JP2001217775A - Optical receiver, optical transmitter, optical amplifying repeater and optical signal monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical signal monitoring system for monitoring a fault/quality without depending on a modulation system/signal format/signal bit rate when a fault occurs on an optical signal path on an optical network for handling multimedia services having various modulation systems/signal formats/signals bit rates. SOLUTION: An optical layer in an optical network system converts an electric signal to an optical signal of a suitable carrier wavelength and performs signal transmission by applying time division multiplexing to a plurality of optical signals with a single wavelength or applying wavelength division multiplexing to the optical signals of a plurality of carrier wavelengths. The optical layer does not depend on the modulation system, signal format or signal bit rate of a signal to be handled. Therefore, by performing the analog monitoring of the noise deterioration and waveform distortion of the optical signal on the optical layer, the fault/quality can be monitored without depending on the modulation system, signal format or signal bit rate of the signal. By using this method, the identification of a fault block and route switching are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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 an efficient and flexible optical network 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 for providing a media service.

[0002]

2. Description of the Related Art Optical time division large quantity (OTDM)
Division Multiplexing is a method of transmitting a plurality of optical signals of the same carrier light wavelength multiplexed on one optical fiber on a time axis. In addition, wavelength division multiplexing (WDM; Wave)
In length division multiplexing, a plurality of optical signals having different carrier light wavelengths are multiplexed and transmitted in one optical fiber. Both OTDM and WDM are useful technologies for expanding transmission capacity.

On the other hand, in the conventional point-to-point communication, a synchronous optical communication network (SONET; Synchronous Optical Network) that bundles signals using time division multiplexing in a frame provided by the synchronous network.
twork) / Synchronous Digital Hierarchy (SDH; Synchro)
Nous Digital Hierarchy) transmission system and the like are used. In this SONET / SDH transmission method, overhead is determined in order to perform efficient signal transmission, and a parity check called Bit Interleaved Parity is performed using the overhead, and the repeater checks the parity. This is performed between the multiplexing terminal stations and between the multiplexing terminal stations to obtain a faulty section identification and a switching start signal.

On the other hand, as a method of monitoring an optical signal in the state of light, there is a method of monitoring an optical signal-to-noise ratio by measuring an optical spectrum.

[0005]

In recent years, the demand for multimedia services has rapidly increased, and it has become necessary to increase the communication capacity of individual services. In addition, various signal bit rates for video, audio, data, etc. There is a long-felt need for a network that can efficiently handle signal formats.

However, in the signal quality monitoring system such as the SONET / SDH transmission system described above, the bit rate, signal format, and modulation format (NRZ (Non Return t
o A reception system (clock detection circuit, reception circuit, frame detection circuit, parity detection circuit, or error detection circuit composed of a parity check circuit or an error detection circuit) corresponding to RZ (Return to Zero; return to zero) is required. Become. Therefore, there is a point that a single receiving system cannot cope with a signal of an arbitrary bit rate, a signal format, or a modulation format. Also, in this conventional optical signal monitoring system, it was necessary to perform electrical signal processing after replacing the optical signal with an electrical signal. Therefore, in consideration of economy, it is difficult to apply the optical signal to an optical amplification repeater system. When is detected, it is not possible to identify in which section between the optical amplification repeaters a failure has occurred.

Further, the conventional monitoring method using optical spectrum measurement has a point that transmission deterioration due to waveform distortion which is sufficiently considered as a network failure in an optical network cannot be detected.

[0008] From the above, it is essential 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 can expand the communication capacity by using optical time division multiplexing or wavelength division multiplexing,
It is very promising in that it is transparent to the signal bit rate, signal format and modulation format. However, optical signal monitoring systems suitable for such optical networks are:
Not yet established.

[0009] The present invention has been made in view of the above points, and its object is to provide a large communication capacity per service.
An optical receiver for realizing an economical and reliable optical network system capable of accommodating multimedia services having various signal formats and signal bit rates,
An object of the present invention is to provide an optical transmitter, an optical amplifier repeater, and an optical signal monitoring system.

[0010]

To achieve the above object, according to the present invention, there is provided an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer. The nodes are
A pair of optical signal transmitting terminals and a plurality of pairs of optical signal transmitting terminals and optical signal receiving terminals, wherein the optical signal transmitting terminals of one optical node and the optical signals of another optical node are arranged at the optical signal receiving terminals. A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of an optical signal transmitted through an optical signal path between signal receiving end stations, and a signal-to-noise ratio coefficient measuring unit in a state where there is no obstacle beforehand when a system is introduced. An initial state storage unit that stores the measured signal-to-noise ratio coefficient, and a signal-to-noise ratio coefficient value obtained by measuring the signal-to-noise ratio coefficient measurement unit at a certain time interval during system operation, when the signal-to-noise ratio coefficient value is introduced. An optical signal monitoring unit that has an optical signal quality evaluation unit that compares the value of the signal-to-noise ratio coefficient stored in the initial state storage unit and performs analog monitoring independent of the optical signal modulation format, format, and bit rate; The optical signal monitoring A control channel for transmitting the monitoring information of the optical signal to the optical signal transmitting end station, and an optical signal deterioration or an optical signal waveform distortion caused by a failure in the optical signal path based on the optical signal quality evaluation of the optical signal quality evaluation unit. And sends monitoring information including the recognized information to the monitoring information control unit of the optical signal transmitting terminal through the control channel, wherein the monitoring information is located at the optical signal receiving terminal. A control unit, comprising: a path switching unit disposed in the optical signal transmission terminal station, which performs path switching based on monitoring information from the monitoring information control unit of the optical signal transmission terminal station. .

According to a second aspect of the present invention, there is provided an optical signal monitoring system in an optical network having a hierarchical structure including an optical layer, wherein each of a plurality of optical nodes constituting the optical network has a pair. Or a plurality of pairs comprising an optical signal transmitting terminal station and an optical signal receiving terminal station, each of which is 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 that is arranged in all or a part of the optical amplification relay system and measures the signal-to-noise ratio coefficient of an optical signal, An initial state storage unit for storing the signal-to-noise ratio coefficient measured by the measurement unit; and a signal-to-noise obtained by measuring the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation. An optical signal quality evaluation unit that compares the value of the coefficient with the value of the signal-to-noise ratio coefficient stored in the initial state storage unit at the time of introduction, and performs analog monitoring independent of the optical signal modulation format, format, and bit rate. An optical signal monitoring unit, a control channel for transmitting monitoring information of the optical signal monitoring unit to the optical signal receiving terminal, and a failure in the optical signal path based on the optical signal quality evaluation by the optical signal quality evaluation unit. Recognize that a network failure has occurred due to optical signal deterioration or optical signal waveform distortion due to such, etc., and send monitoring information including the recognition information to the inspection information control unit of the optical signal transmitting terminal using the control channel. Sending, a monitoring information control unit disposed in the optical amplification relay system, and disposed in the optical signal transmission terminal station, based on the monitoring information from the monitoring information control unit of the optical signal transmission terminal station. Serial characterized by comprising a faulted segment identification unit network failure to identify an optical amplification repeater section caused.

Here, a path switching unit, which is arranged in the optical signal transmitting terminal and switches the path based on the monitoring information from the monitoring information control unit, is provided in addition to the faulty section identification unit. It can be a feature.

The optical layer is a SONET / SD.
The optical signal transmitting end of a certain optical node can be accommodated by converting electrical signals of various modulation formats, formats and bit rates such as H frames, ATM cells and IP packets into optical signals of an appropriate carrier wavelength. An optical signal is terminated between a station and the optical signal receiving terminal of another optical node, and an optical signal path independent of a modulation format, a format, and a bit rate is provided for each termination of the optical signal. Is formed.

The signal-to-noise ratio coefficient measuring 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, where N and M are positive numbers, a is an offset frequency), and an 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; Signal-to-noise ratio coefficient evaluation means for evaluating a signal-to-noise ratio coefficient using an amplitude histogram obtained from the optical signal intensity distribution in time.

The signal-to-noise-ratio coefficient measuring unit may determine whether an optical signal having a bit rate of f0 (bit / s) and a repetition frequency of f1 (Hz) (f1 = (N / M) f0 +
a, N, and M are positive numbers, a is an offset frequency), and a cross-correlation optical signal having an optical frequency different from these two lights is obtained by 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 generating means for generating, an optical signal intensity distribution measuring means for performing an electric signal processing after converting the correlated optical signal into an electric signal to measure an intensity distribution of the optical signal, and the light within a certain average time; Signal-to-noise ratio coefficient evaluation means for evaluating a signal-to-noise ratio coefficient using an amplitude histogram obtained from a signal intensity distribution.

Further, the signal-to-noise ratio coefficient evaluation means includes:
Histogram evaluation means for obtaining an amplitude histogram from the intensity distribution of the optical signal within a certain average time; and an amplitude histogram distribution function corresponding to “level 1” from the amplitude histogram portion higher than a predetermined intensity threshold (A) distribution function evaluation means for estimating g1 and estimating an amplitude histogram distribution function g0 corresponding to “level 0” from the amplitude histogram portion lower than the separately determined intensity threshold (B); The average intensity and the standard deviation value of each of “level 0” are obtained from the amplitude histogram distribution functions g1 and g0, respectively, and the difference between the average intensity of each of “level 1” and “level 0” and “level 1” Optical signal quality evaluation means for evaluating a signal-to-noise ratio coefficient obtained as a ratio of the sum of respective standard deviation values of “level 0” It may be characterized in that.

The distribution function evaluation means obtains two local maximum values from the amplitude histogram obtained from the intensity distribution of the optical signal to be measured, and sets a higher amplitude intensity as the intensity threshold (A), Is set as the intensity threshold (B).

In order to achieve the above object, an invention according to a ninth aspect of the present invention relates to an optical transmitter of an optical network having a hierarchical structure including an optical layer, wherein the optical amplifier repeater is connected between 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, and an optical amplification relay section in which a network failure has occurred based on the monitoring information from the monitoring information control unit. And a failure section identification unit for identification.

Here, it is possible to further include a path switching unit for switching the path of the transmission path based on the monitoring information from the monitoring information control unit.

In order to achieve the above object, according to an eleventh aspect of the present invention, in an optical receiver of an optical network having a hierarchical structure including an optical layer, an optical splitter for extracting a part of an optical signal transmitted through the optical network. And a signal-to-noise ratio coefficient measuring unit for measuring the signal-to-noise ratio coefficient of the optical signal extracted by the optical splitter, and the signal-to-noise ratio coefficient measuring unit measured beforehand when the system was installed without any obstacles. An initial state storage unit for storing a signal-to-noise ratio coefficient, and a signal-to-noise ratio coefficient value obtained by measuring the signal-to-noise ratio coefficient measurement unit at regular time intervals during operation of the system; 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 storage unit; and a network fault based on the optical signal quality evaluation performed by the optical signal quality evaluation unit. There recognizes that has occurred, characterized by comprising a monitoring information control unit sends the monitoring information including the recognition information to the optical transmitter.

To achieve the above object, an invention according to claim 12 is an optical amplifier repeater for an optical network having a hierarchical structure including an optical layer, wherein the optical amplifier amplifies an optical signal transmitted through the optical network; An optical splitter 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 the optical signal extracted by the optical splitter, An initial state storage unit for storing the signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measurement unit in a state where there is no obstacle in advance, and 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 obtained by the comparison with the value of the signal-to-noise ratio coefficient stored in the initial state storage unit at the time of introduction. Based on the optical signal quality evaluation of quality evaluation unit 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.

In order to achieve the above object, an invention according to claim 13 is an optical amplifying repeater of an optical network having a hierarchical structure including an optical layer, wherein an optical branch for extracting a part of an optical signal transmitted through the optical network is provided. , A signal-to-noise ratio coefficient measuring unit for measuring the signal-to-noise ratio coefficient of the optical signal extracted by the optical splitter, and the signal-to-noise ratio coefficient measuring unit for measuring the signal-to-noise ratio coefficient in a state where there is no obstacle before introducing the system An initial state storage unit for storing the obtained 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 certain time interval 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 state storage unit; and a network based on the optical signal quality evaluation performed by the optical signal quality evaluation unit. Recognizes that a failure has occurred, characterized by comprising a monitoring information control unit sends the monitoring information including the recognition information to the optical transmitter.

[0023]

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

(First Embodiment) FIGS. 1A and 1B
Shows the configuration of the optical network according to the first embodiment of the present invention. FIG. 1A shows an optical network having a ring configuration provided with a protection line, and includes an optical ADM ring and the like. FIG. 1B shows an optical network having a mesh configuration.

In both cases, the optical network is SO
A hierarchical structure including an optical layer that can accommodate electrical signals of various modulation formats, formats, and bit rates such as NET / SDH frames, ATM cells, and IP packets by converting them into optical signals of an appropriate carrier wavelength. Prepare. Each of the optical nodes 102 constituting the optical network includes one or a plurality of pairs of optical signal transmitting terminal stations and optical signal receiving terminal stations (transmitting and receiving terminal stations 104). An optical signal is terminated between the terminal station 104 and the optical signal receiving terminal station 104 of another optical node. Also, an optical signal path independent of the modulation format, format, and bit rate is formed at each end of the optical signal. Here, a case where an optical signal is passed through the optical node 102 is also included. Further, a case where optical amplification relay is performed between the optical transmitting and receiving terminal stations 104 is also included.

In the present invention, as will be described later, the optical signal receiving terminal monitors the optical signal, and sends the monitoring information to the optical signal transmitting terminal by using the control channel between the optical transmitting and receiving terminals.
Optical signal switching is performed appropriately based on the monitoring information.

FIG. 2 shows an example of the configuration inside the optical transmitting / receiving terminal 104 according to the first embodiment of the present invention. The signal accommodated in the upper optical layer is the optical transmitter 20 of the optical signal transmitting terminal 202.
4 via the path switching unit 206 and the transmission path 212
Sent to. In the optical signal receiving terminal station 216, a part of the input optical signal is split by the optical splitter 218, and the optical signal monitoring unit 220 monitors the optical signal using the split optical signal.

The optical signal monitoring section 220 comprises a signal-to-noise ratio coefficient measuring section 222, an initial state storage section 224, and an optical signal quality evaluation section 226.
Performs analog monitoring independent of the bit rate. The signal-to-noise ratio coefficient measuring unit 222 measures the signal-to-noise ratio coefficient of the optical signal transmitted on the transmission line 212 between the optical signal transmitting terminal 202 of a certain optical node and the optical signal receiving terminal 216 of another optical node. I do. The initial state storage unit 224 stores the signal-to-noise ratio coefficient measurement unit 222 in a state in which there is no obstacle before the system is introduced.
Is stored. The optical signal quality evaluation unit 226 stores the value of the signal-to-noise ratio coefficient obtained by measuring the signal-to-noise ratio coefficient measurement unit 222 at regular time intervals during system operation, at the time of introduction, into the initial state storage unit 224.
Is compared with the value of the signal-to-noise ratio coefficient stored in.

The transmission line 21 is connected between the optical signal receiving terminal 216 of one optical node and the optical signal transmitting terminal 202 of another optical node.
2, a control channel 214 for transmitting monitoring information of the optical signal monitoring unit 220 to the optical signal transmitting terminal 202 is provided, and an optical signal receiving terminal 216 and an optical signal transmitting terminal 2 are provided.
02, monitoring information control units 228 and 210 are provided. The monitoring information control units 228 and 210 recognize, based on the optical signal quality evaluation by the optical signal quality evaluation unit 226, that a network failure has occurred due to optical signal deterioration or optical signal waveform distortion due to a failure in the transmission path 212 or the like. Then, monitoring information including the recognized information is exchanged via the control channel 214.

The optical signal transmitting terminal station 202 has a path switching unit 206
Is provided. Based on the monitoring information from the monitoring information control unit 210, the path switching unit 206 switches the path of the transmission path 212, thereby recovering the network failure.

FIG. 3 shows an operation procedure of path control in the optical signal monitoring system according to the first embodiment of the present invention.

Step S1: The signal-to-noise-ratio measuring unit 222 measures the signal-to-noise-ratio coefficient when introducing the system in a state where there is no obstacle.

Step S2: The signal-to-noise ratio coefficient measured in step S1 is stored in the initial state storage unit 224.

Step S3: After the system operation is started, the signal-to-noise ratio coefficient measuring section 222 measures the signal-to-noise ratio coefficient at regular time intervals.

Step S4: Every time the signal-to-noise ratio coefficient is measured, the measured value is compared with the value in the initial state storage section 224 in the optical signal quality evaluation section 226.

Step S5: Optical signal quality evaluation section 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 that a failure has occurred from the degree of change of the signal-to-noise ratio coefficient value, alarm information indicating that path switching is necessary is also transmitted to the monitoring information control unit 228 as monitoring information.

Step S6: The monitoring information control unit 228 transmits the monitoring information to the monitoring information control unit 210 of the optical signal transmitting terminal 202 using the control channel 214.

Step S7: The monitoring information control section 210 of the optical signal transmitting terminal station 202 informs the path switching section 206 that the path switching is to be performed as necessary based on the received monitoring information.

Step S8: The route switching unit 206 switches the route of the transmission line 212 according to the instruction of the monitoring information control unit 210.

Here, as the signal-to-noise ratio coefficient measuring unit 226, for example, the optical signal quality monitor of Reference [1] can be used (Reference Document [1]: JP-A-11-2).
No. 23575). This eliminates the need for a reception system (clock extraction circuit, reception circuit, frame detection circuit, error detection circuit consisting of a parity check circuit or a 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.

FIGS. 4 and 5 show an example of the configuration of the signal-to-noise ratio coefficient measuring unit 222 using an optical signal quality monitor. FIG. 4 shows a case where the electric sampling oscilloscope 404 is used.
FIG. 5 shows a case where the optical sampling oscilloscope 414 is used.

The electric sampling oscilloscope 4 shown in FIG.
04 is used, a predetermined bit rate f0 (bit
/ S) is converted into an electric intensity modulation signal by the photoelectric conversion unit 402, and the electric sampling oscilloscope 404 converts the light intensity modulation signal into a predetermined clock frequency f1.
(Hz) (f1 = (N / M) f0 + a, N and M are integers,
(a is an offset frequency), the signal intensity distribution over a certain period of time is obtained by sampling the intensity of the electric intensity modulation signal, and the signal processing unit 406 evaluates the signal-to-noise ratio coefficient. The signal processing unit 406 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 electric sampling oscilloscope 404. Signal to noise ratio coefficient evaluation section 410
Calculates the distribution of “level 1” and “level 0” of the binary digital code from the obtained amplitude histogram, calculates the difference between the average intensity of “level 1” and “level 0”, and “level 1” The signal-to-noise ratio coefficient obtained as the ratio of the sum of the standard deviation values of “level 0” is evaluated.

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.

On the other hand, when the optical sampling oscilloscope 414 of FIG. 5 is used, the signal sampling unit 416 obtains the signal intensity distribution for a certain period of time, and then the signal processing unit 416 evaluates the signal-to-noise ratio coefficient. For the optical signal intensity distribution measurement using the optical sampling oscilloscope 414, the optical sampling described in Reference [2] can be used. (Reference [2]: Takara et al. "Ultrafast Optical Waveform Measurement Method by Optical Sampling Using Sum-Frequency Light Generation", IEICE Transactions, B-1, vol. J75-B-1, No. 5 pp. 372-3
80, 1992).

This optical sampling is characterized by using second harmonic generation, sum frequency light generation, difference frequency light generation, four-wave mixing light generation, etc., in order to obtain a cross-correlation signal. From the signal strength distribution.

For example, an optical sampling oscilloscope 4
Reference numeral 14 denotes an optical signal having a predetermined bit rate f0 (bit / s) and a repetition frequency f1 (Hz) (f
1 = (N / M) f0 + a, where N and M are positive numbers and a is an offset frequency), and using a sampling light pulse train whose pulse width is sufficiently narrower than the time slot of the optical signal, a light different from these two lights is used. A cross-correlation optical signal having a frequency is generated, the cross-correlation optical signal is converted into an electric signal, and after the cross-correlation optical signal is photoelectrically converted, electric signal processing is performed to measure the intensity distribution of the optical signal over a certain period of time.

The signal processing section 416 comprises a histogram evaluation section 418 and a signal-to-noise ratio coefficient evaluation section 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
The distribution of the binary digital codes “level 1” and “level 0” is obtained from the obtained amplitude histogram, and the difference between the average intensity of “level 1” and “level 0”, and “level 1” and “level” Evaluate the signal-to-noise ratio coefficient obtained as the ratio of the sum of the standard deviation values of "0".

The configuration of FIG. 5 can be applied to an optical signal having a higher speed than that of FIG.

Next, FIGS. 6 to 9 show an example of an algorithm for measuring the signal-to-noise ratio coefficient in the signal-to-noise ratio coefficient measuring section 222 for monitoring the optical signal quality.

FIG. 6A: An intensity distribution within a certain average time is obtained by optical sampling by the optical sampling oscilloscope 414 or electric sampling by the electric sampling oscilloscope 404.

FIG. 6B: An amplitude histogram is obtained from the obtained intensity distribution.

FIG. 7A: The maximum value when the intensity level of the amplitude histogram is checked from the lower one is defined as m0 '.

FIG. 7B: Integrating the number of sampling points from the sampling point with the highest intensity level to the one with the smaller intensity level,

[0054]

N (middle) = N (total) × D × M (1) (where 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 minimum level of the integrated sampling points when the integration value is equal to the number of sampling points N (middle) obtained from the mark rate (probability of occurrence of level 1 in digital transmission).

FIG. 8A:

[0056]

M1 ′ = 2 × {m (middle) −m0 ′} (1) m1 ′ is determined.

FIG. 8B:

[0058]

A = m1′−alpha (m1′−m0 ′)... (3)

[0059]

[Mathematical formula-see original document] B = m0 '+ alpha (m1'-m0') (4) When the intensity level obtained by
alpha <0.5 real number), and a distribution whose intensity level is equal to or higher than the threshold value A is defined as a level 1 distribution, and a distribution whose intensity level is equal to or less than the threshold value B is defined as a level 0 distribution.

FIG. 9A: In the distribution of level 1 and level 0 determined in FIG.
1, m0 and standard deviations s1, s0.

FIG. 9B: From the average value and the standard deviation obtained in FIG.

[0062]

Q = | m1-m0 | / (s1 + s0) (5) The Q value obtained as follows is used as a quality evaluation parameter as a signal-to-noise ratio coefficient.

FIG. 10 shows an example of the 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 represents the Q value converted from the measured bit error rate (BER), and represents the actual optical signal quality change due to noise. The vertical axis is the signal-to-noise ratio coefficient obtained by the algorithm of FIGS.

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 the noise deterioration, and the path is switched. It can be used as the monitoring information above.

FIG. 11 shows an example of experimental data when there is an influence of chromatic dispersion. As in the case of FIG.
Electrical sampling was used using an NRZ signal at it / s. The value of alpha was 0.3. The horizontal axis represents the Q value converted from the measured bit error rate (BER), and represents the actual optical signal quality change due to noise. The vertical axis is from FIG.
It is a signal-to-noise ratio coefficient obtained by the algorithm of FIG.
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.

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 to noise degradation in the presence of waveform distortion due to chromatic dispersion. It shows that there is also sensitivity.

(Second Embodiment) FIGS.
(B) shows the configuration of the optical network according to the second embodiment of the present invention. In particular, the present embodiment shows an example in which a faulty section is identified for each optical amplification relay section when optical amplification relay is performed between the optical transmitting and receiving terminal stations. FIG. 12A shows an optical network having a ring configuration provided with a protection line 510, and includes an optical ADM ring and the like. FIG. 12B shows an optical network having a mesh configuration.

In both cases (A) and (B) of FIG. 12, each of the optical nodes 502 constituting the optical network includes one or more pairs of optical signal transmitting terminal stations and optical signal receiving terminal stations (transmission and reception). The optical signal is terminated between the optical transmitting / receiving terminal 104 of one optical node and the optical transmitting / receiving terminal 104 of another optical node. Also, a case where an optical signal is passed through the optical node 502 is included.

In the same manner as in the first embodiment, the optical signal receiving terminal monitors the optical signal, sends monitoring information to the optical signal transmitting terminal by using the control channel between the optical transmitting and receiving terminals, Identify the section.

FIG. 13 shows an example of the internal configuration of the optical transmitting / receiving terminal 504 of FIG. Here, components having the same functions as those in the first embodiment of FIG. 2 are denoted by the same reference numerals.
The optical signal accommodated in the optical layer in the optical transmitter 604 of a certain optical signal transmitting terminal 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.
The fault section is identified by a procedure as shown in FIG.

FIG. 14 shows an example of the internal configuration of the optical amplification repeater system 506 of FIG. The optical amplification relay system 506 is connected to the transmission path 212
An optical amplifier 716 for amplifying an optical signal transmitted through
An optical splitter 718 for extracting a part of the amplified optical signal,
An optical signal monitoring unit 720 that monitors the branched optical signal;
The monitoring information from the optical signal monitoring unit 720 is transmitted to the control channel 21.
And a monitoring information control unit 728 for transmitting the signal to the optical signal transmitting terminal station 602 via the communication terminal 2. Optical splitter 718 after optical amplification
The monitoring information is obtained by processing the optical signal branched by the optical signal monitoring unit 720. Here, the optical splitter 712 may be used in a stage preceding the optical amplifier 716.

The optical signal monitoring section 720 is an optical signal receiving terminal station 2.
Similarly to the optical signal monitoring unit 720 of FIG. 16, it is composed of a signal-to-noise ratio coefficient measurement unit 722, an initial state storage unit 724, and an optical signal quality evaluation unit 726. Perform identification.

Next, an operation procedure according to the second embodiment of the present invention will be described with reference to the flowchart in FIG. Note that the same steps as those in the first embodiment of FIG. 3 are denoted by the same step numbers.

Step S1: In the optical signal receiving terminal station 216 and the optical amplification repeater 506, the signal-to-noise ratio coefficients are measured by the signal-to-noise ratio coefficient measurement units 222 and 722 when the system is introduced without any failure.

Step S2: The signal-to-noise ratio coefficients measured in step S1 are stored in the respective initial state storage units 224, 7
Store at 24.

Step S3: After the system operation starts, in the optical signal receiving terminal station 216 and the optical amplification relay system 506, the signal-to-noise ratio coefficients are measured at fixed time intervals by the signal-to-noise ratio coefficient measurement units 222 and 722. .

Step S4: Each time the signal-to-noise ratio coefficient is measured, the respective optical signal quality evaluation sections 226, 726
And the value of the signal to noise ratio coefficient and the initial state storage unit 2
24 and 724 are compared.

Step S5: Optical signal quality evaluation section 226
726, the monitoring information control units 228 and 72 respectively use the change in the signal-to-noise ratio coefficient value from the initial state as monitoring information.
Tell 8 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 path switching is necessary is also transmitted as monitoring information.

Step S 6: The respective monitoring information control units 228 and 728 transmit the monitoring information to the monitoring information control unit 610 of the optical signal transmitting terminal 602 using the control channel 214.

Step S71: The monitoring information control section 610 of the optical signal transmitting terminal station 602 converts the monitoring information sent from the optical signal receiving terminal station 216 and the monitoring information control sections 228 and 728 of the optical amplification relay system 506 into the fault section. The information is transmitted to the identification unit 612.

Step S72: The fault section identification unit 612 of the optical signal transmitting terminal station 602 uses the monitoring information sent from each optical amplifying repeater system 506 and the optical signal receiving terminal station 216 to determine in which section signal degradation has occurred. recognize.

In this case as well, the path switching can be performed simultaneously, as in the first embodiment of the present invention. In such a case, Step S73: The monitoring information control unit 610 of the optical signal transmitting terminal 602 determines whether each of the optical amplification relay systems 506 and the optical signal receiving terminal 2
The path switching unit 606 is notified that the path switching is to be performed as necessary based on the monitoring information sent from the path switching unit 16.

Step S8: The route switching unit 606 switches the route of the transmission line 212 according to the instruction of the monitoring information control unit 610.

The signal-to-noise ratio coefficient measuring units 222 and 722 shown in FIGS. 13 and 14 can use the optical signal quality monitor described in Reference [1]. The configuration and measurement algorithm of the signal-to-noise ratio coefficient unit using the optical signal quality monitor are as shown in FIGS. 4 to 9 in the first embodiment of the present invention.

Also, as in the second embodiment of the present invention,
When analog monitoring is used for the optical amplification relay system 506, an optical signal that has not been subjected to dispersion compensation is monitored.
There is a possibility of monitoring noise degradation when waveform distortion due to chromatic dispersion is large, but as shown in the data example of FIG.
Also in this case, it can be seen that the signal-to-noise ratio coefficient obtained by the optical signal quality monitor can be sufficiently used. Therefore, the signal-to-noise ratio coefficient obtained by the optical signal quality monitor can be used for identifying a faulty section.

(Third Embodiment) Next, FIGS.
Next, as a third embodiment of the present invention, another example of the signal-to-noise ratio coefficient measurement algorithm in the signal-to-noise ratio coefficient measurement units 222 and 722 for monitoring the optical signal quality will be described.

FIG. 16A: First, a certain average is obtained by optical sampling using the optical sampling oscilloscope 414 using the configuration shown in FIG. 5 or electrical sampling using the electrical sampling oscilloscope 404 using the configuration shown in FIG. Find the intensity distribution in time.

FIG. 16B: An amplitude histogram is obtained from the obtained intensity distribution.

FIG. 17 (A): The threshold value A is determined as the first maximum value when the amplitude level is checked from the higher intensity level.

FIG. 17B: The threshold value B is determined as the first maximum value when the intensity histogram is examined from the smaller intensity level in the amplitude histogram.

FIG. 18 (A): In the amplitude histogram, a portion where the intensity level is equal to or higher than the threshold value A is represented by a normal distribution g1.
And fitting (approximately) using the least squares method
Then, the average value m1 of the level 1 and the standard deviation s1 are obtained.

FIG. 18 (B): As in FIG. 18 (A), the intensity level of the amplitude histogram
The following portion is assumed to be a normal distribution g0, and fitting is performed by the least square method or the like, and an average value m0 of level 0 and a standard deviation s0 are obtained.

FIG. 19: FIGS. 18A and 18B
From the average values m1 and m0 and the standard deviations s1 and s0

[0094]

Q = | m1−m0 | / (s1 + s0) (6) The Q value obtained as follows is used as an optical signal quality evaluation parameter as a signal-to-noise coefficient.

As the above distribution functions g0 and g1, a chi-square distribution can be assumed (reference document [3]: D.
Marcuse, "Derivation of Analytycal Expressions fo
r the Bit-Error Probability in Lightwave Systems w
ith Optical Amplifiers, "IEEE J. Lightwave Techno
l, Vol. 8, No. 12, pp 1816-1823, 1990).

(Fourth Embodiment) FIGS. 20 to 23 show, as a fourth embodiment of the present invention, the measurement of the signal-to-noise ratio coefficient in the signal-to-noise ratio coefficient measurement units 222 and 722 for monitoring the optical signal quality. The following shows another example of the algorithm. 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.

20A: First, a certain average is obtained by optical sampling by the optical sampling oscilloscope 414 using the configuration as shown in FIG. 5 or electrical sampling by the electric sampling oscilloscope 404 using the configuration as shown in FIG. Find the intensity distribution in time.

FIG. 20B: An amplitude histogram is obtained from the obtained intensity distribution.

FIG. 21 (A): The threshold value B is determined as the first maximum value when the amplitude histogram is examined from the smaller intensity level.

FIG. 21B: Integrating the number of sampling points from the sampling point with the highest intensity level to the one with the smaller intensity level,

[0101]

N (middle) = N (total) × D × M (7) (where N (total) is the total number of sampling points, D is the duty ratio of the optical signal (ratio between pulse width and time slot), M
Is the minimum level of the integrated sampling points when the integrated value is equal to the number of sampling points N (middle) obtained by the mark rate (probability of occurrence of level 1 in digital transmission).

FIG. 22A:

[0103]

The threshold value A is calculated by the following formula: threshold value A = 2 × {m (middle) −threshold value B} (8)

FIG. 22B: In the amplitude histogram, a portion where the intensity level is equal to or higher than the threshold value A is represented by a normal distribution g1.
And a part where the intensity level is equal to or lower than the threshold value B is assumed to be a part of the normal distribution g0, and fitting is performed by a least square method or the like to obtain the average values m1 and m of the level 1 and the level 0.
0 and standard deviations s1 and s0 are obtained.

FIG. 23: Average value m obtained in FIG.
From 1, m0 and standard deviation s1, s0

[0106]

Q = | m1−m0 | / (s1 + s0) (9) The Q value obtained as follows is used as an optical signal quality evaluation parameter as a signal-to-noise coefficient.

As the distribution functions g0 and g1, a chi-square distribution can be assumed (reference document [3]).

The third embodiment of the present invention described above has the advantage that it is the simplest method, but its application range is N
Limited to RZ signal. On the other hand, the fourth embodiment is more complicated than the third embodiment, but has an advantage that it can be applied to not only the NRZ signal but also the RZ signal.
However, as shown in the above equation (7), it is necessary to know the duty ratio D and the mark rate M of the signal pulse in advance.

(Fifth Embodiment) FIGS. 24 to 27 show a fifth embodiment of the present invention, in which signal-to-noise ratio coefficient measurement units 222 and 722 for monitoring an optical signal quality monitor. The following shows another example of the algorithm. The present embodiment is different from the above-described third and fourth embodiments of the present invention in the portion for obtaining the thresholds A and B in the algorithm.

FIG. 24A: First, a certain average is obtained by optical sampling by the optical sampling oscilloscope 414 using the configuration as shown in FIG. 5 or electrical sampling by the electric sampling oscilloscope 404 using the configuration as shown in FIG. Find the intensity distribution in time.

FIG. 24B: An amplitude histogram is obtained from the obtained intensity distribution.

FIG. 25A: The threshold value B is determined as the first maximum value when the amplitude level is checked from the smaller intensity level.

FIG. 25 (B): In the amplitude histogram, a portion whose intensity level is equal to or lower than the threshold value B is represented by a normal distribution g0.
, And fitting is performed by the least squares method or the like, and an average value m0 of level 0 and a standard deviation s0 are obtained.

FIG. 26A: Distribution g obtained by subtracting the function g0 obtained in FIG. 25B from the entire amplitude histogram.
1x is obtained, and a first maximum value when the intensity level is checked from the larger intensity level in the distribution g1x is determined as the threshold value A.
g1x is considered to be a superposition of the distribution function g1 of the level 1 and the distribution function gx of the cross point.

FIG. 26 (B): Assuming that a portion of the distribution g1x whose intensity level is equal to or higher than the threshold value A is a part of the normal distribution g1 and fitting by a least square method or the like, the average value of the level 1 is obtained. m1 and standard deviation s1 are obtained.

FIG. 27: FIG. 26 (B) and FIG. 25 (B)
From the average values m1 and m0 and the standard deviations s1 and s0

[0117]

Q = | m1−m0 | / (s1 + s0) (10) The Q value obtained as follows is used as a signal-to-noise coefficient as an optical signal quality evaluation parameter.

As the distribution functions g0 and g1, a chi-square distribution can be assumed (reference document [3]).

Although the fifth embodiment is more complicated than the fourth embodiment, it can be applied to the RZ signal, and it is not necessary to know the duty ratio and the mark ratio of the signal pulse in advance. There are advantages.

(Other Embodiments) An object of the present invention is to provide a storage medium storing program codes of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide the system or apparatus with the storage medium. It is needless to say that the present invention is also achieved when the computer (or CPU or MPU) of the apparatus reads out and executes 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, a hard disk, or the like can be used.

[0121]

As described above, according to the present invention,
Modulation of signals in an optical network including an optical layer that accommodates 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 an appropriate carrier wavelength. It enables fault and quality monitoring independent of the system, signal format, and signal bit rate.
Further, according to the present invention, it is possible to economically identify a faulty section in the optical layer and switch the route.

[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 illustrating a configuration example in an optical transmitting / receiving terminal station 104 according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation procedure of path control 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 electric 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 illustrating an initial stage of a signal-to-noise ratio coefficient measurement algorithm according to 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, following FIG. 8;

FIG. 10 is a graph showing an example of experimental data of a signal-to-noise ratio coefficient obtained by the procedures 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 represents the Q value. Is the signal-to-noise ratio coefficient obtained by the algorithm of FIGS.

FIG. 11 is a graph showing an example of experimental data when there is an influence of chromatic dispersion; the horizontal axis represents a Q value converted from the measured bit error rate, and the vertical axis represents a signal obtained by the algorithm of FIGS. This is the noise ratio coefficient.

FIG. 12 is a block diagram illustrating a configuration of an optical network according to a second embodiment of the present invention, wherein (A) is an optical network having a ring configuration including a protection line, and (B) is an optical network having a mesh configuration. .

FIG. 13 is a block diagram illustrating an internal configuration of a transmitting / receiving terminal according to the second embodiment of the present invention.

FIG. 14 is a block diagram showing an internal configuration of the optical amplification relay system of FIG.

FIG. 15 is a flowchart illustrating 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 illustrating an initial stage of a signal-to-noise ratio coefficient measurement algorithm according to the third embodiment of the present invention.

FIG. 17 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the third embodiment of the present invention, following FIG. 16;

FIG. 18 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the third embodiment of the present invention, following FIG. 17;

FIG. 19 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the third embodiment of the present invention, following FIG. 18;

FIG. 20 is a conceptual diagram illustrating an initial stage of a signal-to-noise ratio coefficient measurement algorithm according to the fourth embodiment of the present invention.

FIG. 21 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the fourth embodiment of the present invention, following FIG. 20;

FIG. 22 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to 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 according to the fourth embodiment of the present invention, following FIG. 22;

FIG. 24 is a conceptual diagram showing the first stage of the signal-to-noise ratio coefficient measurement algorithm according to the fifth embodiment of the present invention.

FIG. 25 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the fifth embodiment of the present invention, following FIG. 24;

FIG. 26 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the fifth embodiment of the present invention, following FIG. 25;

FIG. 27 is a conceptual diagram showing a signal-to-noise ratio coefficient measurement algorithm according to the fifth embodiment of the present invention, following FIG. 26;

[Explanation of symbols]

 102, 502 Optical node 104, 504 Optical signal transmitting / receiving terminal station 108, 508 Working line 110, 510 Protection 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 line 214 Control channel 216 Optical signal receiving terminal station 218, 718 Optical splitter 220, 720 Optical signal monitoring unit 222, 722 Signal to noise ratio coefficient measuring unit 224, 724 Initial state storage Units 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 processing unit 408, 418 Histogram evaluation unit 410, 420 Signal to noise ratio coefficient evaluation unit 414 Optical Sump Ring oscilloscope 506 optical amplifier repeater system 612 fault section identifying unit 716 optical amplifier

 ──────────────────────────────────────────────────の Continuing from the front page (72) Kentaro Uchiyama 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Yoshiaki Yamabayashi 2--3, Otemachi, Chiyoda-ku, Tokyo No. 1 Nippon Telegraph and Telephone Corporation F-term (reference) 2G086 CC04 KK01 5K002 AA01 AA03 BA04 CA13 DA05 DA11 EA05 EA31 EA33 FA01

Claims (13)

[Claims] 1. An optical signal monitoring system in an optical network having a hierarchical structure including an optical layer, wherein the plurality of optical nodes constituting the optical network each include one or more pairs of an optical signal transmitting terminal station and an optical signal. A receiving terminal station, which is disposed at the optical signal receiving terminal station and transmits an optical signal path between the optical signal transmitting terminal station of a certain optical node and the optical signal receiving terminal station of another optical node. A signal-to-noise ratio coefficient measurement unit that measures a signal-to-noise ratio coefficient, and 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 where there is no obstacle at the time of system introduction. The signal-to-noise ratio coefficient stored in the initial state storage unit when the value of the signal-to-noise ratio coefficient obtained by measuring the signal-to-noise ratio coefficient measurement unit at a certain time interval during system operation is introduced. And an optical signal quality evaluation section for comparing a value,
An optical signal monitoring unit that performs analog monitoring independent of an 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; 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 deterioration or optical signal waveform distortion caused by a failure in the optical signal path, and controls the monitoring information including the recognized information. A monitoring information control unit disposed at the optical signal receiving terminal station for sending to a monitoring information control unit of the optical signal transmitting terminal station via a channel, based on monitoring information from the monitoring information control unit of the optical signal transmitting terminal station; An optical signal monitoring system, comprising: a path switching unit disposed in the optical signal transmitting terminal station for performing a path switching by using a switch. 2. An optical signal monitoring system in an optical network having a hierarchical structure including an optical layer, wherein the plurality of optical nodes constituting the optical network each include one or more pairs of an optical signal transmitting terminal station and an optical signal. A receiving terminal station, and arranged in all or a 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 a signal-to-noise ratio coefficient of an optical signal, and a signal-to-noise ratio coefficient measured by the signal-to-noise ratio coefficient measuring unit beforehand when the system is installed without any obstacles. The initial state storage unit, and the value of the signal-to-noise ratio coefficient obtained by measuring the signal-to-noise ratio coefficient measurement unit at a certain time interval during system operation is introduced into the initial state storage unit. An optical signal monitoring unit that has an optical signal quality evaluation unit that compares the value of the stored signal-to-noise ratio coefficient and performs analog monitoring independent of the optical signal modulation format, format, and bit rate; and the optical signal monitoring unit. A control channel for transmitting monitoring information of the optical signal to the optical signal receiving terminal; and an optical signal deterioration or an optical signal waveform distortion caused by a failure in the optical signal path based on the optical signal quality evaluation by the optical signal quality evaluation unit. The monitoring is disposed in the optical amplification relay system, by recognizing that a network failure has occurred, and transmitting monitoring information including the recognition information to a monitoring information control unit of the optical signal transmitting terminal using the control channel. An information control unit, which is disposed in the optical signal transmitting terminal, and in which the optical amplifier relay in which the network failure has occurred based on monitoring information from the monitoring information control unit of the optical signal transmitting terminal. Optical signal monitoring system characterized by comprising a faulted segment identification unit for identifying between. 3. The apparatus according to claim 1, further comprising: a path switching unit disposed at said optical signal transmitting terminal, for switching a path based on monitoring information from said monitoring information control unit, in addition to said faulty section identification unit. The optical signal monitoring system according to claim 2, wherein 4. The optical layer accommodates 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 an appropriate carrier wavelength. Wherein an optical signal is terminated between the optical signal transmitting terminal of one optical node and the optical signal receiving terminal of another optical node, and at each termination of the optical signal, a modulation format ·format·
4. The optical signal monitoring system according to claim 1, wherein an optical signal path independent of a bit rate is formed. 5. The signal-to-noise ratio coefficient measuring 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) by sampling the intensity of the electric intensity modulation signal.
Optical signal intensity distribution measuring means for measuring the intensity distribution of the optical signal; signal-to-noise ratio coefficient evaluating means for evaluating 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 according to any one of claims 1 to 4, further comprising: 6. The signal-to-noise ratio coefficient measuring unit, wherein an optical signal having a bit rate f0 (bit / s) and a repetition frequency f1 (Hz) (f1 = (N / M) f0 +
a, N, and M are positive numbers, a is an offset frequency), and a cross-correlation optical signal having an optical frequency different from these two lights is obtained by 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 generating means for generating, an optical signal intensity distribution measuring means for measuring the intensity distribution of the optical signal by converting the correlated optical signal into an electric signal and then performing an electric signal processing, and the light within a certain average time 5. An optical signal monitoring system according to claim 1, further comprising signal-to-noise ratio coefficient evaluation means for evaluating a signal-to-noise ratio coefficient using an amplitude histogram obtained from a signal intensity distribution. . 7. The signal-to-noise ratio coefficient estimating means includes: a histogram estimating means for obtaining an amplitude histogram from an intensity distribution of the optical signal within a certain average time; and a signal intensity higher than a predetermined intensity threshold (A). An amplitude histogram distribution function g1 corresponding to “level 1” is estimated from the amplitude histogram part, and an amplitude histogram distribution function g0 corresponding to “level 0” from the amplitude histogram part lower than the separately determined intensity threshold (B).
Distribution function evaluation means for estimating the amplitude histogram distribution functions g1 and g
0, and the signal-to-noise ratio obtained as the ratio of the difference between the average intensity of each of “Level 1” and “Level 0” and the standard deviation of “Level 1” and “Level 0”. The optical signal monitoring system according to claim 5, further comprising: an optical signal quality evaluation unit that evaluates a coefficient. 8. 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 a higher amplitude intensity as the intensity threshold (A), The optical signal monitoring system according to claim 7, wherein one is set as the intensity threshold (B). 9. An optical transmitter in an optical network having a hierarchical structure including an optical layer, wherein an optical receiver and an optical amplification repeater connected in the middle of the optical receiver and a network failure has occurred from the optical receiver. A monitoring information control unit that receives monitoring information including the recognition information of the above, and a failure section identification unit that identifies an optical amplification relay section in which a network failure has occurred based on the monitoring information from the monitoring information control unit. Features an optical transmitter. 10. The optical transmitter according to claim 9, further comprising a path switching unit that switches a transmission path based on the monitoring information from the monitoring information control unit. 11. An optical receiver for an optical network having a hierarchical structure including an optical layer, wherein the optical splitter extracts a part of an optical signal transmitted through the optical network, and the optical signal extracted by the optical splitter. A signal-to-noise ratio coefficient measuring unit for measuring the signal-to-noise ratio coefficient of the system, 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 at the time of system introduction. And the value of the signal-to-noise ratio coefficient stored in the initial state storage unit when introducing the value of the signal-to-noise ratio coefficient obtained by measuring the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation. An optical signal monitoring unit having an optical signal quality evaluation unit for comparing with the optical signal quality evaluation unit, based on the optical signal quality evaluation of the optical signal quality evaluation unit, recognizes that a network failure has occurred, and A monitoring information control unit for sending monitoring information including the monitoring information to the optical transmitter. 12. An optical amplifier repeater for an optical network having a hierarchical structure including an optical layer, wherein the optical amplifier amplifies an optical signal transmitted through the optical network, and a part of the optical signal amplified by the optical amplifier. An optical splitter for extracting a signal to noise, a signal to noise ratio coefficient measuring unit for measuring a signal to noise ratio coefficient of the optical signal extracted by the optical splitter, An initial state storage unit that stores the signal-to-noise ratio coefficient measured by the measurement unit, and a signal-to-noise ratio coefficient value obtained by measuring the signal-to-noise ratio coefficient measurement unit at a certain time interval 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 initial state storage unit at the time of introduction, and based on the optical signal quality evaluation of the optical signal quality evaluation unit. It recognizes that the network failure, the optical amplifier repeater, characterized by comprising a monitoring information control unit sends the monitoring information including the recognition information to the optical transmitter. 13. An optical amplifying repeater of an optical network having a hierarchical structure including an optical layer, wherein the optical splitter extracts a part of an optical signal transmitted through the optical network, and the light extracted by the optical splitter. A signal-to-noise ratio coefficient measuring unit for measuring a signal-to-noise ratio coefficient of a signal, and an initial state storage 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 at the time of system introduction. Unit, the value of the signal-to-noise ratio coefficient obtained by measuring the signal-to-noise-ratio coefficient measured by the signal-to-noise ratio coefficient measurement unit at regular time intervals during system operation, An optical signal monitoring unit having an optical signal quality evaluation unit for comparing the value with a value; and recognizing that a network failure has occurred based on the optical signal quality evaluation of the optical signal quality evaluation unit, and A monitoring information control unit for sending monitoring information including information to the optical transmitter.