FDE-MIMO等化器910によりFDE-MIMO等化処理されたサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を入力し、TDE-MIMO等化処理されたサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を出力する。また、各サブキャリア信号は、X偏波成分/Y偏波成分を含んでいる。
図11は、本実施の形態に係るTDE-MIMO等化器の具体的な構成を示している。図11に示すように、TDE-MIMO等化器120は、比較例と同様に、TDE-MIMOコア等化器121、フィルタ係数更新部122、FIRフィルタ123を含む。この例では、上記のFDE-MIMO等化器110と同様、サブキャリア信号SUB[N]と対象サブキャリア信号とし、サブキャリア信号SUB[N-1]、SUB[N]及びSUB[N+1]をサブキャリア信号SUBGとする。TDE-MIMO等化器120は、FDE-MIMO等化器110によりFDE-MIMO等化処理されたサブキャリア信号SUB[N]と隣接サブキャリア信号SUB[N+1]及びSUB[N-1]を入力し、FDE-MIMO等化処理されたサブキャリア信号SUB[N]を出力する。また、各サブキャリア信号は、X偏波成分/Y偏波成分を含んでいる。
実施の形態2では、実施の形態1に係る光受信装置のハイブリッド等化器の他の構成例として、チャネル信号の周波数領域端部のサブキャリア信号を処理するハイブリッド等化器の構成例について説明する。
図13及び図14は、本実施の形態に係るFDE-MIMO等化器の具体的な構成を示している。図13及び図14は、例えば、FDE-MIMO等化器110-1または110-5の構成例である。基本的な構成は、実施の形態1で説明したFDE-MIMO等化器110と同様である。
図15及び図16は、本実施の形態に係るTDE-MIMO等化器の具体的な構成を示している。図15及び図16は、例えば、TDE-MIMO等化器120-1または120-5の構成例である。基本的な構成は、実施の形態1で説明したTDE-MIMO等化器120と同様である。
(付記A1)
周波数軸上に多重するサブキャリア信号を単一偏波信号とし、対象のサブキャリア信号の上下の周波数にそれぞれ連続して多重されるサブキャリア信号数をN(Nは自然数)とした場合において、
(2N+1)×(2N+1)周波数領域MIMO等化と(2N+1)×1時間領域MIMO等化を逐次的に受信処理を行う波長多重光伝送方式。
(付記A2)
付記A1においてサブキャリア信号を偏波多重信号とし、MIMO等化の次数を偏波多重数分だけ倍増することを特徴とする波長多重光伝送方式。
(付記A3)
付記A1または付記A2において多重されるサブキャリア信号数Nを1とすることを特徴とする波長多重伝送方式。
(付記A4)
周波数軸上に多重するサブキャリア信号を単一偏波信号とし、対象のサブキャリア信号の上下の周波数にそれぞれ連続して多重されるサブキャリア信号数をN(Nは自然数)とした場合において、
(2N+1)×(2N+1)周波数領域MIMO等化器と(2N+1)×1時間領域MIMO等化器を結合して線形等化を行う波長多重光伝送方式の受信装置。
(付記A5)
付記A4においてサブキャリア信号を偏波多重信号とし、MIMO等化の次数を偏波多重数分だけ倍増することを特徴とする波長多重光伝送方式の受信装置。
(付記A6)
付記A4またはA5において多重されるサブキャリア信号数Nを1とすることを特徴とする波長多重伝送方式の受信装置。
(付記B1)
受信される光マルチキャリア信号内の対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記連続サブキャリア信号を生成する周波数領域MIMO等化器と、
前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する時間領域MIMO等化器と、
を備える、光信号処理回路。
(付記B2)
前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記周波数領域MIMO等化器の入力×出力は、(2N+1)×(2N+1)であり、
前記時間領域MIMO等化器の入力×出力は、(2N+1)×1である、
付記B1に記載の光信号処理回路。
(付記B3)
前記N個のサブキャリア信号は、それぞれM個の偏波信号に偏波多重されており、
前記周波数領域MIMO等化器の入力×出力は、M(2N+1)×M(2N+1)であり、
前記時間領域MIMO等化器の入力×出力は、M(2N+1)×Mである、
付記B2に記載の光信号処理回路。
(付記B4)
前記Nは1である、
付記B2又はB3に記載の光信号処理回路。
(付記B5)
前記連続サブキャリア信号は、前記対象サブキャリア信号に対してクロストークを生じさせるサブキャリア信号を含む、
付記B1乃至B4のいずれか一項に記載の光信号処理回路。
(付記B6)
前記連続サブキャリア信号は、周波数領域で前記対象サブキャリア信号と重なり合うサブキャリア信号を含む、
付記B1乃至B5のいずれか一項に記載の光信号処理回路。
(付記B7)
前記連続サブキャリア信号は、周波数領域で前記対象サブキャリア信号と隣り合うサブキャリア信号を含む、
付記B1乃至B6のいずれか一項に記載の光信号処理回路。
(付記B8)
前記連続サブキャリア信号は、周波数軸上で連続する第1~第3のサブキャリア信号を含み、
前記周波数領域MIMO等化器は、
前記第1のサブキャリア信号と前記第2のサブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記第1のサブキャリア信号を生成する第1の周波数領域処理回路と、
前記第1のサブキャリア信号と前記第2のサブキャリア信号と前記第3のサブキャリア信号とに基づいて、周波数領域MIMO等化処理後の前記第2のサブキャリア信号を生成する第2の周波数領域処理回路と、
前記第2のサブキャリア信号と前記第3のサブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記第3のサブキャリア信号を生成する第3の周波数領域処理回路と、
を備える、付記B1乃至B7のいずれか一項に記載の光信号処理回路。
(付記B9)
前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3の周波数領域処理回路を動作しないよう制御する、
付記B8に記載の光信号処理回路。
(付記B10)
前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3の周波数領域処理回路の動作を停止する、または、前記第3の周波数領域処理回路の演算係数をゼロに設定する、
付記B9に記載の光信号処理回路。
(付記B11)
前記連続サブキャリア信号は、周波数軸上で連続する第1~第3のサブキャリア信号を含み、
前記時間領域MIMO等化器は、前記第1のサブキャリア信号と前記第2のサブキャリア信号と前記第3のサブキャリア信号とに基づいて、時間領域MIMO等化処理後の前記第2のサブキャリア信号を生成する時間領域処理回路を備える、
付記B1乃至B7のいずれか一項に記載の光信号処理回路。
(付記B12)
前記時間領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記時間領域処理回路のうち前記第3のサブキャリア信号の演算を行う回路を動作しないよう制御する、
付記B11に記載の光信号処理回路。
(付記B13)
前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3のサブキャリア信号の演算を行う回路の動作を停止する、または、前記第3のサブキャリア信号の演算を行う回路の演算係数をゼロに設定する、
付記B12に記載の光信号処理回路。
(付記B14)
光マルチキャリア信号を受信する光受信機と、複数の周波数領域MIMO等化器と、複数の時間領域MIMO等化器と、を備え、
前記複数の周波数領域MIMO等化器のそれぞれは、前記受信される光マルチキャリア信号内の前記周波数領域MIMO等化器ごとに選択された対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記の連続サブキャリア信号を生成し、
前記複数の時間領域MIMO等化器のそれぞれは、前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する、
光受信装置。
(付記B15)
前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記複数の周波数領域MIMO等化器の入力×出力は、(2N+1)×(2N+1)であり、
前記複数の時間領域MIMO等化器の入力×出力は、(2N+1)×1である、
付記B14記載の光受信装置。
(付記B16)
受信される光マルチキャリア信号内の対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記連続サブキャリア信号を生成し、
前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する、
光信号処理方法。
(付記B17)
前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記周波数領域MIMO等化処理の入力×出力は、(2N+1)×(2N+1)であり、
前記時間領域MIMO等化処理の入力×出力は、(2N+1)×1である、
付記B16に記載の光信号処理方法。
2、2a、2b FDE-MIMO等化器
3、3a、3b TDE-MIMO等化器
4 光受信機
5 光受信装置
6 波長多重光伝送システム
10 光送信装置
11 光送信機
12 合波器
20 光受信装置
21 分波器
22 光受信機
31 光ファイバ伝送路
32 ROADM機器
100 ハイブリッドMIMO等化器
110 FDE-MIMO等化器
111 FFT回路
112 FDE-MIMOコア回路
113 IFFT回路
114 フィルタ係数乗算器
120 TDE-MIMO等化器
121 TDE-MIMOコア等化器
122 フィルタ係数更新部
123 FIRフィルタ
Claims (17)
- 受信される光マルチキャリア信号内の対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記連続サブキャリア信号を生成する周波数領域MIMO等化器と、
前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する時間領域MIMO等化器と、
を備える、光信号処理回路。 - 前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記周波数領域MIMO等化器の入力×出力は、(2N+1)×(2N+1)であり、
前記時間領域MIMO等化器の入力×出力は、(2N+1)×1である、
請求項1に記載の光信号処理回路。 - 前記N個のサブキャリア信号は、それぞれM個の偏波信号に偏波多重されており、
前記周波数領域MIMO等化器の入力×出力は、M(2N+1)×M(2N+1)であり、
前記時間領域MIMO等化器の入力×出力は、M(2N+1)×Mである、
請求項2に記載の光信号処理回路。 - 前記Nは1である、
請求項2又は3に記載の光信号処理回路。 - 前記連続サブキャリア信号は、前記対象サブキャリア信号に対してクロストークを生じさせるサブキャリア信号を含む、
請求項1乃至4のいずれか一項に記載の光信号処理回路。 - 前記連続サブキャリア信号は、周波数領域で前記対象サブキャリア信号と重なり合うサブキャリア信号を含む、
請求項1乃至5のいずれか一項に記載の光信号処理回路。 - 前記連続サブキャリア信号は、周波数領域で前記対象サブキャリア信号と隣り合うサブキャリア信号を含む、
請求項1乃至6のいずれか一項に記載の光信号処理回路。 - 前記連続サブキャリア信号は、周波数軸上で連続する第1~第3のサブキャリア信号を含み、
前記周波数領域MIMO等化器は、
前記第1のサブキャリア信号と前記第2のサブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記第1のサブキャリア信号を生成する第1の周波数領域処理回路と、
前記第1のサブキャリア信号と前記第2のサブキャリア信号と前記第3のサブキャリア信号とに基づいて、周波数領域MIMO等化処理後の前記第2のサブキャリア信号を生成する第2の周波数領域処理回路と、
前記第2のサブキャリア信号と前記第3のサブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記第3のサブキャリア信号を生成する第3の周波数領域処理回路と、
を備える、請求項1乃至7のいずれか一項に記載の光信号処理回路。 - 前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3の周波数領域処理回路を動作しないよう制御する、
請求項8に記載の光信号処理回路。 - 前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3の周波数領域処理回路の動作を停止する、または、前記第3の周波数領域処理回路の演算係数をゼロに設定する、
請求項9に記載の光信号処理回路。 - 前記連続サブキャリア信号は、周波数軸上で連続する第1~第3のサブキャリア信号を含み、
前記時間領域MIMO等化器は、前記第1のサブキャリア信号と前記第2のサブキャリア信号と前記第3のサブキャリア信号とに基づいて、時間領域MIMO等化処理後の前記第2のサブキャリア信号を生成する時間領域処理回路を備える、
請求項1乃至7のいずれか一項に記載の光信号処理回路。 - 前記時間領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記時間領域処理回路のうち前記第3のサブキャリア信号の演算を行う回路を動作しないよう制御する、
請求項11に記載の光信号処理回路。 - 前記周波数領域MIMO等化器は、前記第3のサブキャリア信号が入力されない場合、前記第3のサブキャリア信号の演算を行う回路の動作を停止する、または、前記第3のサブキャリア信号の演算を行う回路の演算係数をゼロに設定する、
請求項12に記載の光信号処理回路。 - 光マルチキャリア信号を受信する光受信機と、複数の周波数領域MIMO等化器と、複数の時間領域MIMO等化器と、を備え、
前記複数の周波数領域MIMO等化器のそれぞれは、前記受信される光マルチキャリア信号内の前記周波数領域MIMO等化器ごとに選択された対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記の連続サブキャリア信号を生成し、
前記複数の時間領域MIMO等化器のそれぞれは、前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する、
光受信装置。 - 前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記複数の周波数領域MIMO等化器の入力×出力は、(2N+1)×(2N+1)であり、
前記複数の時間領域MIMO等化器の入力×出力は、(2N+1)×1である、
請求項14記載の光受信装置。 - 受信される光マルチキャリア信号内の対象サブキャリア信号を含む連続サブキャリア信号に基づいて、周波数領域MIMO等化処理後の前記連続サブキャリア信号を生成し、
前記周波数領域MIMO等化処理後の前記連続サブキャリア信号に基づいて、時間領域MIMO等化処理後の前記対象サブキャリア信号を生成する、
光信号処理方法。 - 前記連続サブキャリア信号は、前記対象サブキャリア信号の上下の周波数にそれぞれ連続して多重されるN個(Nは自然数)のサブキャリア信号を含み、
前記周波数領域MIMO等化処理の入力×出力は、(2N+1)×(2N+1)であり、
前記時間領域MIMO等化処理の入力×出力は、(2N+1)×1である、
請求項16に記載の光信号処理方法。
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