JP6066964B2 - Dispersion measuring device, clock correcting device, and transmitting device used in optical communication system - Google Patents

Description

  The present invention relates to a dispersion measurement device, a clock correction device, and a transmission device used in an optical communication system, and to an apparatus for measuring characteristics of an optical transmission line.

  2. Description of the Related Art Optical communication systems that transmit information using optical signals are widely used. In an optical communication system, a plurality of nodes are connected by an optical transmission line. Each node transmits and receives optical signals to and from other nodes via the optical transmission path.

  In general, the optical transmission line is constituted by an optical fiber. The optical fiber has a dispersion characteristic that the propagation speed varies depending on the wavelength of the transmitted light. Therefore, when an optical signal having a broad wavelength spectrum is transmitted from a node on the transmission side, the timing at which each wavelength component of the optical signal reaches the reception side differs for each wavelength component. Therefore, the optical signal received on the receiving side may be distorted and the pulse width may be widened. Thus, some nodes that constitute an optical communication system measure the dispersion characteristics of an optical transmission line. The node on the reception side executes processing for compensating for the distortion component in accordance with the dispersion characteristic for the received optical signal. Alternatively, the transmission-side node transmits an optical signal including a distortion component in advance according to the dispersion characteristic, and the optical signal with the distortion component compensated is received by the reception-side node.

  Patent Documents 1 and 2 below describe techniques for measuring dispersion characteristics of an optical transmission line. In the optical transmission system described in Patent Document 1, the propagation delay time of the optical transmission line is measured for one wavelength component, and the dispersion characteristic is obtained based on the measurement result. This propagation delay time is measured after a measurement signal is transmitted from one node, until the measurement signal is returned from the other node that has received the measurement signal, and the measurement signal is received by the other node. Measured based on time. Further, in another optical transmission system described in Patent Document 1, two measurement signals having different wavelengths are transmitted from one node at the same time, and two optical signals are received by the other node based on the time difference. Dispersion characteristics are required.

  In the optical network described in Patent Document 2, each node distributes a measurement signal from another node, receives a part thereof, and transfers the remaining part to the other node. The measurement signal includes information for identifying the transmission source node. Each node identifies a transmission source node based on the received measurement signal, and obtains a chromatic dispersion amount for the optical transmission path to the transmission source. The measurement signal includes two optical signals having different wavelengths, and each node obtains a chromatic dispersion amount based on a time difference at which the two optical signals are received.

JP 2003-121303 A JP 2009-147417 A

  As described in Patent Documents 1 and 2, two optical signals having different wavelengths are received, and in the process of obtaining the dispersion characteristics based on the time difference when these optical signals are received, two optical signals are transmitted simultaneously. Is done. In such processing, since it is necessary to transmit two optical signals simultaneously, an optical transmitter is required for each of the two optical signals, which may increase the size of the transmission-side apparatus.

  An object of the present invention is to reduce the size of an apparatus for measuring characteristics of an optical transmission line.

  The present invention provides a dispersion measuring apparatus used in an optical communication system, a receiving unit that receives an optical signal from an optical transmission line, a time when the first optical signal is received, and a second wavelength that is different from that of the first optical signal. A reception difference measuring unit for obtaining reception difference information indicating a difference from a time when the optical signal is received; and transmission difference information indicating a time difference when the first optical signal and the second optical signal are transmitted. A transmission difference measurement unit obtained based on information included in at least one of a signal and the second optical signal, a wavelength difference between the first optical signal and the second optical signal, the reception difference information, and the transmission difference information And a dispersion analysis unit for obtaining dispersion characteristics of the optical transmission line based on the above.

  Preferably, the reception difference measurement unit obtains the reception difference information based on a timing indicated by a clock signal, and the reception unit receives two calibration optical signals having the same wavelength from the optical transmission line. The reception difference measuring unit obtains reception calibration information indicating a time difference when the two calibration optical signals are received based on a timing indicated by the clock signal, and the transmission difference measuring unit is configured to determine the two calibration optical signals. Transmission calibration information indicating a time difference at which the transmission optical signal is transmitted is obtained based on information included in at least one of the two calibration optical signals, and the dispersion measuring device is configured to obtain the reception calibration information and the transmission Based on the calibration information, the two calibration light signals are transmitted. And time unit of the time difference which, a correction value determination section for determining a correction value for correcting the relationship between the time unit of the clock signal, the variance analysis part obtains the dispersion characteristics by using the correction value.

  According to the present invention, in the clock correction device used in the optical communication system, based on the receiving unit that receives two calibration optical signals having the same wavelength from the optical transmission line, and the timing indicated by the clock signal, A reception difference measuring unit that obtains reception calibration information indicating a time difference when two calibration light signals are received, and transmission calibration information that indicates a time difference when the two calibration light signals are transmitted. A relationship between a transmission difference measurement unit obtained based on information included in at least one of the signals, a time unit of the time difference based on the reception calibration information and the transmission calibration information, and a time unit of the clock signal A correction value determining unit for obtaining a correction value for correcting And wherein the door.

  Further, the present invention provides a dispersion measuring apparatus used in an optical communication system, wherein a receiving unit that receives an optical signal from an optical transmission line, a time when the first optical signal is received, and a wavelength different from the first optical signal. A reception difference measuring unit for obtaining a time when the second optical signal is received, information indicating a time when the first optical signal is transmitted from the first optical signal and the second optical signal, and the second light An extraction unit that extracts information indicating the time at which the signal was transmitted; a first propagation time measurement unit that obtains a first propagation time from when the first optical signal is transmitted until it is received by the reception unit; A second propagation time measuring unit that obtains a second propagation time from when the second optical signal is transmitted until it is received by the receiving unit; and a wavelength difference between the first optical signal and the second optical signal, Based on the first propagation time and the second propagation time, Characterized in that it comprises a dispersion analyzer for obtaining the dispersion characteristic of the optical transmission line, the.

  The present invention also provides a signal generator that generates two signals in a transmitter used in an optical communication system, and a transmitter that transmits two optical signals based on the two signals to an optical transmission line at different timings. The signal generator includes information indicating a time difference for transmitting the two optical signals in at least one of the two optical signals.

  According to the present invention, a device for measuring the characteristics of an optical transmission line can be reduced in size.

It is a figure which shows the optical communication system which concerns on embodiment. It is a figure which shows the structure of a 2nd node. It is a figure which shows the node apparatus which concerns on a 1st modification. It is a figure which shows the node apparatus which concerns on a 2nd modification.

  FIG. 1 shows an optical communication system according to an embodiment of the present invention. The optical communication system includes a first node device 10, an optical transmission line 34, and a second node device 36. The optical transmission line 34 is configured by an optical fiber. The first node device 10 and the second node device 36 are connected by an optical transmission line 34 and perform optical communication via the optical transmission line 34. As will be described later, the second node device 36 obtains the dispersion characteristic of the optical transmission line 34 using two optical signals transmitted from the first node device 10 having different wavelengths. The second node device 36 performs distortion compensation processing on the transmission signal or the reception signal when performing communication using the dispersion characteristic.

  The configuration of each unit of the first node device 10 will be described. The first node device 10 includes an optical signal transmission unit 12, an optical communication unit 32, and a signal coupling / separation unit 30.

  The signal coupling / separating unit 30 is connected to the optical transmission line 34. The signal coupling / separating unit 30 couples or separates paths through which the optical signal is transmitted. That is, the signal coupling / separating unit 30 extracts the optical signal having the wavelength λj from the optical signal received from the optical transmission line 34 and outputs the optical signal to the optical communication unit 32. The signal coupling / separating unit 30 transmits the optical signal having the wavelength λk output from the optical communication unit 32 to the optical transmission line 34. Further, the signal coupling / separating unit 30 transmits the first optical signal having the wavelength λ 1 and the second optical signal having the wavelength λ 2 output from the optical signal transmitting unit 12 to the optical transmission line 34.

  The wavelength λk may be equal to the wavelength λ1 or the wavelength λ2. In this case, the optical communication unit 32 is connected to an input terminal common to the optical signal transmission unit 12 in the signal coupling / separation unit 30. Similarly, wavelength λj may also be equal to wavelength λ1 or wavelength λ2.

  The optical communication unit 32 receives the optical signal having the wavelength λj transmitted from the second node device 36 to the optical transmission line 34 via the signal coupling / separating unit 30. In addition, the optical communication unit 32 transmits a signal having the wavelength λk to the second node device 36 via the signal coupling / separating unit 30 and the optical transmission line 34. As a result, the optical communication unit 32 performs optical communication with the second node device 36.

  The configuration of the optical signal transmitter 12 and the processing executed by the optical signal transmitter 12 will be described. The optical signal transmitting unit 12 transmits the first optical signal and the second optical signal having different wavelengths to the second node device 36 via the signal coupling / separating unit 30 and the optical transmission path 34. As a result, the optical signal transmission unit 12 causes the second node device 36 to obtain the dispersion characteristics of the optical transmission line 34 using the first optical signal and the second optical signal.

  The optical signal transmission unit 12 includes a transmission information generation unit 14, a transmission side clock generation unit 18, a timing information generation unit 20, a signal generation unit 16, and a transmission unit 22. The transmission information generation unit 14 outputs arbitrary transmission target information to be transmitted to the second node device 36 to the signal generation unit 16. The transmission target information may include an ID (IDentification) assigned to the first node device 10 as a transmission ID. Further, the transmission target information may include signal identification information that allows the second node device 36 to recognize that the signal is a signal for obtaining a dispersion characteristic.

  The sending clock generation unit 18 generates a sending clock signal and outputs it to the timing information generation unit 20. The timing information generation unit 20 generates transmission side time information based on the transmission side clock signal and outputs it to the signal generation unit 16. The sending side time information is the time specified by the pulse interval of the sending side clock signal such as hour, minute, second, tenth of a second, hundredth of a second, thousandth of a second, etc. It may be a numerical value representing In addition, the timing information generation unit 20 cyclically sends pulses of the sending clock signal in a cycle N such as 0, 1, 2,..., N−1, 0, 1, 2,. And the count value may be output as sending side time information.

  The signal generation unit 16 generates a packet including the transmission target information output from the transmission information generation unit 14 and the transmission side time information output from the timing information generation unit 20, and outputs the packet to the transmission unit 22. The sending side time information included in the packet indicates the time when the packet was generated. The time from when a packet is generated until it is transmitted as an optical signal is constant. Therefore, a time after a certain time until the packet is transmitted from the time indicated by the sending side time information is the time when the packet is transmitted.

  The transmission unit 22 includes a first carrier generator 26, a second carrier generator 28, and a transmission side conversion unit 24. The first carrier generator 26 generates light having a wavelength λ1 and outputs the light to the transmission side conversion unit 24. The second carrier generator 28 generates light having the wavelength λ <b> 2 and outputs the light to the transmission side conversion unit 24.

  The transmission side conversion unit 24 generates a first optical signal and a second optical signal having different wavelengths by the following processing, and transmits these two optical signals through the signal coupling / separation unit 30 at different timings. 34. That is, when the first packet is output from the signal generation unit 16, the transmission side conversion unit 24 modulates the light output from the first carrier generator 26 with the first packet to generate the first light of wavelength λ1. A signal is generated and output to the optical transmission line 34 via the signal coupling / separating unit 30. Next, when the second packet is output from the signal generation unit 16, the transmission-side conversion unit 24 modulates the light output from the second carrier generator 28 with the second packet to generate the second wavelength λ2. An optical signal is generated and output to the optical transmission line 34 via the signal coupling / separating unit 30. As a result, the first optical signal and the second optical signal having different wavelengths are output to the optical transmission line 34 at different timings. The transmission side converter 24 may alternately transmit the first optical signal and the second optical signal generated in this way.

  FIG. 2 shows the configuration of the second node device 36. The second node device 36 includes a signal coupling / separating unit 56, a dispersion measuring unit 40, and an optical communication unit 54. The signal coupling / separating unit 56 is connected to the optical transmission line 34. The signal coupling / separating unit 56 couples or separates paths through which the optical signal is transmitted. That is, the signal coupling / separating unit 56 extracts the optical signal having the wavelength λ1 and the optical signal having the wavelength λ2 from the optical signals received from the optical transmission line 34, and receives the optical signals from the receiving side converting unit 42 in the dispersion measuring unit 40. Output to. The signal coupling / separating unit 56 extracts an optical signal having a wavelength λk from the optical signal received from the optical transmission path 34 and outputs the optical signal to the optical communication unit 54. Further, the signal coupling / separating unit 56 transmits the optical signal having the wavelength λj output from the optical communication unit 54 to the optical transmission line 34. The wavelength λk may be equal to the wavelength λ1 or the wavelength λ2. In this case, the optical communication unit 54 is connected to an output terminal common to the dispersion measuring unit 40 in the signal coupling / separating unit 56. Similarly, wavelength λj may also be equal to wavelength λ1 or wavelength λ2.

  The optical communication unit 54 receives the optical signal having the wavelength λk transmitted from the first node device 10 to the optical transmission line 34 via the signal coupling / separating unit 56. In addition, the optical communication unit 54 transmits the signal having the wavelength λj to the first node device 10 via the signal coupling / separating unit 56 and the optical transmission line 34. As a result, the optical communication unit 54 performs optical communication with the first node device 10.

  The optical communication unit 54 acquires the dispersion measurement value ν of the optical transmission line 34 from the dispersion measurement unit 40. The dispersion measurement value ν is obtained by measuring a dispersion value defined as the spread of the propagation delay time with respect to the spread of the wavelength spectrum for the optical transmission line 34. The optical communication unit 54 performs distortion compensation processing based on the dispersion measurement value ν. In other words, the optical communication unit 54 performs processing for compensating the distortion component for the received optical signal according to the dispersion measurement value ν. Alternatively, the optical communication unit 54 transmits an optical signal including a distortion component in advance according to the dispersion measurement value ν so that the first node device 10 receives an optical signal with the distortion component compensated.

  The dispersion measurement value ν is obtained by the second node device 36 receiving the first optical signal and the second optical signal, and the dispersion measurement unit 40 measuring the difference in propagation time between these two optical signals.

  The first optical signal and the second optical signal are transmitted from the first node device 10 when the optical communication unit 54 transmits a request signal to the first node device 10, for example. The first optical signal and the second optical signal may be alternately transmitted from the first node device 10 at a predetermined cycle.

  The configuration of the dispersion measuring unit 40 and the processing executed by the dispersion measuring unit 40 will be described. The variance measurement unit 40 includes a reception side conversion unit 42, a reception side clock generation unit 46, an information extraction unit 44, a reception difference measurement unit 48, a transmission difference measurement unit 50, and a variance analysis unit 52. The reception side conversion unit 42 constitutes a reception unit that receives an optical signal from the optical transmission line 34 via the signal coupling / separation unit 56. The receiving side conversion unit 42 converts the first optical signal having the wavelength λ1 output from the signal coupling / separating unit 56 into the first packet P1, and corresponds to the timing at which the first optical signal is output from the signal coupling / separating unit 56. At the timing, the first packet P1 is output to the information extraction unit 44. The receiving side conversion unit 42 converts the second optical signal having the wavelength λ2 output from the signal coupling / separating unit 56 into the second packet P2, and at the timing when the second optical signal is output from the signal coupling / separating unit 56. At a corresponding timing, the second packet P2 is output to the information extraction unit 44.

  Thereby, the receiving side conversion unit 42 outputs the first packet P1 to the information extraction unit 44 at a timing according to the reception timing of the first optical signal, and the information extraction unit 44 responds to the reception timing of the first optical signal. The first packet P1 is acquired at the same timing. Similarly, the receiving side conversion part 42 outputs the 2nd packet P2 to the information extraction part 44 at the timing according to the reception timing of the 2nd optical signal, and the information extraction part 44 respond | corresponds to the reception timing of the 2nd optical signal. The second packet P2 is acquired at the same timing.

  The receiving clock generation unit 46 generates a receiving clock signal and outputs it to the information extraction unit 44. The information extraction unit 44 generates reception side time information based on the reception side clock signal. The receiving side time information is the time specified by the pulse interval of the receiving side clock signal, such as hour, minute, second, tenth of a second, hundredth of a second, thousandth of a second, and so on. It may be a numerical value representing Further, the information extraction unit 44 cyclically receives the pulses of the receiving side clock signal at a period M such as 0, 1, 2,..., M−1, 0, 1, 2,. It is possible to count and generate the count value as side time information.

  The information extraction unit 44 measures the first reception time R1 when the first packet P1 is acquired based on the reception side time information, and outputs the first reception time R1 to the reception difference measurement unit 48. In addition, the information extraction unit 44 measures the second reception time R2 when the second packet P2 is acquired based on the reception side time information, and outputs the second reception time R2 to the reception difference measurement unit 48.

  The reception difference measurement unit 48 obtains a reception difference R21 obtained by subtracting the first reception time R1 from the second reception time R2, and outputs the reception difference R21 to the variance analysis unit 52.

  Even if the time when the second packet P2 is output to the information extraction unit 44 is always later than the time when the first packet P1 is output to the information extraction unit 44 by design, the receiving time information May be a negative value, the reception difference R21 may be a negative value. In this case, a value obtained by adding M to the reception difference R21 is newly set as the reception difference R21.

  The information extraction unit 44 extracts the transmission side time information from the first packet P1, and obtains the first transmission time T1 at which the first optical signal was transmitted. Similarly, the transmission side time information is extracted from the second packet P2, and the second transmission time T2 at which the second optical signal is transmitted is obtained. The information extraction unit 44 outputs the first transmission time T1 and the second transmission time T2 to the transmission difference measurement unit 50.

  The transmission difference measurement unit 50 obtains a transmission difference T21 obtained by subtracting the first transmission time T1 from the second transmission time T2, and outputs the transmission difference T21 to the variance analysis unit 52.

  By design, even when the time when the second optical signal is transmitted is always later than the time when the first optical signal is transmitted, the sending side time information is cyclically counted in the period N. If it is a count value, the transmission difference T21 may be a negative value. In this case, a value obtained by adding N to the transmission difference T21 is newly set as the transmission difference T21.

  The dispersion analysis unit 52 obtains a propagation time difference D between the first optical signal and the second optical signal. Here, the propagation time difference D is a difference in propagation time from the first node device 10 to the second node device 36, which is obtained for the first optical signal and the second optical signal. The time from when the first optical signal is transmitted from the first node device 10 to when it is received by the second node device 36 is defined as a first propagation time t1, and after the second optical signal is transmitted from the first node device 10. When the time until reception by the second node device 36 is the second propagation time t2, the propagation time difference D is D = t2-t1 = R21-T21.

  The variance analysis unit 52 subtracts the transmission difference T21 from the reception difference R21 according to (Equation 1) to obtain the propagation time difference D.

  The dispersion analysis unit 52 obtains the dispersion measurement value ν based on the following (Equation 2) based on the wavelength λ1 of the first optical signal, the wavelength λ2 of the second optical signal, and the propagation time difference D. The dispersion analysis unit 52 outputs the dispersion measurement value ν to the optical communication unit 54.

  As described above, the optical communication unit 54 performs the compensation processing based on the dispersion measurement value ν when performing optical communication with the first node device 10.

  According to the communication system according to the present embodiment, the optical signal transmission unit 12 in the first node device 10 transmits the first optical signal and the second optical signal having different wavelengths at different timings. Therefore, the transmission unit 22 in the first node device 10 does not need to include the transmission side conversion unit 24 for each of the first optical signal and the second optical signal, and the scale of the first node device 10 is reduced.

  The configuration in which the optical signal transmission unit 12 is provided in the first node device 10 and the dispersion measurement unit 40 is provided in the second node device 36 has been described above. In addition to such a configuration, the optical signal transmission unit 12 may be provided in the second node device 36, and the dispersion measurement unit 40 may be provided in the first node device 10. Each node device may include both the optical signal transmission unit 12 and the dispersion measurement unit 40.

  A plurality of node devices including both the optical signal transmission unit 12 and the dispersion measurement unit 40 may be connected to the optical transmission line 34. In this case, each node device receives the first optical signal and the second optical signal transmitted from the other node devices. When the transmission ID is included in the packet generated by the transmission-side node device, the information extraction unit 44 in the second node device 36 on the reception side extracts the transmission ID from the packet and outputs it to the optical communication unit 54. The optical communication unit 54 stores the transmission ID and the dispersion measurement value ν in association with each other. As a result, when communicating with any one of a plurality of node devices connected to the optical transmission line 34, the optical communication unit 54 specifies the dispersion measurement value ν corresponding to the node device. Then, compensation processing is performed when optical communication with the node device is performed.

  In the above description, the embodiment in which the sending time information is included in each of the first optical signal and the second optical signal transmitted from the first node device 10 has been described. As described above, the transmission time information may be included in each optical signal, and at least one of the first optical signal and the second optical signal may include the transmission difference T21. The transmission difference T21 may be stored in advance in the first node device 10, or may be measured in the first node device 10 based on the sending clock signal.

  In this case, the transmission difference measurement unit 50 is configured in the information extraction unit 44 as in the node device 58 according to the first modification shown in FIG. At least one of the first packet P1 and the second packet P2 output from the receiving side conversion unit 42 includes a transmission difference T21. The transmission difference measurement unit 50 extracts the transmission difference T21 from the first packet P1 or the second packet P2, and outputs the transmission difference T21 to the variance analysis unit 52.

  FIG. 4 shows a node device 60 according to the second modification. This node device 60 includes a first propagation time measurement unit 62 and a second propagation time measurement unit 64 in place of the reception difference measurement unit 48 and the transmission difference measurement unit 50 shown in FIG. Here, the first propagation time measurement unit 62 subtracts the first transmission time T1 from the first reception time R1 output from the information extraction unit 44 to obtain the first propagation time t1, and outputs it to the variance analysis unit 52. . The second propagation time measurement unit 64 subtracts the second transmission time T2 from the second reception time R2 output from the information extraction unit 44 to obtain a second propagation time t2, and outputs the second propagation time t2.

  The variance analysis unit 52 subtracts the first propagation time t1 from the second propagation time t2 to obtain the propagation time difference D. That is, D = t2-t1.

  The dispersion analysis unit 52 obtains the dispersion measurement value ν based on the above (Equation 2) based on the wavelength λ1 of the first optical signal, the wavelength λ2 of the second optical signal for measurement, and the propagation time difference D. The dispersion analysis unit 52 outputs the dispersion measurement value ν to the optical communication unit 54. As described above, the optical communication unit 54 performs the compensation processing based on the dispersion measurement value ν when performing optical communication with the first node device 10.

  In the optical communication system shown in FIG. 1 and FIG. 2, the sending side clock signal and the receiving side clock signal are separately generated in the first node device 10 and the second node device 36. When there is a difference between the pulse interval of the sending clock signal and the pulse interval of the receiving clock signal, the time unit of the transmission difference T21 and the time unit of the reception difference R21 represent different time lengths. Therefore, if the transmission difference T21 is simply subtracted from the reception difference R21, an error occurs in the propagation time difference D, and it may be difficult to obtain an accurate propagation time difference D.

    Therefore, the second node device 36 may obtain a correction value C for the transmission difference T21 by a calibration process described below, and obtain the propagation time difference Dc according to (Equation 3).

  In the calibration process, two calibration optical signals having the same wavelength are transmitted from the first node device 10 at different timings, and the second node device 36 obtains a correction value C based on these calibration optical signals. It is.

  The two calibration optical signals are transmitted from the first node device 10 when the optical communication unit 54 transmits a calibration request signal to the first node device 10, for example. Also, the two calibration optical signals may be transmitted from the first node device 10 at a predetermined period in a time zone different from the time zone in which the first optical signal and the second optical signal are transmitted. .

  1 generates a first calibration optical signal and a second calibration optical signal having the same wavelength by the following processing, and signals these two calibration optical signals at different timings. The light is output to the optical transmission line 34 via the coupling / separation unit 30. That is, when the first packet is output from the signal generation unit 16, the transmission side conversion unit 24 modulates the light output from the first carrier generator 26 with the first packet to perform the first calibration of the wavelength λ1. The optical signal is generated and output to the optical transmission line 34 via the signal coupling / separating unit 30. Next, when the second packet is output from the signal generation unit 16, the transmission-side conversion unit 24 modulates the light output from the first carrier generator 26 with the second packet to generate the second wavelength λ1. A calibration optical signal is generated and output to the optical transmission line 34 via the signal coupling / separating unit 30. Accordingly, the first calibration optical signal and the second calibration optical signal having the same wavelength are output to the optical transmission line 34 at different timings. The transmission target information included in each calibration optical signal may include signal identification information that causes the second node device 36 to recognize that the signal is a signal for executing calibration processing.

  Similar to the first optical signal and the second optical signal described above, the first calibration optical signal and the second calibration optical signal are received by the second node device 36. The reception difference measurement unit 48 in FIG. 2 performs the reception difference R21 on the first calibration optical signal and the second calibration optical signal by the same processing as the processing performed on the first optical signal and the second optical signal. Is determined as a reception calibration time CR21. Further, the transmission difference measurement unit 50 calculates the transmission difference T21 for the first calibration optical signal and the second calibration optical signal by the same processing as the processing performed on the first optical signal and the second optical signal. This is determined as the transmission calibration time CT21. The reception difference measurement unit 48 and the transmission difference measurement unit 50 output the reception calibration time CR21 and the transmission calibration time CT21 to the variance analysis unit 52, respectively.

  The variance analysis unit 52 includes a correction value determination unit, and obtains a value obtained by dividing the reception calibration time CR21 by the transmission calibration time CT21 as the correction value C, as shown in (Equation 4).

  The dispersion analysis unit 52 uses the reception difference R21 and transmission difference T21 obtained for the first optical signal and the second optical signal and the correction value C to obtain the propagation time difference Dc based on (Equation 3). Then, the dispersion measurement value ν is obtained based on an expression in which the propagation time difference D in (Expression 2) is replaced with the propagation time difference Dc.

  The correction value C is a value indicating how many times the time unit of the receiver time information represents a time longer than the time unit of the sender time information. By multiplying the transmission difference T21 by the correction value C, the transmission difference T21 is converted from the time unit of the sending side time information to the time unit of the receiving side time information.

  If there is no difference between the pulse interval of the sending clock signal and the pulse interval of the receiving clock signal, the time unit of the transmission difference T21 and the time unit of the reception difference R21 are the same, and the correction value C is 1. It becomes.

  Instead of the propagation time difference Dc defined by (Equation 3), the propagation time difference Dct obtained by (Equation 5) based on the time unit of the transmission difference T21 may be used.

  According to the process of obtaining the propagation time difference using the correction value C, the propagation time difference is obtained after the time unit of the transmission difference T21 and the time unit of the reception difference R21 are aligned. Thereby, the propagation time difference is accurately obtained, and the measurement accuracy of the dispersion measurement value is improved.

DESCRIPTION OF SYMBOLS 10 1st node apparatus, 12 Optical signal transmission part, 14 Transmission information generation part, 16 Signal generation part, 18 Transmission side clock generation part, 20 Timing information generation part, 22 Transmission part, 24 Transmission side conversion part, 26 1st carrier Generator, 28 second carrier generator, 30, 56 signal coupling / separating unit, 32, 54 optical communication unit, 34 optical transmission line, 36 second node device, 40 dispersion measuring unit, 42 receiving side converting unit, 44 information extraction 46, receiving clock generation unit, 48 reception difference measurement unit, 50 transmission difference measurement unit, 52 dispersion analysis unit, 58, 60 node device, 62 first propagation time measurement unit, 64 second propagation time measurement unit.

Claims (5)

In a dispersion measuring device used in an optical communication system,
A receiver for receiving an optical signal from the optical transmission path;
A reception difference measurement unit for obtaining reception difference information indicating a difference between a time when the first optical signal is received and a time when the second optical signal having a wavelength different from that of the first optical signal is received;
A transmission difference measuring unit that obtains transmission difference information indicating a time difference between transmission of the first optical signal and the second optical signal based on information included in at least one of the first optical signal and the second optical signal; ,
A dispersion analysis unit for obtaining dispersion characteristics of the optical transmission line based on a wavelength difference between the first optical signal and the second optical signal, the reception difference information, and the transmission difference information;
A dispersion measuring apparatus comprising: The dispersion measuring apparatus according to claim 1,
The reception difference measurement unit obtains the reception difference information based on the timing indicated by the clock signal,
The receiving unit receives two calibration optical signals having the same wavelength from the optical transmission line,
The reception difference measuring unit obtains reception calibration information indicating a time difference when the two calibration optical signals are received based on a timing indicated by the clock signal,
The transmission difference measurement unit obtains transmission calibration information indicating a time difference at which the two calibration optical signals are transmitted based on information included in at least one of the two calibration optical signals,
The dispersion measuring device includes:
Based on the reception calibration information and the transmission calibration information, a correction value for obtaining a correction value for correcting the relationship between the time unit of the time difference between the two calibration optical signals and the time unit of the clock signal With a decision unit,
The dispersion analysis unit is characterized in that the dispersion characteristic is obtained using the correction value. In a clock correction device used in an optical communication system,
A receiving unit that receives two calibration optical signals having the same wavelength from the optical transmission line;
A reception difference measuring unit for obtaining reception calibration information indicating a time difference between the two calibration optical signals received based on the timing indicated by the clock signal;
A transmission difference measuring unit for obtaining transmission calibration information indicating a time difference between the two calibration optical signals transmitted based on information included in at least one of the two calibration optical signals;
Based on the reception calibration information and the transmission calibration information, a correction value determining unit for obtaining a correction value for correcting the relationship between the time unit of the time difference and the time unit of the clock signal;
A clock correction apparatus comprising: In a dispersion measuring device used in an optical communication system,
A receiver for receiving an optical signal from the optical transmission path;
A reception difference measuring unit for obtaining a time when the first optical signal is received and a time when a second optical signal having a wavelength different from that of the first optical signal is received;
An extraction unit for extracting information indicating the time when the first optical signal was transmitted and information indicating the time when the second optical signal was transmitted from the first optical signal and the second optical signal;
A first propagation time measurement unit that obtains a first propagation time from when the first optical signal is transmitted until it is received by the receiving unit;
A second propagation time measurement unit for obtaining a second propagation time from when the second optical signal is transmitted until it is received by the receiving unit;
A dispersion analysis unit for obtaining dispersion characteristics of the optical transmission line based on a wavelength difference between the first optical signal and the second optical signal, the first propagation time, and the second propagation time;
A dispersion measuring apparatus comprising: In a transmission device used in an optical communication system,
A signal generator for generating two signals;
A transmitter that transmits two optical signals based on the two signals to the optical transmission line at different timings, and
The signal generator is
Information indicating a time difference for transmitting the two optical signals is included in at least one of the two optical signals.

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