Equalization device and equalization method

Abstract

When reducing the difference in transmission signal quality between channels, a penalty is incurred for the less noisy channels. Thus, an equalization apparatus according to an exemplary aspect of the present invention includes processing means for performing a process associated with a signal using a transfer function having coefficients, the signal propagating through each of a plurality of channels, and coefficient generating means for generating coefficients based on channel quality information for each of the plurality of channels.

Description

Technical Field

[0001] The present invention relates to an equalization device, an optical transmission system, and an equalization method, and particularly to an equalization device, an optical transmission system, and an equalization method used in a wavelength division multiplexing system.

Background Art

[0002] In order to meet the requirement of higher communication capacity in optical fiber transmission, technological development has led to the development of multiplexing technologies related to resources from a number of perspectives, such as wavelength division multiplexing (WDM) and space division multiplexing (SDM).

[0003] When multiplexing technology is applied, signals are transmitted simultaneously in multiple channels, for example, in multiple cores within a multi-core fiber (MCF) in SDM. In particular, for uncoupled MCFs, the difference in Q factor (Q factor) between channels occurs according to the individual losses and gains in each core and other multi-channel components. Furthermore, the difference in Q value is further increased due to the noise figure and gain control of erbium-doped fiber amplifiers (EDFAs) in long-distance transmission systems such as undersea transmission. The aforementioned difference in Q value has become a bottleneck for the overall transmission capacity. Therefore, it is required to equalize the difference in Q value between channels in multiplex transmission.

[0004] Patent Document 1 (PTL1) describes a transmitter that can eliminate the difference in Q value between channels in SDM. The data of two channels are equally separated and mixed by a 2×2 matrix on the transmitter side. Then, the received signal is restored by the inverse matrix of the 2×2 matrix. Therefore, each restored signal receives an average channel noise. As a result, the difference in Q value between the two channels is equalized.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The related transmitter disclosed in Patent Document 1 can reduce the difference in transmission signal quality due to the difference between two channels to a specific level. However, the related transmitter imposes a penalty on a channel that is originally less noisy. This is because the transmission matrix used in the related transmitter is designed to equally mix the signals of the two channels regardless of the channel state. Therefore, a penalty is imposed on a channel that is originally less noisy, resulting in an unnecessary degradation of the performance of the entire multi-transmission system during this equalization procedure.

[0007] An exemplary object of the present invention is to provide an equalization device, an optical transmission system, and an equalization method that solve the above-mentioned problem of imposing a penalty on a channel with less noise when reducing the difference in transmission signal quality between channels.

Means for Solving the Problems

[0008] An equalization device according to an exemplary aspect of the present invention includes processing means for executing a process associated with a signal propagating through each of a plurality of channels using a transfer function having coefficients, and coefficient generation means for generating coefficients based on channel quality information for each of the plurality of channels.

[0009] An optical transmission system according to an exemplary aspect of the present invention includes transmission processing means for receiving an input of data transmitted through a plurality of channels and converting the data into a signal using a first transmission matrix having coefficients so as to give more signal power to a channel having a lower channel quality, reception processing means for receiving an input of the signal after propagation through the plurality of channels and restoring the propagated signal to data using a second transmission matrix that is the inverse matrix of the first transmission matrix, and coefficient generation means for generating coefficients based on channel quality information for each of the plurality of channels.

[0010] An equalization method according to an exemplary embodiment of the present invention includes executing a process associated with a signal propagating through each of a plurality of channels using a transfer function having coefficients, and generating the coefficients based on channel quality information for each of the plurality of channels.

Advantages of the Invention

[0011] An exemplary advantage according to the present invention is that it is possible to equalize the difference in transmission signal quality between channels with a minimum penalty.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0013] Embodiments of the present invention will be described below with reference to the drawings. The direction of the arrow in the drawings indicates an example of the direction and does not limit the direction of the signal between the blocks. [First Embodiment]

[0014] FIG. 1 is a block diagram showing the configuration of an equalizer according to a first embodiment of the present invention. The equalizer 100 includes a processing unit (processing means) 110 and a coefficient generation unit (coefficient generation means) 120.

[0015] The processing unit 110 is configured to execute a process associated with a signal using a transfer function having coefficients. The signal propagates through each of a plurality of channels. The coefficient generation unit 120 is configured to generate coefficients based on channel quality information for each of the plurality of channels.

[0016] According to the equalizer 100 of the present embodiment, since the process associated with the signal is executed based on the channel quality information for each of the plurality of channels, it is possible to equalize the difference in transmission signal quality between channels with a minimum penalty.

[0017] As shown in FIG. 2, the processing unit 110 may include a transmission processing unit (transmission processing means) 111. The transmission processing unit 111 receives an input of data transmitted through a plurality of channels and converts the data into a signal using a first transfer matrix as a transfer function so as to give more signal power to channels having lower channel quality.

[0018] In addition, the processing unit 110 may include a reception processing unit (reception processing means) 112. The reception processing unit 112 is configured to receive an input of a signal after propagation through a plurality of channels and restore the propagated signal to data using a second transfer matrix as a transfer function. The second transfer matrix is the inverse matrix of the first transfer matrix.

[0019] The transfer function may include a square matrix having the same number of columns as the number of a plurality of channels. The square matrix is represented as a product for each component of a coefficient matrix and an orthogonal matrix. The coefficient generation unit 120 is configured to determine the matrix components of the coefficient matrix.

[0020] The channel quality information includes, for each of the plurality of channels, one of a noise power level, a signal-to-noise ratio (SNR), and a bit error rate (BER).

[0021] The plurality of channels are different cores of a multi-core fiber (MCF) through which a signal propagates. Alternatively, the plurality of channels are different wavelengths in wavelength division multiplexing through which a signal propagates.

[0022] Next, an equalization method according to the present embodiment will be described.

[0023] In the equalization method, first, a process associated with a signal is executed using a transfer function having coefficients. The signal propagates through each of the plurality of channels. The coefficients are generated based on channel quality information for each of the plurality of channels.

[0024] The execution of the process associated with the signal may include receiving an input of data transmitted through a plurality of channels and converting the data into a signal using a first transfer matrix as a transfer function so as to give more signal power to channels having lower channel quality.

[0025] The execution of the process associated with the signal may also include receiving the input of the signal after propagation through a plurality of channels, and using a second transfer matrix as a transfer function to restore the propagated signal to data. The second transfer matrix is the inverse matrix of the first transfer matrix.

[0026] In the equalization method, the transfer function may include a square matrix having the same number of columns as the number of a plurality of channels. The square matrix is represented as the product of each component of the coefficient matrix and the orthogonal matrix.

[0027] In the equalization method, the channel quality information includes one of a noise power level, a signal-to-noise ratio (SNR), and a bit error rate (BER) for each of the plurality of channels.

[0028] As described above, according to the equalization apparatus 100 and the equalization method of the present embodiment, it is possible to equalize the difference in the transmission signal quality between channels with a minimum penalty. [Second Embodiment]

[0029] Next, a second embodiment of the present invention will be described.

[0030] FIG. 3 is a block diagram showing an optical transmission system 1000 according to a second embodiment of the present invention. The optical transmission system 1000 includes a transmission processing unit (transmission processing means) 1100, a reception processing unit (reception processing means) 1200, and a coefficient generation unit (coefficient generation means) 1300.

[0031] The transmission processing unit 1100 is configured to receive the input of data transmitted through a plurality of channels and convert the data into a signal using a first transfer matrix having coefficients so as to give more signal power to channels having lower channel quality. The reception processing unit 1200 is configured to receive the input of the signal after propagation through a plurality of channels and restore the propagated signal to data using a second transfer matrix that is the inverse matrix of the first transfer matrix. The coefficient generation unit 1300 is configured to generate coefficients based on channel quality information for each of the plurality of channels.

[0032] The optical transmission system 1000 further includes a transmitter (transmission means) 1400, a receiver (reception means) 1500, and a channel monitor (channel monitoring means) 1600.

[0033] The transmitter 1400 is configured to perform an electro - optical modulation process on a signal. The receiver 1500 is configured to perform an opto - electrical demodulation process on the propagated signal. The channel monitor 1600 is configured to acquire channel quality information from the receiver 1500. In this case, the coefficient generation unit 1300 acquires the channel quality information from the channel monitor 1600.

[0034] As shown in FIG. 3, the transmission processing unit 1100 is arranged on the transmitter side in a typical optical fiber transmission system. The reception processing unit 1200 and the channel monitor 1600 are arranged on the receiver side. For example, the coefficient generation unit 1300 can also be arranged on the receiver side. The feedback path 1700 is configured to connect the coefficient generation unit 1300 to the transmission processing unit 1100 and the reception processing unit 1200.

[0035] Next, the operation of the optical transmission system 1000 will be described.

[0036] The transmission processing unit 1100 is configured to process the input data A and the input data B by a predetermined operation. In the transmission processing unit 1100, the transfer matrix (the first transfer matrix) is used to process the input data A and the input data B. Then, the output processed data are the signals C and D. The relationship between the input data and the output data of the transmission processing unit 1100 is represented by Equation (1). Note that the data A and the data B are symbols modulated in a general modulation format such as QPSK (quadrature phase shift keying), 16QAM (quadrature amplitude modulation), and 64QAM.

Equation

Number

[0037] To show an essential explanation of this transfer matrix, the transfer matrix is configured in such a form that it separates a plurality of input data A and input data B into two parts in a specific ratio and mixes them to form output processing data C and D. The specific ratio is determined by the coefficient generation unit 1300 using the channel quality information from the channel monitor 1600.

[0038] Note that Equation (2) represents an example of a transfer matrix having coefficients. Another exemplary transfer matrix is represented by Equation (3).

Number

[0039] Any other matrix configured as a product for each component of the coefficient matrix and the orthogonal matrix can be used as the transfer matrix. The schematic form is represented by Equation (4).

Number

[0040] That is, the first transfer matrix includes a square matrix having the same number of columns as the number of a plurality of channels. The square matrix is represented as a product for each component of the coefficient matrix and the orthogonal matrix. In this case, the coefficient generation unit 1300 is configured to determine the matrix components of the coefficient matrix.

[0041] The output of the transmission processing unit 1100 is connected to transmitters 1 and 2. Transmitters 1 and 2 are configured to perform necessary operations on the input signals such as electro-optical modulation and amplification, and make the input signals suitable for being transmitted through channels 1 and 2. The signals output from transmitters 1 and 2 are transmitted through channels 1 and 2.

[0042] Receivers 1 and 2 are configured to receive signals and convert optical signals into electrical signals. The reception processing unit 1200 receives the outputs of receivers 1 and 2. In the reception processing unit 1200, the inverse matrix of the transfer matrix in the transmission processing unit 1100 is used to restore the mixed data C and D to the original data A and B. The details of this operation inside the reception processing unit 1200 are represented by Equation (5).

Number

[0043] The channel monitor 1600 is configured to acquire channel quality information from receivers 1 and 2. In this embodiment, the channel quality information is indicated by the noise power that can be measured by receivers 1 and 2. The noise power measured in channel 1 is represented by N1. The noise power measured in channel 2 is represented by N2. The coefficient generation unit 1300 generates coefficients for the transfer matrix and the inverse transfer matrix using the following Equations (6) and (7).

Number

Number

[0044] In this embodiment, the channel quality information may also be indicated by the signal-to-noise ratio (SNR) at the receiver side. The SNR measured in Channel 1 is represented by SNR1. The SNR measured in Channel 2 is represented by SNR2. Then, the coefficient generation unit 1300 generates coefficients for the transmission matrix and the inverse transmission matrix using the following equations (8) and (9). [Number] [Number]

[0045] It should be noted that the above-described configurations of the channel monitor 1600 and the coefficient generation unit 1300 are examples of this embodiment. The channel quality information is not limited to the noise power level and the SNR. The channel quality information includes the bit error rate (BER) or the Q value. The Q value is defined as the minimum SNR required to obtain a specific BER for a given signal. Any other information indicating the difference in channel quality between channels may be included in the channel quality information of this embodiment. In addition, any other method of obtaining the channel quality information and any other indicator indicating the channel quality information may be included in this embodiment.

[0046] By using an equalization device including the transmission processing unit 1100, the reception processing unit 1200, and the coefficient generation unit 1300, more signal power is allocated to a channel having a higher noise power. As a result, the SNR of the transmission signal can be equalized in both channels.

[0047] On the receiver side, the transmitted mixed signal is restored to the original data A and B. Since the channel noise power information is acquired by the channel monitor 1600, the transmission matrix represented by Equation (4) having the coefficients determined by the coefficient generation unit 1300 can be shown to minimize the added noise. As a result, according to the above-described equalization device of this embodiment, the difference in signal quality between different channels can be reduced with a minimum penalty.

[0048] It should also be noted that the configuration of the optical transmission system of this embodiment can be scaled to a multiplexing transmission system having more than two channels. FIG. 4 shows the configuration of an optical transmission system 1001 as an example of a three-channel configuration. The most different point in this configuration is the transfer matrix having coefficients inside the transmission processing unit 1100 and the reception processing unit 1200. The transfer matrix configured to process three-channel data is represented by Equation (10).

Number

[0049] In a general case, for an N-channel transmission system where N is an arbitrary natural number, the transfer matrix configured to process N-channel data is represented by Equation (11).

Number

[0050] As an example, when a complex Hadamard matrix is used as the orthogonal matrix of Equation 11, the transformation matrix is represented by Equation (12). F N represents an example of a complex Hadamard matrix in the form of a Fourier matrix.

Number

[0051] Note that the orthogonal matrix used in the transfer matrix of this embodiment is not limited to the aforementioned example. Any other orthogonal matrix such as a discrete Fourier transform (DFT) matrix can be used to form a transfer matrix composed of the product of each component of the coefficient matrix and the orthogonal matrix.

[0052] Note that the coefficient generation unit 1300 is not limited to the receiver-side arrangement. According to a practical arrangement, as shown in FIG. 5, the coefficient generation unit 1300 can be arranged on the transmitter side. The channel monitor 1600 acquires channel information on the receiver side. Then, the channel information is given to the coefficient generation unit 1300 through the feedback path 1. The coefficient generation unit 1300 generates optimization coefficients for the transfer matrix and the inverse transfer matrix. The coefficients for the inverse transfer matrix on the receiver side are given through the feedback path 2.

[0053] Next, the operation method of the optical transmission system 1000 according to this embodiment will be described. FIG. 6 shows a flowchart for explaining the operation method of the optical transmission system 1000 according to this embodiment.

[0054] In the operation method of the optical transmission system 1000, first, channel quality information is acquired (step S10). The channel quality information is the aforementioned SNR, noise power, or any other information indicating channel quality information. The channel quality information is acquired by the channel monitor 1600.

[0055] Next, the coefficients are updated (step S20). Note that all default coefficients are set to 1, which means that equalization is disabled at the start. This process is executed to accurately monitor the channel quality information. When the channel quality information is acquired, the coefficient generation unit 1300 generates optimization coefficients for the transfer matrix and the inverse transfer matrix.

[0056] The transfer matrix in the transmission processing unit 1100 and the inverse transfer matrix in the reception processing unit 1200 are updated using the updated coefficients obtained from the coefficient generation unit 1300 through the feedback path (step S30). After the transfer matrix and the inverse transfer matrix are updated, the process proceeds to S10 so that the optical transmission system 1000 is repeatedly equalized. Even when the characteristics of the channel quality change due to other factors such as physical shape deformation or temperature change, the operation method can stably maintain an advantageous effect.

[0057] As an example, the plurality of channels shown in FIGS. 3, 4, and 5 described in the foregoing embodiment are different cores of a multi-core fiber (MCF) through which a signal propagates. Crosstalk, and thus the noise of each channel, varies depending on the shape of the fiber. For this reason, the equalizer is determined as described in the foregoing embodiment in order to eliminate the difference in channel performance with a minimum penalty.

[0058] As an alternative example, the plurality of channels shown in FIGS. 3, 4, and 5 described in the foregoing embodiment are different wavelengths in wavelength division multiplexing (WDM) through which a signal propagates. Since the noise depends on the wavelength characteristics that vary for different wavelengths, the noise of each channel is different. For this reason, the equalizer is determined as described in the foregoing embodiment in order to eliminate the difference in channel performance with a minimum penalty.

[0059] As described above, according to the optical transmission system 1000 and the operation method of the optical transmission system 1000 of the present embodiment, it is possible to equalize the difference in the transmission signal quality between channels with a minimum penalty. [Third Embodiment]

[0060] Next, a third embodiment of the present invention will be described.

[0061] FIG. 7 is a block diagram showing an optical transmission system 2000 according to a third embodiment of the present invention. The optical transmission system 2000 includes a transmission processing unit (transmission processing means) 2100, a reception processing unit (reception processing means) 2200, and a coefficient generation unit (coefficient generation means) 2300. The transmission processing unit 2100, the reception processing unit 2200, and the coefficient generation unit 2300 constitute an equalization device. The optical transmission system 2000 further includes a transmitter (transmission means) 2400, a receiver (reception means) 2500, a channel monitor (channel monitoring means) 2600, and a channel 2700.

[0062] The transmission processing unit 2100 is configured to process the first data and the second data into a first processed signal and a second processed signal using a third transfer matrix (H TX ) as a transfer function so as to give more signal power to channels having lower channel quality. The first processed signal is transmitted through a first channel among a plurality of channels. The second processed signal is transmitted through a second channel among a plurality of channels. The first channel and the second channel have the largest difference in channel quality.

[0063] The reception processing unit 2200 is configured to restore the first processed signal after propagating through the first channel and the second processed signal after propagating through the second channel into the first data and the second data using a fourth transfer matrix as a transfer function. The fourth transfer matrix is the inverse matrix of the third transfer matrix (H TX -1 ).

[0064] The coefficient generation unit 2300 is configured to generate coefficients of a conversion matrix based on channel quality information regarding each of a plurality of channels. The channel monitoring unit 2600 is configured to acquire channel quality information.

[0065] As described above, in the optical transmission system 2000 according to the present embodiment, the transmission processing unit 2100 equalizes only the difference in channel quality between the highest-quality channel and the lowest-quality channel. Therefore, the computational requirements are reduced.

[0066] The transmitter 2400 is configured to perform an electro - optical (E / O) modulation process on the signal. The receiver 2500 is configured to perform an optical - electrical (O / E) demodulation process on the propagated signal. As shown in FIG. 7, for example, the channel 2700 is a different core among the multi - core fibers (MCFs) through which the signal propagates.

[0067] Next, the operation of the optical transmission system 2000 will be described.

[0068] The optical transmission system 2000 starts an equalization process before normal transmission. The transfer matrix H TX and the inverse matrix H TX -1 are set to an identity matrix as shown below to bypass all data.

Equation

[0069] The channel monitor 2600 measures the noise power as the channel quality in each core. In this example, the order of the measured noise power magnitudes in each core is represented as core 2 < core 1 < core 4 < core 3. Since the signals passing through core 2 and the signals passing through core 3 have the largest difference in channel quality such as the Q - value, the data for core 2 and the data for core 3 are processed by the transfer matrix H TX and the inverse matrix H TX -1 However, the data for core 1 and the data for core 4 are not processed, that is, bypassed.

[0070] The transfer matrix H TX is configured to equalize the data for core 2 and the data for core 3 according to the information from the channel monitor 2600 as follows.

Equation

[0071] Inverse matrix H TX -1 is configured to restore the signals passing through core 2 and the signals passing through core 3. Then, the normal transmission of the optical transmission system 2000 starts.

[0072] As the optical transmission system 2001 shown in FIG. 8, a first selector (first selection means) 2110 and a second selector (second selection means) 2210 may be further included. The first selector 2110 and the second selector 2210 are included in the equalizer.

[0073] The first selector 2110 is configured to select a first processing signal for the first channel, select a second processing signal for the second channel, and select other data for other channels among the plurality of channels. The second selector 2210 is configured to select the first data and the second data obtained by restoring the first processing signal and the second processing signal, and select other data propagated through other channels.

[0074] Next, the operation of the optical transmission system 2001 will be described.

[0075] The optical transmission system 2001 starts an equalization process before normal transmission. All selectors are set to let all data proceed directly, that is, proceed on the solid line rather than the dashed line in FIG. 8.

[0076] Transmission matrix H TX is configured to equalize the data for core 2 and the data for core 3 according to the information from the channel monitor 2600 as follows.

Equation

[0077] The selector is also configured to equalize the data for core 2 and the data for core 3 and bypass the data for core 1 and the data for core 4. That is, the SEL (selector) 2, SEL3, SEL6, and SEL7 shown in FIG. 8 are switched, and the other selectors remain as they are.

[0078] Next, the equalization method according to this embodiment will be described. FIG. 9 shows a flowchart for explaining the equalization method according to this embodiment.

[0079] In the equalization method, first, a process associated with a signal is performed using a transfer function having coefficients. The signal propagates through each of a plurality of channels. The coefficients are generated based on channel quality information for each of the plurality of channels.

[0080] The generation of the coefficients includes measuring the channel quality of each of the plurality of channels (step S100). The execution of the process associated with the signal includes processing the data transmitted through the channel having the largest difference in channel quality so as to give more signal power to the channels having lower channel quality (step 200).

[0081] As described above, according to the optical transmission systems 2000 and 2001 and the equalization method of this embodiment, it is possible to equalize the difference in transmission signal quality between channels with a minimum penalty. In addition, the computational requirements for the equalization process can also be reduced. [Fourth Embodiment]

[0082] Next, a fourth embodiment of the present invention will be described.

[0083] FIG. 10 is a block diagram showing an optical transmission system 3000 according to a fourth embodiment of the present invention. The optical transmission system 3000 includes a transmission processing unit (transmission processing means) 3100, a reception processing unit (reception processing means) 3200, and a coefficient generation unit (coefficient generation means) 3300. The transmission processing unit 3100, the reception processing unit 3200, and the coefficient generation unit 3300 constitute an equalization device. The optical transmission system 3000 further includes a transmitter (transmission means) 3400, a receiver (reception means) 3500, a channel monitor (channel monitoring means) 3600, and a channel 3700.

[0084] The optical transmission system 3000 further includes a first multiplexer (first multi-selection means) 3110 and a second multiplexer (second multi-selection means) 3210. The first multiplexer 3110 and the second multiplexer 3210 can connect any one of the input ports (a, b, c, d) to any one of the output ports (m, n, p, q). The first multiplexer 3110 and the second multiplexer 3210 are included in the equalization device.

[0085] The transmission processing unit 3100 is configured to process the first data and the second data into a first processed signal and a second processed signal using a third transfer matrix (H TX ) as a transfer function so as to give more signal power to channels having lower channel quality. The first multiplexer 3110 is configured to select the first processed signal for a first channel among a plurality of channels and select the second processed signal for a second channel among the plurality of channels. The first channel and the second channel have the largest difference in channel quality.

[0086] The second multi - selector 3210 is configured to select, for the reception processing unit 3200, the first processed signal after propagation through the first channel and the second processed signal after propagation through the second channel. The reception processing unit 3200 is configured to restore the first processed signal and the second processed signal selected by the second multi - selector 3210 to the first data and the second data using a fourth transfer matrix as a transfer function. The fourth transfer matrix is the inverse matrix of the third transfer matrix (H TX -1 ).

[0087] The coefficient generation unit 3300 is configured to generate coefficients of the conversion matrix based on channel quality information for each of a plurality of channels. The channel monitoring unit 3600 is configured to acquire channel quality information.

[0088] The transmitter 3400 is configured to perform an electro - optical (E / O) modulation process on the signal. The receiver 3500 is configured to perform an opto - electrical (O / E) demodulation process on the propagated signal. As shown in FIG. 10, for example, the channel 3700 is a different core among the multi - core fibers (MCF) through which the signal propagates.

[0089] According to the optical transmission system 3000, even if the transmission processing unit 3100 is fixed at a predetermined position, it is possible to equalize the difference in transmission signal quality between channels with a minimum penalty. That is, even if the transmission processing unit 3100 is arranged between data lane 3 and data lane 4 as an example shown in FIG. 10, the first multi - selector 3110 and the second multi - selector 3210 can be used to equalize the difference in quality between the signals propagating through core 2 and core 3.

[0090] Next, the operation of the optical transmission system 3000 will be described.

[0091] The optical transmission system 3000 starts an equalization process before normal transmission. The transfer matrix H TX and the inverse matrix H TX-1 is set to an identity matrix as shown below to bypass all data.

Number

[0092] The first multi - selector 3110 and the second multi - selector 3210 are set to connect the input ports to the output ports as follows, that is, a - m, b - n, c - p, d - q.

[0093] The channel monitor 3600 measures the noise power as the channel quality in each core. In this example, the order of the measured noise power magnitudes in each core is represented as core 2 < core 1 < core 4 < core 3. Since the signals passing through core 2 and the signals passing through core 3 have the largest difference in channel quality such as Q - value, the data for core 2 and the data for core 3 are processed by the transfer matrix H TX and the inverse matrix H TX -1 However, the data for core 1 and the data for core 4 are not processed, that is, bypassed.

[0094] The transfer matrix H TX is configured to equalize the data for core 2 and the data for core 3 according to the information from the channel monitor 3600 as follows.

Number

[0095] The first multi - selector 3110 and the second multi - selector 3210 are also configured to equalize the data for core 2 and the data for core 3, which means advancing data 4 to core 2. That is, the first multi - selector 3110 and the second multi - selector 3210 are set to connect the input ports to the output ports as follows, that is, a - m, b - q, c - p, d - n.

[0096] Inverse matrix H TX -1 is configured to restore the signal passing through core 2 and the signal passing through core 3.

[0097] As a result, data 3 and data 4 are equalized by the transfer matrix H 2 and σ 3 having coefficients σ TX and then transmitted through core 2 and core 3. This means that the data transmitted through the lowest - quality core and the highest - quality core is equalized.

[0098] Then, the normal transmission of the optical transmission system 3000 starts.

[0099] As the optical transmission system 3001 shown in FIG. 11, the first optical multi - selector 3120 and the second optical multi - selector 3220 can be used instead of the first multi - selector 3110 and the second multi - selector 3210. That is, the equalization of the data for core 2 and the data for core 3 can be performed in the optical domain.

[0100] As described above, according to the optical transmission systems 3000 and 3001 of the present embodiment, the difference in the transmission signal quality between channels can be equalized with a minimum penalty.

[0101] All or part of the embodiments disclosed above can be described as follows in the following appendices, but are not limited thereto.

[0102] (Appendix 1) Processing means for executing a process associated with signals propagating through each of a plurality of channels using a transfer function having coefficients, and coefficient generation means for generating the coefficients based on channel quality information regarding each of the plurality of channels. An equalization device comprising the same.

[0103] (Appendix 2) The processing means includes transmission processing means, and the transmission processing means receives an input of data transmitted through the plurality of channels and uses a first transfer matrix as the transfer function to give more signal power to channels having lower channel quality. The equalization device according to Appendix 1, which is configured to convert the data into the signal.

[0104] (Appendix 3) The processing means includes reception processing means, and the reception processing means receives an input of the signal after propagation through the plurality of channels and uses a second transfer matrix as the transfer function to restore the propagated signal to the data. The equalization device according to Appendix 2, wherein the second transfer matrix is an inverse matrix of the first transfer matrix.

[0105] (Appendix 4) The transfer function includes a square matrix having the same number of columns as the number of the plurality of channels, and the square matrix is represented as a product of components of a coefficient matrix and an orthogonal matrix. The equalization device according to any one of Appendices 1, 2, and 3.

[0106] (Appendix 5) The coefficient generation means is configured to determine matrix components of the coefficient matrix. The equalization device according to Appendix 4.

[0107] (Appendix 6) The channel quality information includes, for each of the plurality of channels, one of a noise power level, a signal-to-noise ratio, and a bit error rate. The equalization device according to any one of Appendices 1, 2, 3, 4, and 5.

[0108] (Appendix 7) The plurality of channels are different cores of the multi-core fiber through which the signal propagates. The equalization device according to any one of Appendices 1, 2, 3, 4, 5, and 6.

[0109] (Appendix 8) The plurality of channels are different wavelengths in wavelength division multiplexing through which the signal propagates, and the equalization device according to any one of Appendices 1, 2, 3, 4, 5, and 6.

[0110] (Appendix 9) Transmission processing means for receiving an input of data transmitted through a plurality of channels and converting the data into a signal using a first transfer matrix having coefficients so as to give more signal power to channels having lower channel quality; receiving processing means for receiving an input of the signal after propagation through the plurality of channels and restoring the propagated signal to the data using a second transfer matrix which is the inverse matrix of the first transfer matrix; and coefficient generation means for generating the coefficients based on channel quality information for each of the plurality of channels. An optical transmission system comprising:

[0111] (Appendix 10) Further comprising transmission means for performing an electro-optical modulation process on the signal, receiving means for performing an opto-electrical demodulation process on the signal after propagation, and channel monitoring means for acquiring the channel quality information from the receiving means, wherein the coefficient generation means acquires the channel quality information from the channel monitoring means. The optical transmission system according to Appendix 9.

[0112] (Appendix 11) The first transfer matrix includes a square matrix having the same number of columns as the number of the plurality of channels, and the square matrix is represented as a product of components of a coefficient matrix and an orthogonal matrix. The optical transmission system according to Appendix 9 or 10.

[0113] (Appendix 12) The coefficient generation means is configured to determine matrix components of the coefficient matrix. The optical transmission system according to Appendix 11.

[0114] (Appendix 13) The channel quality information includes, for each of the plurality of channels, one of a noise power level, a signal-to-noise ratio, and a bit error rate. The optical transmission system according to any one of Appendices 9, 10, 11, and 12.

[0115] (Appendix 14) The plurality of channels are different cores among the multi-core fibers through which the signal propagates, and the optical transmission system according to any one of Appendices 9, 10, 11, 12, and 13.

[0116] (Appendix 15) The plurality of channels are different wavelengths in wavelength division multiplexing through which the signal propagates, and the optical transmission system according to any one of Appendices 9, 10, 11, 12, and 13.

[0117] (Appendix 16) Executing a process associated with a signal using a transfer function having coefficients, the signal propagating through each of a plurality of channels, and generating the coefficients based on channel quality information for each of the plurality of channels. An equalization method including:

[0118] (Appendix 17) The execution of the process associated with the signal includes receiving an input of data transmitted through the plurality of channels and using a first transfer matrix as the transfer function to convert the data into the signal so as to give more signal power to channels having lower channel quality. The equalization method according to Appendix 16.

[0119] (Appendix 18) The execution of the process associated with the signal includes receiving an input of the signal after propagation through the plurality of channels and using a second transfer matrix as the transfer function to restore the propagated signal to the data. The second transfer matrix is the inverse matrix of the first transfer matrix. The equalization method according to Appendix 17.

[0120] (Appendix 19) The transfer function includes a square matrix having the same number of columns as the number of the plurality of channels, and the square matrix is represented as a product of components of a coefficient matrix and an orthogonal matrix. The equalization method according to any one of Appendices 16, 17, and 18.

[0121] (Supplementary Note 20) The channel quality information includes, for each of the plurality of channels, one of a noise power level, a signal-to-noise ratio, and a bit error rate, and is an equalization method described in any one of Supplementary Notes 16, 17, 18, and 19.

[0122] (Supplementary Note 21) The processing means includes transmission processing means, and the transmission processing means uses a third transfer matrix as the transfer function to give more signal power to channels having lower channel quality, and processes the first data and the second data into a first processed signal and a second processed signal. The first processed signal is transmitted through a first channel among the plurality of channels, the second processed signal is transmitted through a second channel among the plurality of channels, and the first channel and the second channel have the largest difference in channel quality. The equalization device described in Supplementary Note 1.

[0123] (Supplementary Note 22) The processing means includes reception processing means, and the reception processing means uses a fourth transfer matrix as the transfer function to restore the first processed signal after propagating through the first channel and the second processed signal after propagating through the second channel to the first data and the second data. The fourth transfer matrix is the inverse matrix of the third transfer matrix. The equalization device described in Supplementary Note 21.

[0124] (Supplementary Note 23) First selection means for selecting the first processed signal for the first channel, selecting the second processed signal for the second channel, and selecting other data for other channels among the plurality of channels; and the first data and the second data obtained by restoring the first processed signal and the second processed signal. Second selection means for selecting and selecting the other data propagated through the other channels. The equalization device described in Supplementary Note 22.

[0125] (Appendix 24) Further comprising a first multi-selection means, the processing means includes a transmission processing means, and the transmission processing means uses a third transfer matrix as the transfer function to provide more signal power to a channel having a lower channel quality, and is configured to process the first data and the second data into a first processed signal and a second processed signal. The first multi-selection means is configured to select the first processed signal for a first channel among the plurality of channels and select the second processed signal for a second channel among the plurality of channels. The equalization device according to Appendix 1, wherein the first channel and the second channel have the largest difference in channel quality.

[0126] (Appendix 25) Further comprising a second multi-selection means, the processing means includes a reception processing means, and the second multi-selection means is configured to select, for the reception processing means, the first processed signal after propagating through the first channel and the second processed signal after propagating through the second channel. The reception processing means is configured to restore the first processed signal and the second processed signal selected by the second multi-selection means to the first data and the second data using a fourth transfer matrix as the transfer function. The equalization device according to Appendix 24, wherein the fourth transfer matrix is an inverse matrix of the third transfer matrix.

[0127] (Appendix 26) The generation of the coefficients includes measuring the channel quality of each of the plurality of channels, and the execution of the process associated with the signal includes processing data transmitted through a channel having the largest difference in channel quality so as to provide more signal power to a channel having a lower channel quality. The equalization method according to Appendix 16.

[0128] As described above, the present invention has been described with reference to the embodiments (and examples), but the present invention is not limited to the above embodiments (and examples). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0129] This application claims priority based on International Application PCT / JP2021 / 022600 filed on June 15, 2021, and incorporates herein by reference all of its disclosures.

Explanation of Signs

[0130] 100 Equalizer 110 Processing Unit 111 Transmission Processing Unit 112 Reception Processing Unit 120 Coefficient Generation Unit 1000, 2000, 2001, 3000, 3001 Optical Transmission System 1100, 2100, 3100 Transmission Processing Unit 1200, 2200, 3200 Reception Processing Unit 1300, 2300, 3300 Coefficient Generation Unit 1400, 2400, 3400 Transmitter 1500, 2500, 3500 Receiver 1600, 2600, 3600 Channel Monitor 1700 Feedback Path 2110 First Selector 2210 Second Selector 2700, 3700 Channel 3110 First Multi-Selector 3210 Second Multi-Selector 3120 First Optical Multi-Selector 3220 Second Optical Multi-Selector

Claims

1. Processing means for executing a process associated with a signal propagating through each of three or more channels using a transfer function having coefficients; Coefficient generation means for generating the coefficients based on channel quality information for each of the three or more channels; Comprising: The processing means includes transmission processing means; The transmission processing means uses a third transfer matrix as the transfer function to convert first data and second data into a first processed signal and a second processed signal; The coefficients of the third transfer matrix, which are the coefficients of the transfer function, are coefficients that give more signal power to the channel with the lowest channel quality selected from among the three or more channels in order to reduce the difference between the channel with the lowest channel quality and the channel with the highest channel quality; The first processed signal is transmitted through a first channel among the three or more channels; The second processed signal is transmitted through a second channel among the three or more channels; One of the first channel and the second channel is the channel with the lowest channel quality, and the other is the channel with the highest channel quality; Equalizer.

2. The processing means includes reception processing means; The reception processing means uses a fourth transfer matrix as the transfer function to restore the first processed signal after propagating through the first channel and the second processed signal after propagating through the second channel to the first data and the second data; The fourth transfer matrix is the inverse matrix of the third transfer matrix; The equalizer according to claim 1.

3. First selection means for selecting the first processed signal for the first channel, selecting the second processed signal for the second channel, and selecting other data for other channels among the three or more channels; Further comprising second selection means for selecting the first data and the second data obtained by restoring the first processed signal and the second processed signal, and selecting the other data propagating through the other channels; The equalizer according to claim 2.

4. Processing means for executing a process associated with a signal propagating through each of three or more channels using a transfer function having coefficients; Coefficient generation means for generating the coefficient based on channel quality information for each of the three or more channels; First multi-selection means; comprising; The processing means includes transmission processing means; The transmission processing means uses a third transfer matrix as the transfer function to convert first data and second data into a first processed signal and a second processed signal; The coefficients of the third transfer matrix, which are the coefficients of the transfer function, are coefficients that give more signal power to the channel with the lowest channel quality selected from among the three or more channels in order to reduce the difference between the channel with the lowest channel quality and the channel with the highest channel quality; The first multi-selection means selects the first processed signal for a first channel among the three or more channels and selects the second processed signal for a second channel among the three or more channels; One of the first channel and the second channel is the channel with the lowest channel quality, and the other is the channel with the highest channel quality; Equalization device.

5. Further comprising second multi-selection means; The processing means includes reception processing means; The second multi-selection means selects, for the reception processing means, the first processed signal after propagation through the first channel and the second processed signal after propagation through the second channel; The reception processing means uses a fourth transfer matrix as the transfer function to restore the first processed signal and the second processed signal selected by the second multi-selection means to the first data and the second data; The fourth transfer matrix is the inverse matrix of the third transfer matrix; The equalization device according to claim 4.

6. Performing a process associated with a signal propagating through each of three or more channels using a transfer function having coefficients; Generating the coefficients based on channel quality information for each of the three or more channels; The generating of the coefficients includes measuring the channel quality of each of the three or more channels; The coefficients of the transfer function are coefficients that give more signal power to the channel with the lowest channel quality selected from among the three or more channels in order to reduce the difference between the channel with the lowest channel quality and the channel with the highest channel quality; The execution of the process associated with the signal includes processing data transmitted through a channel having a channel quality difference between the channel with the lowest channel quality selected from among the three or more channels and the channel with the highest channel quality, so as to provide more signal power to the channel with the lowest channel quality selected from among the three or more channels. Equalization method.

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