JP4728990B2 - Optical line monitoring method, optical line monitoring system, optical line monitoring device and program thereof - Google Patents

Description

  The present invention relates to a technique for monitoring an optical communication line, particularly an optical line of a high-density wavelength division multiplexing optical transmission system.

  There are roughly two known methods for monitoring a transmission medium (hereinafter referred to as an optical line) of an optical transmission system. One is a method of measuring the loss distribution of the optical line using an optical pulse tester, and the other is a method of measuring the loss of the optical line in general using a light source and an optical power meter, and from the result, It is to judge pass / fail.

  In any method, in order to perform an in-service test, a monitoring wavelength (light source) different from the communication wavelength is prepared, and a large number of optical filters are arranged in the entire section of the optical line so that the service signal and the monitoring signal It is necessary to take care not to deteriorate the mutual quality. In other words, it is necessary to install an optical filter for blocking the monitoring light at the transmission / reception end of the transmission device, and an optical filter for blocking the communication light on the optical pulse tester side and the optical power meter side. There is a problem that an increase is inevitable. In addition, the second method cannot identify an abnormal position such as a bend in the optical line, so that there is a problem that the monitoring accuracy of the optical fiber is lacking.

Furthermore, in recent high-density wavelength division multiplexing optical transmission systems, the power transmitted through one optical fiber reaches 1 W, and if a gap is generated between the fibers due to aging degradation of the optical filter, a fiber fuse may be caused. Yes (see Non-Patent Document 1). In particular, care is required in a filter of a type in which a groove is embedded in an optical fiber such as a dielectric multilayer filter. Under such circumstances, it is impossible to install an optical filter, and it is necessary to perform in-service monitoring itself.
IEICE Transactions Volume: J86-C, p. 3, 252-261 “Study of Fiber Fuse Generation Mechanism in Single Mode Optical Fiber”

As described above, in the existing optical line monitoring method, it is necessary to provide an optical filter having a required optical characteristic and a monitoring light source for implementation in service, which increases the cost of monitoring equipment. In addition, in-service monitoring is not performed in high-power transmission systems due to the problem of equipment reliability.
The present invention has been made in view of the above circumstances, and an object thereof is an optical line monitoring method, an optical line monitoring system, and an optical line monitoring capable of monitoring an optical line of a wavelength division multiplexing optical transmission system with high accuracy in service. The object is to provide a device and its program at low cost.

  In order to achieve the above object, according to one aspect of the present invention, in an optical line monitoring method for identifying an occurrence point of an abnormal loss in an optical line that transmits wavelength-division multiplexed light in which a plurality of wavelength lights are multiplexed, The return light power measurement value SA is obtained by measuring, for each wavelength, the return light power of the wavelength light included in the incident wavelength multiplexed light at the transmission end of the optical line in a state without the abnormal loss. A normal-time measurement step, an abnormal-time measurement step of measuring the return light power at the transmitting end of the wavelength light in the abnormal loss state for each wavelength, and obtaining the return light power measurement value SB, and A step of measuring the transmission power Io at a wavelength signal transmission end for each wavelength; and when the optical line is divided into sections of the number of wavelength lights, at the transmission end obtained individually for each section. A calculation step for calculating the total sum S ′ over the total section of the return optical power for each wavelength, a measurement value SB for each wavelength of the return optical power measured in the abnormality measurement step, and a calculation value calculated in the calculation step An optical line monitoring method is provided, comprising: a specifying step of specifying the magnitude of the abnormal loss and the occurrence location in a section where the difference from the sum S ′ for each wavelength is minimum.

  In particular, in the calculation step, the return light generated in the section from the transmitting end to the section adjacent to the section including the location where the abnormal loss is generated is caused by wavelength multiplexed light that is not attenuated by the abnormal loss, and is attenuated by the abnormal loss. Assuming that the return to the transmission end is not received, the return light generated in the section from the occurrence location of the abnormal loss to the reception end of the optical line including the occurrence location of the abnormal loss was attenuated by the abnormal loss. It is assumed that the optical loss is caused by wavelength-division multiplexed light and is attenuated by the abnormal loss, and returns to the transmitting end. An abnormal loss factor A that is a loss factor of optical power based on the abnormality and a loss that is known from the characteristics of the optical line. Based on the coefficient N, the backscattering coefficient R, the transmission power Io, and the measured values SA and SB, the return light beam for each wavelength at the transmission end. Processing is performed to calculate separately over S 'for each of the sections. Note that the assumption in this calculation step is not an artificial agreement, but is a premise necessary for calculation processing using hardware.

  By taking such measures, the transmission power and return light power of each wavelength light included in the wavelength division multiplexed light are measured for each wavelength, and the magnitude and occurrence location of the abnormal loss are determined by arithmetic processing using each value. It becomes possible to specify. Since this method can be implemented even with data transmission light in which each wavelength light is modulated, it is possible to accurately detect the magnitude of the abnormal loss and the location of occurrence thereof using this data transmission light. This can be expected to reduce the cost of monitoring equipment for the transmission system and improve the reliability of the system.

  According to the present invention, an optical line monitoring method, an optical line monitoring system, an optical line monitoring device, and a program thereof capable of monitoring an optical line of a wavelength division multiplexing optical transmission system with high accuracy in service are provided at low cost. can do.

  FIG. 1 is a diagram showing an embodiment of an optical line monitoring system according to the present invention. This system includes a plurality of transmission units 1-1 to 1-n that transmit transmission lights having different wavelengths. The transmission lights transmitted from the transmission units 1-1 to 1 -n with wavelengths λ 1 to λn are wavelength multiplexed by the wavelength multiplexing unit 2, and the generated wavelength multiplexed light 11 is incident on one optical fiber 9. . The wavelength multiplexed light 11 reaches the wavelength demultiplexing unit 2 ′ through the optical fiber 9 and is separated into each wavelength light λ1 to λn. These wavelength lights λ1 to λn are respectively incident on the receiving units 10-1 to 10-n and subjected to reception processing such as data reproduction.

  On the transmission end side of the optical fiber 9, a wavelength-independent optical coupler 3 having a signal light power measurement port 4 and a backscattered light power measurement port 5 is provided. Both the signal light power measurement port 4 and the backscattered light power measurement port 5 are connected to an optical power meter 8 via an optical port selection switch 6 and a wavelength selection filter 7. The optical power meter 8 measures the transmission power of each wavelength light in the wavelength multiplexed light 11 and the reception power of the return light 12 generated by backscattering of each wavelength light for each wavelength. This measurement data is notified to the monitoring apparatus 100 via the communication line L.

  FIG. 2 is a functional block diagram showing the monitoring device 100 of FIG. The monitoring device 100 is realized as a computer having a CPU and a memory. The monitoring apparatus 100 is connected to the communication line L (FIG. 1) via the interface unit (I / F) 21 and acquires measurement data obtained by the optical power meter 8. These data are stored in a storage unit 24 such as an HDD (hard disk drive). In addition, the monitoring apparatus 100 includes a display unit 22 for displaying various data and an input / output unit 23 as a user interface.

The monitoring device 100 further includes a CPU 25 and a program memory 26. Among these, the program memory 26 stores a calculation processing program 26a and a specific processing program 26b in which instructions necessary for processing functions according to this embodiment are described. The calculation processing program 26a and the specific processing program 26b can be recorded on a recording medium such as a CD-ROM or downloaded via a communication line.
The CPU 25 reads each program from the program 26 and performs arithmetic processing by hardware, and includes a calculation processing unit 25a and a specific processing unit 25b as its processing functions.

  The calculation processing unit 25a divides the optical fiber 9 line into sections of the number of wavelength lights, and calculates the sum S ′ over the total section of the return light power in the transmission units 1-1 to 1-n obtained individually for each section. Calculate for each wavelength. The specific processing unit 25b compares the measured value S of the return optical power acquired by the interface unit 21 with the sum S ′ calculated by the calculation processing unit 25a, and determines a section where the difference between the two is minimum in the optical fiber 9. Identifies the magnitude and location of abnormal losses. Hereinafter, this process will be described in detail.

In the processing by the calculation processing unit 25a, the return light 12 generated in the section from the transmission end of the wavelength multiplexed light 11 to the location where the abnormal loss occurs is generated from the wavelength multiplexed light 11 that has arrived without being attenuated by the abnormal loss, and returns In this case, it is assumed that the signal returns to the transmitting end without being attenuated by the abnormal loss. In addition, the return light 12 generated in the section from the location where the abnormal loss occurs to the receiving end (including the location where the abnormal loss occurs) is generated from the wavelength multiplexed light 11 that has arrived after being attenuated by the abnormal loss. It is assumed that the signal returns to the transmitting end after being attenuated by the abnormal loss.
Acquired or calculated in the course of processing, transmission power Io for each wavelength (.lambda.i), values such as the return light power S (λ i) and the calculation value S '(λ i) is stored in the storage unit 24. Next, the measurement process in the above configuration will be described.

FIG. 3 is a flowchart showing a procedure for estimating the magnitude and location of abnormal loss in the system of FIG. In the following, the optical fiber 9 is considered by dividing it into n (n is the number of wavelength lights) small sections. The length of each small section is assumed to be equal, and therefore the length Δx of each small section is L / n where L is the length of the optical fiber. The position of each small section is expressed as xk using the index k to distinguish each other. Specifying the occurrence location of the abnormal section is equivalent to specifying the index k .

First, the received light power S (λ i) of the return light 12 with no abnormal loss in the optical fiber 9 is obtained (step S1). A part of the return light 12 in FIG. 1 is guided to the backscattered light power measurement port 5 via the wavelength-independent optical coupler 3, passes through the optical port selection switch 6, and then enters the wavelength selection filter 7. . The wavelength selection filter 7 selects the return light 12 for each wavelength light λi (i: 1 to n) and makes one wavelength light incident on the optical power meter 8. The optical power meter 8 measures the reception power of each wavelength light λi and notifies the monitoring device 100 of the value. The monitoring device 100 divides the received power of each wavelength light λi by the transmittance from the backscattered light power measurement port 5 to the wavelength filter 7, and determines the received light power S (λ i) for each communication wavelength λi of the return light 12. Ask. As a result, the return light power SA (λ i) in a normal state in which the optical fiber 9 is not bent, twisted, or poorly connected is initially measured.

When the optical fiber 9 is bent, twisted, or poorly connected, the return light power SA (λ i) changes due to the abnormal loss. The monitoring apparatus 100 monitors the notified data every moment, and when the occurrence of abnormal loss is detected (step S2), the return light power SB (λ i) in that state is calculated for each wavelength (step S3). ).

  Next, the monitoring apparatus 100 obtains the transmission power Io (λi) of each wavelength light of the wavelength multiplexed light 11 (step S4). That is, in FIG. 1, a part of the wavelength multiplexed light 11 is guided to the signal light power measurement port 4 through the wavelength-independent optical coupler 3, passes through the optical port selection switch 6, and then enters the wavelength selection filter 7. The The wavelength selection filter 7 selects the wavelength multiplexed light 11 for each wavelength light λi and makes one wavelength light incident on the optical power meter 8. The optical power meter 8 measures the reception power of each wavelength light λi and notifies the monitoring device 100 of the value. The monitoring device 100 divides the transmission power of each wavelength light λi by the transmittance from the backscattered light power measurement port 5 to the wavelength filter 7, and determines the transmission power Io (λi) for each communication wavelength λi of the wavelength multiplexed light 11. Ask.

Then the monitoring device 100, the estimated of the generated position xk abnormal losses, the estimated abnormal loss coefficient A (xk) (step S5). The unit of the abnormal loss coefficient A (xk ) is [Np / m], and the accuracy depends on the length Δ x ( = L / n) [m ] of the small section for calculating the abnormal loss. The procedure will be described in detail below.

FIG. 4 is a schematic diagram showing attenuation curves of transmitted light and backscattered light in the optical line. 4, reference numeral 13 denotes an attenuation curve P (λi , xk ) of the wavelength multiplexed light 11, 14 denotes an abnormal loss coefficient A (xk ) due to bending of the optical fiber, and 15 denotes a Rayleigh backscattering coefficient R (λi , xk ). and 16 denotes the total power S of the return light resulting from Dear location xk [m] (λi, xk ).

Intensity P (.lambda.i, xj) when the wavelength of the wavelength .lambda.i output intensity Io (.lambda.i) passes through the position xj of the optical fiber 9 is given by the following equation (3). The alpha (.lambda.i, xk) Equation (3) is the loss coefficient at position xk.

Total intensity of length backscattered light returning from the optical fiber 9 L S (λ i), the intensity P (.lambda.i, xj) passing Dear location xj obtained as the sum of the intensity of return light resulting from wavelength light. This is expressed by the following equation (4). R (.lambda.i, xj) of the formula (4) is a backscatter coefficient of wavelength .lambda.i in position xj.

In Expression (4), j and k are natural numbers up to 1, 2,..., N, and n corresponds to the number of wavelength lights. The loss coefficient α (λi , x k) is caused by the following factors (A) to (D). That is, (A) Rayleigh scattering loss, (B) loss due to fiber non-uniformity, (C) absorption loss of impurities and fiber materials, (D) fiber bending and twisting, poor connection, and the like.

In general, the factors (A) to (C) are unavoidable in principle due to the material structure of the optical fiber for 1.55 μm band light propagating through an SM (Single Mode) fiber. That factor (A) ~ (C) is shown a is wavelength dependent and unique loss optical fiber, becomes substantially uniform value in the fiber throughout the change per position x k can be ignored. Therefore, the loss factor due to these factors (A) to (C) is a function of only the wavelength λi, and is assumed to be the loss factor N (λi).
In contrast factor (D), since it is due to the shape is not a normal optical fiber, the loss inherent in position x k [m], the function of the abnormal loss factor, position x k [m] A (x k). Note that the wavelength dependence of an abnormal optical fiber is extremely small.

More loss coefficient since alpha (.lambda.i, x k) is, the unique loss factor in the optical fiber depends on the wavelength λ N (λi), the position x k to depend abnormal loss coefficient A (x k) It can be separated and expressed as the following formula (5).

Substituting equation (5) into equation (6), and separated into a loss factor depends on the wavelength N (.lambda.i) position x k to depend abnormal loss coefficient A and (x k) the next n-dimensional simultaneous equations ( 6) is obtained . Equation (6) corresponds to the return light intensity S (λ i) for each wavelength.

Equation (6), to obtain the position x k dependent abnormally loss coefficient A (x k), and separated in the other loss factor N and (.lambda.i), the following matrix equation (7).

  The backscattering coefficient R (λi) is given by the following equation (8) because the Rayleigh scattering, the relative refractive index difference, and the core refractive index specific to the optical fiber 9 are clear.

Equation (7) transmission power Io for each wavelength of the wavelength-multiplexed light 11 in (.lambda.i), received power S (lambda i) of the return beam 12 for each wavelength is known amount both obtained from the measured values. Further, the loss coefficient N (λi) and the backscattering coefficient R (λi) specific to the optical fiber 7 are also known. These by obtaining the algebraic solution of the simultaneous equations are substituted into equation (7), it is possible to calculate the position x k for each of the abnormal loss coefficient A (x k) [Np / m].

This abnormal loss coefficient A (x k) can be calculated by two methods. One is a method of obtaining a matrix product by multiplying the inverse matrix of the matrix depending on the wavelength λi on the right side of Equation (7) from the left side of both sides of Equation (7).

The other is a method of utilizing the fact that a matrix which depends on the right side of the position xk of formula (7) is exponential is clear. That is, to calculate the exponential portion (exp (-A (xk) Δ x)) ( the S ') abnormal loss position location xk and abnormal loss coefficient A (xk) and return light power as a parameter in, its value is closer to the measured return light power SB (λ i) in step S3 in FIG. 3, an abnormal loss position location xk and abnormal loss coefficient a (xk) and a method for determining the.

In the above calculations, the former (the method of using the matrix product), the abnormal loss occurrence location even if a plurality, it is possible to determine its position xk and abnormal loss coefficient A (xk) uniquely. The latter method (asymptotic method) assumes a section of xk (where k = 1, 2,..., N) obtained by dividing the optical fiber 9 to be monitored into n equal parts, and an abnormal loss occurs only in one section. Based on the assumption that Next, an example of measurement performed using the system of FIG. 1 will be described.

  FIG. 5 is a diagram illustrating an example of a system for monitoring an optical line using the monitoring device 100 of FIG. In FIG. 5, the wavelength tunable light source 17 and the broadband light source 18 are used in the transmitter, and these output lights are multiplexed by the wavelength multiplexing coupler 3 'and transmitted to the optical fiber 9'. The optical fiber 9 ′ is terminated by a terminator 19. It is assumed that the optical fiber 9 'has four optical fiber bobbins fused together, and each optical fiber bobbin is sequentially at a distance of 5km, 5km, 15km, and 14km from the wavelength multiplexing coupler 3'. Reference numeral 20 denotes a bent portion at a point of 5 km from the wavelength multiplexing coupler 3 'side, and reference numeral 21 denotes a bent portion at a point of 25 km.

The bending portions 20 and 21 generated bending loss of about 6.5 dB (3.84 × 10 ⁻³ Np / m). However, in the example of FIG. 5, instead of giving both losses in one measurement, the bending loss is given one by one and the measurement is performed twice. Assuming such a simulation system, 46 continuous light beams arranged at intervals of about 0.8 nm in the L band (wavelengths 1550 to 1585 nm) are sequentially transmitted from the wavelength variable light source 17. Furthermore, in order to simulate an actual wavelength division multiplexing optical transmission system, light of 1520 to 1600 nm is generated from the broadband light source 18, multiplexed by the wavelength multiplexing coupler 3 ′, and transmitted to the optical fiber 9 ′. Table 1 shows the experimental results obtained using such a simulated line.

In Table 1, S (5 km) is the return optical power S (λ i) when there is a bending loss at the 5 km point 20, and S (25 km) is the return optical power S (λ i) when there is a bending loss at the 25 km point 21. It is.

Based on the result of Table 1 and Expression (8), the matrix element of Expression (7) becomes a known amount. By utilizing this, abnormal loss factor A a (xk) as a fitting parameter for unknown ^{e -2A (xk) Δx} which depends on the longitudinal Direction xk, which is measured values return light power S and (lambda i) as the difference between the calculated value S '(λ i) is minimized, and determined the position xk and abnormal loss coefficient a (xk) using a least square approximation. Note that although the fitting parameters a is abnormal loss coefficient A (xk) is a 0.5dB intervals range 0～10DB, the line length L = 39km for the location xk, the number of communication wavelength as 46, sub-sections Development was performed at intervals of length Δx (39 km / 46).

Result of the calculation, when there is a bending loss to 5km point 20, the point of 4239.1m 7.0dB / Δ x (= 1.9 × 10 -3 Np / Δ x) abnormal loss coefficient A (xk) The bending loss was determined. If there is a bend loss in 25km point 21, the point of 25,434.8m 7.0dB / Δ x bending ^{(= 1.9 × 10 -3 Np /} Δ x) abnormal loss coefficient A (xk) Loss was sought.

  FIG. 7 and FIG. 8 show the result of comparison between the value calculated in this embodiment and the loss distribution waveform of the simulated line measured by OTDR (Optical Time Domain Reflectmetry) with a wavelength of 1580 nm. The values plotted at a plurality of points are the values calculated in this embodiment, and the solid line waveform is due to OTDR.

Figure 6 is a <If there is a bending loss to 5km point 20>, the difference between the abnormal loss position by position xk and OTDR abnormal loss occurrence position is indicated as 721M. Figure 7 is a <If there is a bending loss to 25km point 21>, the difference between the abnormal loss position by position xk and OTDR abnormal loss occurrence position is indicated as 845M. From the above, it was possible to detect that an abnormal loss of about 7 dB occurred with accuracy within 1 km in both the simulated line having a bend at 5 km and the simulated line having a bend at 25 km.

FIG. 8 is a diagram showing the wavelength dependence of the abnormal loss coefficient A (xk ) accompanying the difference in bending strength. In the experiment of FIG. 5, the abnormal loss factor A (xk ) is 1.9 × 10 ⁻³ (Np / Δx), and when compared with the broken line 25 of FIG. Can be estimated. The bending loss given to the simulated track used in the experiment was created with a mandrill having a radius of 5 mm. From the above, it was confirmed that the present embodiment is effective in estimating the magnitude of abnormal loss and its occurrence interval.

As described above, in this embodiment, the transmission power Io (λi) of each wavelength light multiplexed on the wavelength multiplexed light 11 and the normal return light power SA (λ i) of the optical fiber 9 to be monitored Then, the return light power SB (λ i) at the time of abnormality is measured. And from each measured value, calculates the equation (7) by abnormal loss position location xk and abnormal loss coefficient A (xk) and return light power S as a parameter ', the value is abnormal when the return light power SB (lambda i as approaches), so that determining the abnormal loss position location xk and abnormal loss coefficient a (xk).

  Since it did in this way, it becomes unnecessary to have the optical filter and monitoring light source which have a required optical characteristic like the existing technique. Furthermore, there is no need for light of a wavelength exclusively for testing. Therefore, there is an effect that the cost of the monitoring facility can be suppressed. Furthermore, since an optical signal for data transmission can be used as it is, an in-service test can be performed. That is, at the same time as reducing monitoring equipment costs, even in high-power transmission systems such as wavelength division multiplexing optical transmission systems, detect increases in optical line losses during service and estimate the magnitude of abnormal losses and their abnormal loss intervals. Will be able to. As a result, it is possible to reduce the cost of the monitoring equipment and promote the improvement of the reliability of the system. From these facts, it is possible to confirm the effectiveness of the optical line monitoring method, the optical line monitoring system, the optical line monitoring device and the program capable of monitoring the optical line of the wavelength division multiplexing optical transmission system with high accuracy in service. It was.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The figure which shows embodiment of the optical-line monitoring system concerning this invention. The functional block diagram of the monitoring apparatus 100 of FIG. The flowchart which shows the procedure which estimates the generation | occurrence | production location of the abnormal loss area in the system of FIG. The schematic diagram which shows the attenuation curve of the transmitted light and backscattered light in an optical line. The figure which shows the example of the system which monitors an optical line using the monitoring apparatus 100 of FIG. The figure which compares and shows the result obtained by embodiment of this invention, and the result obtained by OTDR when there exists a bending loss from the transmission point of the wavelength division multiplexed light 11 to 5 km point 20. FIG. The figure which compares and shows the result obtained by embodiment of this invention, and the result obtained by OTDR when there exists a bending loss from the transmission point of the wavelength division multiplexed light 11 to 25 km point 21. FIG. The figure which shows the wavelength dependence of the abnormal loss factor A (xk ) accompanying the difference in bending strength.

Explanation of symbols

  1-1 to 1-n: transmitting unit, 2 ... wavelength multiplexing unit, 2 '... wavelength demultiplexing unit, 3 ... wavelength-independent optical coupler, 4 ... signal light power measurement port, 5 ... backscattered light power measurement port , 6 optical port selection switch, 7 wavelength selection filter, 8 optical power meter, 9 optical fiber, 10-1 to 10-n receiving unit, 11 wavelength multiplexed light, 12 return light, 100 monitoring Device, L ... communication line, 17 ... wavelength variable light source, 18 ... broadband light source, 3 '... wavelength multiplexing coupler, 19 ... terminator, 9' ... optical fiber, 20, 21 ... bending portion

Claims (8)

In the optical line monitoring method for identifying the occurrence point of abnormal loss in the optical line that transmits the wavelength division multiplexed light in which a plurality of wavelength lights are multiplexed,
Measurement of the return light power by measuring the return light power at the transmission end of the optical line in the state without the abnormal loss of the wavelength light included in the wavelength multiplexed light incident on the optical line for each wavelength. A normal measurement step for obtaining a value SA;
An abnormal-time measurement step of measuring the return light power at the transmission end of the wavelength light in the abnormal loss state for each wavelength to obtain the measurement value SB of the return light power;
Measuring the transmission power Io at the transmission end of the wavelength light for each wavelength;
When dividing the optical line into sections of the number of wavelength light, a calculation step of calculating, for each wavelength, the sum S ′ over the total section of the return optical power at the transmitting end, which is obtained individually for each section;
The magnitude of the abnormal loss in the interval where the difference between the measured value SB of each wavelength of the return light power measured in the abnormal time measurement step and the total sum S ′ for each wavelength calculated in the calculation step is minimum. And a specifying step for specifying the occurrence location,
The calculating step includes:
The return light generated in the section from the transmission end to the section adjacent to the section including the occurrence location of the abnormal loss is generated from the wavelength multiplexed light that is not attenuated by the abnormal loss, and is not attenuated by the abnormal loss. Let ’s go back to the edge,
The return light generated in the section from the occurrence point of the abnormal loss to the receiving end of the optical line including the occurrence point of the abnormal loss is generated from the wavelength multiplexed light attenuated by the abnormal loss and is attenuated by the abnormal loss. And return to the sending end,
An abnormal loss coefficient A that is a loss coefficient of optical power based on the abnormal loss, a loss coefficient N and a backscattering coefficient R that are known from characteristics of the optical line, the transmission power Io, and the measured values SA and SB The optical line monitoring method is a step of individually calculating the return optical power S ′ for each wavelength at the transmitting end for each section based on the above. i is a natural number from 1 to the number n of the wavelength light, and each wavelength of the wavelength light is λi,
Let the length of the section be Δx,
The position of each section is expressed as xk, where k is a natural number from 1 to the number n of the wavelength lights ,
The transmit power Io, the sum S ', respectively Io the backscattering coefficient R, the loss factor N, and the abnormal loss factor A as a function of the .lambda.i before Symbol xk (λi), S' ( λ i) , R (λi), N (λi), and A (xk ),
The optical line monitoring method according to claim 1, wherein the calculating step is a step of calculating the sum S ′ using the following equation .

In the optical line monitoring system for identifying the occurrence point of the abnormal loss in the optical line that transmits the wavelength division multiplexed light in which a plurality of wavelength lights are multiplexed,
A transmission unit that makes the wavelength-multiplexed light incident on the optical line;
Measurement of the return light power by measuring the return light power at the transmission end of the optical line in the state without the abnormal loss of the wavelength light included in the wavelength multiplexed light incident on the optical line for each wavelength. A normal measurement unit for obtaining a value SA;
An abnormal-time measuring unit that measures the return light power at the transmission end of the wavelength light in the abnormal state for each wavelength and obtains the measurement value SB of the return light power;
A transmission power measuring unit that measures the transmission power Io at the transmission end of the wavelength light for each wavelength;
When the optical line is divided into sections of the number of wavelength light, a calculation processing unit that calculates the sum S ′ over the total section of the return light power at the transmission end, which is obtained individually for each section, for each wavelength;
The abnormal loss in a section in which the difference between the measured value SB of the return light power for each wavelength measured by the abnormal time measurement unit and the total sum S ′ for each wavelength calculated by the calculation processing unit is minimized. A specific processing unit for specifying the size and the occurrence location,
The calculation processing unit
The return light generated in the section from the transmission end to the section adjacent to the section including the occurrence location of the abnormal loss is generated from the wavelength multiplexed light that is not attenuated by the abnormal loss, and is not attenuated by the abnormal loss. Let ’s go back to the edge,
The return light generated in the section from the occurrence point of the abnormal loss to the receiving end of the optical line including the occurrence point of the abnormal loss is generated from the wavelength multiplexed light attenuated by the abnormal loss and is attenuated by the abnormal loss. And return to the sending end,
The return light generated in the section from the section having the abnormal loss to the receiving end of the optical line including the section having the abnormal loss is generated from the wavelength multiplexed light attenuated by the abnormal loss and is attenuated by the abnormal loss. And return to the transmitting end,
An abnormal loss coefficient A that is a loss coefficient of optical power based on the abnormal loss, a loss coefficient N and a backscattering coefficient R that are known from characteristics of the optical line, the transmission power Io, and the measured values SA and SB Based on the above, the return optical power S ′ for each wavelength at the transmitting end is calculated individually for each section. i is a natural number from 1 to the number n of the wavelength light, and each wavelength of the wavelength light is λi,
Let the length of the section be Δx,
The position of each section is expressed as xk, where k is a natural number from 1 to the number n of the wavelength lights ,
The transmit power Io, the sum S ', respectively Io the backscattering coefficient R, the loss factor N, and the abnormal loss factor A as a function of the .lambda.i before Symbol xk (λi), S' ( λ i) , R (λi), N (λi), and A (xk ),
The optical line monitoring system according to claim 3, wherein the calculation processing unit calculates the sum S ′ using the following equation .

In the optical line monitoring device for identifying the occurrence point of abnormal loss in the optical line that transmits the wavelength division multiplexed light in which a plurality of wavelength lights are multiplexed,
A measured value SA of the return light power at the transmission end of the wavelength light included in the wavelength-multiplexed light incident on the optical line without the abnormal loss, and the abnormal light state of the wavelength light A data acquisition unit for acquiring the measured value SB of the return light power at the transmission end and the transmission power Io at the transmission end of the wavelength light;
When the optical line is divided into sections of the number of wavelength light, a calculation processing unit that calculates the sum S ′ over the total section of the return light power at the transmission end, which is obtained individually for each section, for each wavelength;
The magnitude of the abnormal loss and the occurrence location in the section where the difference between the measured value SB of the return light power for each wavelength and the sum S ′ for each wavelength calculated in the calculation processing unit is minimized are specified. A specific processing unit,
The calculation processing unit
The return light generated in the section from the transmission end to the section adjacent to the section including the occurrence location of the abnormal loss is generated from the wavelength multiplexed light that is not attenuated by the abnormal loss, and is not attenuated by the abnormal loss. Let ’s go back to the edge,
The return light generated in the section from the occurrence point of the abnormal loss to the receiving end of the optical line including the occurrence point of the abnormal loss is generated from the wavelength multiplexed light attenuated by the abnormal loss and is attenuated by the abnormal loss. And return to the sending end,
An abnormal loss coefficient A that is a loss coefficient of optical power based on the abnormal loss, a loss coefficient N and a backscattering coefficient R that are known from characteristics of the optical line, the transmission power Io, and the measured values SA and SB Based on the above, the return optical power S ′ for each wavelength at the transmission end is calculated individually for each section, and the optical line monitoring apparatus. i is a natural number from 1 to the number n of the wavelength light, and each wavelength of the wavelength light is λi,
Let the length of the section be Δx,
The position of each section is expressed as xk, where k is a natural number from 1 to the number n of the wavelength lights ,
The transmit power Io, the sum S ', respectively Io the backscattering coefficient R, the loss factor N, and the abnormal loss factor A as a function of the .lambda.i before Symbol xk (λi), S' ( λ i) , R (λi), N (λi), and A (xk ),
The optical line monitoring apparatus according to claim 5, wherein the calculation processing unit calculates the sum S ′ using the following equation .

Transmission of an abnormal loss occurrence location in an optical line that transmits wavelength multiplexed light, in which a plurality of wavelength lights are multiplexed, in a state without the abnormal loss of the wavelength light included in the wavelength multiplexed light incident on the optical line The measurement value SA of the return light power at the end, the measurement value SB of the return light power at the transmission end in the state of the abnormal loss of the wavelength light, and the transmission power Io at the transmission end of the wavelength light are obtained. A program used for an optical line monitoring device that is specified using a computer including a data acquisition unit,
In the computer,
A command for executing a calculation process for calculating, for each wavelength, the sum S ′ over the total section of the return optical power at the transmitting end, which is obtained individually for each section when the optical line is divided into sections of the number of wavelength light. When,
The magnitude of the abnormal loss and the occurrence location in the section where the difference between the measured value SB of the return light power for each wavelength and the sum S ′ for each wavelength calculated in the calculation processing unit is minimized are specified. Including an instruction for executing a specific process,
The calculation process is as follows:
The return light generated in the section from the transmission end to the section adjacent to the section including the occurrence location of the abnormal loss is generated from the wavelength multiplexed light that is not attenuated by the abnormal loss, and is not attenuated by the abnormal loss. Let ’s go back to the edge,
The return light generated in the section from the occurrence point of the abnormal loss to the receiving end of the optical line including the occurrence point of the abnormal loss is generated from the wavelength multiplexed light attenuated by the abnormal loss and is attenuated by the abnormal loss. And return to the sending end,
An abnormal loss coefficient A that is a loss coefficient of optical power based on the abnormal loss, a loss coefficient N and a backscattering coefficient R that are known from characteristics of the optical line, the transmission power Io, and the measured values SA and SB And a return light power S ′ for each wavelength at the transmitting end is calculated individually for each section. i is a natural number from 1 to the number n of the wavelength light, and each wavelength of the wavelength light is λi,
Let the length of the section be Δx,
The position of each section is expressed as xk, where k is a natural number from 1 to the number n of the wavelength lights ,
The transmit power Io, the sum S ', respectively Io the backscattering coefficient R, the loss factor N, and the abnormal loss factor A as a function of the .lambda.i before Symbol xk (λi), S' ( λ i) , R (λi), N (λi), and A (xk ),
The program according to claim 7, wherein the calculation process is a process of calculating the sum S ′ using the following equation .

Images