JP3642710B2 - Optical receiver, optical transmitter, optical amplifying repeater, and optical signal monitoring system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical receiver, an optical transmitter, an optical amplifying repeater, and an optical signal monitoring system in optical communication, and more particularly to efficiently provide multimedia services by constructing an economical and flexible optical network. The present invention relates to an optical signal monitoring technique in an optical network system having a hierarchical structure including an optical layer.
[0002]
[Prior art]
Optical time division Heavy (OTDM: Optical Time Division Multiplexing) is a method of multiplexing and transmitting a plurality of optical signals of the same carrier light wavelength on a time axis in one optical fiber. In addition, wavelength division multiplexing (WDM) is to multiplex and transmit a plurality of optical signals having different carrier light wavelengths in one optical fiber. Both OTDM and WDM are useful techniques for expanding transmission capacity.
[0003]
On the other hand, in conventional point-to-point communication, a synchronous optical network (SONET) / synchronous digital hierarchy (SDH) transmission in which signals are bundled using time division multiplexing into frames provided by the synchronous network. A method is used. In this SONET / SDH transmission system, an overhead is determined in order to perform efficient signal transmission, and a parity check called a bit interleaved parity (Bit Interleaved Parity) is performed by using the overhead. By executing the communication between the communication terminals and between the multiplexed terminals, the failure section identification and the switching activation signal are obtained.
[0004]
On the other hand, as a method of monitoring an optical signal in a light state, there is a conventional optical signal-to-noise ratio monitoring by optical spectrum measurement.
[0005]
[Problems to be solved by the invention]
In recent years, the demand for multimedia services has increased rapidly, and it has become necessary to expand the communication capacity of each service. In addition, the network efficiently supports various signal bit rates and signal formats such as video, audio, and data. Has been longing for.
[0006]
However, in the signal quality monitoring system such as the SONET / SDH transmission method described above, the bit rate, signal format and modulation format (NRZ (Non Return to Zero) or RZ (Return to Zero) of the target signal are set. (Recovery))), a reception system (an error detection circuit including a clock extraction circuit, a reception circuit, a frame detection circuit, a parity check circuit, or a verification circuit) is required. For this reason, there is a point that a single reception system cannot cope with a signal of an arbitrary bit rate, signal format, or modulation format. In addition, in this conventional optical signal monitoring system, it is necessary to perform electrical signal processing after replacing an optical signal with an electrical signal. Therefore, in consideration of economy, it is difficult to apply to an optical amplification repeater system. When is detected, it is impossible to identify up to which section the fault has occurred between the optical amplification repeater systems.
[0007]
Furthermore, the conventional monitoring method using optical spectrum measurement has a point that it cannot detect transmission deterioration due to waveform distortion which can be considered as a network failure in an optical network.
[0008]
From the above, it is indispensable to construct an economical service transfer network that has a large communication capacity per service and supports various signal formats and signal bit rates. Here, the optical network is extremely promising in that the communication capacity can be expanded by using optical time division multiplexing or wavelength division multiplexing, and the signal bit rate, signal format, and modulation format are transparent. However, an optical signal monitoring system suitable for such an optical network has not yet been established.
[0009]
The present invention has been made in view of the above-described points, and its purpose is to provide an economical and reliable system that can accommodate multimedia services having a large communication capacity per service and various signal formats and signal bit rates. An object of the present invention is to provide an optical receiver, an optical transmitter, an optical amplifying repeater, and an optical signal monitoring system for realizing a highly reliable optical network system.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer, wherein a plurality of optical nodes constituting the optical network are one pair or plural pairs, respectively. An optical signal transmitting terminal station and an optical signal receiving terminal station, arranged at the optical signal receiving terminal station, between the optical signal transmitting terminal station of one optical node and the optical signal receiving terminal station of another optical node. A signal-to-noise ratio coefficient measuring unit that measures a signal-to-noise ratio coefficient of an optical signal transmitted through the optical signal path, and a signal-to-noise ratio measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is introduced. An initial state storage unit for storing a coefficient, and a signal to noise ratio coefficient value obtained by measurement by the signal to noise ratio coefficient measurement unit at a fixed time interval during system operation; And an optical signal quality evaluation section for comparing the value of the stored signal-to-noise ratio coefficient, With optical layer An optical signal monitoring unit that performs analog monitoring independent of optical signal modulation format, format, and bit rate, a control channel that transmits monitoring information of the optical signal monitoring unit to the optical signal transmitting terminal station, and the optical signal quality evaluation Based on the optical signal quality evaluation of the unit, recognizes that a network failure has occurred due to optical signal degradation or optical signal waveform distortion caused by a failure in the optical signal path, and controls the monitoring information including the recognized information Based on the monitoring information from the monitoring information control unit of the optical signal transmission terminal station and the monitoring information control unit of the optical signal transmission terminal station, which is sent to the monitoring information control unit of the optical signal transmission terminal station through the channel And a path switching unit disposed in the optical signal transmission terminal station.
[0011]
In order to achieve the above object, an invention according to claim 2 is an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer, wherein a plurality of optical nodes constituting the optical network are one pair or plural pairs, respectively. A plurality of optical amplifiers respectively connected between the optical signal receiving terminal station and the optical signal transmitting terminal station in the middle of the optical signal path and the optical signal transmitting terminal station. A signal-to-noise ratio coefficient measurement unit that is arranged in all or part of the relay system and measures the signal-to-noise ratio coefficient of the optical signal, and the signal-to-noise ratio coefficient measurement unit in a state where there is no obstacle in advance when the system is installed. An initial state storage unit that stores the measured signal-to-noise ratio coefficient, and a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at a fixed time interval during system operation. Optical signal monitoring having an optical signal quality evaluation unit that compares the value of the signal-to-noise ratio coefficient stored in the initial state storage unit at the time of input, and performs analog monitoring independent of the optical signal modulation format, format, and bit rate Caused by a failure in the optical signal path based on the optical signal quality evaluation in the optical signal quality evaluation unit, the control channel for transmitting the monitoring information of the optical signal monitoring unit to the optical signal receiving terminal station, and the optical signal quality evaluation unit Recognizing that a network failure has occurred due to optical signal degradation or optical signal waveform distortion, monitoring information including the recognition information is transmitted to the optical signal transmitting terminal station using the control channel. Monitoring Based on the monitoring information sent from the monitoring information control unit of the optical signal transmission terminal station to the information control unit, arranged in the optical signal transmission terminal station, and the monitoring information control unit arranged in the optical amplification relay system And a failure section identifying unit for identifying the optical amplification repeater section in which the network failure has occurred.
[0012]
Here, the optical signal transmitting terminal station includes a path switching unit that performs path switching based on monitoring information from the monitoring information control unit in addition to the failure section identification unit. be able to.
[0013]
The optical layer can be accommodated by converting electrical signals of various modulation formats, formats, and bit rates such as SONET / SDH frames, ATM cells, and IP packets into optical signals of appropriate carrier wavelengths, An optical signal is terminated between the optical signal transmitting terminal station of a certain optical node and the optical signal receiving terminal station of another optical node, and for each termination of the optical signal, a modulation format, a format, An optical signal path independent of the bit rate can be formed.
[0014]
The signal-to-noise ratio coefficient measurement unit includes a photoelectric conversion unit that converts an optical signal having a bit rate f0 (bit / s) into an electric intensity modulation signal, and a clock frequency f1 (Hz) (f1 = (N / M ) F0 + a, N and M are positive numbers, and a is an offset frequency). The optical signal intensity distribution measuring means for measuring the intensity distribution of the optical signal by sampling the intensity of the electric intensity modulation signal, and within a certain average time And a signal-to-noise ratio coefficient evaluation unit that evaluates a signal-to-noise ratio coefficient using an amplitude histogram obtained from the optical signal intensity distribution.
[0015]
The signal-to-noise ratio coefficient measurement unit includes an optical signal having a bit rate f0 (bit / s), a repetition frequency of f1 (Hz) (f1 = (N / M) f0 + a, N and M are positive numbers, a is an offset frequency), and using a sampling optical pulse train whose pulse width is sufficiently narrower than the time slot of the optical signal, a cross-correlated optical signal generating means for generating a cross-correlated optical signal having an optical frequency different from those of the two lights; Optical signal intensity distribution measuring means for measuring the intensity distribution of the optical signal by performing electric signal processing after converting the correlated optical signal into an electric signal, and an amplitude histogram obtained from the intensity distribution of the optical signal within a certain average time And a signal-to-noise ratio coefficient evaluation unit that evaluates the signal-to-noise ratio coefficient.
[0016]
The signal-to-noise ratio coefficient evaluating means includes a histogram evaluating means for obtaining an amplitude histogram from the intensity distribution of the optical signal within a certain average time, and the amplitude histogram portion higher than a predetermined intensity threshold (A). The amplitude histogram distribution function g1 corresponding to “level 1” is estimated from the above, and the amplitude histogram distribution function g0 corresponding to “level 0” is estimated from the amplitude histogram portion lower than the separately determined intensity threshold (B). The distribution function evaluation means, and the average intensity and standard deviation value of “level 1” and “level 0” are obtained from the amplitude histogram distribution functions g1 and g0, respectively, and each of “level 1” and “level 0” is obtained. Signal-to-noise ratio coefficient obtained as the ratio of the difference in mean value intensity and the sum of the standard deviation values of “Level 1” and “Level 0” By comprising an evaluation for optical signal quality evaluation means it can be characterized.
[0017]
Further, the distribution function evaluating means obtains two maximum values from the amplitude histogram obtained from the intensity distribution of the optical signal to be measured, the higher amplitude intensity is set as the intensity threshold (A), and the lower value is set as the intensity threshold (A). An intensity threshold (B) can be used.
[0018]
In order to achieve the above object, an invention of claim 9 is directed to an optical transmitter of an optical network having a hierarchical structure including an optical layer, an optical amplification repeater connected between the optical receiver and the optical receiver, and the optical transmitter. A monitoring information control unit that receives monitoring information including recognition information that a network failure has occurred from a receiver, and a failure that identifies an optical amplification repeater section in which a network failure has occurred based on the monitoring information from the monitoring information control unit A section identification unit.
[0019]
Here, it may further include a path switching unit that performs path switching of the transmission path based on the monitoring information from the monitoring information control unit.
[0020]
In order to achieve the above object, an invention of claim 11 is an optical receiver of an optical network having a hierarchical structure including an optical layer, and an optical branching device for extracting a part of an optical signal transmitted through the optical network; A signal-to-noise ratio coefficient measurement unit that measures the signal-to-noise ratio coefficient of the optical signal extracted by the optical branching unit, and a signal-to-noise ratio that is measured by the signal-to-noise ratio coefficient measurement unit in a state where there is no obstacle in advance when the system is installed An initial state storage unit that stores a ratio coefficient, and a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation are stored in the initial state storage unit at the time of introduction. An optical signal quality evaluation unit that compares the stored signal-to-noise ratio coefficient value , Analog monitoring independent of optical signal modulation format / format / bit rate using optical layer An optical signal monitoring unit, and a monitoring information control unit that recognizes that a network failure has occurred based on the optical signal quality evaluation of the optical signal quality evaluation unit and sends monitoring information including the recognition information to the optical transmitter; It is characterized by comprising.
[0021]
In order to achieve the above object, an invention according to claim 12 is an optical amplification repeater of an optical network having a hierarchical structure including an optical layer, an optical amplifier for amplifying an optical signal transmitted through the optical network, and the optical amplifier An optical branching device that extracts a part of the optical signal amplified in step 1, a signal-to-noise ratio coefficient measuring unit that measures the signal-to-noise ratio coefficient of the optical signal extracted by the optical branching device, An initial state storage unit that stores the signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measurement unit in a state in which the signal-to-noise ratio coefficient measurement unit is not present, An optical signal monitoring unit comprising: an optical signal quality evaluation unit that compares a value of a signal-to-noise ratio coefficient obtained with a value of a signal-to-noise ratio coefficient stored in the initial state storage unit at the time of introduction; and the optical signal quality evaluation unit Based on the optical signal quality evaluation, it recognizes that the network failure, characterized by comprising a monitoring information control unit sends the monitoring information including the recognition information to the optical transmitter.
[0022]
In order to achieve the above object, the invention of claim 13 is an optical amplifying repeater for an optical network having a hierarchical structure including an optical layer, and an optical branching device for extracting a part of an optical signal transmitted through the optical network; A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of an optical signal taken out by the optical branching unit; and a signal pair measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is introduced. An initial state storage unit for storing a noise ratio coefficient, and the initial state storage unit at the time of introduction of a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation An optical signal monitoring unit including an optical signal quality evaluation unit that compares the value of the signal-to-noise ratio coefficient stored in the network, and a network failure occurs based on the optical signal quality evaluation of the optical signal quality evaluation unit Was recognized that, characterized by comprising a monitoring information control unit sends the monitoring information including the recognition information to the optical transmitter.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0024]
(First embodiment)
1A and 1B show the configuration of an optical network according to the first embodiment of the present invention. FIG. 1A shows an optical network having a ring configuration including a protection line, and includes an optical ADM ring and the like. FIG. 1B shows an optical network having a mesh configuration.
[0025]
In either case, the optical network can accommodate electrical signals of various modulation formats, formats, and bit rates, such as SONET / SDH frames, ATM cells, and IP packets, by converting them into optical signals of appropriate carrier wavelengths. And a hierarchical structure including an optical layer. Each optical node 102 constituting the optical network includes one or more pairs of optical signal transmission terminal stations and optical signal reception terminal stations (transmission / reception terminal stations 104). The optical signal is terminated between the terminal station 104 and the optical signal receiving terminal station 104 of another optical node. In addition, an optical signal path independent of the modulation format, format, and bit rate is formed for each end of the optical signal. Here, the case where an optical signal is passed through in the optical node 102 is also included. Further, the case where optical amplification relay is performed between the optical transmission / reception terminal stations 104 is also included.
[0026]
In the present invention, as described later, optical signal monitoring is performed at the optical signal receiving terminal station, and monitoring information is sent to the optical signal transmitting terminal station using a control channel between the optical transmitting and receiving terminal stations. The optical signal is switched appropriately.
[0027]
FIG. 2 shows a configuration example in the optical transmission / reception terminal station 104 according to the first embodiment of the present invention. The signal accommodated in the higher optical layer is received by the optical transmitter 204 of the optical signal transmission terminal station 202 and transmitted to the transmission path 212 via the path switching unit 206. In the optical signal receiving terminal station 216, a part of the input optical signal is branched by the optical branching unit 218, and the optical signal monitoring unit 220 performs optical signal monitoring using the branched optical signal.
[0028]
The optical signal monitoring unit 220 includes a signal-to-noise ratio coefficient measurement unit 222, an initial state storage unit 224, and an optical signal quality evaluation unit 226, and performs analog monitoring independent of the optical signal modulation format, format, and bit rate. . The signal-to-noise ratio coefficient measuring unit 222 measures the signal-to-noise ratio coefficient of the optical signal transmitted through the transmission path 212 between the optical signal transmitting terminal station 202 of one optical node and the optical signal receiving terminal station 216 of another optical node. To do. The initial state storage unit 224 stores the signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measuring unit 222 in a state in which there is no failure in advance when the system is introduced. The optical signal quality evaluation unit 226 stores the value of the signal-to-noise ratio coefficient obtained by the signal-to-noise ratio coefficient measurement unit 222 at regular time intervals during system operation in the initial state storage unit 224 at the time of introduction. Compare the value of the signal to noise ratio coefficient.
[0029]
In addition to the transmission path 212, monitoring information of the optical signal monitoring unit 220 is transmitted to the optical signal transmitting terminal station 202 between the optical signal receiving terminal station 216 of a certain optical node and the optical signal transmitting terminal station 202 of another optical node. Control information 214 is provided in each of the optical signal receiving terminal station 216 and the optical signal transmitting terminal station 202, respectively. Based on the optical signal quality evaluation in the optical signal quality evaluation unit 226, the monitoring information control units 228 and 210 recognize that a network failure has occurred due to optical signal degradation or optical signal waveform distortion caused by a failure in the transmission path 212 or the like. The monitoring information including the recognized information is exchanged through the control channel 214.
[0030]
A path switching unit 206 is provided in the optical signal transmission terminal station 202. Based on the monitoring information 210 from the monitoring information control unit, the path switching unit 206 performs path switching of the transmission path 212 to recover the network failure.
[0031]
FIG. 3 shows an operation procedure of path control in the optical signal monitoring system according to the first embodiment of the present invention.
[0032]
Step S1: The signal-to-noise ratio coefficient measuring unit 222 measures the signal-to-noise ratio coefficient when the system is introduced without any obstacles.
[0033]
Step S2: The signal-to-noise ratio coefficient measured in step S1 is stored in the initial state storage unit 224.
[0034]
Step S3: After starting the system operation, the signal-to-noise ratio coefficient measuring unit 222 measures the signal-to-noise ratio coefficient at regular time intervals.
[0035]
Step S4: Each time the signal-to-noise ratio coefficient is measured, the measured value is compared with the value in the initial state storage unit 224 in the optical signal quality evaluation unit 226.
[0036]
Step S5: The optical signal quality evaluation unit 226 transmits the change in the signal-to-noise ratio coefficient value from the initial state to the monitoring information control unit 228 as monitoring information. Here, when it is recognized from the degree of change in the signal-to-noise ratio coefficient value that a failure has occurred, alarm information indicating that route switching is necessary is also transmitted to the monitoring information control unit 228 as monitoring information.
[0037]
Step S6: The monitoring information control unit 228 transmits the monitoring information to the monitoring information control unit 210 on the optical signal transmission terminal station 202 side using the control channel 214.
[0038]
Step S7: The monitoring information control unit 210 of the optical signal transmitting terminal station 202 informs the path switching unit 206 that the path switching is performed as necessary based on the received monitoring information.
[0039]
Step S8: The path switching unit 206 performs path switching of the transmission path 212 according to the instruction of the monitoring information control unit 210.
[0040]
Here, for example, the optical signal quality monitor of Reference [1] can be used for the signal-to-noise ratio coefficient measurement unit 226 (Reference [1]: Japanese Patent Laid-Open No. 11-223575). This eliminates the need for a reception system (error detection circuit consisting of a clock extraction circuit, reception circuit, frame detection circuit, parity check circuit, or verification circuit) according to the bit rate, signal format, and modulation format. It can handle signals of any bit rate, signal format, and modulation format.
[0041]
4 and 5 show examples of the configuration of the signal-to-noise ratio coefficient measurement unit 222 using the optical signal quality monitor, FIG. 4 shows a case where the electrical sampling oscilloscope 404 is used, and FIG. 5 shows a case where the optical sampling oscilloscope 414 is used. .
[0042]
When the electrical sampling oscilloscope 404 of FIG. 4 is used, a light intensity modulation signal having a predetermined bit rate f0 (bit / s) is converted into an electrical intensity modulation signal by the photoelectric conversion unit 402, After obtaining the signal intensity distribution in a certain time by sampling the intensity of the electric intensity modulation signal at the clock frequency f1 (Hz) (f1 = (N / M) f0 + a, N, M are integers, a is an offset frequency). The signal processing unit 406 performs signal-to-noise ratio coefficient evaluation. Signal processing Part 4 06 includes a histogram evaluation unit 408 and a signal-to-noise ratio coefficient evaluation unit. The histogram evaluation unit 408 obtains an amplitude histogram from the signal intensity distribution obtained by the electrical sampling oscilloscope 404. The signal-to-noise ratio coefficient evaluation unit 410 obtains the distribution of “level 1” and “level 0” of the binary digital code from the obtained amplitude histogram, and calculates the average value intensity of each of “level 1” and “level 0”. The signal-to-noise ratio coefficient obtained as the ratio of the difference and the sum of the standard deviation values of “level 1” and “level 0” is evaluated.
[0043]
Although the configuration of FIG. 4 is simple, the adaptable optical signal bit rate is limited by the band of the photoelectric conversion unit 402.
[0044]
On the other hand, when the optical sampling oscilloscope 414 of FIG. 5 is used, the signal processing unit 416 performs signal-to-noise ratio coefficient evaluation after obtaining the signal intensity distribution for a certain time by the optical sampling oscilloscope 414. For the optical signal intensity distribution measurement by the optical sampling oscilloscope 414, the optical sampling described in the reference [2] can be used. (Reference [2]: Takara et al. “Ultra high-speed optical waveform measurement method by optical sampling using sum frequency light generation”, IEICE Transactions, B-l, vol. J75-Bl, No. 5 pp.372-380, 1992).
[0045]
This optical sampling is characterized by the use of second harmonic generation, sum frequency light generation, difference frequency light generation, four-wave mixed light generation, etc. in order to obtain a cross correlation signal. Get the distribution.
[0046]
For example, the optical sampling oscilloscope 414 has an optical signal having a predetermined bit rate f0 (bit / s), a repetition frequency of a predetermined f1 (Hz) (f1 = (N / M) f0 + a, N and M are positive numbers, a is an offset frequency), and using a sampling optical pulse train whose pulse width is sufficiently narrower than the time slot of the optical signal, a cross-correlation optical signal having an optical frequency different from these two lights is generated, and the cross-correlation optical signal is After converting into a signal and photoelectrically converting the cross-correlation optical signal, electrical signal processing is performed to measure the intensity distribution of the optical signal over a certain period of time.
[0047]
The signal processing unit 416 includes a histogram evaluation unit 418 and a signal to noise ratio coefficient evaluation unit 420. The histogram evaluation unit 418 obtains an amplitude histogram from the signal intensity distribution obtained by the optical sampling oscilloscope 414. The signal-to-noise ratio coefficient evaluation unit 420 obtains the distribution of “level 1” and “level 0” of the binary digital code from the obtained amplitude histogram, and calculates the average value intensity of each of “level 1” and “level 0”. The signal-to-noise ratio coefficient obtained as the ratio of the difference and the sum of the standard deviation values of “level 1” and “level 0” is evaluated.
[0048]
The configuration of FIG. 5 can be applied to an optical signal faster than that of FIG.
[0049]
Next, FIGS. 6 to 9 show examples of signal-to-noise ratio coefficient measurement algorithms in the signal-to-noise ratio coefficient measurement unit 222 that performs optical signal quality monitoring.
[0050]
6A: The intensity distribution within a certain average time is obtained by optical sampling by the optical sampling oscilloscope 414 or electrical sampling by the electrical sampling oscilloscope 404. FIG.
[0051]
FIG. 6B: An amplitude histogram is obtained from the obtained intensity distribution.
[0052]
(A) in FIG. 7: The maximum value when the amplitude histogram is examined from the smaller intensity level is defined as m0 ′.
[0053]
(B) in FIG. 7: Integrating the number of sampling points from the sampling point with the maximum intensity level toward the smaller intensity level,
[0054]
[Expression 1]
N (middle) = N (total) x D x M (1)
(However, N (total) is the total number of sampling points,
D is the duty ratio of the optical signal (ratio of pulse width to time slot),
M is the mark rate (probability of occurrence of level 1 in digital transmission))
Let m (middle) be the minimum level of the integrated sampling points when the integrated value is equal to the number of sampling points N (middle) obtained in (1).
[0055]
FIG. 8A:
[0056]
[Expression 2]
m1 ′ = 2 × {m (middle) −m0 ′} (2)
Determine m1 ′ obtained by.
[0057]
FIG. 8B:
[0058]
[Equation 3]
A = m1'-alpha (m1'-m0 ') (3)
The intensity level obtained with the threshold A
[0059]
[Expression 4]
B = m0 ′ + alpha (m1′−m0 ′) (4)
The intensity level obtained by Threshold B
(However, alpha is a real number 0 <alpha <0.5)
And a distribution having an intensity level equal to or higher than the threshold A is a level 1 distribution, and a distribution having an intensity level lower than the threshold B is a level 0 distribution.
[0060]
(A) in FIG. 9: Average values m1 and m0 and standard deviations s1 and s0 are obtained in the distribution of level 1 and level 0 determined in FIG. 8B, respectively.
[0061]
(B) in FIG. 9: From the average value and standard deviation obtained in (A) in FIG.
[0062]
[Equation 5]
Q = | m1-m0 | / (s1 + s0) (5)
Is used as a quality evaluation parameter as a signal-to-noise ratio coefficient.
[0063]
FIG. 10 shows an example of experimental data of the signal-to-noise ratio coefficient obtained by the procedure as shown in FIGS. As an example, a 10 Gbit / s NRZ signal was used and electrical sampling was used. The value of alpha was 0.3. The horizontal axis is the Q value converted from the measured bit error rate (BER) and represents the actual change in optical signal quality due to noise. The vertical axis represents the signal-to-noise ratio coefficient obtained by the algorithm shown in FIGS.
[0064]
FIG. 10 shows that the signal-to-noise ratio coefficient using the optical signal quality monitor described in FIG. 4 and FIGS. 6 to 9 can be used as a parameter for knowing noise degradation. It shows that it can be used as monitoring information.
[0065]
FIG. 11 shows an example of experimental data when there is an influence of chromatic dispersion. As in the case of FIG. 10 described above, a 10 Gbit / s NRZ signal was used and electrical sampling was used. The value of alpha was 0.3. The horizontal axis is the Q value converted from the measured bit error rate (BER) and represents the actual change in optical signal quality due to noise. The vertical axis represents the signal-to-noise ratio coefficient obtained by the algorithm shown in FIGS. The triangular plot in FIG. 11 shows the case where the chromatic dispersion value received by the optical signal is 0 ps / nm, and the circle plot shows the case where the chromatic dispersion value received by the optical signal is 1400 ps / nm.
[0066]
FIG. 11 shows that the signal-to-noise ratio coefficient using the optical signal quality monitor is sensitive to waveform distortion due to chromatic dispersion, and also sensitive to noise degradation in the presence of waveform distortion due to chromatic dispersion. It shows that there is.
[0067]
(Second Embodiment)
12A and 12B show the configuration of the optical network according to the second embodiment of the present invention. In particular, in the present embodiment, an example in which a failure section is identified in units of optical amplification repeater sections when performing optical amplification repeater between optical transmission and reception terminal stations is shown. FIG. 12A shows an optical network having a ring configuration including a protection line 510, and includes an optical ADM ring and the like. FIG. 12B shows an optical network having a mesh configuration.
[0068]
In both cases (A) and (B) of FIG. 12, each optical node 502 constituting the optical network has one or more pairs of optical signal transmitting terminal stations and optical signal receiving terminal stations (transmitting / receiving terminal stations 504). The optical signal is terminated between the optical transmission / reception terminal station 104 of one optical node and the optical transmission / reception terminal station 104 of another optical node. The case where an optical signal is passed through in the optical node 502 is also included.
[0069]
As in the first embodiment described above, optical signal monitoring is performed at the optical signal receiving terminal station, monitoring information is sent to the optical signal transmitting terminal station using the control channel between the optical transmitting and receiving terminal stations, and the fault section is identified. I do.
[0070]
FIG. 13 shows an internal configuration example of the optical transmission / reception terminal station 504 of FIG. Here, components having functions similar to those of the first embodiment in FIG. 2 are denoted by the same reference numerals. An optical signal accommodated in the optical layer in the optical transmitter 604 of a certain optical signal transmission terminal station 602 is transmitted to the transmission path 212 via the path switching unit 606. Then, the optical signal monitoring unit 220 performs optical signal monitoring using a part of the optical signal input at the optical signal receiving terminal station 216. The optical signal monitoring unit 220 includes a signal-to-noise ratio coefficient measurement unit 222, an initial state storage unit 224, and an optical signal quality evaluation unit 226, and identifies a fault section in the procedure shown in FIG.
[0071]
FIG. 14 shows an internal configuration example of the optical amplification repeater system 506 of FIG. The optical amplification repeater 506 monitors the branched optical signal, an optical amplifier 716 that amplifies the optical signal transmitted through the transmission line 212, an optical branching device 718 that extracts a part of the amplified optical signal, and the like. The optical signal monitoring unit 720 and the monitoring information control unit 728 that transmits the monitoring information from the optical signal monitoring unit 720 to the optical signal transmission terminal station 602 side via the control channel 212. Monitoring information is obtained by processing the optical signal branched by the optical branching device 718 after optical amplification by the optical signal monitoring unit 720. Here, the optical branching device 712 may be used before the optical amplifier 716.
[0072]
Similar to the optical signal monitoring unit 720 of the optical signal receiving terminal 216, the optical signal monitoring unit 720 includes a signal-to-noise ratio coefficient measurement unit 722, an initial state storage unit 724, and an optical signal quality evaluation unit 726, which will be described later. The failure section is identified by the procedure as shown in FIG.
[0073]
Next, an operation procedure in the second embodiment of the present invention will be described with reference to the flowchart of FIG. Note that the same step numbers are assigned to the procedures having the same contents as in the first embodiment of FIG.
[0074]
Step S1: In the optical signal receiving terminal station 216 and the optical amplifying relay system 506, the signal-to-noise ratio coefficient measuring units 222 and 722 measure the signal-to-noise ratio coefficient when the system without fault is introduced.
[0075]
Step S2: The signal-to-noise ratio coefficient measured in step S1 is stored in the respective initial state storage units 224 and 724.
[0076]
Step S3: After the system operation is started, the signal-to-noise ratio coefficient measurement units 222 and 722 measure the signal-to-noise ratio coefficient at fixed time intervals in the optical signal receiving terminal station 216 and the optical amplification relay system 506.
[0077]
Step S4: Each time the signal-to-noise ratio coefficient is measured, the respective optical signal quality evaluation units 226 and 726 compare the value of the signal-to-noise ratio coefficient with the value of the initial state storage units 224 and 724.
[0078]
Step S5: The optical signal quality evaluation units 226 and 726 transmit the change in the signal-to-noise ratio coefficient value from the initial state to the respective monitoring information control units 228 and 728 as monitoring information. Here, when it is recognized from the degree of change in the signal-to-noise ratio coefficient value that a failure has occurred, alarm information indicating that route switching is necessary is also transmitted as monitoring information.
[0079]
Step S6: Each of the monitoring information control units 228 and 728 transmits the monitoring information to the monitoring information control unit 610 on the optical signal transmission terminal station 602 side using the control channel 214.
[0080]
Step S71: The monitoring information control unit 610 of the optical signal transmitting terminal station 602 receives the monitoring information transmitted from the optical signal receiving terminal station 216 and the monitoring information control units 228 and 728 of the optical amplification relay system 506 as the fault section identifying unit 612. To tell.
[0081]
Step S72: The fault section identification unit 612 of the optical signal transmission terminal station 602 recognizes in which section signal degradation has occurred from the monitoring information sent from each optical amplification relay system 506 and the optical signal reception terminal station 216.
[0082]
In this case as well, path switching can be performed simultaneously as in the first embodiment of the present invention. In that case,
Step S73: The monitoring information control unit 610 of the optical signal transmitting terminal station 602 indicates that the path switching is performed as necessary based on the monitoring information transmitted from each optical amplification relay system 506 and the optical signal receiving terminal station 216. Tell the route switching unit 606.
[0083]
Step S8: The path switching unit 606 performs path switching of the transmission path 212 according to the instruction of the monitoring information control unit 610.
[0084]
For the signal-to-noise ratio coefficient measuring units 222 and 722 of FIGS. 13 and 14, the optical signal quality monitor of the reference [1] can be used. The configuration of the signal-to-noise ratio coefficient unit using the optical signal quality monitor, the measurement algorithm, and the like are as shown in FIGS. 4 to 9 in the first embodiment of the present invention.
[0085]
Further, as in the second embodiment of the present invention, when analog monitoring is used for the optical amplifying and relaying system 506, an optical signal that has not been subjected to dispersion compensation is monitored, so that waveform distortion due to wavelength dispersion is large. However, as shown in the data example of FIG. 11, it can be understood that the signal-to-noise ratio coefficient obtained by the optical signal quality monitor can be used sufficiently. Therefore, the signal-to-noise ratio coefficient obtained by the optical signal quality monitor can be used for identifying the faulty section.
[0086]
(Third embodiment)
Next, FIGS. 16 to 19 show other examples of signal-to-noise ratio coefficient measurement algorithms in the signal-to-noise ratio coefficient measuring units 222 and 722 that perform optical signal quality monitoring as a third embodiment of the present invention. Show.
[0087]
FIG. 16A: First, optical sampling with an optical sampling oscilloscope 414 using the configuration shown in FIG. 5 or electrical sampling with an electrical sampling oscilloscope 404 using the configuration shown in FIG. Find the intensity distribution.
[0088]
FIG. 16B: An amplitude histogram is obtained from the obtained intensity distribution.
[0089]
FIG. 17A: The first maximum value when the amplitude histogram is examined from the larger intensity level is defined as the threshold value A.
[0090]
FIG. 17B: The first maximum value when the amplitude histogram is examined from the smaller intensity level is defined as the threshold value B.
[0091]
(A) in FIG. 18: A portion having an intensity level equal to or greater than the threshold A in the amplitude histogram is assumed to be a normal distribution g1, and fitting (approximation) is performed by the least square method or the like, and the average value m1 of level 1 and the standard The deviation s1 is obtained.
[0092]
FIG. 18B: As in FIG. 18A, assuming that the portion of the amplitude histogram whose intensity level is equal to or lower than the threshold value B is a normal distribution g0, fitting is performed by the method of least squares, etc. An average value m0 of 0 and a standard deviation s0 are obtained.
[0093]
FIG. 19: From the average values m1, m0 and standard deviations s1, s0 obtained in FIG. 18 (A) and FIG. 18 (B).
[0094]
[Formula 6]
Q = | m1-m0 | / (s1 + s0) (6)
Is used as an optical signal quality evaluation parameter as a signal-to-noise coefficient.
[0095]
Chi-square distribution can also be assumed as the above distribution functions g0 and g1 (reference [3]: D. Marcuse, “Derivation of Analytical Expressions for the Bit-Error Probability in Lightwave Systems with Optical Amplifiers,” IEEE J. Lightwave Technol., Vol. 8, No. 12, pp 1816-1823, 1990).
[0096]
(Fourth embodiment)
20 to 23 show still other examples of signal-to-noise ratio coefficient measurement algorithms in the signal-to-noise ratio coefficient measurement units 222 and 722 that perform optical signal quality monitoring as the fourth embodiment of the present invention. This embodiment is different from the above-described third embodiment of the present invention in that the threshold values A and B are obtained in the algorithm.
[0097]
FIG. 20A: First, within an average time by optical sampling by the optical sampling oscilloscope 414 using the configuration shown in FIG. 5 or by electrical sampling by the electrical sampling oscilloscope 404 using the configuration shown in FIG. Find the intensity distribution.
[0098]
(B) in FIG. 20: An amplitude histogram is obtained from the obtained intensity distribution.
[0099]
(A) in FIG. 21: The first maximum value when the amplitude histogram is examined from the smaller intensity level is defined as the threshold value B.
[0100]
(B) of FIG. 21: integrating the number of sampling points from the sampling point with the maximum intensity level toward the smaller intensity level,
[0101]
[Expression 7]
N (middle) = N (total) x D x M (7)
(However, N (total) is the total number of sampling points,
D is the duty ratio of the optical signal (ratio of pulse width to time slot),
M is the mark rate (probability of occurrence of level 1 in digital transmission))
Let m (middle) be the minimum level of the integrated sampling points when the integrated value is equal to the number of sampling points N (middle) obtained in (1).
[0102]
FIG. 22A:
[0103]
[Equation 8]
Threshold A = 2 × {m (middle) −Threshold B} (8)
The threshold value A is obtained by
[0104]
(B) of FIG. 22: In the amplitude histogram, a portion where the intensity level is equal to or greater than the threshold A is assumed to be a part of the normal distribution g1, and a portion where the intensity level is equal to or less than the threshold B is a part of the normal distribution g0. And the average values m1 and m0 of level 1 and level 0 and standard deviations s1 and s0 are obtained by fitting using the least square method or the like.
[0105]
FIG. 23: From the average values m1 and m0 and the standard deviations s1 and s0 obtained in FIG.
[0106]
[Equation 9]
Q = | m1-m0 | / (s1 + s0) (9)
Is used as an optical signal quality evaluation parameter as a signal-to-noise coefficient.
[0107]
A chi-square distribution can be assumed as the distribution functions g0 and g1 (reference document [3]).
[0108]
The third embodiment of the present invention described above has the advantage of being the simplest method, but the range of application is limited to NRZ signals. On the other hand, the fourth embodiment is more complicated than the third embodiment, but has an advantage that it can be applied not only to the NRZ signal but also to the RZ signal. However, as shown in the above equation (7), it is necessary to know in advance the duty ratio D and the mark rate M of the signal pulse.
[0109]
(Fifth embodiment)
24 to 27 show still another example of an algorithm for signal-to-noise ratio coefficient measurement in the signal-to-noise ratio coefficient measurement units 222 and 722 that performs optical signal quality monitoring as a fifth embodiment of the present invention. The present embodiment is different from the third and fourth embodiments of the present invention described above in that the threshold values A and B are determined in the algorithm.
[0110]
FIG. 24A: First, within an average time by optical sampling by the optical sampling oscilloscope 414 using the configuration shown in FIG. 5 or by electrical sampling by the electrical sampling oscilloscope 404 using the configuration shown in FIG. Find the intensity distribution.
[0111]
(B) of FIG. 24: An amplitude histogram is obtained from the obtained intensity distribution.
[0112]
(A) in FIG. 25: The first maximum value when the amplitude histogram is examined from the smaller intensity level is defined as the threshold value B.
[0113]
(B) in FIG. 25: A portion of the amplitude histogram whose intensity level is equal to or less than the threshold value B is assumed to be a part of the normal distribution g0, and fitting is performed by the least square method or the like to obtain the average value m0 of level 0 and the standard Deviation s0 is obtained.
[0114]
26A: A distribution g1x obtained by subtracting the function g0 obtained in FIG. 25B from the entire amplitude histogram is obtained, and an initial maximum value when the distribution g1x is examined from the larger intensity level is obtained. Threshold A is defined. g1x is considered to be a superposition of the level 1 distribution function g1 and the cross point distribution function gx.
[0115]
(B) in FIG. 26: A portion of the distribution g1x where the intensity level is equal to or higher than the threshold A is assumed to be a part of the normal distribution g1, and fitting is performed by the least square method or the like, and the average value m1 of the level 1 and the standard Deviation s1 is obtained.
[0116]
FIG. 27: From the average values m1 and m0 and the standard deviations s1 and s0 obtained in (B) of FIG. 26 and (B) of FIG.
[0117]
[Expression 10]
Q = | m1-m0 | / (s1 + s0) (10)
Is used as an optical signal quality evaluation parameter as a signal-to-noise coefficient.
[0118]
A chi-square distribution can be assumed as the distribution functions g0 and g1 (reference document [3]).
[0119]
The fifth embodiment is more complicated than the fourth embodiment described above, but can be applied to the RZ signal, and there is an advantage that it is not necessary to know the duty ratio and mark ratio of the signal pulse in advance. .
[0120]
(Other embodiments)
An object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus. Needless to say, this can also be achieved by reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. As a storage medium for storing the program code and for storing variable data such as a table, for example, a floppy disk or a hard disk can be used.
[0121]
【The invention's effect】
As described above, according to the present invention, electrical signals having various modulation formats, formats, and bit rates such as SONET / SDH frames, ATM cells, and IP packets are accommodated by converting them into optical signals having appropriate carrier wavelengths. In an optical network including an optical layer, Since analog monitoring is performed using the optical layer, It enables failure and quality monitoring that does not depend on the signal modulation method, signal format, or signal bit rate. Furthermore, according to the present invention, it is possible to economically identify faulty sections and switch paths in the optical layer.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical network according to a first embodiment of the present invention, in which (A) is an optical network having a ring configuration including a protection line, and (B) is an optical network having a mesh configuration. .
FIG. 2 is a block diagram showing a configuration example in an optical transmission / reception terminal station 104 according to the first embodiment of the present invention.
FIG. 3 is a flowchart showing a path control operation procedure in the optical signal monitoring system according to the first embodiment of the present invention;
FIG. 4 is a block diagram illustrating a configuration example of a signal-to-noise ratio coefficient measurement unit when an electrical sampling oscilloscope is used in each embodiment of the present invention.
FIG. 5 is a block diagram illustrating a configuration example of a signal-to-noise ratio coefficient measurement unit when an optical sampling oscilloscope is used in each embodiment of the present invention.
FIG. 6 is a conceptual diagram showing an initial stage of a signal-to-noise ratio coefficient measurement algorithm in the first embodiment of the present invention.
FIG. 7 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the first embodiment of the present invention following FIG. 6;
FIG. 8 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the first embodiment of the present invention following FIG. 7;
FIG. 9 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the first embodiment of the present invention continued from FIG. 8;
FIG. 10 is a graph showing an example of signal-to-noise ratio coefficient experimental data obtained by the procedure shown in FIGS. 6 to 9, wherein the horizontal axis represents the Q value converted from the measured bit error rate, and the vertical axis Is a signal-to-noise ratio coefficient obtained by the algorithm of FIGS.
11 is a graph showing an example of experimental data when there is an influence of chromatic dispersion, in which the horizontal axis is a Q value converted from the measured bit error rate, and the vertical axis is a signal obtained by the algorithm of FIGS. It is a noise-to-noise ratio coefficient.
FIGS. 12A and 12B are block diagrams showing a configuration of an optical network according to a second embodiment of the present invention, in which FIG. 12A is an optical network having a ring configuration including a protection line, and FIG. 12B is an optical network having a mesh configuration; .
FIG. 13 is a block diagram showing an internal configuration of a transmission / reception terminal station according to the second embodiment of the present invention.
14 is a block diagram showing an internal configuration of the optical amplification repeater system in FIG. 13;
FIG. 15 is a flowchart showing an operation procedure of fault section identification and path control in the optical signal monitoring system according to the second embodiment of the present invention.
FIG. 16 is a conceptual diagram showing an initial stage of a signal-to-noise ratio coefficient measurement algorithm in the third embodiment of the present invention.
FIG. 17 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the third embodiment of the present invention continued from FIG. 16;
FIG. 18 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the third embodiment of the present invention continued from FIG. 17;
FIG. 19 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the third embodiment of the present invention continued from FIG. 18;
FIG. 20 is a conceptual diagram showing an initial stage of a signal-to-noise ratio coefficient measurement algorithm in the fourth embodiment of the present invention.
FIG. 21 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fourth embodiment of the present invention continued from FIG. 20;
FIG. 22 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fourth embodiment of the present invention following FIG. 21;
FIG. 23 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fourth embodiment of the present invention continued from FIG. 22;
FIG. 24 is a conceptual diagram showing an initial stage of a signal-to-noise ratio coefficient measurement algorithm in the fifth embodiment of the present invention.
FIG. 25 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fifth embodiment of the present invention continued from FIG. 24;
FIG. 26 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fifth embodiment of the present invention continued from FIG. 25;
FIG. 27 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm in the fifth embodiment of the present invention continued from FIG. 26;
[Explanation of symbols]
102, 502 Optical node
104, 504 Optical signal transmitting / receiving terminal station
108,508 Working line
110, 510 Backup line
112, 512 Optical signal
202, 602 Optical signal transmitting terminal station
204, 604 Optical transmitter
206, 606 Route switching unit
208, 608 switch
210, 610 Monitoring information control unit
212 Transmission path
214 Control channel
216 Optical signal receiving terminal
218, 718 Optical splitter
220, 720 Optical signal monitoring unit
222, 722 Signal-to-noise ratio coefficient measurement unit
224, 724 Initial state storage unit
226, 726 Optical signal quality evaluation unit
228, 728 Monitoring information control unit
230 Optical receiver
402 Photoelectric conversion unit
404 Electric sampling oscilloscope
406, 416 Signal processor
408, 418 Histogram evaluation unit
410, 420 Signal-to-noise ratio coefficient evaluation unit
414 Optical sampling oscilloscope
506 Optical amplification relay system
612 Fault section identification unit
716 Optical amplifier

Claims (13)

In an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer,
Each of the plurality of optical nodes constituting the optical network includes one or more pairs of optical signal transmitting terminal stations and optical signal receiving terminal stations,
A signal-to-noise ratio coefficient of an optical signal, which is disposed in the optical signal receiving terminal station and transmitted through an optical signal path between the optical signal transmitting terminal station of one optical node and the optical signal receiving terminal station of another optical node, A signal-to-noise ratio coefficient measurement unit to be measured, an initial state storage unit that stores the signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measurement unit in a state in which there are no obstacles at the time of system introduction, and constant during system operation The signal-to-noise ratio coefficient value measured by the signal-to-noise ratio coefficient measuring unit at a time interval is compared with the signal-to-noise ratio coefficient value stored in the initial state storage unit at the time of introduction. An optical signal monitoring unit that performs analog monitoring independent of the optical signal modulation format, format, and bit rate using an optical layer, and
A control channel for transmitting monitoring information of the optical signal monitoring unit to the optical signal transmitting terminal station;
Based on the optical signal quality evaluation of the optical signal quality evaluation unit, it recognizes that a network failure has occurred due to optical signal degradation or optical signal waveform distortion caused by a failure in the optical signal path, and includes the recognized information A monitoring information control unit disposed in the optical signal receiving terminal station for sending monitoring information to the monitoring information control unit of the optical signal transmitting terminal station through the control channel;
An optical signal monitoring system comprising: a path switching unit disposed in the optical signal transmission terminal station, wherein the path switching unit performs path switching based on monitoring information from the monitoring information control unit of the optical signal transmission terminal station. . In an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer,
Each of the plurality of optical nodes constituting the optical network includes one or more pairs of optical signal transmitting terminal stations and optical signal receiving terminal stations,
Arranged in all or part of a plurality of optical amplification relay systems respectively connected between the optical signal receiving terminal station and the optical node in the middle of the optical signal path and the optical signal transmitting terminal station. A signal-to-noise ratio coefficient measuring unit for measuring the signal-to-noise ratio coefficient; and an initial state storage unit for storing the signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is installed; The signal-to-noise ratio coefficient value obtained by measuring the signal-to-noise ratio coefficient measurement unit at a fixed time interval during system operation and the signal-to-noise ratio coefficient value stored in the initial state storage unit at the time of introduction An optical signal quality evaluation unit for comparison, an optical signal monitoring unit for analog monitoring independent of the optical signal modulation format, format, and bit rate;
A control channel for transmitting the monitoring information of the optical signal monitoring unit to the optical signal receiving terminal station;
Based on the optical signal quality evaluation in the optical signal quality evaluation unit, it recognizes that a network failure has occurred due to optical signal degradation or optical signal waveform distortion caused by a failure in the optical signal path, and includes the recognition information A monitoring information control unit disposed in the optical amplifying relay system for sending monitoring information to the monitoring information control unit of the optical signal transmitting terminal station using the control channel;
A fault section identifying unit that is disposed in the optical signal transmitting terminal station and identifies an optical amplification repeater section in which the network fault has occurred based on monitoring information from the monitoring information control unit of the optical signal transmitting terminal station. An optical signal monitoring system. 3. The apparatus according to claim 2, further comprising: a path switching unit that is disposed in the optical signal transmission terminal station and performs path switching based on monitoring information from the monitoring information control unit in addition to the failure section identification unit. An optical signal monitoring system according to claim 1. The optical layer can be accommodated by converting electrical signals of various modulation formats, formats, and bit rates such as SONET / SDH frames, ATM cells, and IP packets into optical signals of appropriate carrier wavelengths,
An optical signal is terminated between the optical signal transmitting terminal station of a certain optical node and the optical signal receiving terminal station of another optical node,
4. The optical signal monitoring system according to claim 1, wherein an optical signal path independent of a modulation format, a format, and a bit rate is formed at each end of the optical signal. The signal-to-noise ratio coefficient measurement unit is
Photoelectric conversion means for converting an optical signal having a bit rate f0 (bit / s) into an electric intensity modulation signal;
The intensity distribution of the optical signal is measured by sampling the intensity of the electric intensity modulation signal at a clock frequency f1 (Hz) (f1 = (N / M) f0 + a, N and M are positive numbers, a is an offset frequency). Optical signal intensity distribution measuring means;
5. A signal-to-noise ratio coefficient evaluation unit that evaluates a signal-to-noise ratio coefficient using an amplitude histogram obtained from the optical signal intensity distribution within a certain average time. The optical signal monitoring system described. The signal-to-noise ratio coefficient measurement unit is
An optical signal having a bit rate of f0 (bit / s), a repetition frequency of f1 (Hz) (f1 = (N / M) f0 + a, N and M are positive numbers, a is an offset frequency), and a pulse width is an optical signal Cross-correlation optical signal generating means for generating a cross-correlation optical signal having an optical frequency different from those of the two lights using a sampling optical pulse train sufficiently narrower than the time slot of
Optical signal intensity distribution measuring means for measuring the intensity distribution of the optical signal by performing electric signal processing after converting the correlated optical signal into an electric signal;
5. A signal-to-noise ratio coefficient evaluation unit that evaluates a signal-to-noise ratio coefficient using an amplitude histogram obtained from an intensity distribution of the optical signal within a certain average time. An optical signal monitoring system according to claim 1. The signal-to-noise ratio coefficient evaluation means is
Histogram evaluation means for obtaining an amplitude histogram from the intensity distribution of the optical signal within a certain average time;
The amplitude histogram distribution function g1 corresponding to “level 1” is estimated from the amplitude histogram portion higher than the predetermined intensity threshold (A), and the amplitude histogram lower than the separately determined intensity threshold (B). Distribution function evaluation means for estimating an amplitude histogram distribution function g0 corresponding to “level 0” from the portion;
The average value intensity and standard deviation value of “level 1” and “level 0” are obtained from the amplitude histogram distribution functions g1 and g0, respectively, and the difference between the average value intensity of “level 1” and “level 0” 7. An optical signal quality evaluation means for evaluating a signal-to-noise ratio coefficient obtained as a ratio of the sum of standard deviation values of “level 1” and “level 0”. An optical signal monitoring system according to claim 1. The distribution function evaluation means obtains two maximum values from the amplitude histogram obtained from the intensity distribution of the optical signal to be measured, and sets the intensity threshold (A) as the higher amplitude intensity and the intensity as the lower one. 8. The optical signal monitoring system according to claim 7, wherein the optical signal monitoring system is a threshold value (B). In an optical transmitter of an optical network having a hierarchical structure including an optical layer,
An optical amplification repeater connected in the middle of the optical receiver and the optical receiver, and a monitoring information control unit that receives monitoring information including recognition information that a network failure has occurred from the optical receiver;
An optical transmitter comprising: a failure section identification unit that identifies an optical amplification repeater section in which a network failure has occurred based on the monitoring information from the monitoring information control unit. The optical transmitter according to claim 9, further comprising a path switching unit that performs path switching of a transmission path based on monitoring information from the monitoring information control unit. In an optical receiver of an optical network having a hierarchical structure including an optical layer,
An optical branching device for extracting a part of the optical signal transmitted through the optical network;
A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of an optical signal taken out by the optical branching unit; and a signal pair measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is introduced. An initial state storage unit for storing a noise ratio coefficient, and the initial state storage unit at the time of introduction of a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation An optical signal quality evaluation unit for comparing with the value of the signal-to-noise ratio coefficient stored in the optical signal monitoring unit for performing analog monitoring independent of the optical signal modulation format, format, and bit rate using the optical layer ;
A monitoring information control unit that recognizes that a network failure has occurred based on the optical signal quality evaluation of the optical signal quality evaluation unit, and sends monitoring information including the recognition information to the optical transmitter. And optical receiver. In an optical amplification repeater of an optical network having a hierarchical structure including an optical layer,
An optical amplifier for amplifying an optical signal transmitted through the optical network;
An optical branching device for extracting a part of the optical signal amplified by the optical amplifier;
A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of an optical signal taken out by the optical branching unit; and a signal pair measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is introduced. An initial state storage unit for storing a noise ratio coefficient, and the initial state storage unit at the time of introduction of a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation An optical signal monitoring unit comprising an optical signal quality evaluation unit that compares the value of the signal-to-noise ratio coefficient stored in
A monitoring information control unit that recognizes that a network failure has occurred based on the optical signal quality evaluation of the optical signal quality evaluation unit and sends monitoring information including the recognition information to the optical transmitter. An optical amplification repeater. In an optical amplification repeater of an optical network having a hierarchical structure including an optical layer,
An optical branching device for extracting a part of the optical signal transmitted through the optical network;
A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of an optical signal taken out by the optical branching unit; and a signal pair measured by the signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle in advance when the system is introduced. An initial state storage unit for storing a noise ratio coefficient, and the initial state storage unit at the time of introduction of a signal-to-noise ratio coefficient value obtained by measurement by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation An optical signal monitoring unit comprising an optical signal quality evaluation unit that compares the value of the signal-to-noise ratio coefficient stored in
A monitoring information control unit that recognizes that a network failure has occurred based on the optical signal quality evaluation of the optical signal quality evaluation unit and sends monitoring information including the recognition information to the optical transmitter. An optical amplification repeater.

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