JPH10229367A - Optical repeater and optical transmission terminal equipment - Google Patents

Abstract

(57) Abstract: The present invention relates to an optical repeater and an optical transmission terminal device capable of transmitting a sub-signal used for collecting maintenance information of a relay station in an optical communication system, and performs complicated processing. It is an object of the present invention to provide an optical repeater capable of easily transmitting maintenance information of a relay station building without performing the operation, and an optical transmission terminal device capable of monitoring quality of an optical transmission line and detecting disconnection. SOLUTION: An optical pulse train related to wavelength division multiplexing taken from one optical transmission line of an optical transmission line is branched into a main signal optical pulse sequence and a first sub-signal optical pulse sequence, and the branched main signal optical pulse sequence is divided into the other. Drop-and-add means 1 for transmitting the second sub-signal light pulse train to one of the optical transmission paths while transmitting the second sub-signal light pulse train to the system.
And a second sub-signal light pulse train having a different wavelength.
Wavelength conversion means 2 for converting the signal into a sub-signal light pulse train and outputting the same to the add / drop means 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical repeater and an optical transmission terminal in an optical communication system, and more particularly, to an optical repeater capable of transmitting a sub-signal used for collecting maintenance information of a relay station. The present invention relates to an optical transmission terminal device. In an optical communication system, an installation place of an optical repeater becomes a remote place of several tens to several hundreds kilometers from an installation station of an optical transmission terminal equipment with an improvement in transmission quality of an optical fiber as an optical transmission line. This optical repeater
Since the relay station is installed in an unmanned station, maintenance of the relay station is performed from the terminal station. Therefore, in the optical communication system, it is necessary to collect the maintenance information of the relay station building at the terminal station, and how to secure a line for transmitting the maintenance information of the relay station building is an important issue.

[0002]

2. Description of the Related Art Conventionally, the following three methods have been generally employed. A first method is to install another line (for example, a telephone line or a low-speed dedicated line) that does not depend on the optical communication system and transmit the maintenance information of the relay station building. Second
The method of (1) focuses on the fact that the optical repeater is, in many cases, a regenerative repeater, in which the received light is once converted into an electric signal, and is converted into an optical signal again after regenerating and repeating. This is a method in which maintenance information is time-divisionally superimposed as a sub signal at a stage, converted into an optical signal, and transmitted. The third method is
This method has been proposed in an optical communication system using an optical direct amplifier (optical linear repeater) as an optical repeater. In the optical repeater, a sub signal (maintenance information) is superimposed on a main signal by wavelength division multiplexing (WDM). How to

[0003]

Since the non-repeated distance tends to be extended with the progress of the optical amplification technology, it is difficult to secure another line as in the first method. Also,
Since optical direct amplifiers (optical linear repeaters) tend to be used as optical repeaters, it becomes impossible to superimpose sub-signals as electric signals as in the second method. Therefore,
A third method has been proposed, which uses wavelength division multiplexing (WD).
In the method for configuring the sub-signal line according to M), it is necessary to collect monitoring signals in the optical repeater and make them have a speed corresponding to the speed of the main signal. Is large, and simplification is difficult.

[0004] On the other hand, in a communication system, quality monitoring and disconnection detection of a transmission path are also important issues, but it is very convenient if these can be processed in the process of transmitting a sub signal. The present invention has been created to solve such a problem, and can also perform quality monitoring and disconnection detection of an optical repeater that can easily transmit maintenance information of a relay station building without complicated processing and a transmission path. An object is to provide an optical transmission terminal device.

[0005]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
It is a principle block diagram of the invention as described in 11 and 12. According to the first aspect of the present invention, an optical pulse train related to wavelength division multiplexing taken from one optical transmission line of an optical transmission line pair is branched into a main signal optical pulse train and a first sub-signal optical pulse train, and the branched main signal Add / drop means 1 for transmitting the optical pulse train to the other system and transmitting the second sub-signal optical pulse train to one optical transmission line; and converting the branched first sub-signal optical pulse train to a second sub-signal optical pulse train of a different wavelength. And a wavelength converting means 2 for converting the wavelength into a wavelength and outputting it to the add / drop means 1.

That is, on one side of an optical repeater that connects two optical transmission line pairs, the add / drop unit 1 operates to transmit an optical pulse train related to wavelength division multiplexing, which is taken from one optical transmission line of one optical transmission line pair. Into a main signal light pulse train and a first sub-signal light pulse train. The branched main signal light pulse train is transmitted to the other optical transmission line of the other pair of optical transmission lines (see the right side of FIG. 1) via the other system. , The wavelength converting means 2 converts the light into a second sub-signal light pulse train having a different wavelength.

The converted second sub-signal light pulse train is transmitted by the add / drop unit 1 to one of the pair of optical transmission lines. The second sub-signal light pulse train is transmitted to the same optical transmission line as the first sub-signal light pulse train, but has no problem because the wavelength is different. Similar processing is performed on the other side of this optical repeater, as shown on the right side of FIG. 1, and the branched main signal light pulse train is sent to the other optical transmission line of the pair of optical transmission lines. You.

According to a second aspect of the present invention, in the optical repeater according to the first aspect, the wavelength converting means 2 and the add / drop means 1 are provided.
And a superimposing means 3 for superimposing the maintenance information of the relay station on the second sub-signal light pulse train whose wavelength has been converted by the wavelength converting means 2 and outputting the same to the add / drop means 1. That is, in the optical repeater, when the superimposing means 3 superimposes the maintenance information of the relay station on the second sub-signal optical pulse train, the add / drop means 1 generates the second sub-signal optical pulse train on which the maintenance information is superimposed. Out to the optical transmission line.

As described above, according to the first and second aspects of the present invention, the optical repeater does not generate the sub-signal optical pulse train, but simply changes the wavelength of the sub-signal optical pulse train taken from the optical transmission line. Only the process of sending the signal back to the original optical transmission line is performed. Therefore, the optical repeater does not require a pulse train generating circuit, and can transmit a sub-signal with a simple configuration. FIG.
Is a principle block diagram of the invention according to claims 3, 4, 11, and 12. FIG.

According to a third aspect of the present invention, an optical pulse train for wavelength division multiplexing taken from one optical transmission line of an optical transmission line pair is demultiplexed into a main signal optical pulse train and a first sub-signal optical pulse train, Demultiplexing means 4 for transmitting the split main signal light pulse train to the other system, and wavelength converting means 2 for converting the split first sub-signal light pulse train to a second sub-signal light pulse train of a different wavelength.
And a multiplexing means 5 for wavelength-division multiplexing the main signal light pulse train and the wavelength-converted second sub-signal light pulse train and transmitting the multiplexed light to the other optical transmission line of the pair of optical transmission lines.

That is, on one side of an optical repeater connecting two optical transmission line pairs, the demultiplexing means 4 generates an optical pulse train for wavelength division multiplexing, which is taken from one optical transmission line of one of the optical transmission line pairs. Is demultiplexed into a main signal light pulse train and a first sub-signal light pulse train. The demultiplexed main signal light pulse train is transmitted to the other optical transmission line of the other optical transmission line pair (see the right side of FIG. 2) via the multiplexing means (5) on the other side. The first sub-signal light pulse train that has been waved is
It is converted into a second sub-signal light pulse train having a different wavelength.

The wavelength-converted second sub-signal light pulse train is:
The multiplexing means 5 is a demultiplexing means (4) on the other side.
And a wavelength division multiplexing with the main signal light pulse train input from the optical transmission line, and sends it to the other optical transmission line of one optical transmission line pair. Similar processing is performed on the other side of the optical repeater as shown on the right side of FIG. According to a fourth aspect of the present invention, in the optical repeater according to the third aspect, the second sub-signal light pulse train whose wavelength has been converted by the wavelength converting means 2 is provided between the wavelength converting means 2 and the multiplexing means 5. A superimposing means 3 for superimposing the maintenance information of the relay station and outputting the superimposed information to the multiplexing means 5 is provided.

That is, in the optical repeater, the superimposing means 3 is the second
When the maintenance information of the relay station is superimposed on the sub-signal light pulse train, the multiplexing means 5 sends the second sub-signal light pulse train on which the maintenance information is superimposed to the other optical transmission line. As described above, according to the third and fourth aspects of the present invention, the optical repeater does not generate the sub-signal light pulse train, but simply changes the wavelength of the sub-signal light pulse train taken from one of the optical transmission lines. Only the process of sending the signal to the other optical transmission path is performed again. Therefore, the optical repeater does not require a pulse train generation circuit,
A sub-signal can be transmitted with a simple configuration.

FIG. 3 is a block diagram showing the principle of the present invention. According to a fifth aspect of the present invention, there is provided a converting means 6 for converting a main signal, which is an electric signal, into an optical pulse train, a generating means 7 for generating a first sub-signal optical pulse train, an output of the converting means 6 and a generating means 7. Output and wavelength-division multiplexed and output to one optical transmission line of the pair of optical transmission lines, and add / drop means 8 for taking in a second sub-signal optical pulse train from the one optical transmission line; A monitoring means 9 for monitoring the quality of an optical transmission line to which the optical repeater according to claim 1 is connected by using an optical pulse train.

That is, in the optical transmission terminal equipment, the main signal light pulse train converted by the converting means 6 and the first signal generated by the generating means 7 are generated.
The add / drop unit 8 wavelength-division multiplexes the sub-signal light pulse train with the sub-signal light pulse train and sends out the resulting signal to one of the optical transmission lines of the pair of optical transmission lines. And
When the add / drop unit 8 takes in the second sub-signal optical pulse train sent from the one optical transmission line, the monitoring unit 9
The quality of the optical transmission line is monitored using the second sub-signal light pulse train.

Here, since the sub-signals reciprocate on the same optical transmission line via the optical repeater, the sub-signal path forms a loop. As a result, the optical transmission terminal device that is the source of the sub signal can monitor the transmission system including the optical repeater. For example, when the second sub-signal light pulse train is input, the monitoring means 9 can monitor the presence or absence of an error in the transmission path from the bit state of the second sub-signal light pulse train, and receive the second sub-signal light pulse train. If not, an abnormality in the transmission line including the optical repeater, such as disconnection of the optical transmission line, can be detected.

According to a sixth aspect of the present invention, in the optical transmission terminal device of the fifth aspect, the detecting means 10 for detecting whether maintenance information is superimposed on the received second sub-signal optical pulse train is provided. The monitoring means 11 monitors the quality of the optical transmission line to which the optical repeater according to claim 2 is connected, using the second sub-signal light pulse train when the maintenance information is not detected.

That is, in the optical transmission terminal equipment, the detecting means 10
Detects whether maintenance information is superimposed on the second sub-signal light pulse train captured from the optical transmission line, and
1 monitors the quality of the optical transmission path using the second sub-signal light pulse train when the detection result of the detection means 9 is “maintenance information is not superimposed”. If the detection result of the detection means 10 is “maintenance information is superimposed”, it goes without saying that the maintenance information is to be read.
Does not perform the monitoring operation.

FIG. 4 is a block diagram showing the principle of the present invention. According to a seventh aspect of the present invention, there is provided a converting means 6 for converting a main signal which is an electric signal into an optical pulse train, a generating means 7 for generating a first sub-signal optical pulse train, and an output of the converting means 6 and the generating means 7. A multiplexing means 12 for wavelength-division multiplexing the output with the other optical transmission line of the pair of optical transmission lines, and an optical pulse train related to the wavelength division multiplexing taken from the other optical transmission line of the pair of optical transmission lines. 4. The quality of an optical transmission line to which the optical repeater according to claim 3 is connected by using a demultiplexing means 13 for demultiplexing an optical pulse train and a second sub-signal optical pulse train, and using the demultiplexed second sub-signal optical pulse train. And monitoring means 9 for monitoring the

That is, in the optical transmission terminal station apparatus, the main signal light pulse train converted by the conversion means 6 and the first
The multiplexing means 12 wavelength-division multiplexes the sub-signal light pulse train with the sub-signal light pulse train and sends the resultant signal to one of the optical transmission lines of the pair of optical transmission lines. On the other hand, the demultiplexing means 13 demultiplexes the optical pulse train related to wavelength division multiplexing taken from the other optical transmission line of the pair of optical transmission lines into a main signal optical pulse train and a first sub-signal optical pulse train. The quality of the optical transmission path is monitored using the split second sub-signal light pulse train.

Here, since the sub-signal reciprocates through both optical transmission line pairs via the optical repeater, the path of the sub-signal forms a loop. As a result, the optical transmission terminal device that is the source of the sub signal can monitor the transmission system including the optical repeater. For example, when the second sub-signal light pulse train is input, the monitoring means 9 can monitor the presence or absence of an error in the transmission path from the bit state of the second sub-signal light pulse train, and does not input the second sub-signal light pulse train. In this case, it is possible to detect an abnormality in the transmission path including the optical repeater, such as the disconnection of the optical transmission path.

According to an eighth aspect of the present invention, in the optical transmission terminal device according to the seventh aspect, the detecting means 10 detects whether maintenance information is superimposed on the split second sub-signal optical pulse train. The monitoring means 11 monitors the quality of the optical transmission line to which the optical repeater according to claim 4 is connected, using the split second sub-signal light pulse train when maintenance information is not detected. Features.

That is, in the optical transmission terminal equipment, the detecting means 10
Detects whether the maintenance information is superimposed on the second sub-signal light pulse train demultiplexed by the demultiplexing unit 13, and the monitoring unit 11 determines that the detection result of the detection unit 10 indicates “maintenance information is superimposed. If "no", the quality of the optical transmission path is monitored using the second sub-signal light pulse train. When the detection result of the detection means 10 is “maintenance information is superimposed”, the maintenance information is read, needless to say, and the monitoring means 11 does not perform the monitoring operation.

As described above, in the optical communication system including the optical repeater according to claims 1 and 3 and the optical transmission terminal device according to claims 5 and 7, The optical transmission terminal device can collect the status of the transmission system including the optical repeater, and includes the optical repeater according to claims 2 and 4, and the optical transmission terminal device according to claims 6 and 8. In optical communication systems,
The optical transmission terminal equipment can also collect the maintenance information of the optical repeater more specifically.

According to the ninth aspect of the present invention, one end is connected to the seventh aspect.
Alternatively, the plurality of optical repeaters according to claim 3 or 4 that relay the optical transmission line pair connected to the optical transmission terminal device according to claim 8 in multiple stages, wherein each of the wavelength conversion means 2 The input first sub-signal light pulse train is converted into a second sub-signal light pulse train having a different wavelength.

That is, each of the plurality of optical repeaters is assigned a unique wavelength. Thus, in the optical transmission terminal station device arranged at least at one end of the optical transmission line pair, maintenance information can be collected for each optical repeater. According to a tenth aspect of the present invention, there is provided the optical repeater according to any one of the first, second, third, fourth, and ninth aspects, wherein
Is characterized by comprising a semiconductor laser and a semiconductor optical amplifier that receives a laser beam of the semiconductor laser as converted light and performs a wavelength conversion operation.

That is, the wavelength conversion means can be realized with a simple configuration without employing a special configuration. According to an eleventh aspect of the present invention, in the optical repeater according to any one of the first, second, third, fourth, and ninth aspects, a state change that detects a state change of the relay station building and outputs maintenance information. It is characterized by having a detecting means 13. That is, when a state change of the relay station building occurs, the state change can be detected as quickly as possible.

According to a twelfth aspect of the present invention, in the optical repeater according to the eleventh aspect, the superimposing means 3 is an optical switch whose on / off is controlled in accordance with the output of the state change detecting means 14. I do. That is, the superimposing means can be realized with a simple configuration without adopting a special configuration.

[0029]

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

FIG.
FIG. 2 is a configuration diagram of a first embodiment corresponding to FIG. The first embodiment relates to an information transmission method for collecting maintenance information of a relay station building using one optical transmission line of an optical transmission line pair. The optical transmission terminal equipment 20 installed in the two terminal stations A and B includes an optical transmitter 21, a WDM optical filter 22, and a pulse generator 23.
, An optical transmitter 24, an optical receiver 25, and a detection / reproduction circuit 2
6, an error detection circuit 27, and an optical receiver 28.

The optical transmitter 21 has an input terminal to which a main signal from an external main signal circuit is applied, and an output terminal connected to one input terminal of the WDM filter 22. The output terminal of the pulse generator 23 is connected to the input terminal of the optical transmitter 24, and the output terminal of the optical transmitter 24 is connected to the other input terminal of the WDM filter 22. The WDM filter 22 has an input / output end connected to one end of one optical transmission line of the optical transmission line pair, and an output end connected to an input end of the optical receiver 25. The other end of the one optical transmission line is connected to a relay station.

The output terminal of the optical receiver 25 is connected to the detection / reproduction circuit 2
6 and the error detection circuit 27, respectively. Further, a detection output terminal of the detection and reproduction circuit 26 is connected to a control input terminal of the error detection circuit 27. Then, the optical receiver 28
Has an input terminal connected to one end of the other optical transmission line of the pair of optical transmission lines, and the other end connected to an external main signal circuit. The other end of the other optical transmission line is connected to a relay station.

Next, the optical repeater 30 installed in the repeater station
Are WDM filters 31a and 31b and a wavelength conversion unit 32
a, 32b, optical switches 33a, 33b, control unit 3
4 is provided. The optical amplifier is not shown. WD
The M filters 31a and 31b have input / output terminals connected to the other end of one optical transmission line of the pair of optical transmission lines, and one output terminal connected to the other end of the other optical transmission line via an optical amplifier (not shown). Connected, and the other output terminal is connected to the input terminals of the wavelength converters 32a and 32b. The output terminals of the wavelength conversion units 32a and 32b are connected to the input terminals of the optical switches 33a and 33b, and the output terminals of the optical switches 33a and 33b are connected to the WDM filter 3.
1a and 31b are connected to the input terminals. And the control unit 3
Reference numeral 4 denotes an input terminal to which ON / OFF information from the relay station is applied, and an output terminal connected to the control input terminals of the optical switches 33a and 33b.

Here, the WDM filters 22, 31a, 3
1b is, for example, as shown in FIG.
This is a filter capable of simultaneously realizing the drop and insertion of the optical signal according to M). FIG. 6 is a configuration example of a WDM filter.
This is an AO filter using an acoustic effect. The AO filter is well known and will not be described in detail.

In FIG. 6, port 1 has λ1.
Assuming that an optical signal of a plurality of wavelengths of λn is input and an optical signal of a wavelength λ1 ′ is input to port 2, λ
An optical signal of a plurality of wavelengths of 1... Λn and an optical signal of a wavelength of λ1 ′ are output, and an optical signal of a wavelength λ1 among the optical signals of a plurality of wavelengths of λ1. Is output. This AO filter has reversibility.

Accordingly, the WDM filter 22 wavelength-division multiplexes the main signal light pulse train of wavelength λs and the monitoring light pulse train of wavelength λ1 and sends them to one optical transmission line. Can be captured. Also, the WDM filters 31a, 31b
Splits an optical pulse train for wavelength division multiplexing taken from one optical transmission line into a main signal optical pulse train of wavelength λs and a monitoring optical pulse train of wavelength λ1, and switches optical switches 33a and 33
The superimposed optical pulse train of wavelength .lambda.2 from b can be sent to one of the optical transmission lines.

A reflection type Fabry-Perot filter using a Fabry-Perot resonator is well known as having similar characteristics, and can also be used.
The principle configuration is described in, for example, the document “O plus E, 1994”.
FIG. 12 (b) of the January issue, p. 87. In addition, an EO filter, a tunable DFB filter, a Mach-Zehnder filter, a dielectric multilayer filter, or the like can be used.

The wavelength converters 32a and 32b are WD
The monitoring optical pulse trains input from the M filters 31a and 31b are converted into monitoring optical pulse trains of different wavelengths and provided to the optical switches 33a and 33b. The wavelength converters 22a, 22
2b is specifically configured as shown in FIG. 7, for example. FIG. 7 is an explanatory diagram of the configuration and operation of the wavelength conversion unit.

As shown in FIG. 7A, the wavelength converter 32
a and 32b are semiconductor lasers (hereinafter referred to as “LD”) 4
0 and a semiconductor optical amplifier 41. LD40
Is a laser device that continuously oscillates at a predetermined wavelength, but the oscillation wavelength is variable. The laser light from the LD 40 is provided to the semiconductor optical amplifier 41 as converted light. If the wavelength of the input light is λ1, the semiconductor optical amplifier 41
Upon receiving the continuous light (converted light) having the wavelength λ2 from D40, the input light having the wavelength λ1 is converted into the output light having the wavelength λ2.

More specifically, the wavelength conversion is performed by utilizing the mutual gain modulation effect (XGM) of the semiconductor optical amplifier 41. That is, when the semiconductor optical amplifier 41 is in a gain-saturated state, the number of carriers of the semiconductor optical amplifier 41 fluctuates according to ON / OFF of the incident signal light. When continuous light enters there, the amplification factor of the semiconductor optical amplifier 41 is proportional to the number of carriers, so that intensity modulation occurs in the output. That is, the ON / OFF information of the original signal light is transferred to the signal light of the new wavelength. In this case, the converted output light is a signal obtained by inverting ON / OFF of the original signal light.

In order to set the operation of the semiconductor optical amplifier 41 to a gain-saturated state, it is necessary to set the input power of both the original signal light and the converted light to be large as shown in FIG. 7B. The actual operation waveform of this wavelength conversion is described in the technical report “Technical Report of IEICE. SSE95-143, OCS96-10
0 (1996-02)): Study of optical ADM and optical routing using wavelength division multiplexing technology ”in FIG.
Please refer to.

FIG. 8 is an explanatory diagram of the modulation of the monitoring optical pulse train by the optical switch. As shown in FIGS. 8A and 8B, the optical switches 33a and 33b are turned ON in accordance with ON / OFF information of the relay station building input to the control unit 34.
/ OFF operation to turn ON / OFF the monitoring optical pulse train, which is the input pulse train, to generate an output optical pulse train in which the ON / OFF information of the relay station is superimposed.

Specifically, when the ON / OFF information of the relay station is ON information, the optical switches 33a and 33b are closed, and the input optical pulse train is output as it is. On the other hand, when the ON / OFF information of the relay station is OFF information, the optical switches 33a and 33b are opened, and the input optical pulse train is not output. As a result, the output light pulse train is intensity-modulated by ON / OFF information as shown in (c) of FIG.

Here, various types of optical switches using an electro-optic effect, an acousto-optic effect, a magneto-optic effect, and the like are known. The monitoring light pulse train, which is the input light pulse train, is slower than the main signal light pulse train. Any of these can be used as the optical switches 33a and 33b. Note that the ON / OFF information of the relay station building is usually lower speed information on the order of milliseconds to seconds (several Kb / s). Therefore, if the monitoring light pulse train is set to a high speed on the order of microseconds (several Mb / s), the above-described intensity modulation can secure sufficient characteristics.
In recent years, it is possible to meet the demand for an ultra-high-speed optical transmission system that has been increasing in necessity.

In the above configuration, the correspondence with the claims is as follows. In the branch insertion means 1, 8,
The WDM filters 31a, 31b, 22 correspond. Wavelength conversion units 2 correspond to wavelength conversion units 32a and 32b,
Specifically, the laser diode 40 as a semiconductor laser and the entire semiconductor optical amplifier 41 correspond to each other. Optical switches 33a and 33b correspond to the superposition means 3.

The optical transmitter 21 corresponds to the conversion means 6. The generating means 7 includes a pulse generator 23 and an optical transmitter 24.
The whole corresponds. The error detecting circuit 27 corresponds to the monitoring means 9 and 11. The detection and reproduction circuit 27 corresponds to the detection unit 10. The state change detecting means 14 includes the control unit 3
4 corresponds. The monitoring light pulse train corresponds to the first sub-signal light pulse train. The superimposed light pulse train corresponds to the second sub-signal light pulse train.

Hereinafter, with reference to FIG.
Operations of the first embodiment corresponding to 6, 10 to 12 will be described. In the terminal station A, the optical transmitter 21 converts a main signal pulse train, which is an electric signal input from an external main signal circuit, into a main signal light pulse train having a wavelength λs and outputs the same to the WDM filter 22. The optical transmitter 24 converts a monitoring pulse train, which is an electrical signal generated by the pulse generator 23, into a monitoring light pulse train having a wavelength λ 1 and outputs the converted signal to the WDM filter 22.
As a result, the WDM filter 22 wavelength-division multiplexes (WDM) the input main signal light pulse train of the wavelength λs and the monitoring light pulse train of the wavelength λ1 and sends them out to one optical transmission line of the pair of optical transmission lines.

In the relay station, the optical pulse train related to wavelength division multiplexing from the terminal station A is input to the WDM filter 31a, and is branched into a main signal optical pulse train (λs) and a monitoring optical pulse train (λ1). The branched monitoring optical pulse train (λ1)
The wavelength is converted into a monitoring pulse train of wavelength λ2 by the wavelength converter 32a, and is input to the optical switch 33a. The split main signal light pulse train (λs) is transmitted to the other optical transmission line to the terminal station B via an optical amplifier (not shown).

When there is no state change in the relay station building, ON /
The OFF information is in the OFF state. Therefore, the optical switch 33a outputs the monitoring pulse train of the wavelength λ2 to W
This is given to the DM filter 31a. WDM filter 31a
Sends the input monitoring pulse train of wavelength λ2 to one optical transmission line as a superimposed optical pulse train (λ2). When a state change occurs in the relay station building, the state change of the ON / OFF information is detected by the control unit 24, and an ON / OFF control signal is given to the optical switch 33a. The optical switch 33a is
It opens and closes according to the ON / OFF of the N / OFF control signal, and superimposes ON / OFF information (maintenance information) on the monitoring pulse train (λ2) (FIG. 8 (b) (c)).
2) is sent to one optical transmission line.

In the terminal station A, the WDM filter 22 splits the superimposed optical pulse train (λ 2) input from one of the optical transmission lines, and gives it to the optical receiver 25. The optical receiver 25 performs timing control or the like on the input superimposed optical pulse train,
6 and an error detection circuit 27 in parallel. The detection / reproduction circuit 26 checks whether or not the ON / OFF information is superimposed on the input superimposed light pulse train, and supplies the inspection result to the error detection circuit 46, and the superimposed ON / O signal.
The FF information is extracted and output to the outside. The error detection circuit 27 checks whether or not there is a bit error in the superimposed optical pulse train input from the optical receiver 25 when the inspection result is “ON / OFF information is not superimposed”. The error detection circuit 27 does not perform the bit error detection operation when the inspection result is “ON / OFF information is superimposed”.

On the other hand, in the terminal station A, the main signal light pulse train (λs) is input from the other optical transmission line of the pair of optical transmission lines. In this case, the optical receiver 28 outputs the signal to an external main signal circuit by performing timing control or the like. Similarly, the terminal station B transmits the main signal light pulse train of wavelength λs and the monitoring light pulse train of wavelength λ3 to one optical transmission line by wavelength division multiplexing. The pulse train is converted into a monitoring light pulse train of wavelength λ4, and the superimposed light pulse train is returned to the terminal B. Further, the main signal light pulse train is sent to the terminal A.

As described above, the terminal stations A and B can independently collect maintenance information of the relay station and monitor the quality of the transmission line using one optical transmission line. Next, FIG.
It is a block diagram of 2nd Embodiment corresponding to 4, 7, 8, and 10-12. The same components as those in the first embodiment are denoted by the same reference numerals and names. The second embodiment relates to an information transmission method for collecting maintenance information of a relay station building using both optical transmission line pairs.

Therefore, the optical transmission terminal device 50 installed in the terminal station is configured so as to be clearly distinguished between the transmitting unit 50a and the receiving unit 50b. The transmission unit 50a includes an optical receiver 21, a pulse generator 23, an optical receiver 24, and a multiplexer 52. In the multiplexer 52, the output terminals of the two optical receivers 21 and 24 are connected to two input terminals, respectively, and the output terminal is connected to one end of one optical transmission line of the pair of optical transmission lines.

The receiving section 50b includes a demultiplexer 53, optical receivers 25 and 28, a reproduction detection circuit 26, and an error detector 27. The demultiplexer 53 has an input end connected to one end of the other optical transmission line of the pair of optical transmission lines, one output end connected to the input end of the optical receiver 25, and the other output end connected to the optical receiver 28. Is connected to the input terminal of The output end of the optical receiver 25 is connected to the reproduction detection circuit 26 and the error detector 27, as in the first embodiment.

The optical repeater station 60 installed in the repeater station has a first
Instead of the WDM filters 31a and 31b of the embodiment, splitters 61a and 61b and multiplexers 62a and 62b are provided. It is needless to say that this is not an essential matter, but to indicate various changes. The duplexer 61a,
61b, the input end is connected to the other end of one of the optical transmission lines,
One output terminal is connected to the input terminals of the wavelength converters 32a and 32b, and the other output terminal is connected to one input terminal of the multiplexers 62a and 62b. The output terminals of the optical switches 33a and 33b are connected to one input terminals of the multiplexers 62a and 62b.

The multiplexer combines a plurality of optical signals having different wavelengths into one.
Device that joins the optical fiber of the book,
Although the device performs the reverse operation, it is reversible in principle and is realized by the same device. The main components are:
There are known prisms and diffraction gratings as angle dispersive elements, dielectric multilayer filters as wavelength selecting elements, and the like. In the above configuration, the correspondence with the claims is as follows. The demultiplexer 4 corresponds to the demultiplexers 61a and 61b. The multiplexing means 5 corresponds to the multiplexing devices 62a and 62b. The multiplexer 52 corresponds to the multiplexer 12. The demultiplexer 53 corresponds to the demultiplexer 13. Other correspondences are the same as in the first embodiment.

Next, referring to FIG.
Operations of the second embodiment corresponding to 8, 10 and 12 will be described. In the terminal station, in the transmission section 50a of the optical transmission terminal device 50, the optical transmitter 21 converts a main signal pulse train, which is an electric signal input from an external main signal circuit, into a main signal light pulse train having a wavelength λs. Output to the waver 52. Further, the optical transmitter 24 converts the monitoring pulse train, which is an electric signal generated by the pulse generator 23, into a monitoring light pulse train having a wavelength λ 1 and outputs it to the multiplexer 52. As a result, the multiplexer 52
The input main signal light pulse train of wavelength λs and the monitoring light pulse train of wavelength λ1 are subjected to wavelength division multiplexing (WDM) and transmitted to one optical transmission line of an optical transmission line pair.

In the relay station, an optical pulse train related to wavelength division multiplexing from the terminal station is input to the demultiplexer 61a, and is split into a main signal optical pulse train (λs) and a monitoring optical pulse train (λ1). The demultiplexed monitoring optical pulse train (λ1) is converted into a monitoring pulse train of wavelength λ2 by the wavelength converter 32a and input to the optical switch 33a. The split main signal light pulse train (λs) is input to the multiplexer 62b. Optical switch 3
3a is a wavelength λ2 converted in the same manner as in the first embodiment.
, A superimposed optical pulse train is generated from the monitoring pulse train, and output to the multiplexer 62a.

In the demultiplexer 61b, the optical pulse train for wavelength division multiplexing input from the other optical transmission line pair is demultiplexed into a main signal optical pulse train (λs) and a monitoring optical pulse train (λ3). The optical pulse train (λ3) is supplied to the wavelength conversion unit 32b, and the main signal pulse train (λs) is supplied to the multiplexer 62a. As a result, the multiplexer 62a outputs the main signal light pulse train (λ
s) and the superimposed optical pulse train (λ3) are wavelength division multiplexed and transmitted to the other optical transmission line of one optical transmission line pair. On the other hand, in the multiplexer 62b, since the superimposed optical pulse train of the wavelength λ4 is inputted from the optical switch 33b, it is converted into the main signal optical pulse train (λs).
And wavelength division multiplexing, and sends out to the other optical transmission line of the other optical transmission line pair.

At the terminal station on one end side of one optical transmission line pair, the receiving section 50b of the optical transmission terminal apparatus 50 includes a demultiplexer 53.
Is the superimposed optical pulse train (λ2) input from the other optical transmission line
And gives a detection / reproduction circuit 26 and an error detection circuit 27 via an optical receiver 25. The detection / reproduction circuit 26 and the error detection circuit 27 perform the same operations as those in the first embodiment, and a description thereof will be omitted. It goes without saying that the same operation is performed at the terminal station on one end side of the other optical transmission line pair.

As described above, in the second embodiment, both end stations can collect maintenance information of the relay station and monitor the quality of the optical transmission line using both optical transmission line pairs. Next, FIG.
It is a block diagram of 3rd Embodiment corresponding to Claim 3, 4, 7-12. The third embodiment is an information transmission method when the optical repeaters of the second embodiment are connected in multiple stages.

In this case, the terminal stations A and B at both ends generate a monitoring optical pulse train having a wavelength unique to each optical repeater for each optical repeater, and wavelength-division multiplex with the main signal optical pulse train in order. Alternatively, wavelength division multiplexing is performed in an arbitrary order, and further, all wavelengths are simultaneously wavelength division multiplexed and transmitted to one optical transmission line. In generating the monitoring optical pulse train, a method is employed in which the number of generating systems is equal to the number (the number of optical repeaters × 2) or the number is generated by changing the wavelength.

In each optical repeater, a monitoring optical pulse train having a unique wavelength is fetched, the wavelength converting unit converts the monitoring optical pulse train into a monitoring optical pulse train having a different wavelength, and the optical switch generates a superimposed optical pulse train. Transmit to the other optical transmission line. FIG.
0, the relay station 1 receives the multiplexed optical pulse train of the main signal optical pulse train (λs) and the monitoring optical pulse trains (λin... Λinn) of a plurality of wavelengths from one optical transmission line. The monitoring optical pulse train of wavelength λin is branched from the monitoring optical pulse train (λin... Λinn), and the remaining monitoring optical pulse train (λjn ·
..Λinn) and the main signal light pulse train (λs) are sent to the subsequent stage, while the monitoring light pulse train of wavelength λin is converted into a superimposed light pulse train of wavelength λin + 1, and the main signal light pulse train (λs) from the succeeding stage Are transmitted to the other optical transmission line.

Thus, at both end stations, a plurality of relay stations 1 to N are independently provided, for example, the terminal station A sequentially moves from the relay station 1 to the relay station N, and the terminal station B moves from the relay station N to the relay station N. The maintenance information of the relay station can be collected in order toward the relay station 1. As is clear from the operation description of each of the above embodiments, not only the maintenance information of the relay station building and the quality monitoring of the optical transmission line, but also the time from the transmission of the monitoring optical pulse train to the reception of the superimposed optical pulse train. By monitoring, it is possible to detect an abnormality in the optical transmission line such as disconnection of the optical transmission line or abnormal decrease in the signal level.

[0065]

As described above, according to the first and third aspects of the present invention, the optical repeater does not generate the sub-signal optical pulse train, but simply generates the sub-signal optical pulse train taken from the optical transmission line. It is only necessary to change the wavelength and send it to the optical transmission path again. Therefore, the optical repeater does not require a pulse train generating circuit, and can be easily configured.

According to the second and fourth aspects of the present invention, the optical repeater can superimpose the maintenance information on the sub-signal optical pulse train and send it to the optical transmission line, so that the processing circuit in the optical repeater is small. Becomes Also, a dedicated line for transmitting maintenance information can be eliminated. According to the fifth and seventh aspects of the present invention, the optical transmission terminal apparatus includes a sub-signal reciprocating in the optical transmission path and a path of the sub-signal forming a loop. It is possible to monitor the occurrence of an error in the transmission path from the optical repeater, and to determine whether the transmitted sub-signal pulse train returns or cannot detect the transmitted sub-signal pulse train. Can be detected.

According to the sixth and eighth aspects of the present invention, the optical transmission terminal apparatus collects the maintenance information and determines the quality of the transmission path according to whether the returned sub-signal optical pulse train is superimposed with the maintenance information. Monitoring and transmission system status monitoring can be performed. In summary, an optical communication system including the optical repeater according to claim 1 and the optical transmission terminal device according to claim 5, and the optical repeater according to claim 3 and the optical transmission terminal according to claim 7. In an optical communication system including a station device, the optical transmission terminal device can collect the status of the transmission system including the optical repeater.

Also, an optical communication system comprising the optical repeater according to claim 2 and the optical transmission terminal device according to claim 6,
And in the optical communication system including the optical repeater according to claim 4 and the optical transmission terminal device according to claim 8, the optical transmission terminal device further specifically stores the maintenance information of the optical repeater. Can be collected. In the invention according to claim 9, the plurality of optical repeaters are:
Since a unique wavelength is assigned to each optical repeater, maintenance information can be collected for each optical repeater, and the evaluation of the relay station building in which the state change has occurred can be performed immediately.

According to the tenth aspect of the present invention, the wavelength conversion means can be realized with a simple configuration without adopting a special configuration. According to the eleventh aspect, when a state change of the relay station building occurs, the state change can be detected as quickly as possible. According to the twelfth aspect of the present invention, the superimposing means can be realized with a simple configuration without employing a special configuration.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the invention according to claims 1, 2, 11, and 12;

FIG. 2 is a principle block diagram of the invention according to claims 3, 4, 11, and 12;

FIG. 3 is a principle block diagram of the invention according to claims 5 and 6;

FIG. 4 is a principle block diagram of the invention according to claims 7 and 8;

FIG. 5 is a configuration diagram of a first embodiment corresponding to claims 1, 2, 5, 6, and 10 to 12;

FIG. 6 is a diagram illustrating a configuration example of a WDM filter.

FIG. 7 is a diagram illustrating the configuration and operation of a wavelength conversion unit.

FIG. 8 is an explanatory diagram of modulation of a monitoring optical pulse train by an optical switch.

FIG. 9 is a configuration diagram of a second embodiment corresponding to claims 3, 4, 7, 8, 10 to 12;

FIG. 10 is a configuration diagram of a third embodiment corresponding to claims 3, 4, 7 to 12;

[Explanation of symbols]

 1, 8 add / drop unit 2 wavelength conversion unit 3 superposition unit 4, 12 demultiplexing unit 5, 13 multiplexing unit 6 conversion unit 7 generation unit 9, 11 monitoring unit 10 detection unit 14 state change detection unit 20, 50 optical transmission end Station device 22 WDM filter 23 Pulse generator 26 Detection / reproduction circuit 27 Error detector 30, 60 Optical repeater 31a, 31b WDM filter 32a, 32b Wavelength conversion unit 33a, 33b Optical switch 34 Control unit 40 Laser diode (LD) 41 Semiconductor Optical amplifier 52 Demultiplexer 53 Demultiplexer 61a, 61b Demultiplexer 62a, 62b Demultiplexer

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 17/02

Claims (12)

[Claims] 1. An optical pulse train for wavelength division multiplexing taken from one optical transmission line of an optical transmission line pair is branched into a main signal optical pulse train and a first sub-signal optical pulse train, and the branched main signal optical pulse train is converted into the other. Means for transmitting the second sub-signal light pulse train to the one optical transmission line, and converting the branched first sub-signal light pulse train into the second sub-signal light pulse train having a different wavelength. An optical repeater comprising: a wavelength conversion unit that outputs the signal to the add / drop unit. 2. The optical repeater according to claim 1, wherein a second sub-signal optical pulse train whose wavelength has been converted by the wavelength converter is maintained between the wavelength converter and the add / drop unit. An optical repeater comprising superimposing means for superimposing information and outputting the superimposed information to the add / drop means. 3. An optical pulse train for wavelength division multiplexing fetched from one optical transmission line of an optical transmission line pair is split into a main signal optical pulse train and a first sub-signal optical pulse train, and the split main signal optical pulse train is split. Demultiplexing means for transmitting the first sub-signal light pulse train to the other system.
Wavelength conversion means for converting to a sub-signal light pulse train, wavelength-division multiplexing of the main signal light pulse train demultiplexed by the other system and the wavelength-converted second sub-signal light pulse train, and the other of the optical transmission line pair An optical repeater comprising: a multiplexing means for transmitting the signal to an optical transmission line. 4. The optical repeater according to claim 3, wherein a second sub-signal optical pulse train whose wavelength has been converted by the wavelength converting means is provided between the wavelength converting means and the multiplexing means. An optical repeater comprising a superimposing means for superimposing and outputting the superimposed signal to a multiplexing means. 5. A converting means for converting a main signal, which is an electric signal, into an optical pulse train, a generating means for generating a first sub-signal optical pulse train, a wavelength division multiplexing of an output of said converting means and an output of said generating means. And transmitting to the one optical transmission line of the pair of optical transmission lines and taking in the second sub-signal optical pulse train from the one optical transmission line; and using the taken-in second sub-signal optical pulse train. Claim 1
Monitoring means for monitoring the quality of an optical transmission line to which the optical repeater according to (1) is connected. 6. The optical transmission terminal device according to claim 5, further comprising: detecting means for detecting whether or not the maintenance information is superimposed on the received second sub-signal light pulse train, wherein the monitoring means comprises: 3. An optical transmission terminal apparatus for monitoring the quality of an optical transmission line to which an optical repeater is connected, using the second sub-signal optical pulse train when the maintenance information is not detected. 7. A conversion means for converting a main signal, which is an electric signal, into an optical pulse train, a generation means for generating a first sub-signal optical pulse train, a wavelength division multiplexing of an output of the conversion means and an output of the generation means. Multiplexing means for transmitting to one optical transmission line of the pair of optical transmission lines and an optical pulse train related to wavelength division multiplexing taken from the other optical transmission line of the pair of optical transmission lines and a main signal optical pulse train and a second sub-transmission line. A demultiplexing unit for demultiplexing the optical signal into a signal light pulse train; and a monitoring unit for monitoring the quality of an optical transmission line to which the optical repeater according to claim 3 is connected, using the demultiplexed first sub-signal light pulse train. An optical transmission terminal device comprising: 8. The optical transmission terminal according to claim 7, further comprising: a detecting unit that detects whether the maintenance information is superimposed on the split second sub-signal optical pulse train, and the monitoring unit. Monitoring the quality of an optical transmission line to which the optical repeater according to claim 4 is connected by using the split second sub-signal optical pulse train when the maintenance information is not detected. Transmission terminal equipment. 9. The plurality of optical repeaters according to claim 3 or 4, wherein one end of the optical repeater relays the optical transmission line pair connected to the optical transmission terminal device according to claim 7 or 8 in multiple stages. Is
An optical repeater, wherein each of the wavelength converting means converts the input first sub-signal light pulse train into a second sub-signal light pulse train having a different wavelength. 10. The method of claim 1, 2, 3, 4, or 9.
In the optical repeater described in the paragraph, the wavelength conversion means in the optical repeater includes a semiconductor laser and a semiconductor optical amplifier that performs a wavelength conversion operation by receiving laser light of the semiconductor laser as converted light. An optical repeater characterized by the above-mentioned. 11. The method according to claim 1, wherein
The optical repeater according to claim 1, further comprising a state change detection unit that detects a state change of the relay station building and outputs the maintenance information. 12. The optical repeater according to claim 11, wherein the superimposing means is an optical switch that is turned on and off in accordance with an output of the state change detecting means.