JP5478410B2 - Skew detection device for optical communication system, optical communication system - Google Patents

Description

  The present invention relates to a skew detection apparatus applied to an optical communication system that performs optical DQPSK (differential quadrature phase shift keying) communication, and an optical communication system related thereto.

  In conventional optical DQPSK communication, if there is a skew in the transmission-side electrical signal processing unit, the transmission data sequence is corrupted, but reception is demodulated by combining optical signals. An unexpected data series occurs instead of replacement. Therefore, since there is no means for electrically compensating the skew on the receiving side, the skew is solved by adding redundancy such as equal length wiring or deskew channel in the optical communication system.

  On the other hand, for the purpose of reducing system design load and manufacturing cost, the following Patent Document 1 searches for a combination that can be correctly decoded by applying all combinations of skew compensation values to a specific pattern on the transmission side. This is solved by the technique.

JP 2009-219097 A

  In the method described in Patent Document 1, since the number of skews to be compensated and the number of combinations applied according to the amount of skew increase exponentially, it is unrealistic to grasp the compensation amount depending on the system. Time is required. When DQPSK transmission / reception is performed in the optical transmitter / receiver apparatus, the error rate becomes high when the adjustment of the optical elements is insufficient or when the waveform distortion of the transmission path is large, making it difficult to recognize a specific pattern. Further, when a skew occurs in the transmitter on the reception side, no means for notifying the transmission side of the detected skew amount using the same network is shown, and thus automation is not possible. The conventional apparatus has the above problems.

  The present invention has been made to solve the above-mentioned problems, and it is possible to detect a skew amount in a short time, to cope with a bad optical transmission state by simplified detection of the skew amount, and to cause a skew on the transmission side. It is an object of the present invention to provide a skew detection apparatus and an optical communication system for an optical communication system that enable transmission of information in a state where the information is transmitted.

The present invention relates to a skew detection apparatus for an optical communication system that performs optical DQPSK communication. In a transmission apparatus that multiplexes transmission signals and transmits the signals, a transmission signal in one period pattern is used instead of a transmission signal that is DQPSK encoded. In a pattern generating means for generating the pattern signal in order to multiplex and transmit a pattern signal consisting of a periodic pattern in which a predetermined data location changes, and a receiving apparatus for receiving a received signal from the transmitting apparatus and performing demultiplexing A skew detecting means for detecting a place where a change occurs in a periodic pattern of the pattern signal received and demultiplexed and detecting a skew amount generated in at least one of the transmitting device and the receiving device. The present invention is in a skew detection device for an optical communication system characterized by the above.

  According to the present invention, a skew detection device for an optical communication system and an optical communication capable of detecting a skew amount in a short time, dealing with a bad optical transmission state, and transmitting information in a state where a skew occurs on the transmission side. Can provide a system.

It is a figure which shows the outline | summary of a structure of the optical communication system containing the skew detection apparatus by this invention. The figure which shows an example of the structure for the signal transmission from the transmission side of one transmission / reception apparatus SR of FIG. 1 to the reception side of the other transmission / reception apparatus SR in the optical communication system containing the skew detection apparatus by Embodiment 1 of this invention. It is. It is a figure which shows an example of the pattern output to the transmission I channel and the transmission Q channel in the skew detection apparatus by Embodiment 1 of this invention. It is a figure which shows an example of the pattern in the reception I channel and reception Q channel by the pattern output to the transmission I channel and transmission Q channel shown in FIG. It is a figure which shows an example of the circuit structure of the pattern comparator of FIG. It is a figure which shows an example of the transmission pattern for transmission of the detected skew amount in the skew detection apparatus by this invention. The figure which shows an example of the structure for the signal transmission from the transmission side of one transmission / reception apparatus SR of FIG. 1 to the reception side of the other transmission / reception apparatus SR in the optical communication system containing the skew detection apparatus by Embodiment 2 of this invention. It is. It is a figure which shows the relationship between the reception data series in the reception I channel in the skew detection apparatus by Embodiment 2 of this invention, and a reception Q channel, and the output of a time demultiplexing apparatus.

  Hereinafter, a skew detection apparatus for an optical communication system according to the present invention and an optical communication system related thereto will be described according to each embodiment with reference to the drawings. In each embodiment, the same or corresponding parts are denoted by the same or corresponding reference numerals, and redundant description is omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an outline of the configuration of an optical communication system including a skew detection apparatus according to the present invention. In the optical communication system, the transmission / reception devices SR are connected via an optical transmission line L, and bidirectional optical communication such as optical DQPSK communication is performed between the transmission / reception devices SR. 2 shows an example of a configuration for signal transmission from the transmission side of one transmission / reception apparatus SR of FIG. 1 to the reception side of the other transmission / reception apparatus SR in the optical communication system including the skew detection apparatus according to the first embodiment of the present invention. FIG. Each transmission / reception device SR has a transmission device and a reception device, and bidirectional communication is possible via one optical transmission line L.

  In FIG. 2, when transmitting and receiving a normal signal in the optical communication system, the electrical transmission signal processing circuit 101 on the transmission device S side performs DQPSK modulation on the input signals, which are I-channel and Q-channel transmission signals, by the DQPSK encoder 101a, respectively. The delay generator 102 outputs a transmission I channel signal and a transmission Q channel signal to the optical modulator 104 with a delay set according to a detected skew amount described later. The optical modulator 104 converts the electrical signal input from the electrical transmission signal processing circuit 101 into an optical signal, multiplexes (IQ multiplex), and transmits the optical signal to the receiver R side via the optical transmission line L.

  On the receiving device R side, the received DQPSK-modulated optical signal is subjected to delay interference by the optical delay interferometer 105 and demodulated and demultiplexed (IQ demultiplexed) to output I channel and Q channel signals. The I-channel and Q-channel optical signals output from the optical delay interferometer 105 by the photoelectric elements 106 and 107 are converted into electrical signals. The electric reception signal processing circuit 108 processes the reception signal of the converted electric signal. The electrical reception signal processing circuit 108 is a delay generator 109 that performs a delay process on an input signal according to a delay amount set according to a detected skew amount described later.

  When the skew amount for deskew is detected (at this time, transmission / reception of normal signals is stopped), the electric transmission signal processing circuit 101 on the transmission device S side switches the selectors 101b and 101c constituting the output switching unit. Thus, instead of the output of the DQPSK encoder 101a, the pattern signal generated by the pattern generator 103 is selected and output. The pattern generator 103 outputs a pattern signal at the same timing (the same cycle as the output of the DQPSK encoder 101a) as the path of the main signal input to the electrical transmission signal processing circuit 101. The pattern signal is sent to the receiving device R side through the same path as the transmission signal at the time of transmission / reception of a normal signal. The pattern comparator 110 on the receiving device R side is a comparator with an additional function that obtains a skew amount by comparing between I-channel and Q-channel input data sequences of a certain length. An additional function for obtaining the skew amount from the comparison result may be provided separately as a circuit or a microprocessor (not shown).

  Next, the operation when detecting the skew amount for deskew according to the present invention will be described in more detail. First, a periodic pattern for transmission I channel output and transmission Q channel output is generated from the pattern generator 103, and from the electric transmission signal processing circuit 101 as a transmission I channel signal and a transmission Q channel signal in the same manner as a normal signal. Output. FIG. 3 shows patterns output to the transmission I channel and the transmission Q channel. The transmission I channel is a sequence formed by X (1), which is the first bit of data, and a fixed pattern 201 (I (2), I (3),... I (N)) of N−1 bits. 202, a series 203 formed by X (2) which is the first bit data and the N-1 bit fixed pattern 201, and similarly, X (1, 2,. Output a data sequence 204 composed of a total of M × N bits by a sequence group formed by a fixed pattern 201 having a fixed value M). That is, it is a pattern signal composed of a periodic pattern in which one predetermined data location in one periodic pattern changes.

  As a method for generating data to be output to the transmission I channel, all the sequences may be built in the memory (not shown) for the pattern generator 103 or the electric transmission signal processing circuit 101 in advance, or only the X portion may be included. It may be generated by a circuit. The value of M is 2 or more, and the value of N is two or more times the maximum value of the assumed generated skew amount and more than twice the number of delay bits of the optical delay interferometer 105.

  A data sequence in which a data sequence 205 (Q (1), Q (2),... Q (N)) of an N-bit fixed pattern is repeated M times is output to the transmission Q channel. The optical modulator 104 is driven by the fixed pattern output from the electrical transmission signal processing circuit 101 to transmit an optical signal.

  On the receiving device R side, when the number of delay symbols of the optical delay interferometer 105 is K symbols, the optical delay interferometer 105 interferes with light that arrives at a certain time and light that arrives before K symbols, so that two lights The intensity of the I channel and the intensity of the Q channel corresponding to a phase state obtained by adding 45 ° rotation to the phase difference of λ are output to the photoelectric element 106 and the photoelectric element 107 as a reception I channel output and a reception Q channel output, respectively.

  4 is a sequence generated as a pattern (sequence) of the reception I channel and the reception Q channel after being delayed by the optical delay interferometer 105 based on the pattern (sequence) output to the transmission I channel and the transmission Q channel shown in FIG. Indicates. When the pattern comparator 110 of the electrical reception signal processing circuit 108 compares the N-bit length sequence 301 including X (1) and the next N-bit length sequence 302 including X (2) at the transmission time, When (1) and X (2) are different, the series changes only at the location including X (1) and X (2), and the same data is obtained at other data times. In the case where the pattern comparator 110 is configured by a circuit, for example, when the value of M is 2 and X (2) is the complement of X (1), an N-bit register as shown in FIG. Realization is possible by preparing two (D-type flip-flops D (1) to D (2 × N)) and installing an inversion detection circuit (XOR gate circuit) for each corresponding bit of the two registers. It is. In this circuit, N-bit reception patterns are held twice, the corresponding data locations in the N-bit cycle are compared with each other by the XOR circuit, and the output is sent to the D-type flip-flops (P (1) to P (N)). input. The shift register takes the timing for taking in N bits of data by using the N divided clock of the data clock from the N divider (× N) as the comparison timing. Only the D-type flip-flops (P (1) to P (N)) corresponding to the places where the change occurs in the N-bit periodic pattern outputs 1, and the D-type flip-flops (P (1)) at the other places. ... (P (N)) P outputs 0, so that it is possible to detect a change.

(Detection of skew amount on the receiving device R side)
When there is a skew between the reception I channel signal and the reception Q channel signal before the reception I channel signal and reception Q channel signal output from the optical delay interferometer 105 reach the electrical reception signal processing circuit 108, a pattern In the comparator 110, a difference corresponding to the amount of skew occurs between a location where a change occurs in the received signal sequence in the reception I channel and a location where a change occurs in the received signal sequence in the reception Q channel, and exists in the receiving apparatus (R). The amount of skew to be detected can be detected. By generating a delay according to the amount of skew detected by the delay generator 109, it is possible to compensate for the skew between the received I channel signal and the received Q channel signal in the received signal processing.

  In the transmission apparatus S, even if a skew occurs between the transmission I channel signal and the transmission Q channel signal between the electrical transmission signal processing circuit 101 and the optical modulator 104, values other than X are fixed values. The difference in time at which the change is detected in the device (R) is the same, and the skew amount can be detected in the receiving device (R). Further, whether this change appears in the reception I channel or the reception Q channel depends on data that causes delay interference. Therefore, the transmission device S generates a sequence in which the transmission Q channel is the complement of the sequence 204 to generate the reception device R. The skew amount can be detected for both channels.

(Skew amount detection on transmitting device S side)
Next, the data series 204 is transmitted from the transmission Q channel, the data series 205 is transmitted from the transmission I channel, and the pattern comparator 110 detects a place where a change has occurred in the N-bit reception fixed pattern. Where the pattern comparator 110 changes when the data series 204 is transmitted from the transmission I channel, and where the change occurs in the pattern comparator 110 when the series 204 is transmitted from the transmission Q channel, Since a difference corresponding to the skew amount between the transmission I channel and the transmission Q channel occurs between the electrical transmission signal processing circuit 101 and the optical modulator 104 in the transmission device S, the transmission I channel and the transmission Q channel in the transmission device S It is possible to detect the amount of skew between the two. By generating a delay according to the skew amount of the transmission apparatus S in the delay generator 102, it becomes possible to compensate for the skew between the transmission I channel signal and the transmission Q channel signal.

(Transmission of detected skew amount)
When the transmission device S compensates the skew between the transmission I channel signal and the transmission Q channel signal detected by the reception device R, it is necessary to notify the skew amount generated in the transmission device S from the reception side to the transmission side. The transmission / reception device SR in which the reception device R that has detected the skew amount is present is referred to as node A, and the transmission / reception device SR in which the transmission device S in which skew is present is present as node B. Also in the transmission apparatus S of the node A, when there is a skew between the transmission I channel and the transmission Q channel, normal DQPSK communication cannot be performed. Therefore, the transmission apparatus S of the node B is transferred from the node A to the node B by the following means. The amount of skew is notified.

  The data sequence 204 is transmitted from the transmission I channel output of the node A, and the fixed data sequence 205 is transmitted to the receiving device R of the node B from the transmission Q channel. Here, the amount of skew detected as a data series of X is expressed as a bit having a redundancy such as 8b / 10b (a method in which 2 bits of codeword having redundancy in 8 bits are added to 10 bits). Thus, the skew amount in the transmitting apparatus S of the node B can be received by the pattern comparator (110) of the node B.

  Further, by transmitting a plurality of change points X (X (1), etc.) in one fixed pattern as shown in the sequence 501 shown in FIG. The skew amount can be notified. In this case, the circuit shown in FIG. 5 can be used. Further, the pattern change point X (X (1), etc.) and the data notification change point Y (Y (1 (1)) that can be easily detected in one fixed pattern as shown in the sequence 502 shown in FIG. ) And the like are separately arranged, it is possible to limit the data portions to be changed in the fixed pattern, and at the same time, it is possible to divert the simple pattern comparator shown in FIG.

  That is, a data sequence of a transmission I channel and a transmission Q channel including a pattern change point for skew detection and a change point indicating a skew amount is generated by the pattern generator (103) of the transmission device S of the node A, and It may be received by the pattern comparator (110) of the receiving apparatus, and the detected skew amount in the opposite direction may be transmitted in parallel with the detection of the skew amount. The detected skew amount is output from the pattern comparator (110) of the receiving device in the same transmitting / receiving device to the pattern generator (103) of the transmitting device.

Embodiment 2. FIG.
The first embodiment is an example where the I channel and the Q channel of the transmission apparatus and the reception apparatus have only a single signal input / output in the signal processing circuit. Next, the transmission apparatus includes a plurality of signal processing circuits. An example of an optical communication system in which a signal is time-multiplexed and input to an optical modulator, and a reception signal is time-demultiplexed and input to a signal processing circuit having a plurality of inputs in the receiver. Show.

  7 is an example of a configuration for signal transmission from the transmission side of one transmission / reception apparatus SR of FIG. 1 to the reception side of the other transmission / reception apparatus SR in the optical communication system including the skew detection apparatus according to the second embodiment of the present invention. FIG. The electrical transmission signal processing circuit 601 on the transmission device S side is a signal obtained by converting a plurality of input signals into a transmission signal that has been DQPSK modulated by the DQPSK encoder 601a during transmission / reception of a normal signal, and a skew amount for deskewing. At the time of detection, a plurality of pattern signals generated by the pattern generator 603 are switched by the switching operation of the selectors 601b and 601c constituting the output switching unit to respectively transmit a plurality of transmission I channel signals and transmission Q channels to the time multiplexer 611. Output as a signal.

  The DQPSK encoder 601a performs DQPSK modulation on a plurality of input signals. The pattern generator 603 outputs a plurality of pattern signals at the same timing (the same cycle as the output of the DQPSK encoder 601a) as the path of the main signal input to the electrical transmission signal processing circuit 601. Each of the selectors 601b and 601c switches a signal to be output between a plurality of normal signals during normal communication and a plurality of pattern signals during skew amount detection. The delay generator 602 applies a delay set according to a detected skew amount, which will be described later, to the input signals, and outputs the signals to the time multiplexer 611 as a plurality of transmission I channel signals and transmission Q channel signals, respectively.

  The time multiplexing device 611 time-multiplexes a transmission I channel signal and a transmission Q channel signal each consisting of a plurality of signals, and outputs them as one signal output. The optical modulator 604 converts the time-multiplexed electric signal input from the time multiplexer 611 into an optical signal and IQ-multiplexes it to transmit it to the receiver R via the optical transmission line L.

  On the receiving device R side, the received DQPSK-modulated optical signal is delayed and demodulated by the optical delay interferometer 605, outputs I channel and Q channel signals, and the optical delay interference is generated by the photoelectric elements 606 and 607. The I-channel and Q-channel optical signals output from the total 605 are converted into electrical signals. The time demultiplexer 612 performs time demultiplexing on the input signal and outputs a plurality of signal outputs. The electrical reception signal processing circuit 608 processes the time-demultiplexed signal. The electrical reception signal processing circuit 608 is a delay generator 609 that performs a delay process on the input signal in accordance with a delay amount set in accordance with a detected skew amount described later. Similar to the first embodiment, the pattern comparator 610 is a comparator with an additional function that performs a comparison between input data series having a fixed length to obtain a skew amount. An additional function for obtaining the skew amount from the comparison result may be provided separately as a circuit or a microprocessor (not shown).

(Skew amount detection on the receiver S side)
Next, the operation when detecting the skew amount for deskew according to the present invention will be described in more detail. First, the data sequence 204 including X is generated and transmitted from one output 613 among the h transmission I channel signal outputs of the pattern generator 603. Further, the remaining transmission I channel output and transmission Q channel output generate and transmit a data sequence composed of repetitions of M N-bit fixed data sequences similar to the data sequence 205. The portion corresponding to the N-bit fixed data series may be different for each output.

  FIG. 8 shows the relationship between the received data series in the received I channel and the received Q channel and the output of the time demultiplexer 612. At the output of the optical delay interferometer 605 of the receiving device R, the received data whose data is determined depending on the value of X is the time when X interferes with the light that has reached K bits in advance, and X is delayed by K bits. It occurs at two points of time that interfere with the light that has arrived. The data changes at these two times are output from the separate output ports 616 and 618 of the time demultiplexer 612 and are generated by X by the portion of the pattern comparator 610 connected to each output port. Changes are detected. The multiplicity of the time demultiplexer 611 is the same as the multiplicity of the time demultiplexer 612. Unless the output terminal for outputting the data sequence 204 is changed in the pattern generator 603, the time demultiplexer 612 that is affected by X is affected. The output ports are always 616 and output port 618.

  Out of the output ports of the time demultiplexer 612 that are affected by X in the transmission data sequence in the reception I channel, the output port corresponding to the preceding time is output as the output port 701, and the output port corresponding to the subsequent time is output. The mouth 702 is used. The comparison unit of the pattern comparator 610 prepared for the output port 701 and the output port 702 compares the N × h-bit sequences with each other, and a change caused by the difference between X is detected. Which output port corresponds to the subsequent time can be detected by taking correspondence with the number of delay bits of the optical delay interferometer 605.

  An output port generated between the time demultiplexing device 612 and the electric reception signal processing circuit 608 is obtained by taking a difference between portions where the change is caused by X in the comparison unit corresponding to the output port of the pattern comparator 610. It becomes possible to detect a delay difference between the output port 702 and the output port 701. However, when the processing time of the time demultiplexer 612 defined by the output ports 701 and 702 is shifted by one symbol, correction for one symbol is necessary.

  Of the output ports that are affected by X (1) in the transmission data sequence in the reception Q channel, the output port of the time demultiplexer 612 corresponding to the preceding time is the output port 703, and the time corresponding to the subsequent time When the output port of the inverse multiplexing device 612 is the output port 704, the skew amount between the output port 703 and the output port 704 is obtained through the same process as the detection of the skew amount between the output port 701 and the output port 702. Detection is possible. Further, in the receiving apparatus R, an output port 701 for an output port shift 701 caused by a skew between the reception I channel and the reception Q channel generated between the output of the optical delay interferometer 605 and the output of the time demultiplexing device 612; Processing for associating with the output port 703 can be performed. Further, the difference between the output port 701 and the comparison unit of the pattern comparator 610 corresponding to the output port 701 and the comparison unit of the pattern comparator 610 corresponding to the output port 703 is changed by X. It becomes possible to detect a delay difference from the output port 703.

  Next, a data series 204 including X is generated from an output 614 different from the output 613 among the transmission I channel signal outputs of the pattern generator 603, and the remaining N transmission outputs and N transmission Q channels are output as N times. A sequence composed of repetitions of the bit fixed data sequence 205 is transmitted. At the output port of the time demultiplexer 612 of the receiving device R, a skew difference can be detected for a set of output ports different from the output port 701 and the output port 702. By repeating this for the number of output ports h, the skew difference between the output ports in the reception I and Q channels and the reception I for all the sets of output ports of the time demultiplexer 612 that interfere with each other. And a skew difference between the Q channels can be obtained.

  By applying the skew difference sequentially to all the output ports with reference to the reception timing at one of the output ports, the skew amount of all the output ports in the receiving device R can be obtained. By generating a delay according to the amount of skew detected by the delay generator 609, between the reception I channel signal and the reception Q channel signal between the optical delay interferometer 605 and the electrical reception signal processing circuit 608, and within the reception I channel It becomes possible to compensate for the skew in the reception Q channel.

(Skew amount detection on transmitting device S side)
Assuming that the data sequence 204 is transmitted to the output 613 of the delay generator 602, a preceding change in the output of the optical delay interferometer 605 of the receiving device R is sent to the output port 616 of the time demultiplexing device 612, and a subsequent change is time-reversed. Assume that it appears at the output 618 of the multiplexer 612. Further, assuming that the data series 204 is transmitted to the output 615 of the delay generator 602, and a preceding change in the output of the optical delay interferometer 605 of the receiving device R appears at the output port 618 of the time demultiplexing device 612 of the receiving device R. To do. At this time, when the time to send X (1) in the data series 204 is aligned with the output 613 and the time to send X (1) in the data series 204 to the output 615, the pattern comparator 610 at the output port 618 The difference between the location where the change due to X is detected when the data sequence 204 is transmitted from the output 613 and the location where the change due to X is detected when the data sequence 204 is transmitted from the output 615 is the electrical transmission signal processing circuit 601. The skew difference between the output 613 and the output 615 is from the output of the time multiplex device 611 to the output of the time multiplexer 611.

  By repeating the same method for all the I channel outputs of the electrical transmission signal processing circuit 601, it is possible to detect the skew amount in the transmission I channel inside the transmission apparatus S. In addition, the data series 204 is sequentially transmitted from each transmission Q channel of the electrical reception signal processing circuit 601, and the skew amount between the transmission Q channels can be detected by performing the same operation. Here, by aligning the time at which X (1) in the data sequence 204 is transmitted to the transmission I channel output and the time at which X (1) in the data sequence 204 is transmitted to the transmission Q channel output, the output port of the time demultiplexer 612 is set. Taking the difference between the detected X positions in 618, the amount of skew between the transmission I channel and the transmission Q channel is obtained. By generating a delay according to the skew amount in the delay generator 602, between the transmission I channel signal and the transmission Q channel signal between the electrical transmission signal processing circuit 601 and the optical modulator 604, and within the transmission I channel, the transmission Q channel It is possible to compensate for the skew within.

  When the transmitting device S compensates for the skew amount of the transmission I channel signal and the transmission Q channel signal detected by the receiving device R, X detected by the pattern comparator 610 of the receiving device R is the electric transmission signal processing circuit 601. It is necessary to make it recognize between the transmission apparatus S and the receiving apparatus R of an optical communication system from which output it originated. As a means, initialization is performed with a training pattern or the like, and the order of output in which the data series 204 is output from the electric transmission signal processing circuit 601 is determined in advance, or the skew amount from the reception side to the transmission side in the first embodiment This is possible by means of notifying the transmission skew value each time the transmission data series 204 is output from one output of the electric transmission signal processing circuit 601. Further, as in the means of the first embodiment, it is possible to use a method of transmitting from the output of the electrical transmission signal processing circuit 601 as data to the transmission sequence X as data.

  As described above, the skew amount can be detected by transmitting a limited number of fixed patterns of N × M × 2 × 2h symbols. In the method of trying all the skew amounts between the I channel and the Q channel shown in Patent Document 1 described above, since N-th power of symbol transmission is required, it takes much shorter time than this. A skew amount can be detected. Further, since the detection means is not a data series but a simple data change, it is not easily affected by the deterioration of the transmission path.

  The pattern generators 103 and 603 constitute pattern generation means, the pattern comparators 110 and 610 constitute skew detection means or information detection means, the electric transmission signal processing circuits 101 and 601, the electric reception signal processing circuit 108, Reference numerals 608 each constitute an electric signal processing unit.

  As described above, according to the present invention, in the optical DQPSK communication, the transmission apparatus has a function of generating a periodic pattern that causes a change only in a specific data location before the location where multiplexing (IQ multiplexing) is performed in the system. Has a function of detecting bits that have changed in a periodic pattern with respect to a demultiplexed (IQ demultiplexed) data sequence, and detects the amount of skew generated in the transmitter and receiver.

  In addition, a) a change is caused only in the I channel in the transmission apparatus, b) in the reception apparatus, in the DQPSK detection due to optical delay interference, the change generated on the transmission apparatus side is both the I channel and the Q channel of the reception apparatus. C) In the receiving apparatus, the amount of skew between the I channel and the Q channel generated between the output of the optical delay interferometer and the electrical signal processing unit is determined in the electrical signal processing unit. The amount of skew between IQ channels in the receiving apparatus is detected by means of detecting by obtaining the difference between the time when the change in the periodic pattern is detected in the I channel and the time when the change in the periodic pattern is detected in the Q channel.

  Also, in a device in which the receiving device performs inverse time multiplexing, it detects the amount of skew generated between the time demultiplexing device in the receiving device and the electric signal processing unit, and a) a change occurs only in the I channel in the transmitting device. B) In the receiving apparatus, in the detection of DQPSK by the optical delay interferometer, the change generated in the transmitting apparatus is the change 1 and the change in the signal generated at the timing when the change occurs in the signal sequence in the receiving apparatus. Signal change 2 occurs at the timing when the generated signal is delayed and interferes. C) In the receiving device, change 1 and change 2 are output to different outputs 3 and 4 by the time demultiplexer, d) The electrical signal processing unit obtains the difference between the time of the change occurring at the output 1 and the time of the change occurring at the output 2 to obtain the time demultiplexer and the electrical signal. Detecting the amount of skew generated between the signal processing units, e) detecting the amount of skew with respect to the output of the other time demultiplexing device by delaying the timing at which the change occurs on the transmitting device side by one symbol, By detecting the delay of the number of times corresponding to the number of inverse time multiplexing and the amount of skew, the amount of skew generated in all outputs of the time inverse multiplexing device is detected.

  In addition, a) a change is caused only in the I channel in the transmission device, and a detection time 5 of change in the periodic pattern is obtained in the reception device; b) a change is caused only in the Q channel in the transmission device, and a periodic pattern is obtained in the reception device. The detection time 6 of the change in the medium is obtained. C) By obtaining the difference between the detection time 5 and the detection time 6, the skew amount between the I channel and the Q channel in the transmission apparatus is detected.

  In addition, in the apparatus in which the transmission apparatus performs time multiplexing, a) the transmission apparatus selects one input 7 from the time multiplexing apparatus input sequence and causes a change in a specific place in the periodic pattern; b) the reception apparatus Then, a change in the periodic pattern is detected at time 8. c) In the transmission device, the change of the pattern with respect to the input 7 is stopped, and another input 8 different from the one selected in the above a) in the time multiplexing device input series is stopped. In the periodic pattern given to the input 8, a change is made at the same location as the location where the change was made to the input 7 in the above a), and d) the change of the periodic pattern is detected at the time 9 in the receiving apparatus. e) Obtaining the difference between time 8 and time 9 to detect the amount of skew between the I channel and the Q channel in the transmitter, f) Detecting the amount of skew for the inputs of all the time multiplexing devices By detecting the amount of skew that occurs in all the input by, for detecting a skew amount generated between, and the internal time multiplexing apparatus for an electric signal processing unit and time multiplexer in the transmitter.

  According to the present invention, in optical DQPSK communication, the transmitting apparatus has a function of generating a periodic pattern that changes only at a specific data location before the location where multiplexing is performed in the system, and the receiving device is demultiplexed. In a state where a skew is generated between the I channel and the Q channel in the transmission device due to the change of the periodic pattern, the receiving device has Communicate information.

  In particular, when a skew is generated between the I channel and the Q channel in the transmission apparatus, a change occurs in a specific portion in the periodic pattern generated by the transmission apparatus, and reception is performed by detecting the change pattern in the reception apparatus. Communicate information to the device.

  In addition, when skew is generated between the I channel and Q channel in the transmission device, a change is made at a plurality of specific locations in the periodic pattern generated by the transmission device, and the pattern at the location where the change has occurred is received. Information is transmitted to the receiving device by detection by the device.

  In addition, in a state where a skew is generated between the I channel and the Q channel in the transmission device, a change occurs in a plurality of specific places in the periodic pattern generated by the transmission device, and the reception device depends on the pattern of the portion that caused the change. To communicate information.

  101, 601 Electric transmission signal processing circuit (electric signal processing unit), 101a, 601a DQPSK encoder, 101b, 101c, 601b, 601c selector, 102, 109, 602, 609 delay generator, 103, 603 pattern generator (pattern Generating means), 104,604 optical modulator, 105,605 optical delay interferometer, 106,107,606,607 photoelectric element, 108,608 electric reception signal processing circuit (electric signal processing unit), 110,610 pattern comparator (Skew detection means, information detection means), 611 time multiplexing device, 612 time demultiplexing device, L optical transmission line, R reception device, S reception device, SR transmission / reception device.

Claims (9)

A skew detection apparatus for an optical communication system that performs optical DQPSK communication,
In a transmitting apparatus that multiplexes and transmits a transmission signal, in order to multiplex and transmit a pattern signal composed of a periodic pattern in which a predetermined data location in one periodic pattern changes, instead of a transmission signal that has been DQPSK encoded, Pattern generating means for generating a pattern signal;
In a receiving device that receives a transmission signal from the transmitting device and performs demultiplexing, a place where a change occurs in a periodic pattern of the received and demultiplexed pattern signal is detected, and at least the transmitting device and the receiving device Skew detecting means for detecting the amount of skew generated inside one of the devices;
A skew detection apparatus for an optical communication system, comprising:
The pattern generating means gives a change to a predetermined data location of the periodic pattern of the I channel pattern signal among the pattern signals composed of the I channel and the Q channel,
The skew detection means obtains a difference between a time at which a change in the periodic pattern is detected in the I channel and a time at which a change in the periodic pattern is detected in the Q channel, so that electrical signal processing is performed from the output of the optical delay interferometer of the receiving device. Detecting the amount of skew between the I channel and the Q channel generated between the sections,
The skew detection apparatus for an optical communication system according to claim 1. In the transmission device, the electrical signal processing unit has a plurality of outputs, and is time-multiplexed by the time multiplexing device and input to the optical modulator. In the reception device, the received signal is time-demultiplexed by the time demultiplexing device, In an optical communication system that is input to an electrical signal processing unit having an input,
The pattern generating means changes the predetermined data location of the periodic pattern of the I channel pattern signal among the pattern signals composed of the I channel and the Q channel, and changes the number of times corresponding to the time demultiplexing number of the receiving apparatus. Generate the pattern signal while delaying the given timing one symbol at a time,
The skew detection means detects the difference between the time of the change occurring in the output having a distance corresponding to the delay amount of the delay interferometer of the time demultiplexing device and the electric signal processing unit from the output of the time demultiplexing device of the receiving device. Detecting the amount of skew generated at one output of the output and detecting the amount of skew generated at all outputs of the time demultiplexing device by a pattern signal in which the timing for changing is shifted by one symbol at a time.
The skew detection apparatus for an optical communication system according to claim 1. The pattern generating means generates a pattern signal that changes the pattern signal of the I channel and the pattern signal of the Q channel, and a pattern signal that changes the pattern signal of the Q channel.
The skew detection means calculates a skew amount between the I channel and the Q channel generated in the transmission apparatus from a difference between a time at which a change in the periodic pattern is detected in the I channel and a time at which a change in the periodic pattern is detected in the Q channel. To detect,
The skew detection apparatus for an optical communication system according to claim 1. In the transmission device, the electrical signal processing unit has a plurality of outputs, and is time-multiplexed by the time multiplexing device and input to the optical modulator. In the reception device, the received signal is time-demultiplexed by the time demultiplexing device, In an optical communication system that is input to an electrical signal processing unit having an input,
The pattern generating means generates a pattern signal composed of an I channel and a Q channel for each of a plurality of outputs a plurality of times, and in this case, one of the plurality of outputs is selected in order, and the period of the I channel pattern signal Change the same predetermined data location of the pattern,
The skew detection means detects the amount of skew between the I channel and the Q channel generated in the transmission device from the difference in time at which the change in the periodic pattern is detected in the pattern signal in which the change is applied to the I channel pattern signal of different output And detecting a skew amount generated in all outputs of the transmission signal processing device with respect to the time demultiplexing device,
The skew detection apparatus for an optical communication system according to claim 1. The transmission device and the reception device are respectively a transmission device of one transmission / reception device and a reception device of the other transmission / reception device that perform communication between a pair of transmission / reception devices including the transmission device and the reception device,
The detection result of the skew amount in the transmission device of the communication device of the communication partner obtained by the skew detection means is transferred from the pattern generation device of the transmission device of the same transmission device to the skew detection device of the reception device of the communication device of the communication partner. The skew detection apparatus for an optical communication system according to any one of claims 1, 4, and 5, wherein transmission is performed according to a change in a periodic pattern. In an optical communication system that performs optical DQPSK communication, in order to transmit information to a receiving apparatus in a state where a skew occurs between the I channel and the Q channel in the transmitting apparatus,
The transmission device is provided with pattern generation means for generating the pattern signal for multiplexing and transmitting a pattern signal composed of a periodic pattern whose predetermined portion changes according to information to be transmitted,
The receiving device is provided with information detecting means for detecting the location of the changed portion of the pattern signal received and demultiplexed as information,
An optical communication system.   The pattern generating means generates a pattern signal composed of a periodic pattern in which a predetermined data location in one periodic pattern changes, and the information detecting means changes in the periodic pattern of the pattern signal received and demultiplexed. The optical communication system according to claim 7, wherein a place where the vehicle is present is detected.   The pattern generating means generates a pattern signal composed of a periodic pattern in which a plurality of data locations in one periodic pattern changes, and the information detecting means detects a place where a plurality of changes occur. 8. An optical communication system according to 7.

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