JP5938023B2 - Optical transmission apparatus and optical transmission method - Google Patents

Description

  The present invention relates to an optical transmission device and an optical transmission method.

  In recent years, with the spread of multimedia services and the expansion of the use of ICT (Information and Communication Technology) services, Internet traffic flowing through backbone networks has been increasing year by year. In recent years, digital coherent signal processing technology has been attracting attention as a next-generation optical communication technology that will drive the ever-increasing traffic. In a 40 Gbps (Wavelength Division Multiplexing) system that has already been commercialized, dispersion management, a dispersion compensator, and the like are widely used to correct distortion of an optical signal generated in a transmission path.

  However, since the time slot becomes narrow and the relative influence becomes large in a system of 100 Gbps or more, the conventional dispersion compensation technique has a limit in the compensation amount and the compensation accuracy. On the other hand, by introducing a digital coherent signal processing technique, it is possible to correct distortion in the transmission path by digital signal processing, and it is possible to perform dispersion compensation over a wide range with high accuracy. Also, using digital coherent technology, processing such as phase estimation and polarization separation can be realized by digital signal processing, and technologies such as multilevel modulation and polarization multiplexing, which have been difficult to realize in the past, will be widely used. Became.

  Such digital coherent technology can be realized by using a highly versatile DSP (Digital Signal Processor), and is being introduced into commercial services. DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying) signals are widely used in 100 Gbps optical transmission systems.

T. Kobayashi, S. Yamanaka, H. Kawakami, S. Yamamoto, A. Sano, H. Kubota, A. Matsuura, E. Yamazaki, M. Ishikawa, K. Ishihara, T. Sakano, E. Yoshida, Y. Miyamoto, M. Tomizawa, S. Matsuoka, "8-Tb / s (80x127Gb / s) DP-QPSK L-band DWDM Transmission over 457-km Installed DSF Links with EDFA-only amplification," 15th Optoe Electronics and Communications Conference (OECC2010 ) Technical Digest, July 2010

  In the above-described DP-QPSK signal, four-level phase information is superimposed on each orthogonal polarization. Therefore, it is possible to transmit 25 G × 2 × 2 = 100 Gbit information by using 2-bit information and two polarizations for a 25 GBaud signal. In the digital coherent system, the multiplexed polarization is separated and the phase information is estimated by digital signal processing.

  The QPSK signal maps phase information corresponding to 2 bits on the IQ plane. FIG. 14 is a diagram illustrating a mapping example of a QPSK signal. For example, when 2 bits to be transmitted are 00, the first quadrant on the IQ plane is used, when 2 bits to be transmitted are 01, to the 4th quadrant, and when 2 bits to be transmitted are 10th, In the second quadrant, when 2 bits to be transmitted are 11, mapping is performed in the third quadrant. The IQ mapping rule may be other than this, and as shown in the IQ mapping example 2 in the figure, when the 2 bits are 01, the 2nd quadrant is mapped instead of the 4th quadrant, and the 2 bits are 10. In some cases, it may be mapped to the fourth quadrant instead of the second quadrant.

  In order to minimize the error rate, it is desirable to design the mapping rule so that the Hamming distance between symbols is constant. FIG. 15 is a diagram illustrating IQ mapping when a differential code is used. In the case of a differential code, mapping is performed in advance by associating a combination of information bits to be transmitted with a phase difference of symbols. When 2 bits 00 to be transmitted are associated with 0 °, 10 with 90 °, 01 with -90 ° and 11 with 180 °, 01 is input when the symbol is in the first quadrant as an initial state. Then, the position of the symbol changes by −90 ° and transitions to the fourth quadrant. Subsequently, when 01 is input, the position of the symbol is further changed by −90 ° to shift from the fourth quadrant to the third quadrant.

  As described above, the differential code for mapping information using the phase difference between the preceding and following symbols is widely used in digital coherent systems. Also, in the digital coherent system, since the phase is estimated by the maximum likelihood method, there are cases where the phase cannot be correctly demodulated if the phase slips depending on conditions such as noise. Differential coding plays an important role for such events.

  A DSP or the like that realizes a system of 100 Gbps or more is put into practical use, and it is expected that it will be expanded not only to long-distance applications but also to middle-distance and short-distance applications. It is expected that DSPs supplied from various vendors will be mixed, and it is necessary to adopt a form that can be connected to each other. As described above, since the symbol mapping rule is arbitrary, the definition of the mapping rule is left to the developer. Therefore, when systems having different mapping rules are connected, there is a problem that information cannot be transmitted correctly.

  In view of the above circumstances, an object of the present invention is to provide an optical transmission apparatus and an optical transmission method that can cope with an arbitrary mapping rule.

  In one aspect of the present invention, a transmission signal generation unit that generates a plurality of information bit sequences each having two information bit sequences as a set, and inverts and outputs bits of a predetermined information bit sequence out of the plurality of information bit sequences, A first bit inversion unit that outputs another information bit string as it is, and a plurality of bit strings output from the first bit inversion unit are subjected to differential encoding for each set, and the obtained plurality of bit strings are A differential encoding unit that outputs, a second bit inversion unit that inverts and outputs predetermined bits of the plurality of bit strings output from the differential encoding unit, and outputs the other bits as they are; A lane swap unit that outputs a predetermined set of two bit strings by replacing the plurality of bit strings output from the second bit inverting unit, and outputs the other set of bit strings as they are. An optical transmission device, characterized in that it comprises an optical signal transmitting unit for transmitting and generates a light signal based on the plurality of bit strings output from the flop unit.

  According to another aspect of the present invention, an optical signal receiving unit that generates and outputs a plurality of bit strings each having a set of two bit strings from a received optical signal, and a plurality of bit strings output from the optical signal receiving unit In the lane swap unit that outputs two sets of bit strings in a predetermined set, and outputs the other sets of bit strings as they are, and outputs a plurality of bit strings output from the lane swap unit by inverting predetermined bits. And a second bit inversion unit that outputs other bits as they are, and a plurality of bit sequences obtained by performing differential demodulation for each group on a plurality of bit sequences output from the second bit inversion unit. And a differential demodulator that outputs a first bit of a plurality of bit strings output from the differential demodulator by inverting the bits of a predetermined bit string and outputting the other bit strings as they are. An optical transmission apparatus comprising: a reception signal decoding unit that generates a frame signal from two bit strings for each group for a plurality of bit strings output from the bit inversion part and the first bit inversion part It is.

  Further, according to one aspect of the present invention, in the optical transmission device described above, the set of objects to be replaced in the lane swap unit, the predetermined bit to be subjected to bit inversion in the second bit inversion unit, and the An operation table storing a plurality of combinations of bit strings to be subjected to bit inversion in the first bit inversion unit, and the combination stored in the operation table based on a signal obtained in the reception signal decoding unit And a switching control unit that operates the lane swap unit, the second bit inversion unit, and the first bit inversion unit in accordance with the selected combination.

  One embodiment of the present invention is an optical transmission method performed in an optical transmission device, wherein a transmission signal generation step of generating a plurality of information bit sequences each including two information bit sequences, and among the plurality of information bit sequences, A first bit inversion step for inverting and outputting bits of a predetermined information bit string and outputting other information bit strings as they are, and a plurality of bit strings output in the first bit inversion step for each set A differential encoding step of performing differential encoding and outputting a plurality of obtained bit sequences, and outputting a predetermined bit among a plurality of bit sequences output in the differential encoding step, Are determined for a second bit inversion step for outputting the bits as they are and a plurality of bit strings output in the second bit inversion step. A lane swap step that outputs the other bit strings as they are, and an optical signal transmission step that generates and transmits an optical signal based on the plurality of bit strings output in the lane swap step. An optical transmission method characterized by comprising:

  One embodiment of the present invention is an optical transmission method performed in an optical transmission device, wherein an optical signal receiving step of generating and outputting a plurality of bit sequences each having a set of two bit sequences from a received optical signal; Out of a plurality of bit strings output in the optical signal receiving step, two bit strings of a predetermined set are exchanged and output, and a lane swap step of outputting the other set of bit strings as they are, and output in the lane swap step In a plurality of bit sequences, a predetermined bit is inverted and output, and the other bits are output as they are. A second bit inversion step and a plurality of bit sequences output in the second bit inversion step Differential demodulation step for outputting a plurality of obtained bit strings, and output in the differential demodulation step. Among the plurality of bit strings to be outputted, the bits of the predetermined bit string are inverted and outputted, and the other bit strings are outputted as they are, and the plurality of bit strings outputted in the first bit inversion step On the other hand, the optical transmission method includes a reception signal decoding step of generating a frame signal from two bit strings for each set.

  According to the present invention, replacement of a bit string for a plurality of bit strings including two bit strings, inversion of all bits of a bit string, and inversion of a predetermined bit of a bit string, a mapping rule of differential encoding of a device on the receiving side By combining according to the above, it is possible to cope with an arbitrary mapping rule and obtain a signal that can be demodulated in the receiving apparatus.

It is a block diagram which shows the structure of the optical transmission apparatus 10 in 1st Embodiment. It is a figure which shows an example of the differential encoding (mapping rule) by the differential encoding part 13 in the embodiment. It is a figure which shows an example of the differential encoding with respect to the information bit sequence by the differential encoding part 13 in the embodiment. 6 is a first diagram illustrating an output example when a bit inversion process by an odd / even bit inversion unit 14 and a replacement process by a lane swap unit 15 are performed in the embodiment. FIG. It is a 2nd figure which shows the example of an output at the time of performing the bit inversion process by the odd-numbered even bit inversion part 14, and the replacement process by the lane swap part 15 in the same embodiment. FIG. 11 is a third diagram illustrating an output example when the bit inversion processing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 are performed in the embodiment. It is a figure which shows the example of an output at the time of performing the bit inversion process by the bit inversion part 12, and the replacement process by the lane swap part 15 in the embodiment. It is a figure which shows the response | compatibility with the mapping rule in the differential encoding of the operation | movement of the bit inversion part 12, the odd-even bit inversion part 14, and the lane swap part 15 of the optical transmission apparatus 10 in the embodiment. It is a block diagram which shows the structure of the optical transmission apparatus 20 in 2nd Embodiment. It is a block diagram which shows the structure of the optical transmission apparatus 30 in 3rd Embodiment. It is a figure which shows an example of the operation | movement table which the switching control part 31 in the embodiment has memorize | stored. It is a figure which shows the mapping rule corresponding to each mapping 1-mapping 8 in the operation | movement table shown in FIG. It is a flowchart which shows the operation | movement selection process which the optical transmission apparatus 30 in the embodiment performs. It is a figure which shows the example of a mapping of a QPSK signal. It is the figure which showed IQ mapping when using a differential code | symbol.

  Hereinafter, an optical transmission device and an optical transmission method according to embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration of an optical transmission device 10 according to the first embodiment. FIG. 2 shows a configuration related to transmission of the optical transmission apparatus 10. As shown in the figure, the optical transmission device 10 includes a transmission signal generation unit 11, a bit inversion unit 12, a differential encoding unit 13, an odd / even bit inversion unit 14, a lane swap unit 15, and an optical signal transmission unit 16. It has.

  The transmission signal generation unit 11 generates part or all of the transmission signal transmitted from the own apparatus. The transmission signal generation unit 11 inputs to the bit inversion unit 12 a transmission signal composed of an information bit string of a pair of XI lanes and XQ lanes and an information bit string of a pair of YI lanes and YQ lanes. That is, the transmission signal generation unit 11 generates a 4-lane information bit string and inputs the 4-lane information bit string to the bit inversion unit 12.

  The bit inversion unit 12 inverts and outputs each bit of the information bit string of the lane selected in advance among the four lane information bit strings to be input. The number of lanes to be selected is 0 or more and 4 or less, and a selection may be made so as not to invert bits for the information bit string of any lane. The bit inversion unit 12 inputs the information bit sequence obtained by performing bit inversion on the information bit sequence of the selected lane and the information bit sequence of the unselected lane to the differential encoding unit 13.

  The differential encoding unit 13 performs differential encoding on each of two sets of information bit strings input from the bit inverting unit 12, that is, a set of XI lanes and XQ lanes, and a set of YI lanes and YQ lanes. . The differential encoding unit 13 differentially encodes the result of performing differential encoding on the information bit string of a set of XI lanes and XQ lanes and the information bit string of a set of YI lanes and YQ lanes. The result of performing is input to the odd / even bit inversion unit 14.

FIG. 2 is a diagram illustrating an example of differential encoding (mapping rule) by the differential encoding unit 13 in the present embodiment. In the figure, an example of differential encoding for an information bit sequence of a set of XI lanes and XQ lanes is shown, but the differential encoding for an information bit sequence of a set of YI lanes and YQ lanes is also the same. . a _k and b _k are information bit strings of the XI lane and the XQ lane at time k. XI _k-1 ⁽⁰⁾ and XQ _k-1 ⁽⁰⁾ are outputs one symbol before the time k (result of differential encoding), and XI _k ⁽⁰⁾ and XQ _k ⁽⁰⁾ are times. The output at k.

For example, when (a _k , b _k ) = (0, 0), XI _k ⁽⁰⁾ = XI _k−1 ⁽⁰⁾ , XQ _k ⁽⁰⁾ = XQ _k−1 ⁽⁰⁾ , and IQ The position of the symbol at time k on the plane is the same as the position of the symbol at time (k−1), and the phase difference is 0 °. When (a _k , b _k ) = (1, 1), XI _k ⁽⁰⁾ = ￣XI _k−1 ⁽⁰⁾ , XQ _k ⁽⁰⁾ = ^） XQ _k−1 ⁽⁰⁾ The position of the symbol at time k on the IQ plane transitions to a position obtained by inverting the position of the symbol at time (k−1) with respect to the I axis and the Q axis, and the phase difference is 180 °. In the figure, the ones with a bar on the top represent the inverted bits of “XI _k−1 ⁽⁰⁾ ” and “XQ _k−1 ⁽⁰⁾ ”. In the specification, "XI _k-1 ⁽⁰⁾ " or "XQ _k-1 ⁽⁰⁾ " with a bar (￣) added to "￣XI _k-1 ⁽⁰⁾ " “￣XI _k-1 ⁽⁰⁾ ”.

FIG. 3 is a diagram illustrating an example of differential encoding of an information bit string by the differential encoding unit 13 in the present embodiment. FIG. 3A shows an information bit string input to the differential encoding unit 13. That is, the differential encoding unit 13 includes (0, 1), (1, 1), (1, 1), (0, 1), (0, 0) as information bits (a _k , b _k ). , (1, 0), (1, 1) are sequentially input. FIG. 3B shows the output (XI _k ⁽⁰⁾⁾ of the differential encoding unit 13 when the initial state (XI ₁ ⁽⁰⁾ , XQ ₁ ⁽⁰⁾ ) of the symbol position is ⁽⁰ , ^0). , XQ _k ⁽⁰⁾ ). In accordance with the mapping rule shown in FIG. 2, the differential encoding unit 13 outputs the result of differential encoding of the input information bit string.

  As described above, the differential encoding unit 13 performs differential encoding using the input information bits and the position of the previous symbol.

Returning to FIG. 1, the description of the configuration of the optical transmission apparatus 10 will be continued.
The odd / even bit inversion unit 14 receives a bit sequence of XI lanes and XQ lanes obtained by differential encoding in the differential encoding unit 13 and a bit sequence of YI lanes and YQ lanes. The odd / even bit inversion unit 14 performs bit inversion processing on a predetermined bit for each of the bit strings of the two sets of lanes, and inputs the processing result to the lane swap unit 15. In the bit inversion process, the odd timing bit is inverted, the even timing bit is inverted, the odd and even timing bits are inverted, or the bit is not inverted for all timing bits. Is the process. The odd / even bit inversion unit 14 performs predetermined bit inversion processing for each bit string of the XI lane and the XQ lane and each bit string of the YI lane and the YQ lane.

  The lane swap unit 15 performs a predetermined lane replacement process on each of the two sets of lane bit strings input from the odd / even bit inversion unit 14 and inputs the processing result to the optical signal transmission unit 16. The lane replacement process for a set of XI lanes and XQ lanes is performed by either switching the XI lane bit string and the XQ bit string to be output, or outputting without replacement. In addition, the lane replacement process for the pair of YI lane and YQ lane is either to output the bit string of the YI lane and the bit string of the YQ lane, or to output without switching.

  The optical signal transmission unit 16 performs polarization multiplexing on an optical signal obtained by performing digital / analog conversion and electrical / optical conversion for each of the two sets of lane bit strings input from the lane swap unit 15. , Two orthogonal optical signals are sent to a transmission line such as an optical fiber.

FIG. 4 is a diagram illustrating an output example when the bit inversion processing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 are performed in the present embodiment. In the example shown in the figure, the output of the lane swap unit 15 for the information bit strings of the XI lane and the XQ lane is shown in time series. The information bit string output from the transmission signal generation unit 11 is the information bit string (a _k , b _k ) shown in FIG. 3A, and the initial state of the symbol position is (0, 0). At this time, the bit inverting unit 12 outputs the information bit string input from the transmission signal generating unit 11 to the differential encoding unit 13 as it is.

The output example (XI _k , XQ _k ) illustrated in FIG. 4A is an output result when the bit inversion processing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 are not performed. Information bit string (a _k , b _k ) = {(0, 1), (1, 1), (1, 1), (0, 1), (0, 0), (1, 0), (1, 1)} is output from the transmission signal generation unit 11, the bit strings (XI _k , XQ _k ) output from the lane swap unit 15 are (0, 0), (0, 1), (1, 0). , (0, 1), (1, 1), (1, 1), (0, 1), (1, 0). The phase difference at this time changes as -90 °, 180 °, 180 °, -90 °, 0 °, 90 °, and 180 °.

The output example (XI _k , XQ _k ) shown in FIG. 4B is an output result when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane and the lane swap unit 15 does not perform the replacement process. is there. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (1, 0), (1, 1), (0, 0), (1, 1), (0, 1). , (0, 1), (1, 1), (0, 0). The phase difference at this time changes as 90 °, 180 °, 180 °, 90 °, 0 °, −90 °, and 180 °. As can be seen by comparing FIG. 4A and FIG. 4B, by performing bit inversion on the bit string of the XI lane, −90 ° and 90 ° are switched with respect to the mapping rule shown in FIG. Differential codes are obtained.

The output example (XI _k , XQ _k ) shown in FIG. 4C is an output result when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane and the lane swap unit 15 does not perform the replacement process. is there. The phase difference shown in the figure varies as 90 °, 180 °, 180 °, 90 °, 0 °, −90 °, and 180 °. That is, as in the case of performing bit inversion on the bit string of the XI lane in FIG. 4B, by performing bit inversion on the bit string of the XQ lane, −90 ° and 90 ° with respect to the mapping rule shown in FIG. A differential code in which ° is exchanged is obtained.

In the output example (XI _k , XQ _k ) shown in FIG. 4D, the odd / even bit inversion unit 14 performs bit inversion for the bit string of the XI lane and bit inversion for the bit string of the XQ lane, and the lane swap unit 15 switches. This is the output result when no processing is performed. Comparing FIG. 4 (A) and FIG. 4 (D), it can be seen that the same result is obtained with respect to the phase difference.

The output example (XI _k , XQ _k ) shown in FIG. 4 (E) is an output result when the lane swap unit 15 performs the replacement process without the odd / even bit inversion unit 14 performing the bit inversion. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (0, 0), (1, 0), (0, 1), (1, 0), (1, 1). , (1,1), (1,0), (0,1). The phase difference varies as 90 °, 180 °, 180 °, 90 °, 0 °, −90 °, and 180 °. By performing the replacement process by the lane swap unit 15, as in FIG. 4B and FIG. 4C, the differential code in which −90 ° and 90 ° are replaced with respect to the mapping rule shown in FIG. Is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 4F is an output result when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane, and the lane swap unit 15 performs replacement processing. . The output example (XI _k , XQ _k ) shown in FIG. 4G is an output result when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane, and the lane swap unit 15 performs replacement processing. . Comparing FIG. 4 (F) and FIG. 4 (G) with FIG. 4 (A), it can be seen that the same result is obtained with respect to the phase difference.

In the output example (XI _k , XQ _k ) shown in FIG. 4 (H), the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane and bit inversion on the bit string of the XQ lane, and the lane swap unit 15 switches. This is the output result when processing is performed. In this case, similarly to FIGS. 4B and 4C, a differential code in which −90 ° and 90 ° are interchanged with respect to the mapping rule shown in FIG. 2 is obtained.

FIG. 5 is a diagram illustrating an output example when the bit inversion processing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 are performed in the present embodiment. In the example shown in the figure, the output of the lane swap unit 15 for the information bit strings of the XI lane and the XQ lane is shown in time series. The information bit string output from the transmission signal generation unit 11 is the information bit string (a _k , b _k ) shown in FIG. 3A, and the initial state of the symbol position is (0, 0). At this time, the bit inverting unit 12 outputs the information bit string input from the transmission signal generating unit 11 to the differential encoding unit 13 as it is.

The output example (XI _k , XQ _k ) shown in FIG. 5A is the same as the output example (XI _k , XQ _k ) shown in FIG. 4A, and the bit inversion by the odd / even bit inversion unit 14 is performed. This is an output result when the process and the replacement process by the lane swap unit 15 are not performed. That is, an output result corresponding to the mapping rule shown in FIG. 2 is shown in FIG.

In the output example (XI _k , XQ _k ) shown in FIG. 5B, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane at the odd timing (k = 1, 3, 5, 7). It is an output result when the swap unit 15 does not perform the replacement process. The bit strings (XI _k , XQ _k ) output from the lane swap unit 15 are (1, 0), (0, 1), (0, 0), (0, 1), (0, 1), (1 , 1), (1, 1), (1, 0). The phase difference at this time is converted into 180 °, 90 °, −90 °, 0 °, 90 °, 0 °, and 90 °. In this case, since the phase difference can take 90 ° and −90 ° with respect to the information bit string (a _k , b _k ) = (1, 1), it does not become a differential code (hatched portion). Therefore, the optical transmission apparatus 10 does not use a combination of operations that perform bit inversion on the bit string of the XI lane at odd timing by the odd / even bit inversion unit 14 and do not perform the replacement processing by the lane swap unit 15.

In the output example (XI _k , XQ _k ) shown in FIG. 5C, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane at the odd timing, and the lane swap unit 15 does not perform the replacement process. This is the output result. Also in the phase difference shown in the figure, the phase difference takes 90 ° and −90 ° with respect to the information bit string (a _k , b _k ) = (1, 1) as in the case of FIG. It is not a differential code to obtain (hatched part). Therefore, the optical transmission apparatus 10 does not use a combination of operations that perform bit inversion on the bit string of the XQ lane at the odd timing by the odd / even bit inversion unit 14 and do not perform the replacement processing by the lane swap unit 15.

In the output example (XI _k , XQ _k ) shown in FIG. 5D, the odd / even bit inversion unit 14 performs bit inversion on the bit strings of the XI lane and the XQ lane at the odd timing, and the lane swap unit 15 performs the replacement process. This is the output result when not performed. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (1, 1), (0, 1), (0, 1), (0, 1), (0, 1). , (0,0), (1,0), (1,0). The phase difference at this time changes as 90 °, 0 °, 0 °, 90 °, 180 °, −90 °, and 0 °. As can be seen by comparing FIG. 5 (A) and FIG. 5 (D), 90 ° and −90 ° are interchanged, and 0 ° and 180 ° are interchanged with respect to the mapping rule shown in FIG. A differential code is obtained. In the output example shown in FIG. 5D, unlike the output examples in FIG. 5B and FIG. 5C, the phase difference is uniquely determined for the information bit string, and the differential code is established. .

The output example (XI _k , XQ _k ) shown in FIG. 5E is an output when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane at the odd timing, and the lane swap unit 15 performs the replacement process. It is a result. The output example (XI _k , XQ _k ) shown in FIG. 5F is an output when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane at the odd timing, and the lane swap unit 15 performs the replacement process. It is a result. Similarly to the output example of FIG. 5B, in the output examples of FIG. 5E and FIG. 5F, the phase difference is different from the information bit string (a _k , b _k ) = (1, 1). Since it can take 90 ° and −90 °, it does not become a differential code (hatched portion). Therefore, the combination of the operation of performing the bit inversion on the bit string of the XI lane at the odd timing by the odd / even bit inversion unit 14 and performing the replacement process by the lane swap unit 15 and the XQ lane at the odd timing by the odd / even bit inversion unit 14 A combination of operations for performing bit inversion on the bit string and performing a replacement process by the lane swap unit 15 is not used in the optical transmission apparatus 10.

In the output example (XI _k , XQ _k ) shown in FIG. 5G, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane and the XQ lane at the odd timing, and the lane swap unit 15 performs the replacement process. This is the output result when performing. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (1, 1), (1, 0), (1, 0), (1, 0), (0, 0). , (1,1), (0,1), (0,1). The phase difference at this time changes as -90 °, 0 °, 0 °, -90 °, 180 °, 90 °, and 0 °. As can be seen by comparing FIG. 5A and FIG. 5G, a differential code in which 0 ° and 180 ° are interchanged with respect to the mapping rule shown in FIG. 2 is obtained.

FIG. 6 is a diagram illustrating an output example when the bit inversion processing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 are performed in the present embodiment. In the example shown in the figure, the output of the lane swap unit 15 for the information bit strings of the XI lane and the XQ lane is shown in time series. The information bit string output from the transmission signal generation unit 11 is the information bit string (a _k , b _k ) shown in FIG. 3A, and the initial state of the symbol position is (0, 0). At this time, the bit inverting unit 12 outputs the information bit string input from the transmission signal generating unit 11 to the differential encoding unit 13 as it is.

Output example shown in FIG. _{6 (A) (XI k,} XQ k) is an output example _{(XI k,} XQ k) identical to that shown in FIG. 4 (A), the bit inversion by the odd even bit inverting portion 14 This is an output result when the process and the replacement process by the lane swap unit 15 are not performed. That is, the output result corresponding to the mapping rule shown in FIG. 2 is shown in FIG.

In the output example (XI _k , XQ _k ) shown in FIG. 6B, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane at the even timing (k = 2, 4, 6, 8). It is an output result when the swap unit 15 does not perform the replacement process. The bit strings (XI _k , XQ _k ) output from the lane swap unit 15 are (0, 0), (1, 1), (1, 0), (1, 1), (1, 1), (0 , 1), (0, 1), (0, 0). The phase difference at this time changes as 180 °, −90 °, 90 °, 0 °, 90 °, 0 °, and 90 °. In this case, as in the case shown in FIG. 5B and the like, the phase difference can be 90 ° and −90 ° with respect to the information bit string (a _k , b _k ) = (1, 1). It does not become a dynamic code (hatched part). Therefore, a combination of operations in which bit inversion is performed on the bit string of the XI lane at the even timing (k = 2, 4, 6, 8) by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 is not performed is optical transmission. Not used in device 10.

In the output example (XI _k , XQ _k ) shown in FIG. 6C, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane at the even timing, and the lane swap unit 15 does not perform the replacement process. This is the output result. Also in the phase difference shown in the figure, the phase difference takes 90 ° and −90 ° with respect to the information bit string (a _k , b _k ) = (1, 1) as in the case of FIG. 6B. It is not a differential code to obtain (hatched part). Therefore, the optical transmission apparatus 10 does not use a combination of operations that perform bit inversion on the bit string of the XQ lane at the odd timing by the odd / even bit inversion unit 14 and do not perform the replacement processing by the lane swap unit 15.

In the output example (XI _k , XQ _k ) shown in FIG. 6D, the odd / even bit inversion unit 14 performs bit inversion on the bit strings of the XI lane and the XQ lane at the even timing, and the lane swap unit 15 performs the replacement process. This is the output result when not performed. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (0, 0), (1, 0), (1, 0), (1, 0), (1, 1). , (0, 0), (0, 1), (0, 1). The phase difference at this time changes as 90 °, 0 °, 0 °, 90 °, 180 °, −90 °, and 0 °. As can be seen by comparing FIG. 6 (A) and FIG. 6 (D), 90 ° and −90 ° are interchanged, and 0 ° and 180 ° are interchanged with respect to the mapping rule shown in FIG. A differential code is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 6E is an output when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane at the even timing, and the lane swap unit 15 performs the replacement process. It is a result. The output example (XI _k , XQ _k ) shown in FIG. 6F is an output when the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XQ lane at the even timing, and the lane swap unit 15 performs replacement processing. It is a result. Similar to the output example of FIG. 6B, in the output examples of FIGS. 6E and 6F, the phase difference is different from the information bit string (a _k , b _k ) = (1, 1). Since it can take 90 ° and −90 °, it does not become a differential code (hatched portion). Therefore, the combination of the operation of performing the bit inversion for the bit string of the XI lane at the even timing by the odd / even bit inversion unit 14 and the replacement processing by the lane swap unit 15 and the XQ lane at the even timing by the odd / even bit inversion unit 14 A combination of operations for performing bit inversion on the bit string and performing a replacement process by the lane swap unit 15 is not used in the optical transmission apparatus 10.

In the output example (XI _k , XQ _k ) shown in FIG. 6G, the odd / even bit inversion unit 14 performs bit inversion on the bit string of the XI lane and the XQ lane at the even timing, and the lane swap unit 15 performs the replacement process. This is the output result when performing. At this time, the bit string (XI _k , XQ _k ) output from the lane swap unit 15 is (0, 0), (0, 1), (0, 1), (0, 1), (1, 1). , (0,0), (1,0), (1,0). The phase difference at this time changes as -90 °, 0 °, 0 °, -90 °, 180 °, 90 °, and 0 °. As can be seen by comparing FIG. 6A and FIG. 6G, a differential code in which 0 ° and 180 ° are interchanged with respect to the mapping rule shown in FIG. 2 is obtained.

  As can be seen by comparing the output example shown in FIG. 5 with the output example shown in FIG. 6, the bit inversion processing at the odd timing and the bit inversion processing at the even timing can obtain the same result. Therefore, it is possible to change the mapping rule by using either bit inversion at odd timing or bit inversion at even timing.

FIG. 7 is a diagram illustrating an output example when the bit inversion processing by the bit inversion unit 12 and the replacement processing by the lane swap unit 15 are performed in the present embodiment. In the example shown in the figure, the output of the lane swap unit 15 for the information bit strings of the XI lane and the XQ lane is shown in time series. The information bit string output from the transmission signal generation unit 11 is the information bit string (a _k , b _k ) shown in FIG. 3A, and the initial state of the symbol position is (0, 0). At this time, the odd / even bit inversion unit 14 outputs the bit string input from the differential encoding unit 13 to the lane swap unit 15 as it is.

Output example shown in FIG. _{7 (A) (XI k,} XQ k) is output example _{(XI k,} XQ k) that shown in FIG. 4 (A) is the same as, the processing of the bit inversion by the bit inversion unit 12 This is an output result when the replacement processing by the lane swap unit 15 is not performed. That is, the output result corresponding to the mapping rule shown in FIG. 2 is shown in FIG.

The output example (XI _k , XQ _k ) shown in FIG. 7B is an output result when the bit inversion unit 12 performs bit inversion on the bit a _k and the lane swap unit 15 does not perform the replacement process. The bit strings (XI _k , XQ _k ) output from the lane swap unit 15 are (0, 0), (1, 1), (1, 0), (0, 0), (1, 1), (0 , 1), (0, 1), (1, 1). The phase difference at this time changes as 180 °, −90 °, 90 °, 0 °, 90 °, 0 °, and 90 °. As can be seen by comparing FIG. 7A and FIG. 7B, by performing bit inversion on the bit _ak , −90 ° and 180 ° are switched with respect to the mapping rule shown in FIG. Further, a differential code in which 0 ° and 90 ° are interchanged is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 7C is an output result when the bit inversion unit 12 performs bit inversion with respect to the bit b _k and the lane swap unit 15 does not perform replacement processing. The phase difference obtained from the output (XI _k , XQ _k ) in this case changes as 0 °, 90 °, 90 °, 0 °, −90 °, 180 °, and 90 °. As can be seen by comparing FIG. 7A and FIG. 7C, a differential code in which −90 ° and 0 ° are interchanged and 180 ° and 90 ° are interchanged is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 7D is an output result when the bit inversion unit 12 performs bit inversion on the bits a _k and b _k and the lane swap unit 15 does not perform the replacement process. It is. The phase difference obtained from the outputs (XI _k , XQ _k ) in this case changes as 90 °, 0 °, 0 °, 90 °, 180 °, −90 °, and 0 °. As can be seen by comparing FIG. 7A and FIG. 7D, a differential code in which −90 ° and 90 ° are interchanged and 180 ° and 0 ° are interchanged is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 7E is an output result when the bit inversion unit 12 performs bit inversion with respect to the bit a _k and the lane swap unit 15 performs replacement processing. The phase difference obtained from the outputs (XI _k , XQ _k ) in this case changes as 180 °, 90 °, 90 °, 180 °, −90 °, 0 °, and 90 °. As can be seen by comparing FIG. 7A and FIG. 7E, the phase differences 0 °, 90 °, 180 °, and −90 ° in the mapping rule shown in FIG. 2 are changed to −90 °, 0 °, A differential code exchanged at 90 ° and 180 ° is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 7F is an output result when the bit inversion unit 12 performs bit inversion on the bit b _k and the lane swap unit 15 performs replacement processing. The phase difference obtained from the outputs (XI _k , XQ _k ) in this case changes as 0 °, −90 °, −90 °, 0 °, 90 °, 180 °, and −90 °. As can be seen by comparing FIG. 7A and FIG. 7F, the phase differences 0 °, 90 °, 180 °, and −90 ° in the mapping rule shown in FIG. 2 are changed to 90 °, 180 °, − A differential code with 90 ° and 0 ° interchanged is obtained.

The output example (XI _k , XQ _k ) shown in FIG. 7G is an output result when the bit inversion unit 12 performs bit inversion on the bits a _k and b _k and the lane swap unit 15 performs the replacement process. is there. The phase difference obtained from the output (XI _k , XQ _k ) in this case varies as −90 °, 0 °, 0 °, −90 °, 180 °, 90 °, and 0 °. As can be seen by comparing FIG. 7A and FIG. 7G, a differential code in which 0 ° and 180 ° are interchanged with respect to the mapping rule shown in FIG. 2 is obtained.

The optical transmission device 10 according to the present embodiment realizes an arbitrary mapping rule from the mapping rule illustrated in FIG. 2 by combining the operations of the bit inverting unit 12, the odd / even bit inverting unit 14, and the lane swap unit 15. be able to. FIG. 8 is a diagram illustrating the correspondence between the operations of the bit inverting unit 12, the odd / even bit inverting unit 14, and the lane swap unit 15 of the optical transmission apparatus 10 according to this embodiment and the mapping rule in the differential encoding. As shown in the figure, the mapping rule in the differential coding is 0 ° as phase difference information with respect to the input bits (a _k , b _k ), and two types of clockwise (Counterclockwise) and counterclockwise (Counter Clockwise). , 90 °, 180 °, and −90 ° are assigned, and there are a total of 8 combinations. By combining the operations of the bit inverting unit 12, the odd / even bit inverting unit 14, and the lane swap unit 15, eight mapping rules can be realized as shown in FIGS. 4 to 7.

  As described above, the optical transmission device 10 according to the present embodiment can cope with an arbitrary mapping rule by switching the operations of the bit inverting unit 12, the odd / even bit inverting unit 14, and the lane swap unit 15. . As a result, regardless of which of the eight mapping rule definitions in the receiving device, the bit inverting unit 12, the odd / even bit inverting unit 14, and the By switching the operation of the lane swap unit 15, it becomes possible to correctly transmit information in correspondence with the mapping rule between the optical transmission device 10 and the receiving device. The switching of the operation may be performed manually by an administrator who operates or manages the optical transmission device 10, or the synchronization state of the transmission side device or the reception signal in the reception side device or the frame signal can be correctly demodulated. Based on the information on whether or not, a predetermined combination of operations may be sequentially changed.

<Second Embodiment>
FIG. 9 is a block diagram illustrating a configuration of the optical transmission device 20 according to the second embodiment. In the figure, a configuration related to reception of the optical transmission apparatus 20 is shown. As shown in the figure, the optical transmission device 20 includes an optical signal receiving unit 21, a lane swap unit 22, an odd / even bit inverting unit 23, a differential demodulating unit 24, a bit inverting unit 25, and a received signal decoding unit 26. I have.

  The optical signal receiving unit 21 is an electrical signal obtained by performing polarization separation, optical / electrical conversion, etc. on an optical signal received from a transmission line such as an optical fiber, and each of two orthogonal optical signals. Get the corresponding electrical signal. The optical signal receiving unit 21 performs analog / digital conversion on each electric signal to generate two sets of lane bit strings (four lane bit strings). The optical signal receiving unit 21 inputs the bit string of each set of lanes to the lane swap unit 22 as a pair.

  The lane swap unit 22 performs a predetermined lane replacement process for each of the two sets of lane bit strings, and inputs the processing result to the odd / even bit inversion unit 23. The lane replacement process in the lane swap unit 22 corresponds to the process in the lane swap unit 15 in the first embodiment.

  The odd / even bit inversion unit 23 receives a bit string of two sets of lanes input from the lane swap unit 22. The odd / even bit inversion unit 23 performs bit inversion processing on each of the bit strings of the two sets of lanes and inputs the processing result to the differential demodulation unit 24. The bit inversion processing in the odd / even bit inversion unit 23 corresponds to the bit inversion processing in the odd / even bit inversion unit 14 in the first embodiment.

  For each of two sets of lanes input from the odd / even bit inversion unit 23, the differential demodulator 24 performs differential demodulation on the two bit strings in the lane to restore the two bit strings. The differential demodulation in the differential demodulator 24 is performed, for example, corresponding to the differential encoding mapping rule shown in FIG. The differential demodulator 24 inputs a pair of two bit strings obtained by differential demodulation for each lane and inputs them to the bit inverter 25.

  The bit inversion unit 25 inverts and outputs each bit of a bit string selected in advance among the bit strings of two sets (X, Y) of lanes input from the differential demodulation unit 24. The bit string selected from the four bit strings is 0 or more and 4 or less, and any bit string may be selected so as not to invert bits. The bit inverting unit 25 inputs the bit string obtained by performing bit inversion on the selected bit string and the unselected bit string to the reception signal decoding unit 26.

  The reception signal decoding unit 26 generates a frame signal based on two sets of bit strings of the X lane and the Y lane input from the bit inverting unit 25. The reception signal decoding unit 26 generates a frame signal from two sets of bit strings based on a known technique or a known standard.

  By combining the operations of the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25 in the optical transmission apparatus 20 according to the present embodiment, the inverse conversion of the conversion illustrated in FIGS. 4 to 7 can be performed. The differential code obtained based on any differential encoding mapping rule can be converted into a differential code corresponding to the mapping rule shown in FIG. That is, the optical transmission device 20 can demodulate a differential code signal obtained based on an arbitrary differential encoding mapping rule based on the mapping rule in the differential demodulation unit 24 of the own device, The frame signal can be generated correctly.

<Third Embodiment>
FIG. 10 is a block diagram illustrating a configuration of the optical transmission device 30 according to the third embodiment. In the figure, a configuration related to reception of the optical transmission device 30 is shown. As shown in the figure, the optical transmission device 30 includes an optical signal receiver 21, a lane swap unit 22, an odd / even bit inverter 23, a differential demodulator 24, a bit inverter 25, a received signal decoder 26, and A switching control unit 31 is provided. The optical transmission device 30 in the present embodiment is different from the optical transmission device 20 (FIG. 9) in the second embodiment in that a switching control unit 31 is provided. In the optical transmission device 30, the same reference numerals are given to the same functional units as those of the optical transmission device 20, and the description thereof is omitted.

The switching control unit 31 determines the operations of the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25 based on a predetermined operation table. FIG. 11 is a diagram illustrating an example of an operation table stored in the switching control unit 31 according to the present embodiment. As shown in the figure, the operation table includes “No.” indicating the mapping number, “lane swap part”, “odd even bit inversion part”, “bit inversion part a _k ”, and “bit inversion part b _k ”. And have items. Each row in the operation table is provided for each combination of operations corresponding to, for example, the mapping rule shown in FIG. In the figure, combinations of operations of the functional units corresponding to eight mapping rules are defined. For example, in the combination of operations corresponding to mapping 1 (index 1), the lane swap unit 22 does not perform lane replacement processing (OFF), the odd / even bit inversion unit 23 does not perform bit inversion processing (OFF), bit This is a combination of operations in which the inversion unit 25 does not perform bit inversion processing on the bits a _k and b _k (OFF, OFF).

  FIG. 12 is a diagram showing mapping rules corresponding to mapping 1 to mapping 8 in the operation table shown in FIG. The eight mapping rules shown in FIG. 12 correspond to the eight mapping rules shown in FIG.

FIG. 13 is a flowchart illustrating an operation selection process performed by the optical transmission device 30 according to the present embodiment. When the operation selection process is started in the optical transmission device 30, the switching control unit 31 performs initialization by substituting 1 into the internal variable Index (step S1).
The switching processing unit 31 reads a combination of operations corresponding to the value of the internal variable Index from the operation table, and sets the read combination of operations for the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25. (Step S2).

  The switching control unit 31 acquires the frame synchronization information output from the received signal decoding unit 26 (step S3), and determines whether or not synchronization has been achieved with the acquired frame synchronization information (step S4). For the frame synchronization information, a known signal pattern can be used. For example, FAS information in an OTN frame may be used. Further, the minimum number of symbols required for the frame synchronization information is 1 bit or more. For example, an OTUk frame alignment signal (FAS), that is, “1111.0110.111.100110.111.0110.0010.1000.0010.1000 Some or all of 48 bits such as “.0010.1000” may be used. The frame synchronization information used in the optical transmission device 30 may be another signal.

In the determination in step S4, if synchronization is possible (step S4: YES), the switching control unit 31 uses the combination of operations corresponding to the current value of the internal variable Index to lane swap unit 22, odd-numbered even bit inversion unit 23. And the operation of the bit inverting unit 25 is continued (step S6), and the operation selection process is terminated.
On the other hand, in the determination of step S4, when synchronization could not be performed (step S4: NO), the switching control unit 31 increments the value of the internal variable Index by 1 (step S5), returns the process to step S2, and performs step S2. The subsequent processing is repeated.

  As described above, the optical transmission device 30 according to the present embodiment performs trials by sequentially selecting combinations of operations of the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25 that are predetermined in the operation table. Then, based on the frame synchronization information output from the received signal decoding unit 26, a combination of operations to be set in each functional unit is determined. Thereby, according to the frame signal output from the reception signal decoding unit 26 in the optical transmission device 30, the operations of the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25 are not manually determined. A combination of operations corresponding to the mapping rule in the transmission side device can be set for the lane swap unit 22, the odd / even bit inversion unit 23, and the bit inversion unit 25. As a result, the optical transmission device 30 can demodulate a differential code signal obtained based on an arbitrary differential encoding mapping rule based on the mapping rule in the differential demodulation unit 24 of the own device. The frame signal can be generated correctly.

  You may make it implement | achieve the optical transmission apparatus in each embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” is a program that dynamically holds a program for a short time, like a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention. For example, since the symbol mapping rule depends on the vendor of the signal processing circuit or the like, the processing of the bit inversion unit may be usually the same unless the optical transmission device is changed during operation, but the operation is performed when the mapping rule is changed. The operation in the bit inversion unit may be changed.

  Further, in each of the above-described embodiments, the configuration in which the bit inversion unit and the odd / even bit inversion unit are provided as different functional units has been described, but the functional unit may be provided in the optical transmission apparatus as one functional unit. In the optical transmission apparatus, the odd-numbered even-bit inversion unit and the lane swap unit may be switched in order.

  In the third embodiment, when determining a combination of operations of the functional units corresponding to the optical signal received by the switching control unit 31, a bit string other than that, for example, an error is used instead of the frame synchronization information. You may make it determine the combination of the operation | movement which should be selected using a rate.

  The present invention can be applied to applications in which it is essential to cope with an arbitrary differential encoding mapping rule.

DESCRIPTION OF SYMBOLS 10, 20, 30 ... Optical transmission apparatus 11 ... Transmission signal generation part 12 ... Bit inversion part (1st bit inversion part)
13 ... Differential encoding unit 14 ... Odd / even bit inversion unit (second bit inversion unit)
DESCRIPTION OF SYMBOLS 15 ... Lane swap part 16 ... Optical signal transmission part 21 ... Optical signal reception part 22 ... Lane swap part 23 ... Odd / even bit inversion part (2nd bit inversion part)
24 ... Differential demodulation unit 25 ... Bit inversion unit (first bit inversion unit)
26 ... Received signal decoding unit 31 ... Switching control unit

Claims (5)

A transmission signal generation unit that generates a plurality of information bit strings each having two information bit strings as a set;
A first bit inversion unit that inverts and outputs the bits of a predetermined information bit sequence out of the plurality of information bit sequences, and outputs the other information bit sequence as it is;
A differential encoding unit that performs differential encoding for each set of a plurality of bit strings output from the first bit inversion unit, and outputs the obtained plurality of bit strings;
A second bit inversion unit that inverts and outputs predetermined bits of the plurality of bit strings output from the differential encoding unit, and outputs the other bits as they are;
A lane swap unit for outputting a plurality of bit strings output from the second bit inverting unit by exchanging a predetermined set of two bit strings and outputting another set of bit strings as it is,
An optical transmission device comprising: an optical signal transmission unit that generates and transmits an optical signal based on a plurality of bit strings output from the lane swap unit. An optical signal receiving unit that generates and outputs a plurality of bit strings each having a pair of two bit strings from the received optical signal;
Among the plurality of bit strings output from the optical signal receiving unit, a lane swap unit that outputs a set of two bit strings interchanged and outputs another set of bit strings as it is,
A plurality of bit strings output from the lane swap unit, a second bit inversion unit that inverts and outputs predetermined bits and outputs the other bits as they are;
A differential demodulator that performs differential demodulation for each set of a plurality of bit strings output from the second bit inversion unit, and outputs the obtained plurality of bit strings;
From a plurality of bit strings output from the differential demodulator, a bit of a predetermined bit string is inverted and output, and another bit string is output as it is from the first bit inverter and the first bit inverter An optical transmission apparatus comprising: a reception signal decoding unit that generates a frame signal from two bit strings for each set of output bit strings. The optical transmission device according to claim 2,
A set of bits to be replaced in the lane swap unit, the predetermined bit to be bit-inverted in the second bit inversion unit, and a plurality of bit sequences to be bit-inverted in the first bit inversion unit An action table that stores the combination of
Based on the signal obtained in the received signal decoding unit, any one of the combinations stored in the operation table is selected, and the lane swap unit, the second bit inversion unit, and the first combination are selected according to the selected combination. An optical transmission device further comprising: a switching control unit that operates the bit inverting unit of An optical transmission method performed in an optical transmission device,
A transmission signal generating step for generating a plurality of information bit sequences each having two information bit sequences as a set;
A first bit inversion step of inverting and outputting a bit of a predetermined information bit string out of the plurality of information bit strings and outputting the other information bit string as it is;
A differential encoding step of performing differential encoding for each set of the plurality of bit strings output in the first bit inversion step, and outputting the obtained plurality of bit strings;
A second bit inversion step of inverting and outputting predetermined bits of the plurality of bit strings output in the differential encoding step, and outputting other bits as they are;
A lane swap step for outputting a plurality of bit strings output in the second bit inversion step by exchanging a predetermined set of two bit strings and outputting the other bit strings as they are;
And an optical signal transmission step of generating and transmitting an optical signal based on the plurality of bit strings output in the lane swap step. An optical transmission method performed in an optical transmission device,
An optical signal receiving step of generating and outputting a plurality of bit strings each having a set of two bit strings from the received optical signal;
Among the plurality of bit strings output in the optical signal receiving step, a lane swap step for switching and outputting two bit strings of a predetermined set, and outputting the other bit strings as they are,
A second bit inversion step of inverting and outputting a predetermined bit in the plurality of bit strings output in the lane swap step, and outputting the other bits as they are;
A differential demodulation step of performing differential demodulation for each group on the plurality of bit strings output in the second bit inversion step, and outputting the obtained plurality of bit strings;
In the first bit inversion step and the first bit inversion step, the bit of a predetermined bit sequence is inverted and output among the plurality of bit sequences output in the differential demodulation step, and the other bit sequence is output as it is. An optical transmission method comprising: a received signal decoding step of generating a frame signal from two bit strings for each set of a plurality of output bit strings.

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