JPH10256995A - Optical line monitor system and terminal station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make monitor light pass through a branch station. SOLUTION: A trunk station 10 is connected to a branch station 14 through an optical fiber line pair 18, and the branch station 14 is connected to another branch station through an optical fiber line pair 20. In the branch station 14, a wavelength demultiplexing element 42a demultiplexes wavelengths of transmission light on an up line from the trunk station 10. An add/drop element 44a drops an optical signal to the branch station 14 and adds an optical signal to be sent. A wavelength multiplexing element 46a multiplexes wavelength light, which have wavelengths other than that of signal light from the add/drop element 44a and are demultiplexed by the wavelength demultiplexing element 42a, with signal light from the element 44a and outputs the resultant light to the up line. A wavelength demultiplexing element 42b, an add/drop element 44b, and a wavelength multiplexing element 46b act on a down line in the same manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical line monitoring system and a terminal station, and more particularly, to an optical line monitoring system and a terminal station for monitoring an optical transmission line of an optical transmission system.

[0002]

2. Description of the Related Art An optical transmission system in which one or more branch stations are connected to an optical transmission line between two trunk stations is generally constructed as shown in FIG.
0. That is, between the two trunk stations 150, 152, the trunk stations 150, 152
For direct communication between them, a trunk optical fiber pair 154 composed of an upstream optical fiber and a downstream optical fiber is connected. Branch station 15
, 156-N are adjacent trunk stations 150, 152 and branch stations 156-1, 15
, 156-N, two optical fiber pairs 158-1, 158-2,.
Connect via N + 1. For example, the branch station 156-1
Is connected to the trunk station 150 via the optical fiber pair 158-1.
And the branch station 15 via the optical fiber pair 158-2.
6-2. In the same manner, the branch station 158-N is finally connected to the optical fiber pair 158-N + 1.
Through the trunk station 152. Thus, the trunk station 150 and the branch stations 156-1 to 158-N
And the trunk station 152 are serially connected in this order.

The optical fiber pairs 158-1, 158-2,.
.., 158-N + 1, a portion parallel to the trunk optical fiber 154 is formed into an optical cable (trunk cable) together with the trunk optical fiber pair 154, and the optical fiber pair 158-1, 1, 1
The remaining portions of 58-2,..., 158-N + 1 are connected to the same branch stations 156-1 to 156-N to form an optical cable (branch cable) together.

[0004] Branch units 160-1 to 160-N are provided at the junction of the trunk cable and the branch cable. In the branch units 160-1 to 160-N, the same branch station 1
Optical fiber pair 158- connected to 56-1 to 156-N
1-158-N + 1, and the branch stations 156-1 to 15-1
It is common to incorporate an optical switch that can bypass 56-N. Breakage of branch cable or branch station 156
-1 to 156-N, the optical fiber pairs 158-1, 158-2,...
, 158-N + 1 so that the optical line can be used as much as possible.

Thus, a plurality of terminal stations 150, 156-
Conventionally, when monitoring an optical transmission line in an optical transmission system in which 1 to 156-N and 152 are serially connected, the optical fiber pair 158-1 and 158-1 are basically connected in the same direction as the connection between two points.
, 158-N + 1 were monitored. For example, a monitoring light signal for monitoring disconnection and increase in transmission loss is input to one end of each line, and its reflected light or an optical loopback circuit that weakly couples the upstream line and the downstream line is looped back to the other line. By observing the surveillance light level being returned,
The status of each position on the transmission path can be monitored in detail.

[0006]

As described above, in the conventional example, as the number of intermediate branch stations increases, the number of monitoring light transmitters and monitor light receivers increases proportionally. Of course, each branch station 156
-1 to 156-N are monitored by the trunk station 150.
Alternatively, it is necessary to secure a signal channel to be notified to the same 152. That is, in the conventional example, the trunk station 150 or 15
2 is an optical fiber pair 158-1, 158-2,.
The entire optical transmission line consisting of 58-N + 1 could not be remotely monitored as a whole.

An object of the present invention is to provide an optical line monitoring system capable of monitoring the status of an optical line with a simpler configuration.

Another object of the present invention is to provide an optical line monitoring system and a terminal station capable of monitoring an optical line of an optical transmission system in which three or more stations are serially connected with a very simple configuration.

[0009]

According to the present invention, a monitor light is looped back from at least one of an upstream optical line, a downstream optical line, and at least one of the upstream optical line and the downstream optical line.
In an optical transmission system in which three or more stations are serially connected by an optical transmission line having the above-described loopback means, at least one station is provided with a monitor light generating means for generating monitor light, and a monitor light which returns the monitor light. The monitoring station includes an analysis unit for performing analysis. A station other than the monitoring station includes a monitoring light connection unit that separates the monitoring light from the input light and sends out the light as it is to an optical line connected to the opposite station.

Thus, the monitoring light and its loopback light can pass through stations other than the monitoring station, and the monitoring station can monitor the entire optical transmission line.

The monitoring light connection means includes, for example, a demultiplexing means for demultiplexing the monitoring light from the input light, and a multiplexing means for multiplexing the monitoring light demultiplexed by the demultiplexing means with the signal light to be output. Consists of As a result, transmission light unnecessary for the corresponding station is output through.

The demultiplexing means comprises, for example, a wavelength separating means for separating the input light into a predetermined wavelength band, and the multiplexing means, for example, should output the predetermined wavelength component including the monitoring light wavelength-separated by the wavelength separating means. It comprises wavelength multiplexing means for wavelength multiplexing signal light. As a result, the required wavelength light can be freely extracted at the corresponding station.

[0013] The monitoring light connection means also extracts a specific wavelength component from the input light and outputs the same from the first port, and outputs other than the specific wavelength component from the second port. Multiplexing means for multiplexing an optical signal to be transmitted with an optical signal from two ports. As a result, transmission light unnecessary for the corresponding station is output through.

The demultiplexing means converts the input light of port A to port B
, A first optical circulator of three ports A, B, and C for outputting input light of port B from port C, and first reflecting means for passing the specific wavelength and reflecting other wavelength components. And one end of the first reflection means is connected to the port B of the first optical circulator,
Is the first port of the demultiplexing means, and the port C of the first optical circulator is the second port of the demultiplexing means. As a result, it is possible to extract the desired wavelength while passing through the monitoring light or the like without the adverse effect of repeating the wavelength division multiplexing.

The multiplexing means converts the input light of port A to port B
And a second optical circulator of three ports A, B and C for outputting the input light of port B from port C and outputting the input light of port B, and second reflecting means for passing the specific wavelength and reflecting other wavelength components. And the port A of the second optical circulator is connected to the second port of the demultiplexer, one end of the second reflector is connected to the port B of the second optical circulator, The optical signal to be transmitted is input to the other end of the second reflection means, and the combined light is output from the port C of the second optical circulator. Thus, the desired wavelength can be multiplexed and the monitoring light can be passed through without the adverse effect of repeating the wavelength division multiplexing.

[0016]

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

FIG. 1 and FIG. 2 are schematic block diagrams showing an overall configuration of an embodiment of the present invention. FIG. 1 and FIG.
2 is continued on the right side of FIG. In this embodiment, a loop-back optical circuit is provided for returning upstream and downstream propagating light and its reflected light and scattered light to downstream and upstream, respectively, at appropriate positions or distance intervals of the optical transmission line. This loopback optical circuit is usually provided in an optical amplification repeater. With the loopback optical circuit, the status of the upstream optical line can be monitored by return light of the downstream optical line, and the status of the downstream optical line can be monitored by return light of the upstream optical line.

In this embodiment, two trunk stations 10, 1
2, there are two branch stations 14, 16 and trunk station 1
0 and the branch station 14, between the branch station 14 and the branch station 16,
In addition, between the branch station 16 and the trunk station 12, pairs of optical fiber lines 18, 20, and 22 each consisting of upstream and downstream are connected. That is, the trunk station 10 and the optical fiber line pair 1
8, branch station 14, optical fiber line pair 20, branch station 16,
The optical fiber line pair 22 and the trunk station 12 are connected in series in this order.

Each of the optical fiber line pairs 18, 20, and 22 generally has a configuration in which a plurality of transmission optical fibers 24 are relay-connected by one or more optical amplification relay units 26. However, if the distance is short, a relayless system may be used. The optical amplification repeater unit 26 includes optical amplifiers 28 and 30 arranged on the upstream line and the downstream line, respectively.
And a loopback optical circuit 32 for transmitting the propagation light and the reflected light of the upstream line and the downstream line to the output stages of the optical amplifiers 30 and 28.
Consists of

FIG. 4 shows a specific configuration of the loopback optical circuit 32. The loopback optical circuit 32 includes the optical amplifier 2
The 2 × 2 branch couplers 32a and 32b for branching a part of the outputs of the second and third branch couplers 32b and 32b.
2x2 high loss couplers 32c and 32d coupled to 2a
Consists of That is, the branch coupler 32a is connected to the optical amplifier 28.
Is supplied to the high-loss coupler 32c, and the high-loss coupler 32c supplies the light from the branch coupler 32a from the cross port to the branch coupler 32b with high loss. The branching coupler 32b supplies the light from the high-loss coupler 32c to the output side of the optical amplifier 30 so as to travel in the signal transmission direction.

Light (that is, reflected light) that travels in a reverse direction on a signal transmission line (for example, an up line) connected to the optical amplifier 28 and enters the optical amplification repeater unit 26 is transmitted to the branch coupler 3.
2a couples to the high loss coupler 32d. The high loss coupler 32d inputs the light from the branch coupler 32a from the through port to the high loss coupler 32c with low loss. The high-loss coupler 32c outputs the light from the high-loss coupler 32d to the branch coupler 32b with low loss, and the branch coupler 32b causes the light from the high-loss coupler 32c to travel to the output side of the optical amplifier 30 in the signal transmission direction. To supply.

Similarly, the light transmitted through the signal transmission line (for example, the down line) connected to the optical amplifier 30 and the reflected light thereof are coupled to the signal transmission line connected to the optical amplifier 28 in the signal transmission direction. You.

The trunk station 10 of the optical fiber line pair 18
A part of the optical fiber line pair 20, a central part of the optical fiber line pair 20, and a part of the optical fiber line pair 22 on the side of the trunk station 12, as described in the conventional example, directly connect the light between the trunk stations 10 and 12. An optical cable (trunk cable) is integrated with the fiber transmission line. Also, the optical fiber line pair 18
Of the branch station 14 side and the part of the optical fiber line pair 20 on the branch station 14 side together are an optical cable (branch cable).
The portion of the optical fiber line pair 20 on the branch station 16 side and the portion of the optical fiber transmission line 22 on the branch station 16 side are also converted into an optical cable (branch cable). A branch unit 3 is connected to the junction between the trunk cable and the branch cable.
4,36 are placed.

The branching units 34 and 36 are one-input two-output optical switches 38a and 40a, two-input one-output optical switches 38b and 40b, and optical switches 38a and 38, respectively.
0a is connected to one input of each of the optical switches 38b and 40b by bypass paths 38c and 40c.

For example, in the optical branching unit 34, the input of the optical switch 38a is connected to the trunk station 10 side (ie, the trunk cable portion) of the optical fiber line pair 18, and the other output of the optical switch 38a is The optical fiber line pair 18 is connected to the branch station 14 side (that is, a branch cable portion connected to the branch station 14). The other input of the optical switch 38b is connected to the branch station 14 side (that is, a branch cable portion connected to the branch station 14) of the optical fiber line pair 20, and the output of the optical switch 38b is connected to the optical fiber line pair 2
0 (i.e., trunk cable section). The same applies to the optical switches 40a and 40b. The input of the optical switch 40a is connected to the central portion (ie, trunk cable portion) of the optical fiber line pair 20, and the other output of the optical switch 40a is connected to the optical fiber line pair. 20 is connected to the branch station 14 side (that is, a branch cable portion connected to the branch station 14). The other input of the optical switch 40b is
The optical switch 40b is connected to the branch station 14 side (that is, a branch cable portion connected to the branch station 14) of the optical fiber line pair 18, and the output of the optical switch 40b is connected to the trunk station 10 side (that is, trunk) of the optical fiber line pair 18.・ Cable section).

Optical switches 38a, 38b; 40a, 40
b is normally in the connection state shown in FIG. If any abnormality occurs in a branch cable, for example, a branch cable connected to the branch station 14, in the branch unit 34, the optical switch 38a is switched to the bypass path 38c side, and the optical switch 38b selects an optical signal from the bypass path 38c. Is switched as follows. Thus, the optical signal transmitted from the trunk station 10 bypasses the branch station 14 and propagates toward the branch unit 36. The optical signal transmitted from the branch station 16 to the optical fiber line pair 20 is Is propagated toward the trunk station 10 by double bypassing.

The branch stations 14 and 16 have basically the same configuration except for the difference in the signal wavelength to be added / dropped. That is, the branch stations 14 and 16 respectively include, for each of the upstream line and the downstream line, the wavelength separation elements 42a and 42b for separating the input light into the predetermined wavelength light, and the respective wavelength lights separated and output by the wavelength separation elements 42a and 42b. Add / drop elements 44a and 44b for adding / dropping a predetermined signal light among
Wavelength multiplexing elements 46a and 46b for wavelength multiplexing the signal light from the add / drop elements 40a and 40b with the wavelengths separated by the wavelength separating elements 42a and 42b at other wavelengths and outputting the resulting signals to the upstream line and the downstream line, respectively. And a signal light transmitting / receiving device 74 for receiving the signal light dropped by the add / drop elements 44a and 44b and transmitting the signal light to be added by the add / drop elements 44a and 44b. Wavelength separation elements 42a and 42b and wavelength multiplexing element 46
a and 46b are composed of, for example, an arrayed waveguide grating. The add / drop elements 44a and 44b are connected to the branch stations 14 and 16 respectively.
Are provided for wavelengths that are allowed to be transmitted / received, and when only reception is allowed, the function may be limited to the demultiplexing function.

The branch stations 14 and 16 are further provided with amplification units 50 and 50 having exactly the same configuration as the optical amplification repeater unit 26 at the input and output portions. These are for compensating for the loss in the wavelength separation elements 42a and 42 and the wavelength multiplexing elements 46a and 46b, and for enabling monitoring by monitoring light to a deeper depth.

The monitoring light Sm propagating in the same direction as the signal light on the upstream optical line (or downstream optical line) is transmitted to the optical amplification repeater unit 2.
6 is looped back to the downstream optical line (or upstream optical line) by the loopback optical circuit 32, and propagates in the same direction as the transmission direction of the main transmission light on the downstream optical line (or upstream optical line).
In this way, the monitoring light Sm is
The loop back is made at 6 and the trunk station returns to the originating trunk station, for example, the trunk station 10. By using a well-known method, only the monitoring light component is extracted from the main transmission light on the downstream optical line, and the level is analyzed on the time axis, so that the status of each transmission distance can be observed and monitored. The monitoring light and its return light only pass through the branch stations 14 and 16 as they are, and the upstream optical line and the downstream optical line are respectively connected to the branch stations 14 and 1.
It is equivalent to being directly connected within 6.

FIG. 5 is a schematic block diagram showing the configuration inside the trunk stations 10 and 12. The trunk stations 10 and 12 have basically the same configuration. That is, the trunk stations 10 and 12 serve as the transmission system, respectively, as the signal light generators 60a and 60a.
b, monitoring light generators 62a and 62b, signal light generator 6
0a, 60b output light (signal light) and monitoring light generator 62
A multiplexer 6 for multiplexing the output light (monitoring light Sm) of the optical signals a and 62b
4a and 64b, and as a receiving system, demultiplexers 66a and 66b for demultiplexing the received light into signal light and monitoring light Sm, and a signal light for receiving and processing the signal light demultiplexed by the demultiplexers 66a and 66b. Receivers 68a, 68b, duplexers 66a, 66b
Analysis devices 70a and 7 that analyze the monitoring light demultiplexed by the
0b. Further, the trunk stations 10 and 12 further
Each has loopback optical circuits 72a and 72b for weakly coupling the upstream optical line and the downstream optical line to each other.

The operation will be described by taking the case where the trunk station 10 monitors the optical line up to the trunk station 12 as an example. In the trunk station 10, the signal light generating device 60a generates the signal light Sac toward the branch station 14 and the signal light Sad toward the branch station 16, and the monitoring light generating device 62a sets a predetermined (wavelength and / or pattern). Of monitoring light Sm. Multiplexer 64a
Combines the output lights Sac and Sad of the signal light generation device 60a and the monitoring light Sm output from the monitoring light generation device 62a, and outputs the multiplexed light to the upstream line of the optical fiber line pair 18.

The branch station 14 transmits the signal light Sac to itself.
And the signal light Scd for the branch station 16 and the signal light Scb for the trunk station 12 as necessary.
Is output to the upstream line of the optical fiber line pair 20. Similarly, the branch station 16 transmits the signal light Sad and Sc to itself.
d, and outputs the signal light Sdb to the trunk station 12 to the upstream line of the optical fiber line pair 20 as necessary. Monitoring light Sm output from trunk station 10
Pass through the branch stations 14 and 16.

In the trunk station 12, the demultiplexer 66b separates the signal light from the received light and applies it to the signal light receiving device 68b. The signal light receiving device 68b receives and processes the signal light Scb from the branch station 14 and the signal light from the branch station 16. The signal light generator 60b generates signal lights Sbc and Sbd for the branch stations 14 and 16, and the signal lights are transmitted to the multiplexer 64b.
Via the optical fiber line pair 22 to the downstream optical line. The loopback optical circuit 72b includes the optical fiber line pair 2
The monitoring light Sm input from the second upstream line is looped back to the downstream line of the optical fiber line pair 22. This looped-back monitoring light Sm is transmitted to the optical fiber line pair 22, 20, 1
The signal propagates through the downstream line 8 and passes through the branch stations 16 and 14 again to be input to the trunk station 10.

In the trunk station 10, the optical fiber line pair 1
8 (the signal light Sca from the branch station 14)
The signal light Sda from the branch station 16 and the monitoring light Sm that has looped back are input to the duplexer 66a.
The demultiplexer 66a separates the signal lights Sca, Sda and the monitoring light Sm, and separates the signal lights Sca, Sda into a signal light receiving device 68a.
Then, the monitoring light Sm is applied to the analyzer 70a. Duplexer 6
6a may be an optical device that supplies a part of the input light to the analyzer 70a and the rest to the signal light receiver 68a. The signal light receiving device 68a receives the input signal light Sc
a and Sda are received. A reference signal (electric signal), which is a reference of the monitoring light Sm output from the monitoring light generator 62, is input to the analyzer 70a, and is used to analyze the loopback monitoring light Sm from the duplexer 66a. I do.

The supervisory light generator 62b and the analyzer 70b of the trunk station 12 also provide the optical fiber line pair 18,
Obviously, one can monitor 20,22.

FIG. 6 shows a more general configuration of the optical transmission system of the trunk station 10. The monitoring signal generation circuit 80 generates a monitoring signal (electric signal), and the switch 82 connects the output signal of the monitoring signal generation circuit 80 to a transmission processing system of an optical line to which monitoring light is to be transmitted. Here, two optical lines #
1, # 2 (for example, the optical line via the branch station described in the embodiment shown in FIG. 1 and the optical line directly connected between the trunk stations). The monitoring light source 84 generates monitoring light according to a monitoring signal from the switch 82. Signal light generation circuit 86-1
To 86-n are input transmission signals (electric signals), respectively.
Signal light having different wavelengths is generated according to # 1 to #n. The multiplexer 88 multiplexes (wavelength division multiplexed) the output light (monitoring light) of the monitoring light source 84 and the output light (signal light) of the signal light generation circuits 86-1 to 86-n, and outputs a signal of line # 1. (For example, an optical line passing through the branch station described in the embodiment shown in FIG. 1).
For the line # 2 (for example, an optical line directly connected between trunk stations), the monitoring light source 84 and the signal light generating circuits 86-1 to 86 are also provided.
A circuit configuration similar to that of −n and the multiplexer 88 is provided.

If a monitoring signal of the same wavelength is acceptable for each of the optical lines # 1 and # 2, the configuration shown in FIG. 7 can be changed.
The same components as those in FIG. 6 are denoted by the same reference numerals. The monitoring light source 90 generates monitoring light according to the output signal of the monitoring signal generation circuit 80. The optical switch 92 converts the monitoring light output from the monitoring light source 90 into a multiplexer 88 for the optical line # 1 or a multiplexer (not shown) for the optical line # 2. Selectively. As in the case of FIG. 6, the multiplexer 88 is provided with a monitor light (optical switch 9).
2) and output light (signal light) of the signal light generation circuits 86-1 to 86-n are multiplexed (wavelength multiplexed) and output to the line # 1. Also for the line # 2, the signal light generation circuit 86-1
86-n and the same circuit configuration as the multiplexer 88.

FIG. 8 is a schematic block diagram showing an example of an optical receiving apparatus for receiving and processing light from an optical line. Duplexer 1
Reference numeral 10 denotes the light (the monitoring light and the signal light of each wavelength) from the optical line # 1 is demultiplexed into the respective wavelengths, the monitored light is supplied to the monitoring light receiving circuit 112, and the demultiplexed signal light is transmitted into the signal light. Receiving circuit 114
-1 to 114-n. The monitoring light receiving circuit 112 photoelectrically converts the monitoring light and outputs a monitoring signal (electric signal). The signal light receiving circuits 114-1 to 114-n convert signal light into electric signals and output transmission signals # 1 to #n. Also for the optical line # 2, the duplexer 110 and the monitoring light receiving circuit 1
12 and circuits corresponding to the signal light receiving circuits 114-1 to 114-n. Monitor signal switch 116
Selects a monitoring signal from the monitoring light receiving circuit 112 or a monitoring signal from the monitoring light receiving circuit (not shown) of the optical line # 2 and supplies the selected signal to the analysis circuit 118. The analysis circuit 118 determines the presence / absence and level of the monitor signal from the monitor signal switch 116, and changes in the level on the time axis.
The situation of # 2 is analyzed.

FIG. 9 is a block diagram showing a schematic configuration of another example of an optical receiver for receiving and processing light from an optical line. The demultiplexer 120 demultiplexes the light (the monitoring light and the signal light of each wavelength) from the optical line # 1 into each wavelength, and outputs the demultiplexed monitoring light to the optical switch 1
22, a signal light receiving circuit 124-1 converts the demultiplexed signal light to a signal light receiving circuit 124-1.
To 124-n. Signal light receiving circuits 124-1 to 124-1
124-n converts the signal light into an electric signal, and transmits a transmission signal # 1.
To #n. Also for the optical line # 2, the demultiplexer 12
0 and signal light receiving circuits 124-1 to 124-n are provided. The optical switch 122 selects the monitoring light from the demultiplexer 120 or the monitoring light from a similar demultiplexer (not shown) on the optical line # 2, and the monitoring light receiving circuit 1
26. The monitoring light receiving circuit 126 photoelectrically converts the monitoring light and outputs a monitoring signal (electric signal). Analysis circuit 1
Reference numeral 28 denotes an optical line # based on the presence / absence and level of a monitoring signal from the monitoring light receiving circuit 126 and a level change on the time axis.
The situation of # 1 and # 2 is analyzed.

In the above embodiment, for example, an arrayed waveguide grating is used for wavelength separation and wavelength multiplexing at the branch stations 14 and 16, but a plurality of arrayed waveguide gratings are manufactured with exactly the same wavelength separation (multiplexing) characteristics. Is extremely difficult and some individual differences are inevitable. Such a difference greatly degrades the transmission characteristics by accumulation, even if the difference is small. Such a problem can be avoided, for example, by adopting a configuration in which only a desired wavelength component is added / dropped by an optical circulator and an optical fiber grating and other wavelength components are bypassed, as shown in FIG.

Reference numerals 130 and 132 denote well-known three-port optical circulators which output the input light of the port A from the port B and output the input light of the port B from the port C. Propagation light including light is input, and port C of optical circulator 130 is connected to port A of optical circulator 132. The output light from the port C of the optical circulator 132 propagates toward the subsequent branch station or trunk station. Optical circulator 13
Ports 0 and 132 are provided with a reflection element (for example, a plurality of optical fibers so as to have a desired wavelength reflection / passing characteristic) that transmits only the wavelength to be added / dropped by this branch station and reflects other wavelength components. 134 and 136 are connected. Reflective element 134, 1
The other end of 36 is connected to a signal light transmitting / receiving device 138.

The propagating light input to the port A of the optical circulator 130 is directly output from the port B of the optical circulator 130 and input to the reflection element 134. The reflection element 134 passes only a specific wavelength component, Since the signal is reflected, unnecessary signal components (signal light and monitoring light directed to another station) at the branch station are input to the port B of the optical circulator 130 again, output from the port C, and output from the port C of the optical circulator 132. A, output from the port B, and input to the reflection element 136. Since the reflection element 136 has the same wavelength reflection characteristic as the reflection element 134, the signal light and the monitoring light directed to other stations are reflected by the reflection element 136 and input again to the port B of the optical circulator 132, and Output from C.

The signal light that has passed through the reflection element 134 is received and processed by the signal light transmitting / receiving device 138. The signal light output from the signal light transmitting / receiving device 138 passes through the reflection element 136 and enters the port B of the optical circulator 132. Therefore,
The light output from the port C of the optical circulator 132 is a signal light and a monitor light directed to another station, among the propagation lights input to the port A of the optical circulator 130, which are newly generated at this branch station. The signal light is wavelength division multiplexed.

The reflective elements 134 and 136 have the advantages that there is no difficulty in manufacturing such as an arrayed waveguide grating, that there is little adverse effect when connected in multiple stages, and that the system has a high tolerance to variations in reflection wavelength characteristics. There is.

Although the embodiment shown in FIG. 1 has a straight configuration in which the trunk stations 10 and 12 are arranged at both ends, as shown in FIG. 12, the trunk station 10 and the trunk station 12 are united into a single unit. One station 140 may be used as a loop configuration or a ring configuration in which an optical transmission line is terminated at the trunk station 140. 12, the same components as those in FIG. 1 are denoted by the same reference numerals. The counterclockwise transmitted light is denoted as S +,
Clockwise transmitted light is denoted by S-.

Further, all the stations are connected to the branch units 34 and 3
6 has a complete ring configuration connected to an optical fiber line pair via a branch unit similar to that of 6, and includes a monitoring light generating device for generating monitoring light and an analyzing device for receiving and analyzing the monitoring light. Monitoring station.

[0047]

As can be easily understood from the above description, according to the present invention, it is possible to collectively monitor a series of a plurality of optical lines which relay a plurality of stations with one monitor light, and Can be greatly simplified. That is, 3
The status of each optical line that serially connects the above stations can be monitored with one monitoring light, and the cost of monitoring can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of the left half of an embodiment of the present invention.

FIG. 2 is a schematic configuration block diagram of a right half of the present embodiment.

FIG. 3 is a diagram showing a relationship between FIG. 1 and FIG. 2;

FIG. 4 is a diagram showing a circuit configuration of a loopback optical circuit 26.

FIG. 5 is a schematic block diagram of the trunk stations 10 and 12;

6 is a schematic block diagram of an example of an optical transmission device provided in the trunk station 10. FIG.

FIG. 7 is a schematic configuration block diagram of a modified example of the optical transmission device provided in the trunk station 10.

FIG. 8 is a schematic configuration block diagram of an example of an optical receiver that receives and processes light from an optical line.

FIG. 9 is a schematic configuration block diagram of another example of an optical receiving device that receives and processes light from an optical line.

FIG. 10 is a schematic configuration block diagram of a general example of an optical transmission system.

FIG. 11 is a diagram showing another configuration for adding / dropping a specific wavelength and bypassing other wavelengths.

FIG. 12 is a schematic block diagram of a modified embodiment having a loop configuration.

[Explanation of symbols]

10, 12: Trunk station 14, 16: Branch station 18, 20, 22: Optical fiber transmission line pair 24: Optical fiber for transmission 26: Optical amplification repeater unit 28, 30: Optical amplifier 32: Loopback circuit 32a, 32b : Branch couplers 34c, 34d: high loss couplers 34, 36: branch units 38a, 38b; 40a, 40b: optical switches 38c, 40c: bypass paths 42a, 42b: wavelength separating elements 44a, 44b: add / drop elements 46a, 46b. : Wavelength multiplexing element 48: Signal light transmitting / receiving device 50: Amplifying unit 60a, 60b: Signal light generating device 62a, 62b: Monitoring light generating device 64a, 64b: Multiplexer 66a, 66b: Demultiplexer 68a, 68b: Signal light Receiving device 70a, 70b: analysis device 72a, 72b: loopback optical circuit 80: monitoring Signal generation circuit 82: Switching device 84: Monitoring light source 86-1 to 86-n: Signal light generation circuit 88: Multiplexer 90: Monitoring light source 92: Optical switching device 110: Demultiplexer 112: Monitoring light reception circuit 114-1 to 114-n: signal light receiving circuit 116: monitoring signal switching device 118: analysis circuit 120: duplexer 122: light switching device 124-1 to 124-n: signal light receiving circuit 126: monitoring light receiving circuit 128: analysis circuit 130, 132: optical circulator 134, 136: fiber grating 138: signal light transmitting / receiving device 140: trunk station 150, 152: trunk station 154: trunk optical fiber pair 156-1, 156-2,... , 156-N: branch station 158-1, 158-2,..., 158-N + 1: branch optical fiber pair 160-1 to 160-N: branch unit knit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideaki Tanaka 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside the International Telegraph and Telephone Corporation (72) Inventor Koji Goto 2-3-3, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. 2 International Telegraph and Telephone Co., Ltd. (72) Inventor Shu Yamamoto 2-3-2 Nishi Shinjuku, Shinjuku-ku Tokyo 3-2 Kokusai Telegraph and Telephone Corporation

Claims (12)

[Claims] 1. An optical transmission line comprising at least one of an upstream optical line, a downstream optical line, and one or more loopback means for looping monitoring light from at least one of the upstream optical line and the downstream optical line to the other. An optical transmission line monitoring system for monitoring an optical line between each of the stations, wherein at least one station comprises a monitoring light generating means for generating a monitoring light, A monitoring station comprising: a monitoring light connecting means for separating the monitoring light from the input light and transmitting the light as it is to an optical line connected to the opposite station. An optical line monitoring system, comprising: 2. The monitoring light connecting means multiplexes the monitoring light demultiplexed by the demultiplexing means from the input light to the signal light to be output. 2. The optical line monitoring system according to claim 1, comprising a multiplexing unit. 3. The demultiplexing means comprises wavelength separating means for separating the input light into a predetermined wavelength band, and the multiplexing means comprises:
3. The optical line monitoring system according to claim 2, further comprising wavelength multiplexing means for wavelength-multiplexing the signal light to be output to a predetermined wavelength component including the monitoring light separated by the wavelength separating means. 4. The demultiplexing means for extracting a specific wavelength component from the input light, outputting the specific wavelength component from the input light, and outputting a component other than the specific wavelength component from a second port, 2. A multiplexing means for multiplexing an optical signal to be transmitted with an optical signal from the second port of the demultiplexing means.
2. The optical line monitoring system according to 1. 5. A first optical circulator of three ports A, B, and C for outputting input light of port A from port B and outputting input light of port B from port C. A first reflecting means that transmits a specific wavelength and reflects other wavelength components, one end of the first reflecting means is connected to the port B of the first optical circulator,
The other end of the first reflecting means is the first port of the demultiplexing means, and the port C of the first optical circulator is the second port of the demultiplexing means. Optical line monitoring system. 6. The three-port A, B, and C second optical circulator for outputting the input light of the port A from the port B and outputting the input light of the port B from the port C. The second optical circulator is connected to the second port of the demultiplexing unit, and the second optical circulator is connected to the second port of the second optical circulator. The second port is connected to port B of the circulator.
5. The optical signal to be transmitted is input to the other end of the second reflecting means, and the combined light is output from the port C of the second optical circulator. Optical line monitoring system. 7. The optical line monitoring system according to claim 1, wherein both ends of the optical transmission line are connected to different stations. 8. The optical line monitoring system according to claim 1, wherein both ends of the optical transmission line are connected to one monitoring station. 9. A demultiplexing means for demultiplexing monitoring light and signal light from input light, and an add / drop means for adding / dropping a predetermined signal light out of the signal light demultiplexed by the demultiplexing means. A signal light transmitting / receiving means for receiving and processing the signal light dropped by the add / drop means and supplying a signal light to be added to the add / drop means; a monitoring light split by the splitting means; An end comprising: a signal light which is demultiplexed by the demultiplexing means and which is not input to the add / drop means; and a multiplexing means which multiplexes the signal light supplied from the add / drop means. Bureau. 10. A specific wavelength component is extracted from input light and output from a first port, and a component other than the specific wavelength component is extracted from a second port.
A demultiplexing means for outputting an optical signal from the first port of the demultiplexing means and outputting an optical signal to be transmitted to the transmission line; and an output from the transmitting and receiving means. A terminal station comprising: an optical signal to be multiplexed; and multiplexing means for multiplexing the optical signal from the second port of the demultiplexing means and outputting the multiplexed signal to the transmission line. 11. The first optical circulator of three ports A, B, and C for outputting the input light of the port A from the port B and outputting the input light of the port B from the port C. A first reflecting means that transmits a specific wavelength and reflects other wavelength components, one end of the first reflecting means is connected to the port B of the first optical circulator,
The other end of the first reflecting means is the first port of the demultiplexing means, and the port C of the first optical circulator is the second port of the demultiplexing means. Terminal. 12. The three-port A, B, and C second optical circulator for outputting the input light of the port A from the port B and outputting the input light of the port B from the port C. The second optical circulator is connected to the second port of the demultiplexing unit, and the second optical circulator is connected to the second port of the second optical circulator. The second port is connected to port B of the circulator.
Is connected to one end of the reflection means, an optical signal to be transmitted from the transmission / reception means is input to the other end of the second reflection means, and the port C of the second optical circulator is connected to the transmission path. Item 14. The terminal according to item 10.