JP2007093359A - Wavelength dispersion measuring device, optical communication system, and wavelength dispersion measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength dispersion measuring device capable of accuracy improvement and speed heightening of dispersion measurement. <P>SOLUTION: This wavelength dispersion measuring device is equipped with a wavelength dispersion measuring means 10 wherein a wavelength dispersion slope is provided on the transmission end side of a known optical fiber transmission path 17, and a wavelength conversion means 11 provided on the reception end side. The wavelength conversion means 11 receives the first and second light modulation signals for wavelength dispersion measurement, generates the third and fourth light modulation signals having each wavelength different from those of both modulation signals and not sandwiching a zero dispersion wavelength of the optical fiber transmission path 17, and transmits them toward the wavelength dispersion measuring means 10. The wavelength dispersion measuring means 10 generates the first and second light modulation signals and transmits them toward the wavelength conversion means 11, receives the third and fourth light modulation signals transmitted from the wavelength conversion means 11, detects the mean value of wavelength dispersion of the optical fiber transmission path 17 from each wavelength of both light modulation signals and correlation between both light modulation signals, and measures the wavelength dispersion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dispersion value measuring apparatus and method for measuring chromatic dispersion in an optical fiber transmission line. The present invention also relates to an optical communication system capable of measuring chromatic dispersion characteristics of an optical fiber transmission line.

  As a method for measuring the chromatic dispersion of an existing optical fiber transmission line in an optical communication system or an optical communication system network, conventionally, a signal for measuring chromatic dispersion is transmitted from the transmission end side of the optical fiber transmission line, and is transmitted to the reception end side. A method for measuring chromatic dispersion has been proposed. In this method, in order to obtain chromatic dispersion information on the transmitting end side, the basic information for obtaining the chromatic dispersion or chromatic dispersion of the optical fiber transmission line measured on the receiving end side is sent to the transmitting end on a separate line. This is realized by replying (see, for example, Patent Documents 1 to 3). As another method, a chromatic dispersion measuring means is provided on the transmission end side, a chromatic dispersion measurement signal is sent from the transmission end side, and this measurement signal is directly sent to the other end of the optical fiber transmission line. The method of measuring the chromatic dispersion with the chromatic dispersion measuring means on the transmission end side (for example, refer to Patent Document 4 or 5), the wavelength conversion at the other end of the optical fiber transmission line, and the return end side A method (for example, see Patent Document 6) of measuring chromatic dispersion with the above chromatic dispersion measuring means has also been proposed.

Japanese Patent Laid-Open No. 11-046881 JP 2000-019068 A JP 2002-357509 A JP 08-334436 A JP 2000-329653 A JP 2000-329652 A

  However, when the transmission rate of the optical signal handled in the optical communication system is high and the transmission distance is long, the total chromatic dispersion amount of the optical fiber transmission line is large, and the allowable residual dispersion is small. It is necessary to improve the accuracy of the dispersion compensation amount in each optical communication node. In addition, the introduction of a tunable dispersion compensation device is indispensable due to an increase in transmission rate, and a high-speed dispersion measurement technique for adaptive equalization accompanying transmission path parameter fluctuation is required. In addition, in order to reduce the influence of the nonlinear optical effect of the optical fiber transmission line as much as possible, highly accurate pre-dispersion compensation or dispersion pre-equalization processing on the transmission side is important. Along with these trends, as a chromatic dispersion measurement technique on the transmission end side, a method for improving all of the measurement dynamic range, measurement accuracy, and measurement speed is desired. However, there is no method that satisfies all the current conditions.

  The present invention has been made in order to solve the above-mentioned problem, and is provided with means for measuring chromatic dispersion at both ends of an optical fiber transmission line, and is composed of two different wavelengths transmitted from the transmission side. A wavelength dispersion measuring apparatus, an optical communication system, and an optical communication system capable of improving the accuracy and speed of dispersion measurement by converting the wavelength of the optical modulation signal for dispersion measurement at the receiving end and turning it back, and improving the dynamic range in addition A chromatic dispersion measuring method is provided.

  The present invention has been made to solve the above-described problems, and a chromatic dispersion measuring apparatus according to the present invention is a chromatic dispersion measurement provided on the transmitting end side of an optical fiber transmission line having a known chromatic dispersion slope. And a chromatic dispersion measuring device for measuring chromatic dispersion of the optical fiber transmission line, the wavelength conversion means comprising: a wavelength converting unit provided on a receiving end side of the optical fiber transmission line; Both modulated signals are received by receiving the first and second optical modulation signals for chromatic dispersion measurement transmitted from the dispersion measuring means, and performing wavelength conversion based on the wavelengths of the first and second optical modulation signals. The third and fourth optical modulation signals having different wavelengths that are different from each other and sandwiching the zero dispersion wavelength of the optical fiber transmission line in between are generated and transmitted to the chromatic dispersion measuring means. The chromatic dispersion measurement The means generates the first and second optical modulation signals for measuring the chromatic dispersion having different wavelengths that are sandwiched between the zero dispersion wavelengths of the optical fiber transmission line, and directs them to the wavelength converting means. And transmitting the third and fourth optical modulation signals transmitted from the wavelength conversion means, and from the wavelength of both optical modulation signals and the correlation between both optical modulation signals, An average value of chromatic dispersion is detected, and chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope.

  The optical communication system according to the present invention includes a transmitting end node provided with chromatic dispersion measuring means, a receiving end node provided with wavelength converting means, and a wavelength connecting the transmitting end node and the receiving end node. An optical communication system including one or a pair of optical fiber transmission lines with known dispersion slopes, wherein the wavelength conversion means includes first and second wavelength dispersion measuring units transmitted from the wavelength dispersion measuring means. Are received and modulated based on the wavelengths of the first and second optical modulation signals, so that the zero dispersion wavelength of the optical fiber transmission line is different between the two modulation signals. Third and fourth optical modulation signals having different wavelengths that are not sandwiched are generated and transmitted to the chromatic dispersion measuring means, and the chromatic dispersion measuring means transmits the zero dispersion of the optical fiber transmission line. Wavelength between The first and second optical modulation signals for measuring chromatic dispersion having different wavelengths that are not sandwiched are generated and transmitted to the wavelength converting means, and the first optical signal transmitted from the wavelength converting means is transmitted. 3. Receiving the fourth optical modulation signal, detecting the average value of the chromatic dispersion of the optical fiber transmission line from the wavelength of the two optical modulation signals and the correlation between the two optical modulation signals, The chromatic dispersion of the optical fiber transmission line is measured from the dispersion slope.

  The chromatic dispersion measuring method according to the present invention is a chromatic dispersion measuring method for measuring chromatic dispersion of an optical fiber transmission line having a transmitting end and a receiving end and a known chromatic dispersion slope, and at the receiving end side, Both modulated signals are received by receiving the first and second optical modulation signals for chromatic dispersion measurement transmitted from the transmitting end side and converting the wavelengths based on the wavelengths of the first and second optical modulation signals. And generating third and fourth optical modulation signals having different wavelengths that are not sandwiched between the zero dispersion wavelengths of the optical fiber transmission line and transmitting them to the transmission end, On the transmitting end side, the first and second optical modulation signals for measuring chromatic dispersion having different wavelengths sandwiching the zero dispersion wavelength of the optical fiber transmission line are generated, and this is generated on the receiving end side To the transmission end side Receiving the transmitted third and fourth optical modulation signals, detecting the average value of the chromatic dispersion of the optical fiber transmission line from the correlation between the wavelengths of the optical modulation signals and the optical modulation signals; The chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope.

  According to this invention, at both ends of an optical fiber transmission line with a known chromatic dispersion slope, for example, a chromatic dispersion measuring means is provided on the transmitting end side, a wavelength converting means is provided on the receiving end side, and transmitted from the chromatic dispersion measuring means. The wavelength modulation measuring optical modulation signal composed of two different wavelengths is converted by the wavelength converting means and turned back, and the wavelength dispersion measuring means returns the correlation between the wavelengths of the two optical modulation signals and the two optical modulation signals. The average value of the chromatic dispersion of the optical fiber transmission line is detected from this, and the chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope, thereby improving the accuracy and speed of dispersion measurement. In addition to the dynamic range.

  Hereinafter, a chromatic dispersion measuring apparatus, an optical communication system, and a chromatic dispersion measuring method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a configuration diagram of an optical communication system according to this embodiment of the present invention. In FIG. 1, the optical communication system includes an optical fiber transmission line 17 and a transmission end node 100 and a reception end node 110 provided at both ends of the transmission line 17. The transmitting end node 100 and the receiving end node 110 are connected to the optical fiber transmission line 17 via optical multiplexing / demultiplexing means 14a and 14b, respectively. The transmitting end node 100 is provided with chromatic dispersion measuring means 10, and the receiving end node 110 is provided with wavelength converting means 11. Here, the chromatic dispersion measuring means 10 and the wavelength converting means 11 constitute a chromatic dispersion measuring device that measures the chromatic dispersion of the optical fiber transmission line 17.

  The chromatic dispersion measuring means 10 on the transmission end side includes first and second optical transmission units 12a and 12b that transmit optical signals, transmission control means 15 that controls transmission timing, and third optical signals that are received. , Fourth optical receivers 13c and 13d, and chromatic dispersion detecting means 16 for detecting the chromatic dispersion of the optical fiber transmission line 17 from the received optical signal.

  On the other hand, the wavelength conversion means 11 on the receiving end side includes first and second optical receivers 13a and 13b that receive an optical signal, and third and fourth optical transmitters that convert the wavelength of the received optical signal and return it. 12c, 12d.

  First and second optical modulation signals pulse-modulated with first and second wavelengths λ1 and λ2, respectively, are output from the first and second optical transmission units 12a and 12b of the transmission end node 100, respectively. The pulse transmission timing is controlled by the transmission control means 15. The output optical modulation signals of wavelengths λ1 and λ2 are multiplexed by the optical multiplexing / demultiplexing means 14a on the transmission end node 100 side, and sent to the optical fiber transmission line 17.

  The first and second optical modulation signals having wavelengths λ1 and λ2 that have passed through the optical fiber transmission line 17 are demultiplexed for each wavelength by the optical multiplexing / demultiplexing means 14b on the receiving end node 110 side, and the first and second optical signals are demultiplexed. The optical signal of the modulation signal 2 is input to the first and second optical receivers 13a and 13b, respectively. In the wavelength conversion unit 11, the first optical receiver 13a photoelectrically converts the optical signal having the wavelength λ1, and then drives the third optical transmitter 12c with the electric signal. Similarly, the second optical receiver 13b photoelectrically converts the optical signal having the wavelength λ2, and then drives the fourth optical transmitter 12d with the electric signal. The driven third optical transmitter 12c and fourth optical transmitter 12d each output an optical modulation signal toward the transmitting end node 100 side. At this time, the optical modulation signals output from the third optical transmission unit 12c and the fourth optical transmission unit 12d correspond to the optical modulation signals received by the corresponding first and second optical reception units 13a and 13b, respectively. The third and fourth light modulation signals having wavelengths λ1 + Δλ and λ2 + Δλ, which are third and fourth wavelengths shifted by Δλ, are output.

  The optical modulation signals of wavelengths λ1 + Δλ and λ2 + Δλ output from the third and fourth optical transmitters 12c and 12d, respectively, are multiplexed again by the optical multiplexing / demultiplexing means 14b on the receiving end node 110 side and transmitted to the optical fiber transmission line 17. Is done. In this way, it is possible to suppress unnecessary crosstalk by using different wavelengths for the forward path and the return path of the optical fiber transmission path 17. The wavelength-modulated optical modulation signal propagated through the optical fiber transmission line 17 is wavelength-demultiplexed by the optical multiplexing / demultiplexing means 14a on the transmitting end node 100 side, and the optical signal having the wavelength λ1 + Δλ is the third optical receiver 13b. And an optical signal having a wavelength of λ2 + Δλ is input to each of the fourth optical receivers 13d and subjected to photoelectric conversion. The chromatic dispersion measuring means 10 calculates the chromatic dispersion of the optical fiber transmission line 17 from the result of time correlation measurement between two signals having different wavelengths subjected to photoelectric conversion.

  FIG. 2 is a block diagram showing details of the wavelength converting means 11 of FIG. The wavelength converter 11 converts the optical signal of λ1 into a wavelength of λ1 + Δλ, and converts the optical signal of λ2 into a wavelength of λ2 + Δλ. The wavelength converting means 11 has the first and second optical receivers 13a and 13b and the third and fourth optical transmitters 12c and 12d as described above.

  The first optical receiver 13a includes photoelectric conversion means (first photoelectric conversion means) 21a and data identification / reproduction means (first data identification / reproduction means) 22a. The third optical transmitter 12c includes an amplifying unit (third amplifying unit) 23a, a light modulating unit (third light modulating unit) 24a, and a light source (third light source) 25a.

  Further, the second optical receiver 13b includes photoelectric conversion means (second photoelectric conversion means) 21b and data identification / reproduction means (second data identification / reproduction means) 22b. The fourth optical transmitter 12d includes an amplifying unit (fourth amplifying unit) 23b, a light modulating unit (fourth light modulating unit) 24b, and a light source (fourth light source) 25b.

  The optical modulation signal having the wavelength λ1 received by the wavelength conversion unit 11 is first converted into an electrical signal by the photoelectric conversion unit 21a, and then subjected to waveform shaping by the data identification / reproduction unit 22a. Correspondingly, a light source 25a that emits light with a wavelength of λ1 + Δλ by the light modulation means 24a based on the electrical signal that is reproduced by the data identification / reproduction means 22a and amplified by the amplification means 23a. It is generated by modulating the light from.

  Similarly, the received optical modulation signal having the wavelength λ2 is first converted into an electrical signal by the photoelectric conversion means 21b, and then subjected to waveform shaping by the data identification / reproduction means 22b. Then, the light modulation signal having the wavelength λ2 + Δλ is generated by the light modulation unit 24b based on the electric signal reproduced by the data identification reproduction unit 22b and amplified by the amplification unit 23b. Generated by modulation.

  If the electrical pulse train output from the photoelectric conversion means 21a and 21b has little distortion and the amplitude is sufficiently large, the data identification / reproduction means 22a and 22b and the amplification means 23a and 23b may be omitted. Here, the delay in the path from the photoelectric conversion means 21a, 21b to the light modulation means 24a, 24b can be a constant delay amount regardless of the wavelength of the optical signal to be handled. The wavelength dependence of the delay due to the conversion can be ignored.

  FIG. 3 is a block diagram showing details of the chromatic dispersion measuring means 10 of FIG. As described above, the chromatic dispersion measuring unit 10 includes the first and second optical transmission units 12a and 12b, the third and fourth optical reception units 13c, the transmission control unit 15, and the chromatic dispersion detection unit 16. Have. The first optical transmitter 12a includes an amplifying unit (first amplifying unit) 33a, a light modulating unit (first light modulating unit) 34a, and a light source (first light source) 35a. The second optical transmitter 12b includes an amplifying unit (second amplifying unit) 33b, a light modulating unit (second light modulating unit) 34b, and a light source (second light source) 35b.

  The third optical receiver 13c includes a photoelectric conversion means (third photoelectric conversion means) 31a and a data identification / reproduction means (third data identification / reproduction means) 32a. The fourth optical receiver 13d includes photoelectric conversion means (fourth photoelectric conversion means) 31b and data identification / reproduction means (fourth data identification / reproduction means) 32b. The transmission control unit 15 includes a data generation unit 36 and a timing control unit 37. The chromatic dispersion detection unit 16 includes a delay difference comparison unit 38 and a chromatic dispersion calculation unit 39.

  The transmission timing of the optical modulation signals of wavelengths λ1 and λ2 on the transmitting end node 100 side is different from the driving method of the optical modulating means 24a and 24b on the receiving end node 110 side, and the optical modulation is performed based on the pulse train from the data generating means 36. The means 34a and 34b are driven at substantially the same timing. At this time, the start timing of the transmission pulse train from the data generation means 36 is controlled by the timing control means 37.

  On the other hand, in the receiving operation, after the photoelectric conversion means 31a and 31b photoelectrically convert the two wavelengths λ1 + Δλ and λ2 + Δλ, the data identification / reproduction means 32a and 32b perform data reproduction as necessary. The delay difference between these signals is extracted by the delay difference comparison means 38.

  In the present embodiment, the extraction of the inter-signal delay difference performed by the delay difference comparison means 38 is performed by extracting the relative delay difference between the two wavelengths as described above. However, the delay difference may be extracted by measuring how much the two wavelengths are delayed with respect to the trigger signal using the trigger signal obtained from the timing control means 37 as a reference for delay measurement.

  The chromatic dispersion of the optical fiber transmission line 17 is detected by the chromatic dispersion calculating means 39 according to the following procedure based on the inter-signal delay difference extracted by the delay difference comparing means 38. FIG. 4 is a graph for explaining the chromatic dispersion calculation method performed by the chromatic dispersion calculating means 39, where the upper graph shows the wavelength dependence of the group delay, and the lower graph shows the wavelength dependence of the chromatic dispersion.

  In a normal transmission wavelength band, the group delay can be approximated as a quadratic function, and the chromatic dispersion can be approximated as a linear function. The wavelength differential of the group delay is chromatic dispersion, and the wavelength differential of chromatic dispersion is the chromatic dispersion slope. Here, let ΔDa be the delay difference resulting from propagation of the optical signals of wavelengths λ1 and λ2 through the optical fiber transmission line 17, and ΔDb be the delay difference resulting from propagation of the optical signal of λ1 + Δλ and λ2 + Δλ through the optical fiber transmission line 17. In the configuration of the present embodiment, the delay difference ΔT detected by the chromatic dispersion measuring means 10 is

ΔDa = a (λ2 ² −λ1 ² ) + b (λ2−λ1)
ΔDb = a [λ2 ² (1 + Δλ / λ2) −λ1 ² (1 + Δλ / λ1)] + b (λ2-λ1)
ΔT = ΔDa + ΔDb + Δτ

  It is expressed. Here, the coefficients a and b are coefficients determined from the quadratic function characteristics of the group delay, and Δτ represents a time difference from when a signal having a wavelength of each wavelength is received to when it is transmitted in the wavelength conversion unit 11. ing.

Here, if Δλ / λ2 << 1, Δλ / λ1 << 1, Δτ≈0,
ΔDa≈ΔDb, ΔT = 2ΔDa
It becomes. As a result, chromatic dispersion is
Average dispersion value = ΔT / (λ2−λ1)
Can be obtained as

Here, it is clear that the average dispersion value obtained above can be regarded as a dispersion value at the center wavelengths (λc) of approximately λ1 and λ2, and there is no problem. From this result, the dispersion value of the specific wavelength λ used in the optical communication system is
Dispersion value (λ) = (λ−λc) × (dispersion slope) + average dispersion value.

  Although not mentioned above, in the present embodiment, since the average dispersion value is detected by the relative delay difference between the two wavelengths, it is applied when the zero dispersion wavelength is included between the two wavelengths to be used. Note that you can't. If you want to find the dispersion of individual wavelengths more accurately without using the typical value as the uniform dispersion slope value, prepare multiple wavelengths to use, or use a tunable light source as the light source to be used. Can respond.

  Further, in this embodiment, a method of reciprocating a two-wavelength optical modulation signal in one optical fiber transmission line 17 is used. However, an optical fiber transmission line 17 having substantially equivalent parameters is used as a return path, and The same effect can be obtained even if the method of the present embodiment is applied to a pair of optical fiber transmission lines that form a pair on the return path.

  In the present embodiment, optical coupling means (optical multiplexing / demultiplexing means 14a and 14b) are used in coupling the return optical modulation signal output to the optical fiber transmission path 17, but a pair of optical fiber transmission paths 17 is used. On the other hand, for example, an optical switch may be provided to switch a reply transmission path, or a single optical fiber transmission path 17 may be switched between transmission and reception by an optical switch.

  Furthermore, it is possible to adjust the measurement resolution and dynamic range by changing the repetition period and pulse width of the pulse train used for delay difference measurement, and an adjustment means for adjusting these measurement resolution and dynamic range is further provided. Also good.

  In addition, all the circuits for pattern generation, pattern comparison, and chromatic dispersion detection can be easily configured by digital circuits by using a pseudo-random sequence as a transmission pulse train and calculating delay differences digitally by pattern comparison. It becomes possible. Even in this case, the dynamic range and resolution of chromatic dispersion to be measured can be adjusted by changing the sequence length and pulse width of the pattern to be used.

  Furthermore, as a pattern comparison method of the pseudo random pattern, an XOR operation may be performed between two wavelengths for each bit in the pattern, and the addition result of the XOR output within the specific pattern length may be used as the correlation result. By using such a method, the delay difference between the two wavelengths can be obtained more easily, which is particularly effective when the chromatic dispersion sign of the transmission path is known in advance.

  In the present embodiment, the location where dispersion measurement is performed is arranged at the transmission end. However, it is also possible to carry out chromatic dispersion measurement only in the forward path from the two-wavelength electrical signal before performing wavelength conversion. . As a result, accuracy can be improved when performing chromatic dispersion measurement using a pair of optical fiber transmission lines.

  By using this measurement method, unnecessary crosstalk can be prevented by folding optical signals of different wavelengths, and chromatic dispersion can be obtained from the round trip time of one optical fiber transmission line. Compared with the case where the optical wavelength dispersion is obtained from one way of the return path, it is possible to ensure about twice the accuracy.

  In addition, by making the transmission data series used for measurement variable, it is possible to perform chromatic dispersion measurement that satisfies both the dynamic range and accuracy. Furthermore, since the dispersion value is measured on the transmission end side, the dispersion value of the optical fiber transmission line can be immediately used for setting dispersion compensation on the transmission side.

  The present invention is useful when measuring the chromatic dispersion of an already installed optical fiber transmission line, and is particularly suitable for measuring the chromatic dispersion of an optical fiber transmission line in a long-distance large-capacity optical transmission system. is there.

It is a block diagram of the optical communication system of one embodiment of this invention. It is a block diagram which shows the detail of the wavelength conversion means of FIG. It is a block diagram which shows the detail of the chromatic dispersion measuring means of FIG. It is a graph for demonstrating the chromatic dispersion calculation method which a chromatic dispersion calculating means performs, the upper graph shows the wavelength dependence of group delay, and the lower graph shows the wavelength dependence of chromatic dispersion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Chromatic dispersion measuring means 11 Wavelength converting means 12a 1st optical transmission part 12b 2nd optical transmission part 12c 3rd optical transmission part 12d 4th optical transmission part 13a 1st optical reception part 13b 2nd optical reception Unit 13c third optical receiver unit 13d fourth optical receiver unit 14a, 14b optical multiplexing / demultiplexing unit 15 transmission control unit 16 chromatic dispersion detection unit 17 optical fiber transmission line 21a first photoelectric conversion unit 21b second photoelectric unit Conversion means 31a Third photoelectric conversion means 31b Fourth photoelectric conversion means 22a First data identification / reproduction means 22b Second data identification / reproduction means 32a Third data identification / reproduction means 32b Fourth data identification / reproduction means 23a Third amplification means 23b Fourth amplification means 33a First amplification means 33b Second amplification means 24a Third light modulation means 24b Fourth light modulation means 3 a first light modulation means 34b second light modulation means 25a third light source 25b fourth light source 35a first light source 35b second light source 36 data generation means 37 timing control means 38 delay difference comparison means 39 wavelength dispersion Arithmetic means λ1 Wavelength of first optical modulation signal λ2 Wavelength of second optical modulation signal λ1 + Δλ Wavelength of third optical modulation signal λ2 + Δλ Wavelength of fourth optical modulation signal

Claims (22)

A chromatic dispersion measuring means provided on the transmitting end side of the optical fiber transmission line having a known chromatic dispersion slope; and a wavelength converting means provided on the receiving end side of the optical fiber transmission line, A chromatic dispersion measuring device for measuring chromatic dispersion,
The wavelength converting means receives the first and second optical modulation signals for wavelength dispersion measurement transmitted from the wavelength dispersion measuring means, and wavelength based on the wavelengths of the first and second optical modulation signals. By converting, the third and fourth optical modulation signals having different wavelengths that are different from both modulation signals and sandwiching the zero-dispersion wavelength of the optical fiber transmission line are generated. Send it to the dispersion measurement means,
The chromatic dispersion measuring means generates the first and second optical modulation signals for measuring chromatic dispersion having different wavelengths that sandwich the zero dispersion wavelength of the optical fiber transmission line, and outputs the first and second optical modulation signals. Transmitting to the conversion means and receiving the third and fourth optical modulation signals transmitted from the wavelength conversion means, and determining the light from the wavelength of both optical modulation signals and the correlation between the optical modulation signals. A chromatic dispersion measuring apparatus, wherein an average value of chromatic dispersion of a fiber transmission line is detected, and chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope. The wavelength conversion unit generates the third and fourth optical modulation signals that are shifted in wavelength by a fixed wavelength from the first and second optical modulation signals, based on the first and second optical modulation signals. The chromatic dispersion measuring device according to claim 1, wherein: The wavelength conversion means operates on the basis of the first and second photoelectric conversion means for converting the first and second optical modulation signals into electric signals, respectively, and operates based on the electric signals. The wavelength according to claim 1, further comprising: third and fourth light modulation means for generating the third and fourth light modulation signals that are wavelength-converted with respect to the light modulation signal. Dispersion measuring device. The chromatic dispersion measuring unit and the wavelength converting unit transmit the first and second optical modulation signals and the third and fourth optical modulation signals, respectively. 4 optical transmission means,
The first and second optical transmission means and the third and fourth optical transmission means can vary the wavelengths of the first and second optical modulation signals and the third and fourth optical modulation signals. The chromatic dispersion measuring device according to any one of claims 1 to 3. The first to fourth optical modulation signals are pulse trains, and the chromatic dispersion measuring means calculates an average value of chromatic dispersion of the optical fiber transmission line from a delay difference between the pulse trains of the third and fourth optical modulation signals. The chromatic dispersion measuring device according to claim 1, wherein the chromatic dispersion measuring device is obtained. The chromatic dispersion measuring means changes either the repetition period or the pulse width of the pulse train according to the magnitude of chromatic dispersion of the optical fiber transmission line and the necessary resolution of chromatic dispersion. 5. The chromatic dispersion measuring device according to 5. The chromatic dispersion measuring apparatus according to claim 5 or 6, wherein the pulse train forms a pseudo-random sequence, and the chromatic dispersion measuring means uses pulse pattern comparison when comparing correlations between modulated signals. The chromatic dispersion measuring means changes either the pulse width of the pseudo-random sequence or the sequence length of the pattern in accordance with the magnitude of chromatic dispersion of the optical fiber transmission line and the necessary resolution of chromatic dispersion. The chromatic dispersion measuring device according to claim 7. The chromatic dispersion measuring apparatus according to any one of claims 1 to 8, further comprising an adjusting unit that adjusts a dispersion compensation amount on a transmission side based on the detected chromatic dispersion. A transmission end node provided with chromatic dispersion measurement means, a reception end node provided with wavelength conversion means, and a single or a pair of light having a known chromatic dispersion slope connecting the transmission end node and the reception end node An optical communication system comprising a fiber transmission line,
The wavelength converting means receives the first and second optical modulation signals for wavelength dispersion measurement transmitted from the wavelength dispersion measuring means, and wavelength based on the wavelengths of the first and second optical modulation signals. By converting, the third and fourth optical modulation signals having different wavelengths that are different from both modulation signals and sandwiching the zero-dispersion wavelength of the optical fiber transmission line are generated. Send it to the dispersion measurement means,
The chromatic dispersion measuring means generates the first and second optical modulation signals for measuring chromatic dispersion having different wavelengths that sandwich the zero dispersion wavelength of the optical fiber transmission line, and outputs the first and second optical modulation signals. Transmitting to the conversion means and receiving the third and fourth optical modulation signals transmitted from the wavelength conversion means, and determining the light from the wavelength of both optical modulation signals and the correlation between the optical modulation signals. An optical communication system, wherein an average value of chromatic dispersion of a fiber transmission line is detected, and chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope. The wavelength conversion unit generates the third and fourth optical modulation signals that are shifted in wavelength by a fixed wavelength from the first and second optical modulation signals, based on the first and second optical modulation signals. The optical communication system according to claim 10. The wavelength conversion means operates on the basis of the first and second photoelectric conversion means for converting the first and second optical modulation signals into electric signals, respectively, and operates based on the electric signals. 13. The light according to claim 10, further comprising: third and fourth light modulation means for generating the third and fourth light modulation signals that have been wavelength-converted with respect to the light modulation signal. Communications system.   The optical communication system according to any one of claims 10 to 12, wherein a plurality of optical communication nodes each having the chromatic dispersion measuring unit and the wavelength converting unit are connected. A chromatic dispersion measuring method for measuring chromatic dispersion of an optical fiber transmission line having a transmitting end and a receiving end and having a known chromatic dispersion slope,
On the receiving end side, the first and second optical modulation signals for chromatic dispersion measurement transmitted from the transmitting end side are received, and wavelength conversion is performed based on the wavelengths of the first and second optical modulation signals. To generate third and fourth optical modulation signals of different wavelengths that are different from both modulation signals and that do not sandwich the zero-dispersion wavelength of the optical fiber transmission line, and direct the signals to the transmitting end. And transmitting the first and second optical modulation signals for measuring chromatic dispersion having different wavelengths that are sandwiched between the zero dispersion wavelengths of the optical fiber transmission line. Is transmitted toward the receiving end side, and the third and fourth optical modulation signals transmitted from the transmitting end side are received, and the correlation between the wavelengths of both optical modulation signals and both optical modulation signals is received. From the average value of chromatic dispersion of the optical fiber transmission line, A chromatic dispersion measuring method, wherein the chromatic dispersion of the optical fiber transmission line is measured from the average value and the dispersion slope. On the receiving end side, based on the first and second optical modulation signals, the first and second optical modulation signals and the third and fourth optical modulation signals shifted in wavelength by a fixed wavelength are generated. The chromatic dispersion measuring method according to claim 14, wherein: On the receiving end side, the first and second optical modulation signals are converted into electric signals, respectively, and the first and second optical modulation means are operated based on the electric signals, whereby the first, The chromatic dispersion measurement method according to claim 14 or 15, wherein the third and fourth optical modulation signals wavelength-converted with respect to the second optical modulation signal are generated. When transmitting the first and second optical modulation signals and the third and fourth optical modulation signals on the transmission end side and the reception end side, the wavelength of the optical modulation signal can be varied. The chromatic dispersion measuring method according to claim 14, wherein: The first to fourth optical modulation signals are set as pulse trains, and an average value of chromatic dispersion in the optical fiber transmission line is calculated from the delay difference between the pulse trains of the third and fourth optical modulation signals on the transmission end side. The chromatic dispersion measuring method according to claim 14, wherein the chromatic dispersion measuring method is obtained.   19. On the transmission end side, either the repetition period or the pulse width of the pulse train is changed according to the magnitude of chromatic dispersion of the optical fiber transmission line and the necessary resolution of chromatic dispersion. The chromatic dispersion measuring method described in 1. The chromatic dispersion measurement method according to claim 18 or 19, wherein the pulse train forms a pseudo-random sequence, and pulse pattern comparison is used when the correlation between modulated signals is compared on the transmission end side. On the transmitting end side, either the pulse width of the pseudo-random sequence or the sequence length of the pattern is changed according to the magnitude of chromatic dispersion of the optical fiber transmission line and the necessary resolution of chromatic dispersion. The chromatic dispersion measuring method according to claim 20. The chromatic dispersion measurement method according to any one of claims 14 to 21, wherein the dispersion compensation amount on the transmission side is adjusted based on the detected chromatic dispersion.

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