JP2010219651A - Optical receiver, signal reproducing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately reproduce original data signals corresponding to received signals. <P>SOLUTION: The optical receiver receives optical signals which are transmitted from an optical transmitter and data signals of which are modulated. The received optical signals are converted to electric signals corresponding to the phase of the optical signals, an identification threshold to be a reference for reproducing the data signals is calculated on the basis of the amplitude of the electric signals, and the data signals are reproduced from differential signals which are signals calculated from the electric signals with the calculated identification threshold as a reference. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical receiver, a signal reproduction method, and a program for reproducing a data signal based on an optical signal.

  When transmitting information at a high bit rate in a WDM (Wavelength Division Multiplexing) optical communication system that transmits information by multiplexing a plurality of optical signals having different wavelengths in one optical fiber, the modulation method is usually differential. A phase shift keying (DPSK) is used. Thereby, it is possible to transmit information at a long distance and at a high bit rate. Hereinafter, the differential phase shift keying method is referred to as DPSK.

  In DPSK, the phase of an optical carrier is determined in accordance with a change between the bit value of a previously transmitted bit and the bit value of a next transmitted bit. Therefore, an optical receiver that receives an optical signal modulated by DPSK and regenerates the original data signal detects the original data by detecting the phase of the next optical carrier with reference to the phase of the transmitted optical carrier. Play the signal. That is, the optical receiver reproduces the original data signal by detecting a relative phase that is a phase difference between two adjacent optical carriers. Hereinafter, an optical signal modulated by DPSK is referred to as a DPSK modulated optical signal.

  FIG. 5 is a block diagram illustrating an example of a configuration of an optical receiver that receives a DPSK modulated optical signal.

  5 includes a 1-bit delay device 121 having a delay element 121-1, a balanced receiver 122 having light receiving elements 122-1 and 122-2, a clock extractor 126, and an identification regenerator. 127.

  The 1-bit delay device 121 receives the DPSK modulated optical signal and demultiplexes the received DPSK modulated optical signal into two optical signals. Then, a delay of a time corresponding to 1 bit is given to one of the demultiplexed optical signals by the delay element 121-1. Then, the two demultiplexed optical signals are combined, and the relative phases of the two optical signals are compared for each bit. As a result of the comparison, when both relative phases match, the 1-bit delay device 121 outputs an optical signal to the light receiving element 122-1 of the balanced receiver 122. On the other hand, as a result of the comparison, if both phases do not match, the 1-bit delay device 121 outputs an optical signal to the light receiving element 122-2 of the balanced receiver 122.

  The balanced receiver 122 converts the optical signal output from the 1-bit delay device 121 into an electrical signal by the light receiving elements 122-1 and 122-2. Then, a differential signal which is a signal obtained by adding the electric signals is output to the clock extractor 126 and the identification regenerator 127.

  The clock extractor 126 extracts a clock component from the differential signal output from the balanced receiver 122 and outputs the extracted clock component to the identification regenerator 127. The clock component is a signal for taking a timing for transmitting and receiving a signal between the signal transmitting side and the receiving side.

  The identification regenerator 127 receives the differential signal output from the balanced receiver 122 and the clock component output from the clock extractor 126. Then, by determining a bit value of “0” or “1” from the differential signal with a predetermined threshold as a reference, the original data signal is reproduced. Then, the data signal reproduced by taking the timing with the received clock component is output.

  Here, when transmission is performed at a very high bit rate of 40 Gbps or more, the influence of the band narrowing effect by the optical demultiplexing unit that multiplexes and separates optical signals is known. The optical demultiplexing unit is a device provided between an optical transmission device that converts a data signal into an optical signal and transmits the optical signal, and an optical reception device. And interleavers.

The band narrowing effect occurs when an optical signal is transmitted at a high bit rate, by narrowing a band allocated to one optical signal in order to share one optical fiber cable with many optical signals. Specifically, it occurs when the bandwidth of the optical signal transmitted and received between the optical transmission device and the optical reception device is wider than the filter bandwidth of the OMUX, ODMUX, and interleaver.
As a result, the band of the optical signal is narrower than the band originally possessed by the optical signal, and the component included in the original data signal is lost. For this reason, the waveform of the optical signal is deteriorated, and the accuracy of reproducing the original data signal in the optical receiving device is lowered. As a result, the bit error rate increases.

  Here, for example, Patent Document 1 discloses an optical transmission system that can maintain a good reception state while narrowing the band of an optical signal. In the technique disclosed in Patent Document 1, waveform deterioration is improved by narrowing the band of the DPSK modulated optical signal using a predetermined transmittance characteristic.

JP 2005-94287 A

  In the technique disclosed in Patent Document 1 described above, waveform degradation is improved by narrowing the band of the DPSK modulated optical signal using a predetermined transmittance characteristic. However, the influence of the band narrowing effect is not uniform, the type of filter of the optical demultiplexing unit, whether the optical signal is a zero return (RZ: Return to Zero) signal or a non-zero return (NRZ: Non Return to Zero) signal, etc. It also changes depending on. The zero return signal is a signal that once returns to “0” after the bit value “1”, and the non-zero return signal is “1” until the next “0” after the bit value “1”. It is a signal that remains.

  Therefore, even if the technique disclosed in Patent Document 1 is used, it is possible to accurately reproduce the original data signal according to the received optical signal in response to the influence of the band narrowing effect that changes depending on various conditions. There is a problem that it is not possible.

  An object of the present invention is to provide an optical receiver, a signal reproduction method, and a program that can accurately reproduce an original data signal in accordance with a received signal.

In order to achieve the above object, the present invention provides:
An optical receiver that receives an optical signal transmitted from an optical transmitter and modulated by a data signal,
The received optical signal is converted into an electrical signal corresponding to the phase of the optical signal, an identification threshold value serving as a reference for reproducing the data signal is calculated based on the amplitude of the electrical signal, and the electrical signal is The data signal is reproduced from the differential signal, which is the calculated signal, with the calculated identification threshold as a reference.

In addition, a signal regeneration method in an optical receiver that receives an optical signal transmitted from an optical transmitter and modulated by a data signal,
A conversion process for converting the received optical signal into an electrical signal corresponding to the phase of the optical signal;
A calculation process for calculating an identification threshold value serving as a reference for reproducing the data signal based on the amplitude of the electrical signal;
Reproduction processing for reproducing the data signal from a differential signal, which is a signal calculated from the electrical signal, with reference to the calculated identification threshold.

In addition, an optical receiver that receives an optical signal that is transmitted from an optical transmitter and that has a modulated data signal,
A conversion function for converting the received optical signal into an electrical signal corresponding to the phase of the optical signal;
A calculation function for calculating an identification threshold value serving as a reference for reproducing the data signal based on the amplitude of the electrical signal;
A reproduction function for reproducing the data signal from the differential signal, which is a signal calculated from the electrical signal, with the calculated identification threshold as a reference is realized.

  According to the present invention, an optical receiving device receives an optical signal transmitted from an optical transmitting device and whose data signal is modulated, and converts the received optical signal into an electrical signal corresponding to the phase of the optical signal. Then, an identification threshold value serving as a reference for reproducing the data signal is calculated based on the amplitude of the electric signal. Then, the data signal is reproduced from the differential signal, which is a signal calculated from the electrical signal, with the calculated identification threshold as a reference.

  Therefore, the original data signal can be accurately reproduced according to the received optical signal.

It is a figure which shows one Embodiment of the WDM optical communication system using the optical receiver of this invention. FIG. 2 is a block diagram illustrating an example of a configuration of the optical receiving device illustrated in FIG. 1. It is a figure which shows the image of the upper limit and lower limit of the amplitude of an electric signal compared with the peak detection result comparator shown in FIG. 2, (a) is the balance between the upper limit and lower limit of the amplitude of an electric signal. The figure which shows the case where it has taken, (b) is a figure which shows the case where the balance of the upper limit of electric signals and a lower limit is not taken. 3 is a flowchart for explaining an operation in which an optical receiver reproduces a data signal in the WDM optical communication system shown in FIGS. 1 and 2. It is a block diagram which shows an example of a structure of the optical receiver which receives a DPSK modulation optical signal.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a WDM optical communication system using an optical receiver of the present invention.

  As shown in FIG. 1, the WDM optical communication system of the present embodiment includes optical transmitters 10-1 to 10-n, optical receivers 20-1 to 20-n, OMUX 30, ODMUX 40, and interleaver 50-1. , 50-2. In the present embodiment, a case where DPSK is used as a modulation method will be described as an example. However, the present invention is not limited to other differential phase shift keying modulation methods such as differential quaternary phase shift keying (DQPSK). : Differential Quadrature Phase Shift keying).

  The optical transmitters 10-1 to 10-n modulate data signals with DPSK and transmit the modulated DPSK modulated optical signals to the optical receivers 20-1 to 20-n.

  The OMUX 30 and the interleaver 50-1 receive and multiplex a plurality of DPSK modulated optical signals transmitted from the optical transmitters 10-1 to 10-n.

  The ODMUX 40 and the interleaver 50-2 separate the multiplexed DPSK modulated optical signal transmitted from the OMUX 30 and the interleaver 50-1. Then, each of the separated DPSK modulated optical signals is transmitted to the optical receivers 20-1 to 20-n.

  FIG. 2 is a block diagram illustrating an example of the configuration of the optical receiver 20-1 illustrated in FIG. The optical receivers 20-2 to 20-n have the same configuration.

  As shown in FIG. 2, the optical receiver 20-1 shown in FIG. 1 includes a 1-bit delay device 21 having a delay element 21-1, a balanced receiver 22 having light receiving elements 22-1 and 22-2, Peak detectors 23 and 24, a peak detection result comparator 25, a clock extractor 26, and an identification regenerator 27 are provided.

  The 1-bit delay device 21 receives the DPSK modulated optical signal and demultiplexes the received DPSK modulated optical signal into two optical signals. Then, a delay of time corresponding to 1 bit is given to one of the demultiplexed optical signals by the delay element 21-1. Then, the two demultiplexed optical signals are combined, and the relative phases of the two optical signals are compared for each bit. As a result of the comparison, if both relative phases match, the 1-bit delay device 21 outputs an optical signal to the light receiving element 22-1 of the balanced receiver 22. On the other hand, as a result of the comparison, if both phases do not match, the 1-bit delay device 21 outputs an optical signal to the light receiving element 22-2 of the balanced receiver 22.

  The balanced receiver 22 converts the optical signal output from the 1-bit delay device 21 into an electrical signal by the light receiving elements 22-1 and 22-2. Then, a differential signal which is a signal obtained by adding the electrical signals is generated, and the generated differential signal is output to the clock extractor 26 and the identification / regenerator 27.

  The peak detector 23 detects the amplitude of the electrical signal converted by the light receiving element 22-1. The peak detector 24 detects the amplitude of the electric signal converted by the light receiving element 22-2. The amplitude of the electrical signal converted by the light receiving elements 22-1 and 22-2 of the balanced receiver 22 depends on the types of filters of the OMUX 30, the ODMUX 40 and the interleavers 50-1 and 50-2, and the optical signal is a zero return signal. Or non-zero return signal.

  The peak detection result comparator 25 compares the upper limit value of the amplitude of the electrical signal detected by the peak detector 23 with the lower limit value of the electrical signal detected by the peak detector 24. Then, an intermediate value thereof is calculated from the upper limit value and the lower limit value. Then, the calculated intermediate value is output to the identification regenerator 27 as an identification threshold value. The identification threshold is a threshold that serves as a reference for the identification regenerator 27 to determine the bit value of “0” or “1” from the electrical signal.

  FIG. 3 is a diagram showing an image of the upper limit value and lower limit value of the amplitude of the electric signal compared by the peak detection result comparator 25 shown in FIG. 2, and (a) shows the upper limit value and lower limit value of the amplitude of the electric signal. The figure which shows the case where the value is balanced, (b) is a figure which shows the case where the balance between the upper limit value and the lower limit value of the electric signal is not taken.

  As shown in FIG. 3, whether the upper limit values 101 and 201 of the electric signal amplitude and the lower limit values 102 and 202 are balanced or not balanced, the identification threshold values 103 and 203 are the upper limit values 101 and 203, respectively. This is an intermediate value between 201 and the lower limit values 102 and 202.

  The clock extractor 26 extracts a clock component from the differential signal output from the balanced receiver 22, and outputs the extracted clock component to the identification / regenerator 27.

  The identification regenerator 27 receives the differential signal output from the balanced receiver 22, the clock component output from the clock extractor 26, and the identification threshold output from the peak detection result comparator 25. Then, the original data signal is reproduced by determining the bit value from the received differential signal with the received identification threshold as a reference. Then, the reproduced data signal is output by timing with the received clock component.

  In the following, an operation in which an optical receiver reproduces a data signal in the WDM optical communication system configured as described above will be described.

  FIG. 4 is a flowchart for explaining an operation in which the optical receivers 20-1 to 20-n reproduce data signals in the WDM optical communication system shown in FIGS. Here, as an example, an operation will be described in which the optical receiver 20-1 regenerates a DPSK modulated optical signal transmitted from the optical transmitter 10-1 into a data signal.

  The optical transmission device 10-1 modulates the data signal with DPSK and transmits the modulated DPSK optical modulation signal to the OMUX 30.

  The DPSK modulated optical signal transmitted from the optical transmitter 10-1 is multiplexed with other optical signals by the OMUX 30 and the interleaver 50-1, and separated by the ODMUX 40 and the interleaver 50-2. Then, the separated DPSK modulated optical signal is transmitted from the ODMUX 40 to the optical receiver 20-1.

  The 1-bit delay device 21 of the optical receiver 20-1 receives the DPSK modulated optical signal transmitted from the ODMUX 40 (step S1).

  The 1-bit delay device 21 that has received the DPSK modulated optical signal demultiplexes the received optical signal into two optical signals. Then, a delay of a time corresponding to 1 bit is given to one of the demultiplexed optical signals by the delay element 21-1.

  Then, the 1-bit delay device 21 combines the two demultiplexed optical signals, and compares the relative phases of the two optical signals for each bit (step S2). As a result of the comparison, when both relative phases match, the 1-bit delay device 21 outputs an optical signal to the light receiving element 22-1 of the balanced receiver 22. On the other hand, as a result of comparison, if both phases do not match, the 1-bit delay device 21 outputs an optical signal to the light receiving element 22-2 of the balanced receiver 22.

  Next, the light receiving elements 22-1 and 22-2 of the balanced receiver 22 that has received the optical signal output from the 1-bit delay device 21 converts the received optical signal into an electrical signal (step S3).

  The balanced receiver 22 generates a differential signal that is a signal obtained by adding the electrical signals converted by the light receiving elements 22-1 and 22-2 (step S4), and the generated differential signal is converted into a clock extractor 26 and It outputs to the identification regenerator 27.

  Here, the peak detector 23 detects the amplitude of the electrical signal converted by the light receiving element 22-1. The peak detector 24 detects the amplitude of the electric signal converted by the light receiving element 22-2.

  The peak detection result comparator 25 compares the upper limit value of the amplitude of the electrical signal detected by the peak detector 23 with the lower limit value of the electrical signal detected by the peak detector 24. Then, an intermediate value between the upper limit value and the lower limit value is calculated (step S5).

  The peak detection result comparator 25 that has calculated the intermediate value outputs the calculated intermediate value to the identification regenerator 27 as the identification threshold value.

  In addition, the clock extractor 26 that has received the differential signal output from the balanced receiver 22 extracts a clock component from the received differential signal, and outputs the extracted clock component to the identification / regenerator 27.

  The identification regenerator 27 receives the differential signal output from the balanced receiver 22, the clock component output from the clock extractor 26, and the identification threshold output from the peak detection result comparator 25. Then, the original data signal is reproduced by determining the bit value from the received differential signal with the received identification threshold as a reference (step S6).

  The discriminating / reproducing unit 27 outputs a data signal reproduced by timing the received clock component.

  As described above, in the present embodiment, the optical receivers 20-1 to 20-n receive the optical signals transmitted from the optical transmitters 10-1 to 10-n, modulated with the data signals, and received. The signal is converted into an electrical signal corresponding to the phase of the optical signal. Then, an identification threshold value serving as a reference for reproducing the data signal is calculated based on the amplitude of the electric signal. Then, the data signal is reproduced from the differential signal, which is a signal obtained by adding the electrical signals, with the calculated identification threshold as a reference.

  Therefore, the original data signal can be accurately reproduced according to the received optical signal.

  In the present invention, the processing in the optical receiver is recorded on a recording medium readable by the optical receiver in addition to the above-described dedicated hardware. The program recorded on the recording medium may be read by the optical receiver and executed. The recording medium that can be read by the optical receiving device refers to a transfer medium such as a floppy disk, a magneto-optical disk, a DVD, and a CD, and an HDD built in the optical receiving device.

10-1 to 10-n Optical transmission device 20-1 to 20-n Optical reception device 21 1-bit delay device 21-1 Delay element 22 Balanced receiver 22-1, 22-2 Light receiving device 23, 24 Peak detector 25 Peak detection result comparator 26 Clock extractor 27 Identification regenerator 30 OMUX
40 ODMUX
50-1, 50-2 Interleaver 101, 201 Upper limit 102, 202 Lower limit 103, 203 Identification threshold

Claims (9)

An optical receiver that receives an optical signal transmitted from an optical transmitter and modulated by a data signal,
The received optical signal is converted into an electrical signal corresponding to the phase of the optical signal, an identification threshold value serving as a reference for reproducing the data signal is calculated based on the amplitude of the electrical signal, and the electrical signal is An optical receiver that reproduces the data signal from a differential signal, which is a calculated signal, using the calculated identification threshold as a reference. The optical receiver according to claim 1,
An optical receiver using an intermediate value between an upper limit value and a lower limit value of the amplitude of the electrical signal as the identification threshold value. The optical receiver according to claim 2,
The received optical signal is demultiplexed into two optical signals, one of the two demultiplexed optical signals is delayed, the optical signal given the delay, and the optical signal not given the delay A 1-bit delay device that generates an optical signal corresponding to the relative phase of the optical signal and outputs the generated optical signal;
A balanced receiver that receives the optical signal output from the 1-bit delay device, converts the received optical signal into an electrical signal, and outputs the differential signal calculated from the electrical signal;
A peak detector for detecting the upper limit and the lower limit from the electrical signal;
A peak detection result comparator for calculating an intermediate value between the upper limit value and the lower limit value detected by the peak detector, and outputting the intermediate value as the identification threshold;
The discrimination threshold output from the peak detection result comparator and the differential signal output from the balanced receiver are received, and a bit value is obtained from the received differential signal with the received identification threshold as a reference. And an identification regenerator that reproduces the data signal by determining. A signal regeneration method in an optical receiver for receiving an optical signal transmitted from an optical transmitter and modulated by a data signal,
A conversion process for converting the received optical signal into an electrical signal corresponding to the phase of the optical signal;
A calculation process for calculating an identification threshold value serving as a reference for reproducing the data signal based on the amplitude of the electrical signal;
And a reproduction process of reproducing the data signal from a differential signal, which is a signal calculated from the electrical signal, using the calculated identification threshold as a reference. The signal reproduction method according to claim 4,
The calculation process is a signal reproduction method in which an intermediate value between an upper limit value and a lower limit value of the amplitude of the electrical signal is used as the identification threshold value. The signal reproduction method according to claim 5, wherein
The conversion process includes
The received optical signal is demultiplexed into two optical signals, one of the two demultiplexed optical signals is delayed, the optical signal given the delay, and the optical signal not given the delay A process of generating an optical signal corresponding to the relative phase of
A process of converting the generated optical signal into an electrical signal;
Generating the differential signal calculated from the electrical signal,
The calculation process is as follows:
Detecting the upper limit and the lower limit from the electrical signal;
Calculating an intermediate value between the detected upper limit value and the lower limit value, and setting the intermediate value as the identification threshold value,
The signal reproduction method, wherein the reproduction process is a process of reproducing the data signal by determining a bit value from the differential signal with the identification threshold as a reference. To an optical receiver that receives an optical signal transmitted from an optical transmitter and modulated by a data signal,
A conversion function for converting the received optical signal into an electrical signal corresponding to the phase of the optical signal;
A calculation function for calculating an identification threshold value serving as a reference for reproducing the data signal based on the amplitude of the electrical signal;
A program for realizing a reproduction function of reproducing the data signal from a differential signal, which is a signal calculated from the electrical signal, with reference to the calculated identification threshold. The program according to claim 7,
The calculation function is a program that uses an intermediate value between an upper limit value and a lower limit value of the amplitude of the electrical signal as the identification threshold value. The program according to claim 8, wherein
The conversion function is
The received optical signal is demultiplexed into two optical signals, one of the two demultiplexed optical signals is delayed, the optical signal given the delay, and the optical signal not given the delay A function of generating an optical signal corresponding to the relative phase of
A function of converting the generated optical signal into an electrical signal;
Generating the differential signal calculated from the electrical signal,
The calculation function is
A function of detecting the upper limit and the lower limit from the electrical signal;
A function of calculating an intermediate value between the detected upper limit value and the lower limit value, and setting the intermediate value as the identification threshold value,
The reproduction function is a program for reproducing the data signal by determining a bit value from the differential signal with the identification threshold as a reference.

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