JP4523540B2 - Optical receiver - Google Patents

Description

  The present invention relates to an optical receiver having a soft decision error correction function.

  Due to the rapid increase in demand for the Internet in recent years, technology development for high speed and large capacity is progressing in order to cope with the increasing traffic volume. In a long-distance optical communication system represented by a submarine cable system responsible for international communications and the like, high-speed and large-capacity data is transmitted over a long distance, so that transmission quality deteriorates due to wavelength dispersion or the like, and bit errors are likely to occur. For this reason, in a long-distance optical communication system, transmission is generally performed by adding FEC (Forward Error Correction) as a high-efficiency error correction code. As an error correction method of FEC, hard decision error correction in which received data is identified by a single classifier has been used. In recent years, in order to improve error correction capability, received data is identified by a plurality of classifiers. Soft-decision error correction performed with a discrimination threshold of Some conventional soft-decision decoding apparatuses perform demultiplexing processing after soft-decision identification to reduce the output (see, for example, Patent Document 1).

JP 2003-163637 A

  In the conventional optical receiver, the demultiplexed data is transferred as it is to the FEC decoding unit, but this configuration can cope with a speed at which the skew generated between the data channels can be ignored, and is currently less than 1 Gbps. Up to. The interface in this speed range is standardized as SFI-4 (Serdes Framer Interface-4) by OIF (Optical Internetworking Forum), and the line rate is 10 Gbps class. For example, if 750 Mbps per channel, 16 Gbps is 12 Gbps. In order to cope with the increasing traffic volume year by year, it is essential to increase the interface speed, and OIF has SFI-5 (Serdes Framer Interface-5) as a 40G class standard. This is a speed of around 3 Gbps per channel, and the skew generated between the data channels cannot be ignored. Therefore, in SFI-5, a deskew channel is prepared in addition to the data channel, and the skew is deleted by performing a deskew process on the receiving side. Since the deskew is performed by comparing the data channel and the deskew channel and detecting coincidence, it is necessary for the data channel to change to some extent in order to perform the deskew normally. For hard decision data, the mark ratio is ½, so it changes sufficiently. However, for soft decision reliability information, such as when the communication quality is good (eg when the S / N is good), the reliability information. However, there is a problem that the deskew cannot be performed and the desired error correction capability cannot be obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical receiver capable of performing deskew regardless of communication quality and obtaining a normal soft decision error correction operation. Is what you get.

  An optical receiving apparatus according to the present invention is an optical receiving apparatus having a soft decision error correction function, wherein photoelectric conversion means for converting an optical signal from a transmission path into an electric signal, and the electric signal as a plurality of identification threshold values. A soft decision discriminating unit that outputs an identification signal corresponding to the identification result and reliability information indicating the reliability of the identification signal, a demultiplexing unit that slows down the identification signal and the reliability information, A reliability information transmission processing unit that processes at least the reliability information before deskewing, a deskew channel generation unit that generates a deskew channel for the identification signal and the reliability information, and deskew the identification signal and the reliability information A deskew unit, a reliability information reception processing unit for processing at least the reliability information after deskew, a predetermined decoding algorithm based on the identification signal and the reliability information It is provided with a a FEC decoding unit that performs error correction in accordance with the rhythm.

  The optical receiving apparatus according to the present invention can perform deskew regardless of communication quality, and has an effect of obtaining a normal soft decision error correction operation.

Embodiment 1 FIG.
An optical receiver according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an optical receiving apparatus according to Embodiment 1 of the present invention. In addition, in each figure, the same code | symbol shows the same or equivalent part.

  The optical receiving apparatus according to the first embodiment is an optical receiving apparatus having a soft decision error correction function for identifying an optical reception signal by a plurality of discriminators using a plurality of discrimination thresholds, and generating a deskew channel of reliability information By performing scrambling before and descrambling after deskewing, deskewing can be performed regardless of the communication quality, and a normal soft decision error correction operation is obtained.

  1, the optical receiver according to the first embodiment includes a photodiode (photoelectric conversion means) 10 that converts an optical reception signal from a transmission path into an electric reception signal, a soft decision identification LSI 100, and a soft decision error. A correction LSI 200 is provided.

  The soft decision identification LSI 100 generates a soft decision identification unit 20, a demultiplexing unit 30, a reliability information transmission processing unit 40 for performing reliability information transmission processing, and a deskew channel for hard decision data and reliability information. A deskew channel generation unit 50 is mounted.

  The soft decision error correction LSI 200 includes a deskew unit 60 that performs deskew processing of hard decision data and reliability information, a reliability information reception processing unit 70 that performs reception processing of reliability information, and an FEC decoding unit 80. ing.

  The soft decision discriminating unit 20 includes a multi-level discriminator 21 (21a to 21g) that discriminates at each discriminating level of the soft decision, and an encoder that converts the output of the multi-level discriminator 21 into 3-bit binary signal information. 22 are included.

  The demultiplexing unit 30 includes a 1:16 demultiplexing circuit 31 (31a to 31c) that performs serial / parallel conversion for each bit.

  The reliability information transmission processing unit 40 includes a scramble circuit 41 (41a to 41b) that scrambles the reliability information.

  The deskew channel generation unit 50 includes a deskew channel generation circuit 51 (51a to 51c) that generates a 1-bit deskew channel from 16 parallel data.

  The deskew unit 60 includes deskew circuits 61 (61a to 61c) that perform deskew processing from 17 parallel data including a deskew channel.

  The reliability information reception processing unit 70 includes a descrambling circuit 71 (71a to 71b) that descrambles the reliability information.

  Next, the operation of the optical receiving apparatus according to the first embodiment will be described with reference to the drawings.

  The received optical signal input from the transmission path is input to the photodiode 10, which converts the optical signal into an electrical signal and outputs the electrical signal to the soft decision identifying unit 20.

  The soft decision discriminating unit 20 inputs the electrical signal input from the photodiode 10 to the multi-level discriminator 21. The multi-level discriminator 21 determines that the information data “0” is lower than the threshold level based on the set threshold value. ", And if it is higher than the threshold level, it is identified as information data" 1 ", and the identification result is output to the encoder 22. FIG. 1 shows the case of seven identification levels as an example.

  The encoder 22 determines the identification signal as a result of performing the hard decision identification and the reliability of the hard decision identification signal based on the identification result output from the multi-level discriminator 21 for each electric signal. The reliability information shown is output. As shown in FIG. 1, when there are seven discriminators 21, the hard decision identification signal is 1 bit, and the reliability information indicating the reliability of the hard decision identification signal is 2 bits. For example, when there are 15 discriminators, the reliability information is 3 bits.

  Here, the hard decision identification signal (hard decision data) and the reliability information will be briefly described. When there are seven discriminators 21, there are eight possible values of the 3-bit binary signal output from the encoder 22, “111, 110, 101, 100,000, 001, 010, 011”. . For example, the most significant bit is a hard decision code and the lower 2 bits are reliability information. As for 2-bit reliability information, “11” has the highest reliability and “00” has the lowest reliability. For example, “111” is the most probable “1”, and “100” is the least probable “1”.

  The signal output from the soft decision identifying unit 20 is input to the 1:16 demultiplexing circuit 31 in the demultiplexing unit 30, converted into a 16-bit parallel signal, and sent to the reliability information transmission processing unit 40. The reason for slowing down is that the subsequent processing speed can be slow. In FIG. 1, the three types of data output from the soft decision identifying unit 20 are converted into parallel data.

  The signal input to the reliability information transmission processing unit 40 is directly output to the deskew channel generation unit 50 for the hard decision code. The reliability information is scrambled and output to the deskew channel generation unit 50. By applying the scramble, the reliability information also changes between “0” and “1” as in the hard decision code.

  The signal input to the deskew channel generation unit 50 is input to the deskew channel generation circuit 51 in the deskew channel generation unit 50. The deskew channel generation circuit 51 generates a deskew channel in accordance with the OIF SFI-5 standard.

  The data output from the deskew channel generation unit 50 is input to the deskew unit 60.

  The signal input to the deskew unit 60 is input to the deskew circuit 61 in the deskew unit 60. The deskew circuit 61 performs deskew according to the OFI SFI-5 standard and outputs 16 parallel data excluding the deskew channel to the reliability information reception processing unit 70.

  The signal input to the reliability information reception processing unit 70 is directly output to the FEC decoding unit 80 for the hard decision code. The reliability information is descrambled to restore the data before scrambled, and is output to the FEC decoding unit 80.

  The FEC decoding unit 80 performs error correction according to a predetermined decoding algorithm and outputs 16 parallel data.

  As described above, in the first embodiment, since the descrambling is performed before the deskew channel of the reliability information is generated and the descrambling is performed after the deskew, the deskew can be performed regardless of the communication quality. A soft decision error correction operation can be obtained.

Embodiment 2. FIG.
An optical receiver according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the optical receiving apparatus according to Embodiment 2 of the present invention.

  The optical receiving apparatus according to the second embodiment is an optical receiving apparatus having a soft decision error correction function in which an optical received signal is identified by a plurality of discriminating thresholds using a plurality of discriminators, before generating a deskew channel for reliability information. By inverting the reliability information corresponding to either hard decision data “0” or “1”, it is possible to perform deskew regardless of the communication quality and obtain a normal soft decision error correction operation. is there.

  2, the optical receiving apparatus according to the second embodiment includes a photodiode (photoelectric conversion means) 10 that converts an optical reception signal from a transmission path into an electric reception signal, a soft decision identification LSI 100, and a soft decision error. A correction LSI 200 is provided.

  The soft decision identification LSI 100 generates a soft decision identification unit 20, a demultiplexing unit 30, a reliability information transmission processing unit 40 for performing reliability information transmission processing, and a deskew channel for hard decision data and reliability information. A deskew channel generation unit 50 is mounted.

  The soft decision error correction LSI 200 includes a deskew unit 60 that performs deskew processing of hard decision data and reliability information, a reliability information reception processing unit 70 that performs reception processing of reliability information, and an FEC decoding unit 80. ing.

  The soft decision discriminating unit 20 includes a multi-level discriminator 21 (21a to 21g) that discriminates at each discriminating level of the soft decision, and an encoder that converts the output of the multi-level discriminator 21 into 3-bit binary signal information. 22 are included.

  The demultiplexing unit 30 includes a 1:16 demultiplexing circuit 31 (31a to 31c) that performs serial / parallel conversion for each bit.

  The reliability information transmission processing unit 40 includes a reliability information inversion circuit (first reliability information inversion circuit) 42 that inverts reliability information corresponding to either hard decision data “0” or “1”. Is included.

  The deskew channel generation unit 50 includes a deskew channel generation circuit 51 (51a to 51c) that generates a 1-bit deskew channel from 16 parallel data.

  The deskew unit 60 includes deskew circuits 61 (61a to 61c) that perform deskew processing from 17 parallel data including a deskew channel.

  The reliability information reception processing unit 70 includes a reliability information inversion circuit (second reliability information inversion circuit) 72 that inverts reliability information corresponding to either hard decision data “0” or “1”. Is included.

  Next, the operation of the optical receiver according to the second embodiment will be described with reference to the drawings. FIG. 3 is a diagram for explaining the operation of the reliability information inversion circuit of the optical receiver according to the second embodiment of the present invention.

  Photodiode 10, soft decision discriminator 20 (multi-level discriminator 21, encoder 22), demultiplexer 30 (1:16 demultiplexer 31), deskew channel generator 50 (deskew channel generator 51), deskew Operations of the unit 60 (the deskew circuit 61) and the FEC decoding unit 80 are the same as those in the first embodiment. In the first embodiment, the reliability information transmission processing unit 40 and the reliability information reception processing unit 70 are provided with the scramble circuit 41 and the descrambling circuit 71. In the second embodiment, the reliability information inversion is performed. A circuit 42 and a reliability information inversion circuit 72 are provided.

  The signal input to the reliability information transmission processing unit 40 inverts reliability information corresponding to either hard decision data “0” or “1” in the reliability information inversion circuit 42.

  This process will be described with reference to FIG. With regard to the hard decision identification signal and the reliability information, when there are seven classifiers 21, the possible values of the 3-bit binary signal output from the encoder 22 are “111, 110, 101, 100,000, 001”. , 010, 011 ”, and the low-order 2-bit reliability information is simply described as“ 11 ”having the highest reliability and“ 00 ”having the lowest reliability. Can be represented in the input field. In this case, when the communication quality is good (such as when the S / N is good), the reliability information does not change much, and “11” is dominant. Here, for example, when the reliability information is inverted when the hard decision data is “0” as shown in the output column of FIG. 3, there is a change between “0” and “1” as shown by shading. It becomes like this.

  The signal input to the reliability information reception processing unit 70 is restored to the original reliability information by performing the reverse process of the reliability information inversion circuit 42 in the reliability information inversion circuit 72.

  As described above, in the second embodiment, the reliability information corresponding to either the hard decision data “0” or “1” is inverted before the deskew channel of the reliability information is generated. Deskew can be performed regardless of the communication quality, and a normal soft decision error correction operation can be obtained.

Embodiment 3 FIG.
An optical receiver according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of the optical receiving apparatus according to Embodiment 3 of the present invention.

  The optical receiving apparatus according to the third embodiment is an optical receiving apparatus having a soft decision error correction function that performs identification of an optical reception signal by a plurality of discriminators using a plurality of discrimination thresholds, before generating a deskew channel for reliability information. By changing the output destination of the hard decision data and the reliability information in a time division manner, it is possible to perform deskew regardless of the communication quality and obtain a normal soft decision error correction operation.

  4, the optical receiving apparatus according to the third embodiment includes a photodiode (photoelectric conversion means) 10 that converts an optical reception signal from a transmission path into an electric reception signal, a soft decision identification LSI 100, a soft decision error, and the like. A correction LSI 200 is provided.

  The soft decision identification LSI 100 generates a soft decision identification unit 20, a demultiplexing unit 30, a reliability information transmission processing unit 40 for performing reliability information transmission processing, and a deskew channel for hard decision data and reliability information. A deskew channel generation unit 50 is mounted.

  The soft decision error correction LSI 200 includes a deskew unit 60 that performs deskew processing of hard decision data and reliability information, a reliability information reception processing unit 70 that performs reception processing of reliability information, and an FEC decoding unit 80. ing.

  The soft decision discriminating unit 20 includes a multi-level discriminator 21 (21a to 21g) that discriminates at each discriminating level of the soft decision, and an encoder that converts the output of the multi-level discriminator 21 into 3-bit binary signal information. 22 are included.

  The demultiplexing unit 30 includes a 1:16 demultiplexing circuit 31 (31a to 31c) that performs serial / parallel conversion for each bit.

  The reliability information transmission processing unit 40 includes a time division allocation circuit (first time division allocation circuit) 43 that changes the output destination of the hard decision data and the reliability information in a time division manner.

  The deskew channel generation unit 50 includes a deskew channel generation circuit 51 (51a to 51c) that generates a 1-bit deskew channel from 16 parallel data.

  The deskew unit 60 includes deskew circuits 61 (61a to 61c) that perform deskew processing from 17 parallel data including a deskew channel.

  The reliability information reception processing unit 70 includes a time division allocation circuit (second time division allocation circuit) 73 that changes the output destination of the hard decision data and the reliability information in a time division manner.

  Next, the operation of the optical receiving apparatus according to the third embodiment will be described with reference to the drawings. FIG. 5 is a diagram for explaining the operation of the time division allocation circuit of the optical receiving apparatus according to Embodiment 3 of the present invention.

  Photodiode 10, soft decision discriminator 20 (multi-level discriminator 21, encoder 22), demultiplexer 30 (1:16 demultiplexer 31), deskew channel generator 50 (deskew channel generator 51), deskew Operations of the unit 60 (the deskew circuit 61) and the FEC decoding unit 80 are the same as those in the first embodiment. In the first embodiment, the reliability information transmission processing unit 40 and the reliability information reception processing unit 70 are provided with the scramble circuit 41 and the descrambling circuit 71. However, in the third embodiment, a time division allocation circuit is provided. 43 and a time division allocation circuit 73 are provided.

  The signal input to the reliability information transmission processing unit 40 changes the output destination in a time division manner with the hard decision data and the reliability information in the time division allocation circuit 43.

  This process will be described with reference to FIG. In FIG. 5, three paths (paths (1) to (3)) are three outputs of the time division allocation circuit 43 (for example, from the top of FIG. 5, the path (1), the path (2), and the path (3)). The inputs of the time division allocation circuit 43 are allocated, for example, from the top of FIG. 5 as a hard decision data path, a reliability information (1) path, and a reliability information (2) path. By changing the output destination at fixed time intervals by the time division allocation circuit 43, the three paths change between “0” and “1”.

  The signal input to the reliability information reception processing unit 70 is restored to the original reliability information by performing a process reverse to the time division allocation circuit 43 in the time division allocation circuit 73.

  As described above, in the third embodiment, the hard decision data and the reliability information are configured to change the output destination in a time division manner before the deskew channel of the reliability information is generated. Therefore, the deskew is performed regardless of the communication quality. And a normal soft decision error correction operation can be obtained.

Embodiment 4 FIG.
An optical receiving apparatus according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of an optical receiving apparatus according to Embodiment 4 of the present invention.

  The optical receiving apparatus according to the fourth embodiment is an optical receiving apparatus having a soft decision error correction function in which an optical received signal is identified by a plurality of discriminators using a plurality of discrimination thresholds. By flowing training data before channel generation, deskew can be performed regardless of the communication quality, and a normal soft decision error correction operation is obtained.

  6, the optical receiving apparatus according to the fourth embodiment includes a photodiode (photoelectric conversion means) 10 that converts an optical reception signal from a transmission path into an electric reception signal, a soft decision identification LSI 100, a soft decision error, and the like. A correction LSI 200 is provided.

  The soft decision identification LSI 100 generates a soft decision identification unit 20, a demultiplexing unit 30, a reliability information transmission processing unit 40 for performing reliability information transmission processing, and a deskew channel for hard decision data and reliability information. A deskew channel generation unit 50 is mounted.

  The soft decision error correction LSI 200 is equipped with a deskew unit 60 that performs deskew processing of hard decision data and reliability information, and an FEC decoding unit 80.

  The soft decision discriminating unit 20 includes a multi-level discriminator 21 (21a to 21g) that discriminates at each discriminating level of the soft decision, and an encoder that converts the output of the multi-level discriminator 21 into 3-bit binary signal information. 22 are included.

  The demultiplexing unit 30 includes a 1:16 demultiplexing circuit 31 (31a to 31c) that performs serial / parallel conversion for each bit.

  The reliability information transmission processing unit 40 includes a training data insertion circuit 44 (44a to 44b) that inserts training data into the reliability information.

  The deskew channel generation unit 50 includes a deskew channel generation circuit 51 (51a to 51c) that generates a 1-bit deskew channel from 16 parallel data.

  The deskew unit 60 includes deskew circuits 61 (61a to 61c) that perform deskew processing from 17 parallel data including a deskew channel.

  Next, the operation of the optical receiving apparatus according to the fourth embodiment will be described with reference to the drawings.

  Photodiode 10, soft decision discriminator 20 (multi-level discriminator 21, encoder 22), demultiplexer 30 (1:16 demultiplexer 31), deskew channel generator 50 (deskew channel generator 51), deskew Operations of the unit 60 (the deskew circuit 61) and the FEC decoding unit 80 are the same as those in the first embodiment. In the first embodiment, the reliability information transmission processing unit 40 is provided with the scramble circuit 41. However, in the fourth embodiment, the training data insertion circuit 44 (44a to 44b) is provided.

  The deskew is performed mainly to absorb a skew generated from a difference in pattern length between substrates on which a plurality of LSIs are mounted or in a substrate on which a plurality of LSIs are mounted. Since the pattern length difference does not change, the deskew may be performed once when the apparatus is started up.

  The signal input to the reliability information transmission processing unit 40 inserts training data having a moderate change of “0” and “1” when the apparatus is started up by the training data insertion circuit 44 and outputs it.

  Since the training data only flows when the apparatus is started up, the reliability information reception processing unit 70 is not required as in the first to third embodiments.

  Note that the scramble circuit 41, the reliability information inversion circuit 42, and the time division allocation circuit 43 of the above first to third embodiments may be used as the reliability information transmission processing unit 40 for inserting training data.

  As described above, in the fourth embodiment, since the training data is flowed before generating the deskew channel of the reliability information at the time of starting the apparatus, the deskew can be performed regardless of the communication quality, and the normal soft decision is performed. An error correction operation can be obtained.

Embodiment 5 FIG.
An optical receiving apparatus according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration of an optical receiving apparatus according to Embodiment 5 of the present invention.

  The optical receiving apparatus according to the fifth embodiment is an optical receiving apparatus having a soft decision error correction function for discriminating received optical signals with a plurality of discriminating thresholds using a plurality of discriminators. By changing the threshold for degree information, deskew can be performed regardless of the communication quality, and a normal soft decision error correction operation is obtained.

  7, the optical receiving apparatus according to the fifth embodiment includes a photodiode (photoelectric conversion means) 10 that converts an optical reception signal from a transmission path into an electric reception signal, a soft decision identification LSI 100, and a soft decision error. A correction LSI 200 is provided.

  The soft decision identification LSI 100 includes a soft decision identification unit 20, a demultiplexing unit 30, and a deskew channel generation unit 50 that generates a deskew channel for hard decision data and reliability information.

  The soft decision error correction LSI 200 is equipped with a deskew unit 60 that performs deskew processing of hard decision data and reliability information, and an FEC decoding unit 80.

  The soft decision discriminating unit 20 includes a multi-level discriminator 21 (21a to 21g) that discriminates at each discriminating level of the soft decision, and an encoder that converts the output of the multi-level discriminator 21 into 3-bit binary signal information. 22 are included.

  The demultiplexing unit 30 includes a 1:16 demultiplexing circuit 31 (31a to 31c) that performs serial / parallel conversion for each bit.

  The deskew channel generation unit 50 includes a deskew channel generation circuit 51 (51a to 51c) that generates a 1-bit deskew channel from 16 parallel data.

  The deskew unit 60 includes a deskew circuit 61 (61a to 61c) that performs deskew processing from 17 parallel data including a deskew channel, and measures the frequency of changes of “0” and “1” in the deskew unit 60 to obtain a multi-level A threshold adjustment circuit 62 that adjusts the threshold of the discriminator 21 is included.

  Next, the operation of the optical receiving apparatus according to the fifth embodiment will be described with reference to the drawings.

  Photodiode 10, soft decision discriminating unit 20 (multi-level discriminator 21, encoder 22), demultiplexing unit 30 (1:16 demultiplexing circuit 31), deskew channel generation unit 50 (deskew channel generation circuit 51), and The operation of the FEC decoding unit 80 is the same as that in the first embodiment. In the first embodiment, the deskew unit 60 includes the deskew circuit 61. However, in the fifth embodiment, a threshold adjustment circuit 62 is added to the deskew unit 60.

  In order to perform deskew, it is necessary to input data having a moderate change between “0” and “1”. It can also be forcibly generated by changing the threshold for hard decision data or reliability information.

  The signal input to the deskew unit 60 measures the frequency of change of “0” and “1” by the threshold adjustment circuit 62. If the frequency of change of “0” and “1” is small, multilevel identification is performed. The threshold value of the device 21 is adjusted.

  As described above, in the fifth embodiment, since the hard decision data or the threshold for reliability information is changed when the apparatus is started up, deskew can be performed regardless of the communication quality, and normal soft decision can be performed. An error correction operation can be obtained.

Embodiment 6 FIG.
An optical receiving apparatus according to Embodiment 6 of the present invention will be described with reference to FIG. FIG. 8 is a block diagram showing the configuration of the deskew unit of the optical receiving apparatus according to Embodiment 6 of the present invention.

  The optical receiving apparatus according to the sixth embodiment has three paths input to the deskew unit in an optical receiving apparatus having a soft decision error correction function in which an optical received signal is identified by a plurality of discriminators using a plurality of discrimination thresholds. By adjusting the skew between them, the data shift between the three paths can be corrected, and a normal soft decision error correction operation can be obtained.

  8, the optical receiving apparatus according to the sixth embodiment includes a photodiode 10, a soft decision discriminating unit 20 (multilevel discriminator 21, encoder 22), and a demultiplexing unit 30 (1:16 demultiplexing circuit 31). ), Reliability information transmission processing unit 40 (scramble circuit 41, reliability information inversion circuit 42, time division allocation circuit 43, training data insertion circuit 44), deskew channel generation unit 50 (deskew channel generation circuit 51), reliability information The reception processing unit 70 (descramble circuit 71, reliability information inversion circuit 72, time division allocation circuit 73) and FEC decoding unit 80 are the same as those in the first to fifth embodiments.

  As shown in FIG. 8, the deskew unit 60 and the deskew circuit 61 (61a to 61c) include a CDR (Clock Data Recovery) 1 (1a to 1c) for recovering a clock and data, and a frame from the input deskew channel. Frame phase detection circuit 2 (2a to 2c) for detecting the phase, phase shifter 3 (3a to 3c) for adjusting the phase of data, and frame phase comparison circuit 4 (4a) for phase comparison of frames with other paths To 4b).

  Next, the operation of the deskew unit of the optical receiver according to the sixth embodiment will be described with reference to the drawings.

  Although the deskew function in the three paths can be performed by the deskew function of SFI-5, a normal soft decision error correction operation cannot be obtained unless the phases of the three paths are matched. In the sixth embodiment, the frame phases of the deskew channels of the three paths are compared, and the data phase between the three paths is adjusted.

  The signal input to the deskew unit 60 is input to the deskew circuit 61. Of the input signals, a 16-bit data channel is input to CDR 1 and a 1-bit deskew channel is input to frame phase detection circuit 2. The CDR1 performs clock and data recovery. The frame phase detection circuit 2 detects the frame overhead in the deskew channel and outputs phase information.

  The phase adjustment between the three paths is based on the phase of one path and the phases of the remaining two paths may be matched. The deskew circuit for the remaining two paths performs frame phase comparison by the frame phase comparison circuit 4. Output phase information. The phase shifter 3 adjusts the delay so that the phases of the three paths are matched.

  As described above, in the sixth embodiment, since the skew between the three paths input to the deskew unit 60 is adjusted, the data shift between the three paths can be corrected, and normal softness can be corrected. A determination error correction operation can be obtained.

  The optical receiver according to the present invention is useful for application to a digital optical transmission system such as a submarine cable system for transmitting high-speed and large-capacity data over a long distance, but the application is not limited thereto. For example, the present invention can be applied to an external storage device using an optical disc such as a CD (compact disc) or a DVD (digital versatile disc) as a recording medium.

  In addition, the optical receiving apparatus according to the present invention is not limited to one using block turbo as a decoding algorithm as long as it uses a soft decision.

It is a block diagram which shows the structure of the optical receiver which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the optical receiver which concerns on Embodiment 2 of this invention. It is a figure for demonstrating operation | movement of the reliability information inversion circuit of the optical receiver which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the optical receiver which concerns on Embodiment 3 of this invention. It is a figure for demonstrating operation | movement of the time division allocation circuit of the optical receiver which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the optical receiver which concerns on Embodiment 4 of this invention. It is a block diagram which shows the structure of the optical receiver which concerns on Embodiment 5 of this invention. It is a block diagram which shows the structure of the deskew part of the optical receiver which concerns on Embodiment 6 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Photodiode, 20 Soft decision discriminating part, 21 Multi-level discriminator, 22 Encoder, 30 Demultiplexing part, 31 1:16 Demultiplexing circuit, 40 Reliability information transmission processing part, 41 Scramble circuit, 42 Reliability information Inversion circuit, 43 Time division allocation circuit, 44 Training data insertion circuit, 50 Deskew channel generation unit, 51 Deskew channel generation circuit, 60 Deskew unit, 61 Deskew circuit, 62 Threshold adjustment circuit, 70 Reliability information reception processing unit, 71 Scramble circuit, 72 reliability information inversion circuit, 73 time division allocation circuit, 80 FEC decoding unit, 100 soft decision identification LSI, 200 soft decision error correction LSI.

Claims (7)

An optical receiver having a soft decision error correction function,
Photoelectric conversion means for converting an optical signal from the transmission path into an electrical signal;
A soft decision identifying unit that identifies the electrical signal based on a plurality of identification thresholds, outputs an identification signal corresponding to an identification result, and reliability information indicating the reliability of the identification signal;
A demultiplexer that slows down the identification signal and the reliability information;
A reliability information transmission processing unit for processing at least the reliability information before deskew;
A deskew channel generation unit for generating a deskew channel of the identification signal and the reliability information;
A deskew unit for deskewing the identification signal and the reliability information;
A reliability information reception processing unit for processing at least the reliability information after deskew;
An optical receiving apparatus comprising: an FEC decoding unit that performs error correction according to a predetermined decoding algorithm based on the identification signal and the reliability information. The reliability information transmission processing unit includes a scramble circuit that scrambles the reliability information,
The optical receiver according to claim 1, wherein the reliability information reception processing unit includes a descrambling circuit that performs a descrambling process on the reliability information. The reliability information transmission processing unit includes a first reliability information inversion circuit that performs inversion processing on a part of the reliability information,
The reliability information reception processing unit includes a second reliability information inversion circuit that performs an inversion process opposite to the first reliability information inversion circuit on a part of the reliability information. Item 4. The optical receiver according to Item 1. The reliability information transmission processing unit includes a first time division allocation circuit that performs a change process on the output destination of the reliability information,
The reliability information reception processing unit includes a second time-division allocation circuit that performs a change process opposite to the first time-division allocation circuit for the output destination of the reliability information. The optical receiver described. An optical receiver having a soft decision error correction function,
Photoelectric conversion means for converting an optical signal from the transmission path into an electrical signal;
A soft decision identifying unit that identifies the electrical signal based on a plurality of identification thresholds, outputs an identification signal corresponding to an identification result, and reliability information indicating the reliability of the identification signal;
A demultiplexer that slows down the identification signal and the reliability information;
A reliability information transmission processing unit for processing at least the reliability information before deskew;
A deskew channel generation unit for generating a deskew channel of the identification signal and the reliability information;
A deskew unit for deskewing the identification signal and the reliability information;
An FEC decoding unit that performs error correction according to a predetermined decoding algorithm based on the identification signal and the reliability information,
The optical receiver according to claim 1, wherein the reliability information transmission processing unit includes a training data insertion circuit that performs training data insertion processing on the reliability information when the apparatus is started up. An optical receiver having a soft decision error correction function,
Photoelectric conversion means for converting an optical signal from the transmission path into an electrical signal;
A soft decision identifying unit that identifies the electrical signal based on a plurality of identification thresholds, outputs an identification signal corresponding to an identification result, and reliability information indicating the reliability of the identification signal;
A demultiplexer that slows down the identification signal and the reliability information;
A deskew channel generation unit for generating a deskew channel of the identification signal and the reliability information;
A deskew unit for deskewing the identification signal and the reliability information;
An FEC decoding unit that performs error correction according to a predetermined decoding algorithm based on the identification signal and the reliability information,
The deskew unit includes a threshold adjustment circuit that adjusts a plurality of discrimination thresholds of the soft decision discrimination unit during deskew. The said deskew part detects the frame phase of the said identification signal and the said reliability information, and adjusts the phase of the said identification signal and the said reliability information, The any one of Claim 1-6 characterized by the above-mentioned. The optical receiver described in 1.

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