JP2001053655A - Monitoring system for wavelength multiplex optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect fault occurrence by monitoring an optical transmission line of a wavelength multiplex optical transmission system with simple constitution without using any light signal for monitoring. SOLUTION: Light signals with different wavelengths λ1 and λ2 from LDs(laser diode) 11 and 12 at a transmission end 10 are multiplexed and transmitted as a multiplex light signal λ1+λ2 to a reception end 30 and PDs(photodiode) 17 and 18 for line monitoring at the transmission end 10 detect variations of the light signals reflected by FBGs 39 and 30 at the reception end 30 to detect a fault occurring to lines 23, 37, and 38.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a monitoring system for a wavelength division multiplexing optical transmission system for monitoring a disconnection in a plurality of optical transmission lines using an optical filter.

[0002]

2. Description of the Related Art Conventionally, in this type of monitoring system, as shown in FIG. 4, for example, a transmitting end 10 such as a center station side and a receiving end 30 such as a subscriber station side are provided with a down line 21 made of an optical fiber. And the upstream line 22, respectively, and separates downstream and upstream signals into separate lines 21, 21.
2 was used for transmission.

That is, in the downstream main signal transmission system,
Laser diodes (hereinafter, referred to as “LD”) 11 and 12 as transmitters are installed at the transmitting end 10.
The optical signals (main signals) of the desired wavelengths λ1 and λ2 output from D11 and D12 are multiplexed by the optical coupler 13 and transmitted to the downlink 21 as a multiplexed optical signal λ1 + λ2. The multiplexed optical signal λ1 + λ2 is distributed by the optical coupler 31 of the receiving end 30, and the wavelengths λ1 and λ2 are selected by band-pass filters (hereinafter referred to as “BPF”) 59 and 60, respectively. , "PD") 32, 33.

In the upstream monitoring signal transmission system, the receiving end 30 receives the multiplexed optical signal λ1 + from the LDs 34 and 35.
Optical signals of wavelengths λ3 and λ4 indicating the state of λ2 (monitoring signals)
Are multiplexed by the optical coupler 36 and transmitted to the upstream line 22 as a multiplexed optical signal λ3 + λ4. The multiplexed optical signal λ3 + λ4
Are distributed by the optical coupler 62 and are monitored by the line monitoring PDs 17 and 18 of the transmitting end 10 via the BPFs 15 and 16 that pass optical signals of wavelengths λ3 and λ4, respectively. As described above, by monitoring the state of the optical signals of the wavelengths λ1 and λ2 using the optical signals of the wavelengths λ3 and λ4, the fault occurrence section in the downstream main signal transmission system has been detected.
Further, in the monitoring system of the wavelength division multiplexing optical transmission system, when a failure such as disconnection occurs, the multiplexed optical signal λ3 + λ4 does not return to the transmitting end 10, so that the transmitting end 10 monitors the presence or absence of an upstream optical signal. It was possible to monitor the up line.

[0005]

However, in the wavelength multiplexing optical transmission system monitoring system, the upstream monitoring signal transmission system needs to be provided completely separately from the downstream main signal transmission system in order to monitor the occurrence of a fault. It is necessary to provide LDs 34 and 35 whose wavelengths are managed at the receiving end 30 to transmit information to the transmitting end 10. Therefore, the above system has a problem that an optical transmission line used only for monitoring and an optical signal for monitoring are separately required.

The present invention has been made in view of the above problems, and has a simple structure without using an optical signal for monitoring.
An object of the present invention is to provide a monitoring system for a wavelength division multiplexing optical transmission system, which can monitor an optical transmission line of the wavelength division multiplexing optical transmission system and detect occurrence of a failure.

[0007]

According to the present invention, there is provided a first optical transmission line for multiplexing optical signals having a plurality of different wavelengths and transmitting a multiplexed optical signal. A distributor for distributing the multiplexed optical signal transmitted by the optical transmission line, a plurality of second optical transmission lines for respectively transmitting the multiplexed optical signal distributed by the distributor, and the plurality of second optical transmission lines An optical filter that transmits an optical signal of a desired wavelength and reflects optical signals of other wavelengths toward the first optical transmission line for each of the multiplexed optical signals transmitted by the optical filter; A receiver for receiving a signal, and a line monitor for receiving an optical signal reflected by the optical filter and returned to the first optical transmission line, wherein the level of the optical signal received by the line monitor changes. The first,
A monitoring system for a wavelength division multiplexing optical transmission system for detecting occurrence of a failure in a second optical transmission line is provided.

That is, in the monitoring system of the wavelength division multiplexing optical transmission system, since the level change of the optical signal reflected by the optical filter is detected by the line monitor, the disconnection of the optical transmission line is detected. , Without using a monitoring optical signal at the signal receiving end,
It is possible to monitor the second optical transmission line and detect occurrence of a failure.

According to the second aspect, the line monitor detects the level of the optical signal of each wavelength, and in addition to the above-described effects, can also specify the broken section.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A monitoring system for a wavelength division multiplexing optical transmission system according to the present invention will be described with reference to FIGS. In addition,
In the following figures, the same components as those in FIG.
For convenience of description, the same reference numerals are added, and the description is omitted. FIG. 1 is a diagram showing a schematic configuration of a wavelength multiplexing optical transmission system monitoring system according to the present invention. In the monitoring system shown in FIG. 1, a transmitting end 10 and a receiving end 30 are connected via a line 23 which constitutes a first optical transmission line of the present invention and can transmit optical signals in both directions of up and down. ing. An optical coupler 24 is connected to the line 23 on the transmission end 10 side, and the optical coupler 24 is also connected to the optical coupler 14.
0 through which the multiplexed optical signal λ1 + λ2 is passed.
And the multiplexed optical signal λ1 from the receiving end 30.
+ Λ2 is distributed and supplied to the line monitoring PDs 17 and 18.

A fiber Bragg grating (hereinafter referred to as "FBG") for reflecting optical signals of predetermined wavelengths λ2 and λ1 is provided on lines 25 and 26 connecting between the optical coupler 14 and the line monitoring PDs 17 and 18 on the transmission end 10 side. 2)
7 and 28, respectively, and a second embodiment of the present invention for connecting between an optical coupler 31 constituting an optical distributor of the present invention and PDs 32 and 33 on a receiving end 30 side constituting a receiver of the present invention. On the lines 37 and 38 constituting the optical transmission lines, FBGs 39 and 40 which constitute an optical filter of the present invention and reflect optical signals of predetermined wavelengths λ2 and λ1 are provided, respectively.

Therefore, the FB is added to the PD 32 of the receiving end 30.
The optical signal of wavelength λ1 that has passed through G39
Optical signals of wavelength λ2 that have passed through the FBG 40 are input. The optical signals reflected by the FBGs 39 and 40 are multiplexed by the optical coupler 31 and are multiplexed optical signals λ1 + λ2.
Is supplied to the transmitting end 10 via the optical couplers 24 and 14 and the lines 25 and 26. The line monitoring PD 17 of the transmitting end 10 has the wavelength λ1 passing through the FBG 27.
The optical signal of wavelength λ2 that has passed through the FBG 28 is input to the line monitoring PD 18.

The line monitoring PD 17 detects a level change of the optical signal of the wavelength λ1, and the line monitoring PD 18 detects a level change of the optical signal of the wavelength λ2, and the line is detected based on the level change of the optical signal. It is possible to detect which of 23, 37 and 38 has a fault.

[0014]

[Table 1]

If, for example, a disconnection is described as an example of the failure, at the break point of the optical fiber, the optical signal is reflected with a loss of about 12 dB. In the FBGs 39 and 40, the optical signal λ
2 and λ1 are totally reflected. In each optical coupler, the level of the optical signal is reduced by 3 dB. Therefore,
As shown in Table 1 above, when the levels of the optical signals detected by the PDs 17 and 18 are both higher than the normal level where no failure occurs, the disconnection state of the line 23 can be detected.
When the PD 17 is higher than the normal level and the PD 18 is lower than the normal level, the disconnection state of the line 37 can be detected. When the PD 17 is lower than the normal level and the PD 18 is higher than the normal level, the disconnection state of the line 38 can be detected.

The optical signals reflected by the FBGs 27 and 28 of the transmitting end 10 return to the receiving end 30 again. However, the optical coupler attenuates the passing light by about 3 dB, so that the optical signal reflected from the transmitting end 10 is attenuated again by passing through the plurality of optical couplers 14, 24, and 31. The effect on the return light is reduced. The optical signals reflected by the FBGs 39 and 40 of the receiving end 10 also return to the transmitting end 10 again. In this case as well, a plurality of optical couplers 31, 24 and
At 13, the effect on the return light at the transmitting end 10 is reduced.

As described above, in the monitoring system of the wavelength division multiplexing optical transmission system, since the level changes of the optical signals reflected by the FBGs 39 and 40 are detected by the line monitoring PDs 17 and 18, the signal receiving ends are used for monitoring. The length of the optical transmission line used only can be reduced, and the line of the wavelength division multiplexing optical transmission system can be monitored and a disconnection can be detected without using an optical signal for monitoring.

Further, the line monitors PD17 and PD18 detect the levels of the optical signals of the wavelengths λ1 and λ2, respectively, so that the broken line can be specified. FIG. 2 is a diagram showing the configuration of an embodiment of a monitoring system for a wavelength division multiplexing optical transmission system according to the present invention. In FIG. 2, the optical couplers 13 and
The isolators 54 and 55 are connected between the optical coupler 14 and the optical coupler 24, respectively.
40, a Fabry-Bello type optical filter combined with an FBG so as to receive only a predetermined wavelength is used.

The isolator 54 has a configuration in which the transmission loss is small with respect to the optical signal from the transmitting end 10 and the transmission loss is large with respect to the optical signal from the receiving end 30. By passing the optical signal λ1 + λ2 and absorbing the multiplexed optical signal λ1 + λ2 reflected from the receiving end 30, the effect of the return light is efficiently prevented. Also,
The isolator 55 has a configuration in which transmission loss is small with respect to the optical signal from the reception end 30 and transmission loss is large with respect to the optical signal from the transmission end 10, and passes through the multiplexed optical signal λ1 + λ2 from the reception end 30. By absorbing the multiplexed optical signal λ1 + λ2 reflected from the transmitting end 10, the effect of the return light is efficiently prevented.

In this wavelength multiplex transmission monitoring system,
The two types of signals output from the signal generators 50 and 51 of the transmitting end 10 are respectively subjected to wavelength λ by E / O converters 52 and 53.
1 and λ2, and are multiplexed via the optical coupler 13.
Is transmitted to the common line 23 via the. Then, the multiplexed optical signal is split into two lines 37 and 38 by an optical coupler 31 provided on the line 23 and transmitted. Each of the branched multiplexed optical signals is converted into a Bragg wavelength λ at a receiving end 30 by using Fabry-Bello type optical filters 39 and 40.
Only the optical signals of 1 and λ2 pass through, and are received by the signal receiving units 43 and 44 via the O / E converters 41 and 42, respectively.

In the multiplexed optical signal, the optical filter 3
The optical signals that have not passed through the transmission terminals 9 and 40, that is, the optical signals having wavelengths λ2 and λ1 other than the predetermined wavelengths λ1 and λ2,
It is reflected back in the 0 direction and returned. In the O / E converters 56 and 57 of the transmitting end 10, the optical coupler 24, the isolator 5
5. The optical signals of the wavelengths λ1 and λ2 reflected via the optical coupler 14 and the FBGs 27 and 28 are taken in. O /
The E converters 56 and 57 output the level of the optical signal to the faulty section detection unit 58. Fault occurrence section detection unit 58
By analyzing the level change patterns of these optical signals, it is possible to identify the location where a failure has occurred. Note that the faulty section detector 58 not only determines the faulty section but also the E / O converters 52 and 53 of the transmitting end 10.
By taking in an alarm from the device, the state of each element or line can be comprehensively determined.

In this embodiment, since a Fabry-Bello type optical filter is used, an optical signal having only a predetermined wavelength can be received at the receiving end. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the optical filters 27 and 28 of the transmitting end 10 need only pass light of a predetermined wavelength and reflect light of other wavelengths. For example, an optical filter of a resin multilayer film can be used.

Further, a circulator can be used instead of the optical coupler 24 of the transmitting end 10 to reduce the optical loss of the line 23. In this case, the optical circulator converts the light input from the optical coupler 13 into the optical coupler 3.
1 is connected to the line 23 so that the light input from the optical coupler 31 is output to the optical coupler 14. Further, when it is only necessary to separate the faulty section between the line 23 and the other lines, or to detect only the presence or absence of a fault, the optical signal split by the optical coupler 24 as shown in FIG. Without branching, a single O /
The signal may be received by the E converter 61. In this case, the O / E converter 61 receives a high-level optical signal that is not attenuated by the optical coupler 31 only when a failure such as a disconnection occurs in the line 23. Can be detected.

[0024]

As described above, according to the present invention, the occurrence of a fault in the optical transmission line is detected by detecting the level change of the optical signal reflected by the optical filter at the receiving end by the line monitor at the transmitting end. Therefore, it is possible to monitor each optical transmission line of the wavelength division multiplexing optical transmission system and detect a disconnection with a simple configuration without using an optical signal for monitoring.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a wavelength multiplexing optical transmission system monitoring system according to the present invention.

FIG. 2 is a diagram illustrating an example of a configuration of a wavelength multiplexing optical transmission system monitoring system according to the present invention.

FIG. 3 is a diagram showing another example of the configuration of the wavelength multiplexing optical transmission system monitoring system according to the present invention.

FIG. 4 is a diagram showing a configuration of a conventional monitoring system for a wavelength division multiplexing optical transmission system.

[Explanation of symbols]

10 Transmitting end 11, 12, 34, 35 LD 13, 14, 24, 31, 36, 62 Optical coupler 15, 16, 59, 60 BPF 17, 18 Line monitoring PD 21-23, 25, 26, 37, 38 Line (optical transmission line) 27, 28, 39, 40 FBG (optical filter) 30 Receiving end 32, 33 PD 41, 42, 56, 57, 61 O / E converter 43, 44 Signal receiving unit 50, 51 Signal transmission Units 52, 53 E / O converters 54, 55 Isolators 58 Faulty section detection unit

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5K002 AA01 AA03 AA05 BA02 BA04 BA05 BA14 BA21 DA02 EA05 EA32 FA01 5K033 AA04 CA17 DA15 DB02 DB22 EA04 5K042 AA08 BA02 CA10 CA11 CA12 CA16 DA16 DA35 EA02 EA08 FA21 FA25 LA15

Claims (2)

[Claims] 1. A first optical transmission line for multiplexing optical signals having different wavelengths and transmitting a multiplexed optical signal, and a distributor for distributing the multiplexed optical signal transmitted through the first optical transmission line. A plurality of second optical transmission lines respectively transmitting the multiplexed optical signals distributed by the distributor; and a desired wavelength of each of the multiplexed optical signals transmitted through the plurality of second optical transmission lines. An optical filter that transmits an optical signal and reflects an optical signal of another wavelength toward the first optical transmission line; a receiver that receives the optical signal that has passed through the optical filter; and an optical filter that is reflected by the optical filter. A line monitor for receiving the optical signal returned to the first optical transmission line, and detecting a failure occurrence in the first and second optical transmission lines based on a level change of the optical signal received by the line monitor. Wavelength division multiplexing optical transmission Transmission monitoring system. 2. The monitoring system according to claim 1, wherein said line monitor detects a level of an optical signal of each wavelength.