Optical transmission device, optical reception device, optical transmission system, and optical transmission method

Abstract

An optical transmission device that transmits a multi-valued modulated optical transmission signal, the optical transmission device being characterized by being provided with: a control encoding unit (27) that performs error correction encoding processing on control information including information of a multi-valued modulation scheme used for a main signal information sequence, and outputs an encoded control information sequence; a main encoding unit (25) that performs error correction encoding processing on the main signal information in accordance with the multi-valued modulation scheme indicated by the control information, and generates an encoded main signal information sequence; a selection circuit (28) that inserts the control information sequence into the main signal information sequence and outputs the control information sequence such that the control information sequence indicates a multi-valued modulation scheme to be used for the immediately following main signal information sequence; and a mapping unit (29) that generates a multi-valued modulated optical transmission signal by performing mapping processing on the control information sequence output by the selection circuit (28) using a predetermined multi-valued modulation scheme and by performing mapping processing on the main signal information sequence output by the selection circuit using a multi-valued modulation scheme indicated by the control information sequence.

Description

Technical Field

[0001] The present disclosure relates to an optical transmitting device, an optical receiving device, an optical transmission system, and an optical transmission method for transmitting a multi-value modulated optical transmission signal. Background Art

[0002] Conventionally, error correction codes have been used in optical transmission systems to achieve high transmission capacity and long-distance transmission. In optical transmission systems that transmit multi-level modulated optical transmission signals, error correction codes corresponding to the multi-level modulation scheme are used. For example, Patent Document 1 discloses an error correction coding device corresponding to the multi-level modulation scheme.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2021 / 199690 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, the conventional technology described above assumes that the multi-value modulation scheme to be used is a single predetermined scheme, and therefore the error correction code format is fixed to a single type. Therefore, when input data shorter than the code format is input, a fixed value is inserted into the information bit sequence to make the data length consistent with the code format, resulting in a problem of reduced transmission efficiency.

[0008] The present disclosure is made in view of the above situation, and its purpose is to obtain an optical transmission device that can improve transmission efficiency.

[0009] Means for solving problems

[0010] In order to solve the above-mentioned problems and achieve the purpose, the optical transmitting device disclosed in the present invention transmits a multi-value modulated optical transmission signal, and is characterized in that the optical transmitting device comprises: a control coding unit, which performs error correction coding processing on control information including information on the multi-value modulation method used for a main signal information sequence, and outputs the encoded control information sequence; a main coding unit, which performs error correction coding processing on the main signal information corresponding to the multi-value modulation method represented by the control information, and generates an encoded main signal information sequence; a selection circuit, which inserts the control information sequence into the main signal information sequence and outputs it, so that the control information sequence represents the multi-value modulation method used for the immediately subsequent main signal information sequence; and a mapping unit, which uses a predetermined multi-value modulation method to map the control information sequence output by the selection circuit, and uses the multi-value modulation method represented by the control information sequence to map the main signal information sequence output by the selection circuit to generate a multi-value modulated optical transmission signal.

[0011] Effects of the Invention

[0012] The optical transmission device disclosed herein has the effect of improving transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram showing the structure of the optical transmission system according to Embodiment 1.

[0014] Figure 2 It shows Figure 1 A diagram showing an example configuration of an optical transmission device.

[0015] Figure 3 It shows Figure 2 A diagram showing a detailed configuration example of an encoding circuit is shown.

[0016] Figure 4 Is used to illustrate Figure 2 Flowchart showing the operation of the optical transmission device.

[0017] Figure 5 It shows Figure 1 FIG. 1 is a diagram showing a configuration of a decoding circuit included in the optical receiving device shown.

[0018] Figure 6 Is used to illustrate Figure 1 Flowchart of the operation of the light receiving device shown.

[0019] Figure 7 is shown for implementing Figure 1 A diagram of dedicated hardware showing the functions of an optical transmitter and an optical receiver.

[0020] Figure 8 is shown for implementing Figure 1 A diagram showing the structure of a circuit for controlling the functions of an optical transmitting device and an optical receiving device.

[0021] Figure 9 This is a diagram showing the frame format of 256QAM (Quadrature Amplitude Modulation).

[0022] Figure 10 This is a diagram showing the frame format of 64QAM.

[0023] Figure 11 This is a diagram showing the frame format of 16QAM.

[0024] Figure 12 is a diagram showing the frame format of QPSK. DETAILED DESCRIPTION

[0025] Hereinafter, an optical transmitting device, an optical receiving device, an optical transmission system, and an optical transmission method according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0026] Implementation method 1.

[0027] Figure 1 This diagram shows the configuration of an optical transmission system 1 according to Embodiment 1. Optical transmission system 1 includes an optical transmitter 2 and an optical receiver 3. The optical transmitter 2 and optical receiver 3 are connected via an optical fiber or the like. Optical transmission system 1 transmits a multi-level modulated optical transmission signal. The optical transmitter 2 generates and transmits the multi-level modulated optical transmission signal. The optical receiver 3 receives the optical transmission signal transmitted by the optical transmitter 2.

[0028] The optical transmitter 2 is capable of performing multi-value modulation processing corresponding to a variety of multi-value modulation schemes. The optical transmitter 2 can select and use a multi-value modulation scheme with high transmission efficiency, consistent with the length of the information bit sequence to be transmitted. The optical receiver 3 must perform reception processing consistent with the modulation scheme used for the optical transmission signal to be received. Therefore, the optical transmitter 2 has the function of transmitting a control signal to the optical receiver 3, notifying the optical receiver 3 of the modulation scheme to be used, before transmitting the main signal containing the information bit sequence to be transmitted. The specific structure and operation are described below.

[0029] Figure 2 It shows Figure 1 The optical transmitter 2 includes a modulation scheme determination unit 20, a fixed value insertion unit 21, a control information generation unit 22, and an encoding circuit 23. In addition, the optical transmitter 2 may also include Figure 2 Structural elements other than those shown.

[0030] The modulation scheme determination unit 20 determines the multi-level modulation scheme to be used for the main signal information including the information bit sequence based on the sequence length of the information bit sequence to be transmitted. The modulation scheme determination unit 20 selects the multi-level modulation scheme to improve transmission efficiency. The modulation scheme determination unit 20 outputs the information bit sequence to be transmitted to the fixed value insertion unit 21 and outputs the determined multi-level modulation scheme to the fixed value insertion unit 21 and the control information generation unit 22, respectively.

[0031] The fixed value insertion unit 21 inserts a fixed value into a bit position that is not a transmission object according to the multi-value modulation method determined by the modulation method determination unit 20, generates main signal information as an information bit sequence corresponding to the maximum multi-value symbol, and outputs it to the control information generation unit 22 and the encoding circuit 23 respectively.

[0032] The control information generation unit 22 generates control information including information indicating the multi-level modulation method determined by the modulation method determination unit 20, and outputs the generated control information to the encoding circuit 23. Furthermore, the control information may include frame information of the main signal information processed by the fixed value insertion unit 21. The frame information includes, for example, information on the sequence length of the information bit sequence to be transmitted, which is included in the main signal information.

[0033] The encoding circuit 23 performs error correction encoding and modulation processing on the main signal information and the control information.

[0034] Figure 3 It shows Figure 2 1 is a diagram showing a detailed configuration example of the encoding circuit 23. The encoding circuit 23 receives input of main signal information and control information including information on a modulation method used for the main signal information.

[0035] The coding circuit 23 includes an interleaver 24, a main coding unit 25, a deinterleaver 26, a control coding unit 27, a selection circuit 28, and a mapping unit 29. Main signal information is input to the interleaver 24, and control information is input to the control coding unit 27.

[0036] The interleaver 24 rearranges the order of the bit sequence of the main signal information in units of multi-value modulation symbols. The interleaver 24 rearranges the order of the bit sequence of the main signal information in accordance with the processing in the main coding unit 25. The interleaver 24 outputs the rearranged main signal information to the main coding unit 25.

[0037] The main encoder 25 encodes the main signal information output by the interleaver 24 based on the control information, generating an encoded main signal information sequence. The main encoder 25 includes an HD-FEC (Hard Decision-Forward Error Correction) encoder 251, a multi-stage encoder 252, and an SD-FEC (Soft Decision-Forward Error Correction) encoder 253.

[0038] The HD-FEC encoder 251 performs encoding based on the frame information included in the control information using an error correction code that assumes hard-decision decoding of the main signal information during decoding in the optical receiver 3. The encoding process performed by the HD-FEC encoder 251 is sometimes referred to as the first encoding process. In the first encoding process, encoding is performed using, for example, Bose Chaudhuri-Hocquenghem (BCH) codes or Reed Solomon (RS) codes, assuming maximum multi-value modulation symbols. Specifically, the HD-FEC encoder 251 also performs error correction encoding on the symbol bits in the fixed-zero rows, creating an information sequence. The HD-FEC encoder 251 outputs the resulting encoded sequence, i.e., the main signal information sequence, to the multi-stage encoder 252.

[0039] The multilevel encoding unit 252 divides the main signal information sequence output by the HD-FEC encoding unit 251 into segments consistent with the multilevel modulation scheme included in the control information, and performs multilevel encoding. The multilevel encoding unit 252 outputs a portion of the multiple bits included in the main signal information sequence after multilevel encoding, which are the bits to be processed by the SD-FEC encoding unit 253, to the SD-FEC encoding unit 253, and outputs the remaining bits to the deinterleaver 26. The bits to be processed by the SD-FEC encoding unit 253 are preferably bits with a high error rate. For example, the error rate of each bit in a multilevel modulation symbol varies depending on the multilevel modulation scheme. Therefore, among the multiple bits in the multilevel modulation symbol, the bit with a high error rate (e.g., the least significant bit (LSB)) can be set as the bit to be processed by the SD-FEC encoding unit 253.

[0040] The SD-FEC encoder 253 encodes the bits output by the multi-stage encoder 252 using an error correction code that assumes soft-decision decoding during decoding in the optical receiver 3. The encoding process performed by the SD-FEC encoder 253 is sometimes referred to as the second encoding process. For example, an LDPC (Low Density Parity Check) code is used in the second encoding process. The SD-FEC encoder 253 outputs the encoded coded sequence to the deinterleaver 26.

[0041] Deinterleaver 26 reorders the main signal information sequence output by main encoder 25 to restore the original sequence. Specifically, deinterleaver 26 reorders the bits included in the main signal information sequence so that the sequence is the same as before reordering by interleaver 24. Deinterleaver 26 outputs the reordered main signal information sequence to selection circuit 28.

[0042] The control coding unit 27 encodes the control information and outputs the encoded control information sequence to the selection circuit 28. The control information includes information indicating the multi-value modulation method used for the main signal information sequence, frame information, and the like. The control coding unit 27 can store the information contained in the control information and provide it to the main coding unit 25. The control coding unit 27 can use an error correction code different from the error correction code used for the main signal information to perform error correction encoding on the control information. The control coding unit 27 preferably uses an error correction code with higher error correction capability than the error correction code used for the main signal information for encoding. Examples of error correction codes used for control information include block codes, LDPC codes, and polar codes. Since the control information sequence has a relatively short information bit length, polar codes are preferred. Even with a short code length, they have high error correction capability and allow for flexible configuration of the coding rate. Using polar codes in the control coding unit 27 can improve decoding performance of the control information. Furthermore, since polar codes can reduce processing delays, the time required for encoding control information can be shortened, and encoding of control information can be performed in parallel with error correction encoding of main signal information.

[0043] Selection circuit 28 selects one of the main signal information sequence output by deinterleaver 26 and the control information sequence output by control coding unit 27, and outputs the selected sequence to mapping unit 29. Specifically, selection circuit 28 inserts the control information sequence into the main signal information sequence and outputs the selected sequence so that the control information sequence indicates the multi-value modulation scheme for the immediately following main signal information sequence.

[0044] The mapping unit 29 maps the coded sequence output by the selection circuit 28 to generate a multi-value modulation symbol sequence. At this point, the mapping unit 29 maps the control information sequence using a predetermined multi-value modulation scheme, and maps the main signal information sequence using the multi-value modulation scheme indicated by the control information. The mapping unit 29 preferably uses a modulation scheme that is highly resistant to transmission noise, such as BPSK (Binary Phase Shift Keying) modulation or QPSK (Quaternary PSK) modulation, for the control information sequence. Furthermore, when mapping the main signal information sequence, the mapping unit 29 excludes the untransmitted fixed bit rows from the multi-value modulation symbol. The mapping unit 29 transmits an optical transmission signal including the mapped multi-value modulation symbol sequence.

[0045] Figure 4 Is used to illustrate Figure 2The flowchart of the operation of optical transmitter 2 is shown in FIG. The modulation scheme determination unit 20 of optical transmitter 2 determines the multi-value modulation scheme to be used for the main signal information sequence based on the sequence length of the information bit sequence to be transmitted (step S101). The fixed value insertion unit 21 inserts a fixed value into the information bit sequence to be transmitted based on the determined multi-value modulation scheme (step S102). The fixed value is preferably set to "0," for example.

[0046] The control information generating unit 22 generates fixed-length control information (step S103) including at least information indicating the multi-value modulation method determined by the modulation method determining unit 20. The control information may further include frame information of the main signal.

[0047] Following the control information, the main signal information is input to the encoding circuit 23. The control encoding unit 27 of the encoding circuit 23 performs error correction encoding processing on the control information (step S104). The control encoding unit 27 performs error correction encoding processing with high error correction capability.

[0048] Furthermore, when the interleaver 24 receives the main signal information, it performs interleaving on the main signal information in parallel with the error correction coding of the control information in step S104 (step S105). Next, the HD-FEC encoder 251 of the main encoder 25 performs the first error correction coding on the main signal information output from the interleaver 24 (step S106). When the HD-FEC encoder 251 outputs the main signal information after the first error correction coding, the multi-stage encoder 252 performs multi-stage coding on the main signal information (step S107). The multi-stage encoder 252 outputs the bits to be processed by the SD-FEC encoder 253 to the SD-FEC encoder 253 and outputs the remaining bits to the deinterleaver 26. The SD-FEC encoder 253 performs the second error correction coding on the input bits (step S108). The deinterleaver 26 performs deinterleaving processing on the main signal information output from the multistage encoding unit 252 and the SD-FEC encoding unit 253 (step S109).

[0049] Here, the process of step S104 and the processes of steps S105 to S109 are performed in parallel. However, the processes of steps S105 to S109 may be performed after the process of step S104.

[0050] Selector circuit 28 inserts a control information sequence before the main signal information sequence (step S110). Selector circuit 28 inserts the control information sequence before the main signal information sequence so that the inserted control information sequence indicates the multi-level modulation scheme used for the immediately following main signal information sequence. Specifically, encoding circuit 23 inputs the target main signal information using the multi-level modulation scheme indicated by the control information after the control information, and the order of input to selector circuit 28 is the same. Selector circuit 28 outputs the fixed-length control information sequence to mapping unit 29, and then outputs the main signal information sequence corresponding to the control information sequence to mapping unit 29.

[0051] The mapping unit 29 performs mapping processing on the input encoded bit sequence (step S111). Specifically, the mapping unit 29 uses a predetermined multi-value modulation method to map the control information sequence. Furthermore, the mapping unit 29 uses the multi-value modulation method indicated by the control information to map the main signal information sequence. The mapping unit 29 transmits the mapped multi-value modulation symbol sequence as an optical transmission signal to the optical receiving device 3 (step S112).

[0052] Figure 5 It shows Figure 1 FIG. 1 is a diagram showing a configuration of a decoding circuit 30 included in the optical receiving device 3 .

[0053] The decoding circuit 30 includes a separation circuit 31, a control signal soft decision generator 32, a control decoding unit 33, an interleaver 34, a main decoding unit 35, and a deinterleaver 36. Furthermore, the optical receiving device 3 may include a demodulation circuit (not shown) in addition to the decoding circuit 30, and the demodulated symbols are input to the decoding circuit 30.

[0054] The separation circuit 31 separates the input demodulated symbols into demodulated symbols for control information and demodulated symbols for main signal information. The separation circuit 31 outputs the demodulated symbols for control information to the control signal soft decision generator 32 and outputs the demodulated symbols for main signal information to the interleaver 34.

[0055] The control signal soft decision generator 32 performs soft decision processing on the demodulated symbols of the control information according to a predetermined control signal modulation scheme to generate soft decision information, and outputs the generated soft decision information to the control decoder 33 .

[0056] The control decoding unit 33 performs error correction decoding on the soft decision information of the control information and outputs a control signal. In addition, the control decoding unit 33 can retain the control information included in the control signal and provide it to the main decoding unit 35.

[0057] The interleaver 34 interleaves the demodulated symbols of the main signal information, thereby changing the order of the main signal in units of multi-value modulation symbols. The interleaver 34 outputs the interleaved main signal information sequence to the main decoding unit 35.

[0058] The main decoding unit 35 includes a main signal soft decision generator 351 , an SD-FEC decoder 352 , a multi-stage / multi-phase decoder 353 , and an HD-FEC decoder 354 . The main decoding unit 35 performs decoding processing on the main signal based on the control information held by the control decoding unit 33 .

[0059] The main signal soft decision generator 351 performs soft decision processing on the main signal to generate soft decision information, and outputs the generated soft decision information to the SD-FEC decoder 352 and the multi-stage / multi-phase decoder 353 .

[0060] The SD-FEC decoding unit 352 performs error correction decoding on a portion of the main signal using soft decision decoding. The SD-FEC decoding unit 352 outputs the processed signal to the multi-stage / multi-phase decoding unit 353. The decoding process performed by the SD-FEC decoding unit 352 is sometimes referred to as the second error correction decoding process.

[0061] The multi-stage / multi-stage decoding unit 353 performs multi-stage / multi-stage decoding using the undecoded portion of the main signal soft decision generator 351 and the SD-FEC-decoded information from the SD-FEC decoder 352. The multi-stage / multi-stage decoding unit 353 outputs the processed signal to the HD-FEC decoder 354.

[0062] The HD-FEC decoding unit 354 performs hard decision decoding on the main signal. The HD-FEC decoding unit 354 outputs the hard decision decoded signal to the deinterleaver 36. The error correction decoding process performed by the HD-FEC decoding unit 354 is sometimes referred to as a first error correction decoding process.

[0063] The deinterleaver 36 restores the order of the interleaved main signal in units of hard-decided multi-value modulation symbols.

[0064] Figure 6 Is used to illustrate Figure 1 The optical receiving device 3 performs a demodulation process on the multi-level modulated optical transmission signal as a received signal (step S201). Next, the separation circuit 31 separates the control signal and the main signal (step S202).

[0065] The control signal soft decision generator 32 generates soft decision information for the control signal (step S203). The control decoder 33 performs soft decision error correction decoding on the control signal (step S204). The control decoder 33 outputs the control signal and stores the control information included in the control signal.

[0066] Furthermore, the interleaver 34 performs interleaving processing on the main signal (step S205). The interleaving processing of the main signal can also be performed in parallel with the soft decision error correction decoding processing of the control signal in step S204. The interleaver 34 outputs the interleaved signal to the main signal soft decision generator 351.

[0067] The main signal soft decision generator 351 generates soft decision information for the main signal based on the multi-level modulation scheme included in the control information stored in the control decoder 33 (step S206). The portion of the generated soft decision information that is subject to soft decision decoding is output to the SD-FEC decoder 352, and the remaining portion is output to the multi-stage / multi-stage decoder 353.

[0068] The SD-FEC decoding unit 352 performs soft decision decoding processing as the second error correction decoding processing on the input portion of the main signal (step S207 ). The SD-FEC decoding unit 352 outputs the processed main signal to the multi-stage / multi-stage decoding unit 353 .

[0069] The multi-stage / multi-stage decoding unit 353 performs multi-stage / multi-stage decoding on the input main signal (step S208). Specifically, based on the SD-FEC decoding result, the multi-stage / multi-stage decoding unit 353 determines a hard decision bit according to the hard decision result of the multi-value demodulated symbol that has not been subjected to the SD-FEC decoding process, and outputs it to the HD-FEC decoding unit 354 along with the multi-value demodulated symbol obtained by the SD-FEC decoding process.

[0070] The HD-FEC decoder 354 performs hard decision decoding, a first error correction decoding process, on the main signal (step S209). By setting untransmitted modulation symbol bits to fixed "0" bits and inputting them based on information contained in the decoded control signal, the probability of uncorrectable errors can be reduced by shortening the error correction code sequence without affecting the error correction process. The HD-FEC decoder 354 outputs the information bit sequence decoded by the hard decision decoding process to the deinterleaver 36.

[0071] The deinterleaver 36 performs deinterleaving processing on the main signal so that the order of the information bit sequence is restored to match the rearrangement by the interleaver 34 (step S210).

[0072] Here, the hardware configuration of the optical transmitter 2 and optical receiver 3 is described. The functions of the optical transmitter 2 and optical receiver 3 are implemented by processing circuits. These processing circuits can be implemented as dedicated hardware or as control circuits using a CPU (Central Processing Unit).

[0073] In the case where the above-mentioned processing circuits are implemented by dedicated hardware, they are implemented by Figure 7 This is achieved by the processing circuit 90 shown. Figure 7 is shown for implementing Figure 1 The figure shows the dedicated hardware for the functions of the optical transmitter 2 and the optical receiver 3. The processing circuit 90 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0074] In the case where the above-mentioned processing circuit is implemented using a control circuit of a CPU, the control circuit is, for example, Figure 8 The control circuit 91 has the structure shown. Figure 8 It is used to implement Figure 1 FIG. 9 is a diagram showing the structure of a control circuit 91 for controlling the functions of the optical transmitting device 2 and the optical receiving device 3. Figure 8 As shown, the control circuit 91 includes a processor 92 and a memory 93. Processor 92 is a CPU, also known as a computing device, microprocessor, microcomputer, or DSP (Digital Signal Processor). Memory 93 may be, for example, a nonvolatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), or EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), or a magnetic disk, floppy disk, optical disk, high-density disk, minidisc, or DVD (Digital Versatile Disk).

[0075] When the above-mentioned processing circuit is implemented by the control circuit 91, it is implemented by the processor 92 reading and executing the program corresponding to the processing of each component stored in the memory 93. In addition, the memory 93 is also used as a temporary storage for each process executed by the processor 92. In addition, the program executed by the processor 92 can be provided in a state stored in a storage medium or via a communication path such as the Internet.

[0076] in addition, Figure 2 、 Figure 3 and Figure 5 The division method of each structural element shown is an example and is not limited to the example shown in the figure. In addition, different processing circuits can be used to implement Figure 2 、 Figure 3 and Figure 5 The multiple structural elements shown can also be realized by a single processing circuit. Figure 2 、 Figure 3 and Figure 5 In addition, it is also possible to Figure 2 、 Figure 3 and Figure 5 The structural elements shown are implemented by being divided into a plurality of processing circuits.

[0077] Next, the frame format used by the optical transmission system 1 is described for each multi-level modulation method. The optical transmission system 1 can encode the main signal information to be transmitted using a multi-level modulation method selected from multiple multi-level modulation methods such as 256QAM, 64QAM, 16QAM, and QPSK. Figure 9 This is a diagram showing the frame format of 256QAM. Assume that the control information is transmitted with a fixed length by QPSK modulation regardless of the modulation method used for the main signal information.

[0078] Regarding the main signal, in the case of 256QAM, the data after dual encoding by SD-FEC and HD-FEC is configured in a part of the least significant bit, i.e., the LSB, and the data encoded only by HD-FEC is configured in the part other than the LSB.

[0079] Figure 10This diagram shows the 64QAM frame format. Regarding the main signal, for 64QAM, data encoded using both SD-FEC and HD-FEC is allocated to a portion of the LSBs, while data encoded using only HD-FEC is allocated to the remaining LSBs and two of the remaining three bits (MSB, SSB, and TSB). The remaining bit (TSB) is fixed to 0 for error correction coding. The fixed 0 portion is not transmitted.

[0080] Figure 11 This diagram shows the 16QAM frame format. For 16QAM, the main signal is encoded using both SD-FEC and HD-FEC for a portion of the LSB. Data encoded using HD-FEC alone is allocated to the remaining LSB and the MSB of one of the three systems other than the LSB. Furthermore, the remaining two systems, SSB and TSB, are fixed to 0 for error correction coding. During transmission, the fixed 0 portion is not transmitted.

[0081] Figure 12 This diagram shows the QPSK frame format. In QPSK, data encoded using both SD-FEC and HD-FEC is allocated to a portion of the LSBs, while data encoded using only HD-FEC is allocated to the remaining LSBs. The remaining three data systems (MSB, SSB, and TSB) are fixed to 0 for error correction. During transmission, the fixed 0 portion is not transmitted.

[0082] With this configuration, the SD-FEC portion can perform the same encoding and decoding processing regardless of the modulation method. The HD-FEC portion can also perform the same encoding and decoding processing, except for the portion where the operation is fixed to 0 according to the modulation method set by the control signal. This can reduce circuit size.

[0083] As described above, the optical transmitter 2 of Embodiment 1 transmits a multi-level modulated optical transmission signal and is characterized in that it includes: a control encoding unit 27 that performs error correction encoding on control information, including information on the multi-level modulation scheme used for a main signal information sequence, and outputs the encoded control information sequence; a main encoding unit 25 that performs error correction encoding on the main signal information corresponding to the multi-level modulation scheme indicated by the control information, and generates an encoded main signal information sequence; a selection circuit 28 that inserts the control information sequence into the main signal information sequence and outputs it so that the control information sequence indicates the multi-level modulation scheme used for the immediately following main signal information sequence; and a mapping unit 29 that performs mapping processing on the control information sequence output by the selection circuit 28 using a predetermined multi-level modulation scheme, and maps the main signal information sequence output by the selection circuit 28 using the multi-level modulation scheme indicated by the control information sequence, thereby generating a multi-level modulated optical transmission signal. With this configuration, the optical transmitter 2 can transmit the control information, including the multi-level modulation scheme used for the main signal information sequence, to the optical receiver 3 before transmitting the main signal information sequence to the optical receiver 3. Therefore, the optical receiving device 3 can process the received main signal based on the control information and change the multi-value modulation method to match the sequence length of the information bit sequence of the main signal information for transmission. When using a fixed multi-value modulation method, it is necessary to use a code format for error correction that is consistent with the multi-value modulation method. If the sequence length of the information bit sequence is shorter than the code length, a fixed length is inserted into the information bit sequence to make it consistent with the code format. Therefore, depending on the sequence length of the information bit sequence, a large number of unnecessary fixed values ​​must be inserted, sometimes reducing transmission efficiency. In contrast, in the above-mentioned structure, the multi-value modulation method can be changed to match the information bit sequence to be transmitted, thereby improving transmission efficiency.

[0084] Furthermore, the control coding unit 27 preferably generates the control information sequence using an error correction code with higher error correction capability than the error correction code used by the main coding unit 25 for the main signal information. If errors exist in the control information, it becomes difficult for the optical receiver 3 to correctly decode the main signal information from the control information. Therefore, it is important to accurately transmit the control information. Therefore, it is preferable to use an error correction code with higher error correction capability for the control information than the error correction code used for the main signal information.

[0085] Furthermore, the control coding unit 27 preferably uses an error-correcting code, such as a polar code, that corresponds to a shorter code length and reduces encoding and decoding processing delays to encode the control information. This reduces the time required for encoding the control information. Therefore, even if the control information encoding process is performed in parallel with the error-correction encoding process for the main signal information, the control information encoding process can be completed before the error-correction encoding process for the main signal information is completed. This reduces the time required for transmission processing compared to starting the error-correction encoding process for the main signal information after the control information encoding process is completed.

[0086] The mapping unit 29 preferably maps the control information sequence using a multi-value modulation scheme with a lower multi-value property than that used for the main signal information sequence. This allows the control information to be transmitted to the optical receiving device 3 more reliably.

[0087] In addition, the object bit sequence for error correction coding processing by the main coding unit 25 is a bit sequence obtained by inserting fixed bits as a non-sent bit sequence into the information bit sequence of the main signal information to be sent, and can be set as a bit sequence corresponding to the maximum multi-value symbol of the multi-value modulation method used for the main signal information sequence.

[0088] Furthermore, the main coding unit 25 can perform a first error correction coding process on the main signal information sequence using an error correction code based on hard decision decoding, and a second error correction coding process on a portion of the main signal information sequence that has undergone the first error correction coding process (e.g., bits corresponding to the least significant bits of the multi-value modulation symbol) using an error correction code based on soft decision decoding. This allows for dual error correction coding of bits with a high error rate, thereby reducing the error rate.

[0089] Furthermore, the control information can also include information indicating the sequence length of the main signal information sequence. This allows the optical receiver 3 to pre-determine the sequence length of the information bit sequence even when shorter information bit sequences are mixed with longer information bit sequences, thereby simplifying processing within the optical receiver 3.

[0090] Furthermore, the optical receiving device 3 receives the multi-value modulated optical transmission signal transmitted by the optical transmitting device 2. The optical receiving device 3 includes a control decoding unit 33 that extracts control information from the optical transmission signal, and a main decoding unit 35 that performs error correction decoding processing on the main signal information sequence contained in the optical transmission signal based on the control information extracted from the optical transmission signal.

[0091] In addition, when the main coding unit 25 of the optical transmitting device 2 performs error correction coding processing on the bit sequence corresponding to the maximum multi-value symbol of the multi-value modulation method used for the main signal information sequence, which is obtained by inserting fixed bits as a non-transmitted bit sequence into the information bit sequence of the main signal information to be transmitted, the main decoding unit 35 of the optical receiving device 3 performs error correction decoding processing after inserting the missing fixed bits into the main signal information sequence contained in the optical transmission signal according to the control information.

[0092] In addition, when the main coding unit 25 of the optical transmitting device 2 performs the first error correction coding processing on the main signal information sequence using the error correction code based on hard decision decoding, and performs the second error correction coding processing on the bit corresponding to the least significant bit of the multi-value modulation symbol in the main signal information sequence that has undergone the first error correction coding processing using the error correction code based on soft decision decoding, the main decoding unit 35 of the optical receiving device 3 performs hard decision decoding processing on the main signal information sequence after determining the hard decision bits other than the least significant bit based on the soft decision decoding result of the least significant bit of the multi-value modulation symbol.

[0093] The optical transmitting device 2 can constitute the optical transmission system 1 together with the optical receiving device 3. In addition, an optical transmission method for transmitting a multi-value modulated optical transmission signal can also be provided. The optical transmission method includes the following steps: the optical transmitting device 2 performs error correction coding processing on control information including information on the multi-value modulation method used for the main signal information sequence to generate an encoded control information sequence; the optical transmitting device 2 performs error correction coding processing corresponding to the multi-value modulation method represented by the control information on the main signal information to generate an encoded main signal information sequence; the optical transmitting device 2 inserts the control information sequence into the main signal information sequence so that the control information sequence represents the multi-value modulation method for the main signal information sequence immediately following it; the optical transmitting device 2 uses a predetermined multi-value modulation method to map the control information sequence; the optical transmitting device 2 uses the multi-value modulation method represented by the control information sequence to map the main signal information sequence; and the optical transmitting device 2 transmits the multi-value modulated optical transmission signal generated by the mapping processing, thereby transmitting the control information before the main signal information.

[0094] The configurations shown in the above embodiments are merely examples, and can be combined with other known technologies, and the embodiments can be combined with each other. Part of the configuration can also be omitted or modified without departing from the spirit of the invention.

[0095] In addition, in the above-mentioned embodiment, an optical transmitting device 2 having a transmitting function and an optical receiving device 3 having a receiving function are shown, but an optical transmission device having both the functions of the optical transmitting device 2 and the functions of the optical receiving device 3 and capable of bidirectional communication can also be provided.

[0096] Label Description

[0097] 1: Optical transmission system; 2: Optical transmitter; 3: Optical receiver; 20: Modulation mode determination unit; 21: Fixed value insertion unit; 22: Control information generation unit; 23: Coding circuit; 24, 34: Interleaver; 25: Main coding unit; 26, 36: Deinterleaver; 27: Control coding unit; 28: Selection circuit; 29: Mapping unit; 30: Decoding circuit; 31: Separation circuit; 32: Control signal soft decision generation unit; 33: Control decoding unit; 35: Main decoding unit; 90: Processing circuit; 91: Control circuit; 92: Processor; 93: Memory; 251: HD-FEC coding unit; 252: Multi-stage coding unit; 253: SD-FEC coding unit; 351: Main signal soft decision generation unit; 352: SD-FEC decoding unit; 353: Multi-stage / multi-stage decoding unit; 354: HD-FEC decoding unit.

Claims

1. An optical transmitting device that transmits a multi-value modulated optical transmission signal, characterized in that: The optical transmitting device comprises: a control coding unit that performs error correction coding processing on control information including information on a multi-value modulation method used for a main signal information sequence and outputs the coded control information sequence; a main encoding unit for performing error correction encoding processing on main signal information corresponding to the multi-value modulation method indicated by the control information to generate the encoded main signal information sequence; a selection circuit that inserts the control information sequence into the main signal information sequence and outputs the sequence so that the control information sequence indicates the multi-value modulation method used for the immediately following main signal information sequence; as well as A mapping unit maps the control information sequence output by the selection circuit using a predetermined multi-value modulation method, and maps the main signal information sequence output by the selection circuit using the multi-value modulation method represented by the control information sequence to generate the multi-value modulated optical transmission signal.

2. The optical transmission device according to claim 1, wherein The control coding unit generates the control information sequence using an error correction code having a higher error correction capability than the error correction code used by the main coding unit for the main signal information.

3. The optical transmission device according to claim 1, wherein The control coding unit performs error correction coding of the control information sequence in parallel with the error correction coding of the main coding unit.

4. The optical transmitting device according to claim 3, wherein: The control coding unit performs error correction coding processing on the control information sequence using a polar code.

5. The optical transmitting device according to claim 1, wherein The mapping unit performs the mapping process on the control information sequence using a multi-value modulation method having a lower multi-value property than the multi-value modulation method used for the main signal information sequence.

6. The optical transmitting device according to claim 1, wherein The main coding unit performs the error correction coding process on a bit sequence corresponding to a maximum multi-value symbol of the multi-value modulation method used for the main signal information sequence, wherein the bit sequence is obtained by inserting fixed bits as a bit sequence not to be transmitted into the information bit sequence of the main signal information to be transmitted.

7. The optical transmitting device according to claim 1, wherein The main coding unit uses an error correction code based on hard decision decoding to perform a first error correction coding process on the main signal information sequence, and uses an error correction code based on soft decision decoding to perform a second error correction coding process on the bit corresponding to the least significant bit of the multi-value modulation symbol in the main signal information sequence that has undergone the first error correction coding process.

8. The optical transmitting device according to claim 1, wherein The control information further includes information indicating the length of the main signal information sequence.

9. An optical receiving device for receiving an optical transmission signal transmitted by the optical transmitting device according to any one of claims 1 to 8, characterized in that: The light receiving device has: a control decoding unit that extracts the control information from the optical transmission signal; and A main decoding unit performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal.

10. An optical receiving device for receiving the optical transmission signal transmitted by the optical transmitting device according to claim 6, characterized in that: The light receiving device has: a control decoding unit that extracts the control information from the optical transmission signal; and a main decoding unit that performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal; The main decoding unit performs the error correction decoding process starting from inserting missing fixed bits into the main signal information sequence included in the optical transmission signal based on the control information.

11. An optical receiving device for receiving the optical transmission signal transmitted by the optical transmitting device according to claim 7, characterized in that: The light receiving device has: a control decoding unit that extracts the control information from the optical transmission signal; and a main decoding unit that performs error correction decoding processing on the main signal information sequence included in the optical transmission signal based on the control information extracted from the optical transmission signal; The main decoding unit determines hard decision bits other than the least significant bit based on a soft decision decoding result of the least significant bit of the multi-value modulation symbol, and then performs hard decision decoding processing on the main signal information sequence.

12. An optical transmission system, characterized in that: The optical transmission system has: The optical transmitting device according to claim 1; and The light receiving device according to claim 9.

13. An optical transmission method for transmitting a multi-value modulated optical transmission signal, characterized in that: The optical transmission method comprises the following steps: The optical transmitting device performs error correction coding processing on the control information including information on the multi-value modulation method used for the main signal information sequence to generate a coded control information sequence; The optical transmitting device performs error correction coding processing corresponding to the multi-value modulation method indicated by the control information on the main signal information to generate the encoded main signal information sequence; The optical transmitting device inserts the control information sequence into the main signal information sequence so that the control information sequence indicates the multi-value modulation method for the main signal information sequence immediately following the control information sequence; The optical transmitting device uses a predetermined multi-value modulation method to perform mapping processing on the control information sequence; The optical transmitting device performs mapping processing on the main signal information sequence using the multi-value modulation method represented by the control information sequence; as well as The optical transmission signal after the multi-value modulation generated by the mapping process is transmitted by the optical transmission device, and the control information is transmitted before the main signal information.

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