JPH10336108A - Optical path monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor the connection of optical space switches for every optical signal by using a pilot signal with a previously assigned fixed frequency and fixing the frequencies of the pilot signal even when optical signal wave length is converted. SOLUTION: The frequencies assigned to respective monitor signal transmitters 11-1 to 11-6 are fixed and made invariant even when the wave lengths of the optical signals for superimposing them are converted and the whole frequencies of the pilot signals to be superimposed with the optical signals which are inputted to the respective optical space switches 13-1 and 13-2 are made to be different. The optical signals with which the pilot signals are superimposed are respectively switched to prescribed optical transmission paths with the optical space switches 13-1 and 13-2. The optical signal S2(λ1) from a transmitting device 12-2 is outputted from a confluent equipment 32-1 which is connected to the optical transmission path 13-1 with a 1×2 optical switch 31-2. Then, the optical signal S2(λ1) is inputted to a connection monitor circuit 42-1 with a branch equipment 41-1 and the pilot signal PTs(f2) to be superimposed with the optical signal is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical path monitoring device for monitoring the connection state of an optical space switch and the setting state of an optical path in an optical path cross-connect system using a wavelength multiplexing technique.

[0002]

2. Description of the Related Art As means for transmitting monitoring information unique to an optical path in a wavelength-division multiplexing transmission line, intensity of an optical signal is modulated with a pilot signal modulated by the monitoring information, and a pilot signal is superimposed on the optical signal and transmitted. There is a way.

FIG. 12 shows a configuration example of a conventional optical path monitoring apparatus for transmitting monitoring information using a pilot signal (see “Signal Tracking and Performance Monitoring In”).
Multi-Wavelength Optical Network ", 22nd European C
onference on Optical Communication Preprints 3.47-3.5
0).

In FIG. 1, a transmitting node 70 and receiving nodes 80-1 and 80-2 are connected via optical transmission lines 101 and 102, respectively. The transmitting node 70 includes supervisory signal transmitters 11-1 to 11-6 that output pilot signals modulated with supervisory information of each optical path, and a transmitting device 12 that intensity-modulates an optical signal (main signal) with each pilot signal. -1 to 12
-6, optical space switches 13-1 and 13-2 for switching the output destination of the optical signal on which the pilot signal is superimposed, and optical signals transmitted from each optical space switch to the optical transmission lines 101 and 102, respectively. It is composed of mergers 14-1 and 14-2. Here, the mergers 14-1 and 14-2
The wavelengths of the optical signals that are merged are different from each other, and the wavelength-multiplexed optical signals are transmitted to the optical transmission lines 101 and 102. The frequency of the pilot signal superimposed on each optical signal is assigned according to the wavelength of each optical signal.

The receiving node 80-1 receives a wavelength-multiplexed optical signal from the optical transmission line 101 and splits a part of the signal, and an optical signal for converting one of the split optical signals into an electric signal. A detector 22; monitoring signal receivers 23-1 to 23-3 for selecting pilot signals of predetermined frequencies from outputs of the optical detector to demodulate monitoring information;
It is composed of a demultiplexer 24 for demultiplexing the other optical signal branched by 1 for each wavelength, and receiving devices 25-1 to 25-3 for respectively receiving optical signals (main signals) of each wavelength. . The same applies to the receiving node 80-2. With the above configuration, the monitoring information and the main signal information are transmitted.

Meanwhile, in the optical path cross-connect system, it is necessary to monitor whether the optical space switch is erroneously connected. FIG. 13 shows a conventional connection monitoring method of the optical space switch 13 (reference: Japanese Patent Application No. Hei 8-2235).
8). Here, an example is shown in which three optical signals are input to the optical space switch 13 and connected to one of the two outputs.

The three optical signals S 1, S 2, and S 3 are respectively supplied to the 1 × 2 optical switches 31-1 and 31-3 of the optical space switch 13.
1-2, 31-3, and are connected to the mergers 32-1, 32-
2 and the mergers 32-1 and 32-
The two are merged and output.

[0008] Here, the frequency of the pilot signal superimposed on each optical signal is determined according to the wavelength of the optical signal.
In the example shown in FIG. 13, the wavelength of the optical signal S1 and the frequency of the pilot signal PT1 are λ1 and f1, the wavelength of the optical signal S2 and the frequency of the pilot signal PT2 are λ3 and f3, and the wavelength of the optical signal S3 and the pilot The frequency of the signal PT3 is λ2 and f2. The optical signal S1 and the optical signal S3 are connected to the merger 32-2, and the optical signal S2 is connected to the merger 31-1.

The mergers 32-1 and 32-3 of the optical space switch 13
The optical signals output from 2-2 are splitters 41-1, 41
The connection monitoring circuit 42
-1 and 42-2. Connection monitoring circuit 42-1,
At 42-2, the level of the pilot signal superimposed on the optical signal is measured, and it is monitored whether the optical signal is output correctly. The connection monitoring circuit 42-1 can confirm that the optical signal S2 is output by detecting the pilot signal PT2 of the frequency f3 superimposed on the optical signal S2. Further, in the connection monitoring circuit 42-2, a pilot signal PT1 of frequency f1 superimposed on the optical signal S1,
By detecting the pilot signal PT3 of the frequency f2 superimposed on the optical signal S3, it can be confirmed that the optical signals S1 and S3 are correctly output. The connection of the optical space switch 13 is monitored by the above procedure.

[0010]

In the conventional connection monitoring method of the optical space switch, the frequency of the pilot signal is assigned according to the wavelength of each optical signal. The example shown in FIG. 13 shows a case where the wavelengths of the three optical signals input to the optical space switch are all different, and the frequencies of the pilot signals are all different.

However, in the optical path network, the wavelength is converted as necessary so that optical signals of the same wavelength do not exist in the optical transmission line. Therefore, the same wavelength may be assigned to a plurality of optical signals output to different optical transmission lines. This example is shown in FIG. Here, the wavelength λ1
Is output to the combiner 32-1 and the optical signal S1 of wavelength λ1 and the optical signal S3 of wavelength λ2 are output to the combiner 32-2. At this time, each optical signal S1, S
2, pilot signals PT1, PT2 superimposed on S3
The frequencies of PT3 are f1, f1, and f2 because they are assigned according to the wavelengths of the optical signals.

The optical signal 2 is input to the connection monitoring circuit 42-1 and a pilot signal PT2 having a frequency f1 is detected. On the other hand, the connection monitoring circuit 42-2 supplies the optical signals S1, S3
Is input, and pilot signals PT of frequencies f1 and f2 are input.
1, PT3 is detected. That is, the pilot signal of the frequency f1 is detected by both the connection monitoring circuits 42-1 and 42-2. Therefore, this frequency f1
Cannot be determined to which of the optical signals S1 and S2 the pilot signal is assigned.
Connection monitoring becomes impossible.

Therefore, the conventional connection monitoring method of the optical space switch 13 can be applied only when the wavelengths of the optical signals input to the optical space switch 13 are all different as shown in FIG.

An object of the present invention is to provide an optical path monitoring apparatus capable of monitoring connection of an optical space switch for each optical signal even when a plurality of optical signals having the same wavelength are input to the optical space switch. Aim.

[0015]

According to the optical path monitoring apparatus of the present invention, when a plurality of optical signals having the same wavelength are input to an optical switch unit, the frequencies of pilot signals superimposed on each optical signal are different from each other. Set as follows. That is, using a pre-assigned fixed frequency pilot signal,
Even when the optical signal wavelength is converted, the frequency of the pilot signal is kept constant. As a result, the frequencies of the pilot signals superimposed on the optical signal input to the optical switch unit are different from each other. Therefore, the connection of the optical switch unit can be monitored by detecting the pilot signal on the output side of the optical switch unit.

At this time, since the frequency and amplitude value of the pilot signal are to be detected, the pilot signal may be either modulated with monitoring information or unmodulated. For example, the connection of the optical switch unit may be monitored using an unmodulated pilot signal, and then the pilot signal modulated with the monitoring information may be transferred.
4).

In this method of assigning pilot signal frequencies, all pilot signal frequencies are surely different on the output side of the optical switch section. However, in an optical transmission line in which optical signals are wavelength-multiplexed, there is a possibility that a pilot signal of the same frequency is superimposed on a plurality of optical signals. In this case, in the configuration of the receiving node shown in FIG.
Interference occurs between pilot signals of the same frequency, and it becomes impossible to transmit monitoring information using the pilot signals.
In the conventional method, a pilot signal frequency is assigned according to the wavelength of each optical signal, so that a pilot signal of the same frequency is not superimposed on a plurality of optical signals on an optical transmission line.

Therefore, the receiving node first demultiplexes the wavelength-multiplexed optical signal, and individually inputs the optical signal of each wavelength to the monitoring signal receiver to detect the pilot signal.
Thereby, interference of pilot signals of the same frequency can be avoided.

As described above, in the optical path monitoring device of the present invention, the frequency of the pilot signal is individually assigned on the transmitting side, and the wavelength division multiplexed optical signal is demultiplexed on the receiving side, and then the pilot signal is individually detected. By doing so, it is possible to simultaneously monitor connection of the optical switch unit and transmit monitoring information by a pilot signal.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.

In the figure, a transmitting node 10 and receiving nodes 20-1 and 20-2 are connected via optical transmission lines 101 and 102, respectively. The transmission node 10 includes supervisory signal transmitters 11-1 to 11-6 that output pilot signals modulated with supervisory information of each optical path, and a transmitter 12 that intensity-modulates an optical signal (main signal) with each pilot signal. -1 to 12
-6, optical space switches 13-1 and 13-2 for switching the output destination of the optical signal on which the pilot signal is superimposed, and optical signals transmitted from each optical space switch to the optical transmission lines 101 and 102, respectively. Combiners 14-1 and 14-2
And branching devices 41-1 to 41-4 for branching a part of the output optical signal of each optical space switch, and connection monitoring circuits 42-1 to 42-4 for monitoring connection of each optical space switch. .

The receiving node 20-1 receives a wavelength-division multiplexed optical signal from the optical transmission line 101, and demultiplexes the signal for each wavelength. Detectors 21-1 to 21-3, and optical detectors 22-1 to 22- which convert optical signals of the respective branched wavelengths into electric signals.
3 and monitoring signal receivers 23-1 to 23-3 for detecting pilot signals of a predetermined frequency from the outputs of the respective optical detectors.
-3, and receiving devices 25-1 to 25-3 that receive the optical signals of the respective wavelengths branched by the branching devices 21-1 to 21-3 and demodulate the main signal. Receiving node 20
The same applies to −2.

Here, the monitoring signal transmitters 11-1 to 11-
3, the frequencies of the pilot signals PT1 to PT3 output from the monitoring signal transmitters 11-4 to 11-3 are denoted by f1, f2, and f3.
Pilot signals PT4 to PT6 output from 11-6
Are f1, f2, and f3.

The wavelengths of the optical signals S1 to S6 output from the transmission devices 12-1 to 12-6 are λ1, λ1, λ2,
λ3, λ2, λ3. The optical signal S2 having the wavelength λ1, the optical signal S5 having the wavelength λ2, and the optical signal S4 having the wavelength λ3 are transmitted to the receiving node 20-1 via the optical transmission path 101, and the wavelength λ
The optical signal S1, the optical signal S3 having the wavelength λ2, and the optical signal S6 having the wavelength λ3 are transmitted through the optical transmission line 102 to the receiving node 20-.
2 is transmitted. FIG. 2 shows an example of pilot signal frequency allocation and an example of optical signal connection by the above setting.
Shown in

The frequency assigned to each of the monitoring signal transmitters 11-1 to 11-6 is fixed, and does not change even if the wavelength of the optical signal on which the monitoring signal transmitter 11-1 is superposed is converted. By this frequency assignment, the frequencies of the pilot signals superimposed on the optical signals input to the optical space switches 13-1 and 13-2 can all be different.

The optical signal on which the pilot signal is superimposed is switched to a predetermined optical transmission line via the optical space switches 13-1 and 13-2. The optical signal S1 (λ1) output from the transmission device 12-1 is connected to the optical multiplexer 102 via the 1 × 2 optical switch 31-1.
-2. The optical signal S2 (λ1) output from the transmission device 12-2 is output from the junction 32-1 connected to the optical transmission line 13-1 via the 1 × 2 optical switch 31-2. Optical signal S3 output from transmitting device 12-3
(Λ2) is output from the junction 32-2 connected to the optical transmission line 102 via the 1 × 2 optical switch 31-3.

As a result, the optical signal S2 (λ1) is input to the connection monitoring circuit 42-1 via the splitter 41-1 and the pilot signal PT superimposed on the optical signal S2 (λ1)
2 (f2) is detected. The frequency f2 of the pilot signal PT2 is the frequency assigned to the monitoring signal transmitter 11-2, and the optical signal S2 is
Is output from the merger 32-1. Similarly, the connection monitoring circuit 42-2 includes the optical signal S1
(Λ1), the pilot signal PT1 (f
1) and a pilot signal PT3 (f3) superimposed on the optical signal S3 (λ2) are detected. Therefore, it can be confirmed that the optical signal S1 and the optical signal S3 are output from the merger 32-2 of the optical space switch 13-1.

The same applies to the connection monitoring circuits 42-3 and 42-4 of the optical space switch 13-2, and the optical signals S output from the monitoring signal transmitters 11-4 to 11-6.
Pilot signals PT4 to PT superimposed on 4-S6
6 and confirming the frequency thereof, the connection of the optical space switch 13-2 can be monitored.

Here, it is assumed that an erroneous connection occurs in the optical space switch 13-1. For example, if the optical signal S3 is erroneously output to the merger 32-1, the connection monitoring circuit 42-1
Thus, the pilot signal PT3 of the frequency f3 is detected. In this case, it can be confirmed that the optical signal S3 on which the pilot signal PT3 is superimposed is erroneously connected, and it is possible to immediately take a measure for failure.

The optical signal S2 (λ1) output from the optical space switch 13-1, the optical signal S4 (λ3) and the optical signal S5 (λ2) output from the optical space switch 13-2 are combined into a merger 14-1. And transmitted to the optical transmission line 101. Optical signals S2, S4, S transmitted through optical transmission line 101
5 is input to the demultiplexer 24 of the receiving node 20-1 and demultiplexed for each wavelength. At this time, the pilot signal superimposed on each optical signal is separated together with the optical signal. That is, the optical signal S2 (λ1) in which the pilot signal PT2 (f2) is superimposed is output to the branch unit 21-1, and the pilot signal PT5 (f2) is output to the branch unit 21-2.
Is output, and an optical signal S5 (λ2) on which the
An optical signal S4 (λ3) in which the pilot signal PT4 (f1) is superimposed on 1-3 is output. By this demultiplexing, it is possible to avoid interference due to pilot signals of the same frequency.

The optical signal S2 split by the splitter 21-1
Part of (λ1) is input to the optical detector 22-1, and the rest is input to the receiving device 25-1. A part of the optical signal S5 (λ2) split by the splitter 21-2 is input to the optical detector 22-2, and the rest is input to the receiver 25-2. Part of the optical signal S4 (λ3) split by the splitter 21-3 is input to the optical detector 22-3, and the rest is input to the receiver 25-3. Thereby, each of the receiving devices 25-1 to 25-
3, the optical signals (main signals) S2, S5, S4 are received, and the monitoring signal receivers 23-1 to 23-3 receive the pilot signal P.
T2, PT5 and PT4 are received.

The receiving node 20-via the optical transmission line 102
The same applies to the wavelength-division multiplexed optical signal input to 2. With the above configuration, the function of monitoring the connection of the optical space switches 13-1 and 13-2 in the transmitting node 10 and the function of transmitting the monitoring information from the transmitting node 10 to the receiving nodes 20-1 and 20-2 are simultaneously realized. Can be.

Conventionally, since a pilot signal is received in a wavelength multiplexed state, the CN of the pilot signal deteriorates. This will be described with reference to FIG. FIG.
(a) shows the power spectrum density of the optical signal on which the pilot signal of the frequency f1 is superimposed. FIG. 3 (b) shows the frequency f
4 shows the power spectral density of an optical signal on which two pilot signals are superimposed. The CN ratio of the pilot signal is given by the ratio of the power of the pilot signal to the power spectral density of the main signal.

On the other hand, when two optical signals are multiplexed,
As shown in FIG. 3C, the power of the pilot signal does not change, and only the power spectral density of the optical signal is added, so that the CN ratio of the pilot signal is relatively deteriorated.
For example, when a pilot signal is received during eight-wave multiplexing and when a pilot signal is received after separation into one wavelength, the latter is improved by about 16 dB in the CN ratio. Therefore, in the configuration of receiving each pilot signal after demultiplexing the wavelength-multiplexed optical signal as in the present invention, the CN ratio can be greatly improved as compared with the conventional configuration.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
An embodiment will be described. This embodiment shows a configuration of an optical path cross-connect system in which an optical space switch for switching connection of an optical path is arranged at a receiving node.

In the figure, transmitting nodes 50-1 and 50-
2 and the receiving node 60 are connected via optical transmission lines 101 and 102, respectively. The transmission node 50-1 includes supervisory signal transmitters 11-1 to 11-3 that output pilot signals modulated with supervisory information of each optical path, and transmission that intensity-modulates an optical signal (main signal) with each pilot signal. Device 12-1
12-3, and a multiplexer 15-1 for multiplexing the optical signal on which the pilot signal is superimposed and transmitting the multiplexed optical signal to the optical transmission line 101. The transmission node 50-2 includes supervisory signal transmitters 11-4 to 11-6 that output pilot signals modulated with the monitoring information of each optical path, and transmission that intensity-modulates an optical signal (main signal) with each pilot signal. Devices 12-4 to 12-6;
It is composed of a multiplexer 15-2 for multiplexing an optical signal on which a pilot signal is superimposed and transmitting the multiplexed optical signal to the optical transmission line 102.

The receiving node 60 inputs the wavelength-multiplexed optical signal from the optical transmission line 101 and
Splitter 26-1 for distributing the light to the optical transmission line 1
Shunt 26-2 for inputting the wavelength-multiplexed optical signal from O.02 and distributing it to optical space switches 27-1 and 27-2, and optical space switch for switching the output destination of the optical signal from optical transmission lines 101 and 102. 27-1 and 27-2 and splitters 41-1 to 4-4 for splitting a part of the output optical signal of each optical space switch.
1-6, connection monitoring circuits 42-1 to 42-6 for monitoring connection of each optical space switch, and wavelength selectors 28-1 to 28-2 for selecting an optical signal of a specific wavelength from the wavelength-multiplexed optical signal.
8-6, splitters 21-1 to 21-6 that split a part of the optical signal of each wavelength selected by each wavelength selector, and convert the split optical signal of each wavelength into an electric signal. Optical detectors 22-1 to 22-6, monitoring signal receivers 23-1 to 23-6 for detecting pilot signals of a predetermined frequency from the outputs of the optical detectors, and splitters 21-1 to 21-. 6
And receiving devices 25-1 to 25-6 for receiving the optical signals of the respective wavelengths and demodulating the main signals.

Here, the frequencies of pilot signals PT1 to PT3 output from supervisory signal transmitters 11-1 to 11-3 of transmitting node 50-1 are all assumed to be f1, and supervisory signal transmitter 11 of transmitting node 50-2 is assumed to be f1. The frequencies of pilot signals PT4 to PT6 output from -4 to 11-6 are all f2. The frequency assigned to each of the monitoring signal transmitters 11-1 to 11-6 is fixed, and does not change even when the wavelength of the optical signal on which it is superimposed is converted.

The wavelengths of the optical signals are allocated such that the same wavelength does not exist in the same transmitting node, and the optical signals S1 to S1 output from the transmitting devices 12-1 to 12-3 are allocated.
The wavelength of S3 is λ1, λ2, λ3, and the transmitting device 12-4
The wavelengths of the optical signals S1 to S3 output from the
1, λ2, λ3. The optical signal S1 having the wavelength λ1 is connected to the receiving device 25-4, the optical signal S2 having the wavelength λ2 is connected to the receiving device 25-1, the optical signal S3 having the wavelength λ3 is connected to the receiving device 25-5, and the wavelength λ1 is connected. Is connected to the receiving device 25-3, the optical signal S5 of the wavelength λ2 is connected to the receiving device 25-2, and the optical signal S6 of the wavelength λ3 is connected to the receiving device 25-6. FIG. 5 shows an example of pilot signal frequency allocation and an example of optical signal connection according to the above settings.

The wavelength-multiplexed optical signals S1 (λ1), S2 (λ2), S3 (λ
3) is transmitted to the receiving node 60 via the optical transmission line 101. Wavelength-multiplexed optical signals S4 (λ2), S5 (λ2), S6 (λ3) output from the transmitting node 50-2.
Is transmitted to the receiving node 60 via the optical transmission line 102. In the receiving node 60, the shunt 2
The optical signal input to 6-1 is an optical space switch 27-1,
27-2, and from the optical transmission line 102 to the shunt 26-
The optical signals input to the optical space switches 27-1 and 27
-2.

The optical signal S1 (λ1) on which the pilot signal PT1 (f1) is superimposed, the pilot signal PT2 (f1)
Is superimposed on the optical signal S2 (λ2), the pilot signal PT
The optical signal S3 (λ3) on which 3 (f1) is superimposed is output from the 2 × 1 optical switch 34-1 via the current splitter 33-1 while being wavelength-multiplexed, and is also output via the current splitter 33-3. 2
It is output from the × 1 optical switches 34-4 and 34-5. Optical signal S4 on which pilot signal PT4 (f2) is superimposed
(Λ1), the optical signal S5 (λ2) on which the pilot signal PT5 (f2) is superimposed, and the optical signal S6 (λ3) on which the pilot signal PT6 (f2) is superimposed are passed through the current divider 33-2 while being wavelength-multiplexed. 2 × 1 optical switch 34-2,3
4-3, and 2 × through the shunt 33-4.
The signal is output from the one optical switch 34-6.

As described above, the optical space switches 27-1 and 27
-2 outputs a wavelength-multiplexed optical signal, but the wavelength-multiplexed optical signal output from the same transmitting node is:
All pilot signals of the same frequency are superimposed.
That is, the pilot signal of the frequency f1 is superimposed on the optical signals S1 to S3, and the pilot signal of the frequency f2 is superimposed on the optical signals S4 to S6. Therefore, the connection monitoring circuit 42-1 detects a pilot signal of the frequency f1. The frequency f1 of the pilot signal is a frequency assigned to the transmission node 50-1, and it can be confirmed that the connection of the optical space switch 27-1 is correct. Similarly, the connection monitoring circuits 42-2 and 42-3 detect the pilot signal of the frequency f2, and can confirm that the connection of the optical space switch 27-1 is correct.

The same applies to the connection monitoring circuits 42-4 to 42-6 connected to the optical space switch 27-2. The pilot signals of the frequencies f1, f1, f2 are detected respectively, and the optical space switch 13- It can be confirmed that the connection of No. 2 is correct.

Here, it is assumed that an erroneous connection occurs in the optical space switch 27-1. For example, 2 × 1 optical switch 3
If 4-1 selects the optical signal from the shunt 33-2 (transmission node 50-2), the connection monitoring circuit 42-1 detects the pilot signal of the frequency f2. As a result, erroneous connection of the optical space switch 27-1 can be detected,
Immediate action can be taken for failure.

The wavelength-division multiplexed optical signal output from the optical space switch 27-1 is coupled to the wavelength selectors 28-1 to 28-3.
Select an optical signal of a predetermined wavelength. The wavelength selector 28-1 selects the optical signal S2 of the wavelength λ2, the wavelength selector 28-2 selects the optical signal S5 of the wavelength λ2, and the wavelength selector 28-3 selects the optical signal S4 of the wavelength λ1. . At this time, the pilot signal superimposed on each optical signal is selected together with the optical signal. That is, the branch 2
An optical signal S2 (λ2) in which the pilot signal PT2 (f1) is superimposed on 1-1 is output, and an optical signal S5 (λ) in which the pilot signal PT5 (f2) is superimposed on the branching unit 21-2.
2) is output and the pilot signal PT
The optical signal S4 (λ1) on which the signal 4 (f2) is superimposed is output. As a result, interference due to pilot signals of the same frequency can be avoided.

The optical signal S2 split by the splitter 21-1
Part of (λ2) is input to the optical detector 22-1, and the rest is input to the receiving device 25-1. A part of the optical signal S5 (λ2) split by the splitter 21-2 is input to the optical detector 22-2, and the rest is input to the receiver 25-2. A part of the optical signal S4 (λ1) branched by the branching unit 21-3 is input to the optical detector 22-3, and the rest is input to the receiving device 25-3. Thereby, each of the receiving devices 25-1 to 25-
3, the optical signals (main signals) S2, S5, S4 are received, and the monitoring signal receivers 23-1 to 23-3 receive the pilot signal P.
T2, PT5 and PT4 are received.

The same applies to the wavelength selectors 28-4 to 28-6 and thereafter for selecting each one wavelength from the wavelength-multiplexed optical signal output from the optical space switch 27-2. With the above configuration, the connection monitoring function of the optical space switches 13-1 and 13-2 in the receiving node 60 and the transmitting node 50
-1, 50-2 to the receiving node 60 at the same time.

Also in this embodiment, since the pilot signal is received after being split into an optical signal of one wavelength, the CN ratio of the pilot signal can be improved as in the first embodiment.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
An embodiment will be described. The feature of this embodiment lies in that the connection of the optical space switch is first monitored with a pilot signal of only a non-modulated carrier, and then a pilot signal modulated with monitoring information is transmitted.

In the figure, a transmitting node 10 'includes a control unit 16 for executing a connection monitoring procedure, and according to the connection monitoring procedure, monitoring signal transmitters 11-1 to 11-6, optical space switches 13-1 and 13-2. , Connection monitoring circuits 42-1 to 42
-4 operate.

That is, the monitor signal transmitters 11-1 to 11-11
-6 outputs a pilot signal of only the carrier when monitoring the connection of each optical space switch, and outputs a pilot signal modulated with the monitoring information of each optical path after the connection monitoring is completed. In order to output a pilot signal of only a carrier, for example, quaternary phase modulation may be performed using digital data (data of which all become 0) such that the amount of phase change of the carrier becomes 0. Connection monitoring circuits 42-1 to 42-
4 monitors connection of each optical space switch by detecting a pilot signal of only a carrier. Sending node 1
Other configurations at 0 ', receiving nodes 20-1, 20
The configuration of -2 is the same as that of the first embodiment shown in FIG.

Here, the monitoring signal transmitters 11-1 to 11-
3, the frequencies of the pilot signals PT1 to PT3 output from the monitoring signal transmitters 11-4 to 11-3 are denoted by f1, f2, and f3.
Pilot signals PT4 to PT6 output from 11-6
Are f1, f2, and f3.

The wavelengths of the optical signals S1 to S6 output from the transmitting devices 12-1 to 12-6 are set to λ1, λ1, λ2,
λ3, λ2, λ3. The optical signal S2 having the wavelength λ1, the optical signal S5 having the wavelength λ2, and the optical signal S4 having the wavelength λ3 are transmitted to the receiving node 20-1 via the optical transmission path 101, and the wavelength λ
The optical signal S1, the optical signal S3 having the wavelength λ2, and the optical signal S6 having the wavelength λ3 are transmitted through the optical transmission line 102 to the receiving node 20-.
2 is transmitted. FIG. 7 shows an example of frequency assignment of pilot signals and an example of connection of optical signals by the above setting.
Shown in

The connection monitoring procedure of the optical space switch in this connection state will be described with reference to the flowchart shown in FIG.
An example in which the switching to the 02 side is performed will be described.

The control section 16 sends a control command to the monitor signal transmitter 11-1 to set the transmission of an unmodulated carrier as the pilot signal PT1. When supervisory signal transmitter 11-1 receives this control command, it transmits pilot signal PT1 of only the carrier of frequency f1. Further, the control unit 16 sends a control command to the connection monitoring circuit 42-2 so as to receive the pilot signal PT1 of the frequency f1. When connection monitoring circuit 42-2 receives this control command, it starts detecting pilot signal PT1 of frequency f1. Further, the control unit 16 includes the optical space switch 13-
1, the switching command is sent so that the optical signal S1 on which the pilot signal PT1 is superimposed is connected to the optical transmission line 102 side.

As a result, a part of the optical signal S1 is
The signal is branched at 1-2 and input to the connection monitoring circuit 42-2, and the pilot signal PT1 superimposed on the optical signal S1 is detected. The frequency f1 of the pilot signal PT1 is a frequency assigned to the monitor signal transmitter 11-1.
The optical signal S1 is transmitted from the optical space switch 13-1 to the optical transmission line 10
It is confirmed that switching has been made to the two sides. The connection monitoring circuit 42-2 notifies the control unit 16 of a confirmation result indicating that the connection has been made normally. On the other hand, when the connection monitoring circuit 42-2 does not detect the pilot signal PT1 of the frequency f1, the control unit 16 is notified that the optical signal S1 on which the pilot signal PT1 is superimposed is erroneously connected.

After being notified of the connection monitoring result of the optical space switch 13-1 from the connection monitoring circuit 42-2, the control unit 16 sends a pilot signal PT1 modulated with the monitoring information to the monitoring signal transmitter 11-1. Is sent. When the supervisory signal transmitter 11-1 receives this control command, it sends out a pilot signal PT1 of frequency f1 on which supervisory information is placed.

The connection monitoring procedure described above is performed for the other optical signals S2 to S2.
The same applies to the connection in S6, and switching of the optical space switch and connection monitoring are performed according to the flowchart shown in FIG.

The transmission of the monitoring information is the same as in the first embodiment, and each pilot signal is received by the receiving nodes 20-1 and 20-2. With such a configuration, the optical space switch 13- in the transmission node 10 '
1 and 13-2 and a function of transmitting monitoring information from the transmitting node 10 'to the receiving nodes 20-1 and 20-2.

Here, when monitoring the connection of the optical space switch,
The reason why the frequency interval between adjacent pilot signals can be reduced by transferring only unmodulated carriers will be described.

FIG. 9 shows a spectrum of a pilot signal of only an unmodulated carrier. The spectrum width of each pilot signal may be theoretically considered to be zero. FIG. 10 shows a spectrum of a pilot signal modulated by the monitoring information. For example, by modulating with supervisory information using a quaternary phase modulation scheme, the spread of the spectrum of the pilot signal increases in proportion to the transmission speed of the supervisory information.

Since a plurality of optical signals output to the same optical transmission line are wavelength-multiplexed and input to the connection monitoring circuit 42, a function of selecting a pilot signal of a certain frequency from among a plurality of pilot signals, for example, The connection monitoring circuit 42-2 in the connection state of FIG. 7 needs a function of selecting pilot signals of frequencies f1 and f3. Here, if the pilot signal is modulated, a band-pass filter having a wide pass band is necessary for spectrum spread, but if the pilot signal is unmodulated, a narrow-band band-pass filter can be used. it can.

As described above, in the case of a modulated pilot signal, a wide frequency interval is required as shown in FIG. 10, and in the case of only a carrier, each pilot signal is narrow in a narrow frequency interval as shown in FIG. Frequency allocation can be performed. That is, if the connection of the optical space switch is monitored using the unmodulated pilot signal, the frequency interval between the pilot signals can be made closer.

After the connection of the optical space switch is monitored, monitoring information is transmitted by a pilot signal.
In the receiving nodes 20-1 and 20-2, the optical signal is wavelength-separated as in the first embodiment, and the supervisory signal receiving circuit 23-
Monitoring information of pilot signals corresponding to each optical signal is received in 1 to 23-3. Here, the optical detectors 22-1 to 22-2
-3 is a single optical signal, and only the pilot signal superimposed on the optical signal is the supervisory signal receiving circuit 2.
3-1 to 23-3. That is, as shown in FIG. 11, since only one pilot signal is received by each monitor signal receiving circuit, there is no need to select a pilot signal using an electric band-pass filter.
As a result, the spectrum of the pilot signal modulated with the monitoring information is spread, but the monitoring information can be received.

[0065]

As described above, the optical path monitoring apparatus of the present invention simultaneously realizes the connection monitoring function of the optical space switch using the detection of the level of the pilot signal and the transmission of monitoring information for each optical path. Can be. Furthermore, in the optical path monitoring device of the present invention, since the pilot signal is detected in a state where the signal is demultiplexed into one wavelength optical signal, the CN ratio of the pilot signal can be improved.

Further, when monitoring the connection of the optical space switch, an unmodulated pilot signal is used, and the pilot signal is modulated with the monitoring information after the connection is monitored, so that the frequency interval of the pilot signal can be reduced. , The frequency can be used effectively.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical path monitoring device of the present invention.

FIG. 2 is a diagram showing an example of assigning pilot signal frequencies and an example of connecting optical signals in the first embodiment.

FIG. 3 is a diagram illustrating a state of deterioration of a CN ratio of a pilot signal during wavelength multiplexing.

FIG. 4 is a block diagram showing a second embodiment of the optical path monitoring device of the present invention.

FIG. 5 is a diagram illustrating an example of assigning pilot signal frequencies and an example of connecting optical signals in the second embodiment.

FIG. 6 is a block diagram showing a third embodiment of the optical path monitoring device of the present invention.

FIG. 7 is a diagram illustrating an example of assigning pilot signal frequencies and an example of connecting optical signals in the third embodiment.

FIG. 8 is a flowchart illustrating a connection monitoring procedure of the optical space switch according to the third embodiment.

FIG. 9 is a diagram showing a spectrum of a pilot signal of only an unmodulated carrier.

FIG. 10 is a diagram showing a spectrum of a pilot signal modulated by monitoring information.

FIG. 11 is a diagram showing a spectrum of a pilot signal input to a supervisory signal receiver of a receiving node.

FIG. 12 is a block diagram illustrating a configuration example of a conventional optical path monitoring device that transmits monitoring information using a pilot signal.

FIG. 13 is a diagram showing a conventional connection monitoring method of the optical space switch 13;

FIG. 14 is a diagram showing an example in which connection monitoring of the optical space switch 13 becomes impossible.

[Explanation of symbols]

 10, 10 ', 50, 70 Transmitting node 11 Monitoring signal transmitter 12 Transmitting device 13 Optical space switch 14, 32 Combiner 15 Combiner 16 Control unit 20, 60, 80 Receiving node 21, 41 Splitter 22 Optical detector Reference Signs List 23 monitoring signal receiver 24 duplexer 25 receiving device 26, 33 shunt 27 optical space switch 28 wavelength selector 31 1 × 2 optical switch 34 2 × 1 optical switch 42 connection monitoring circuit 101, 102 optical transmission line

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04Q 3/52

Claims (4)

[Claims] 1. N × M optical signals input from a plurality of N input optical transmission lines in a state where a plurality of M waves are wavelength-multiplexed,
In an optical path cross-connect system for converting into an arbitrary wavelength and outputting to an arbitrary output optical transmission line, the N × M optical signals have a predetermined frequency individually assigned separately from main signal information. Means for superimposing a pilot signal, a part of the output optical signal strength of the optical switch unit for performing a cross-connect in the optical path cross-connect system is branched, the branched optical signal is converted into an electric signal, and a predetermined frequency is converted. Means for detecting the amplitude value of the pilot signal, means for monitoring the connection state of the optical switch unit from the amplitude value of the pilot signal, and a step of demultiplexing the wavelength division multiplexed optical signal into respective wavelengths. Means for converting the optical signal into an electric signal and receiving a pilot signal superimposed on the optical signal of each wavelength. 2. The optical path monitoring device according to claim 1, wherein a frequency of a pilot signal superimposed on an optical signal input to the optical switch unit is assigned to be different from each other for each input port of the optical switch unit. Characteristic optical path monitoring device. 3. The optical path monitoring device according to claim 1, wherein the connection state of the optical switch unit is monitored from the amplitude value of the pilot signal, and thereafter, a connection monitoring procedure for transmitting monitoring information by the pilot signal is executed. An optical path monitoring device, comprising: 4. The optical path monitoring device according to claim 3, wherein the means for superimposing a pilot signal of a predetermined frequency is used when monitoring a connection state of the optical switch unit according to a connection monitoring procedure of the control unit. Means for superimposing an unmodulated pilot signal, supervising a connection state of the optical switch unit, and then superimposing a pilot signal modulated by the monitoring information; and means for detecting an amplitude value of the pilot signal having a predetermined frequency and the optical switch. The means for monitoring the connection state of the unit is configured to monitor the connection state of the optical switch unit by detecting the amplitude value of an unmodulated pilot signal of a predetermined frequency in accordance with the connection monitoring procedure of the control unit. Characteristic optical path monitoring device.