JP2000031907A - Supervisory signal light bypass circuit, optical amplifying repeater using the same and its supervisory system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit a supervisory signal without giving effect on a main signal light propagated through an optical fiber transmission line. SOLUTION: Optical amplifiers 34a, 34b are inserted respectively to an incoming optical fiber transmission line 31a and an outgoing optical fiber transmission line 31b through which a main signal light and a supervisory signal light from an optical terminal station device are transmitted and supervisory signal optical bypass circuits 32, 33 are placed at both sides of the optical amplifiers 34a, 34b by using them as a border. The configuration consists of photocouplers 32a, 32b provided to each optical fiber transmission line, an optical fiber 32c that interconnects each one terminal of output ports of the photocouplers 32a, 32b, an optical fiber grating 32d that interconnects the other terminals of output ports of the photocoupler 32a, and an optical fiber grating 32e that interconnects the other terminal of output parts of the photocoupler 32b. A supervisory signal light bypass circuit 33 bypasses the supervisory signal light on the optical fiber transmission line 31a to the optical fiber transmission line 31f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supervisory signal light bypass circuit, and an optical amplification repeater and a monitoring system for an optical repeater transmission system using the same. More particularly, the present invention relates to a supervisory signal light from a terminal device. The present invention relates to a monitoring signal light bypass circuit for returning a signal to an apparatus, an optical amplification repeater using the same, and a monitoring method thereof.

[0002]

2. Description of the Related Art In an optical transmission system, it is necessary to monitor an optical amplifying repeater including a transmission line by a terminal device using a monitoring signal light in order to guarantee proper propagation of a signal light. Hereinafter, a conventional optical amplification repeater that can be monitored by monitoring signal light will be described.

FIG. 13 shows a first example of an optical amplifying repeater which can be monitored by a conventional monitoring signal light from a terminal device, which is described in Japanese Patent Application Laid-Open No. 6-204949. FIG.
13 shows the transfer operation of the supervisory signal light in the optical amplifying repeater of FIG. In this optical amplification repeater 1, an optical amplifier 2a and a 2 × 2 optical coupler (referred to as a 2-input and 2-output optical coupler) 3a are arranged from the input side to the output side of the upstream optical fiber transmission line 9a. Similarly, an optical amplifier 2b and an optical coupler (2 × 2) 3b are arranged from the input side to the output side of the downstream optical fiber transmission line 9b.
a, 3b between the upstream and downstream optical attenuators 4a, 4b
b is arranged in a loop.

In such a configuration, the main signal light and another wavelength of the signal light spectrum in FIG. 14 (the vertical axis the light intensity and the horizontal axis optical wavelength) 4 wavelength multiplexing as shown in (lambda ₁ to [lambda] ₄₎ A case where the (λsv) monitor signal light is transmitted from the terminal equipment (not shown) to the upstream optical fiber transmission line 9a will be described.

[0005] The main signal light and the supervisory signal light are supplied to the optical amplifier 2.
a and is branched by the optical coupler 3a. Then, the branched main signal lights λ _{1 to} λ ₄ and the monitoring signal light λsv
Is attenuated by the optical attenuator 4a and is coupled with the signal light propagating through the downstream optical fiber transmission line 9b by the optical coupler 3b.
It is returned to the terminal device that transmitted the main signal lights λ _{1 to} λ ₄ and the supervisory signal light λsv. Thereby, the transmission line monitoring device of the terminal station device can monitor the optical amplification repeater 1.

FIG. 15 shows a second example of an optical amplifying repeater which can be monitored by a conventional monitoring signal light from a terminal equipment, which is described in Japanese Patent Application Laid-Open No. 8-181656. FIG. 16 shows the transfer operation of the supervisory signal light in the optical amplifying repeater of FIG. In the optical amplifying repeater 11, an optical amplifier 12a and an optical coupler (2 × 2) 13a are arranged from the input side to the output side of the upstream optical fiber transmission line 19a, and similarly, the input side of the downstream optical fiber transmission line 19b. Amplifier 12b and optical coupler (2 × 2) 13 from
b, and furthermore, between the optical couplers 13a and 13b, upstream and downstream optical band-pass filters 14a and 14b.
b is arranged in a loop.

[0007] In such a configuration, the main signal light and another wavelength of the signal light spectrum in FIG. 16 (the vertical axis the light intensity and the horizontal axis optical wavelength) 4 wavelength multiplexing as shown in (lambda ₁ to [lambda] ₄₎ The case where the monitor signal light of (λsv) is transmitted from the terminal device (not shown) to the upstream optical fiber transmission line 19a will be described.

The main signal light and the supervisory signal light are supplied to the optical amplifier 1
The signal is amplified at 2a and branched at the optical coupler 13a. The split main signal light λ _{1 to} λ ₄ and the supervisory signal light λsv are transmitted only by the optical bandpass filter 14a at the transmittance shown in FIG.
3b in the coupled signal light propagated through the down optical fiber transmission line 19b, are sent back to the sending end station to the main signal light lambda ₁ to [lambda] ₄ and supervisory signal light signal .lambda.sv. Thereby, the transmission line monitoring device of the terminal station device can monitor the optical amplification repeater 11.

[0009]

However, according to the conventional optical amplifying repeater shown in FIG. 13, the main signal light is transferred to the opposite line together with the supervisory signal light, and the transferred main signal light and the opposite line are transmitted. There is a problem of main signal deterioration such as interference with the main signal light propagating through the main line, and lowering of the main signal level of the opposite line due to mixing of the transferred main signal light. Alternatively, the loss of the return path is set to be large in order to avoid the deterioration of the main signal, so that the level of the reflected monitor signal light is small, and a highly accurate receiving circuit is required in the transmission path monitoring device.

According to the conventional optical amplifying repeater shown in FIG. 15, the supervisory signal light is extracted by the optical filter and transferred to the opposite line. However, it is difficult for the optical filter to narrow the transmission band. Therefore, the adjacent main signal light leaks and is transferred to the opposite line. As a result, there is a problem of main signal deterioration such as interference between the transferred main signal light and the main signal light propagating in the opposite line, and a decrease in the main signal light level of the opposite line due to mixing of the folded main signal light. Alternatively, it is necessary to arrange the wavelength of the monitoring signal light away from the main signal light in order to avoid the deterioration of the main signal, so that there is a problem that the amplification wavelength band of the optical amplifier must be widened.

Accordingly, an object of the present invention is to provide a supervisory signal light bypass circuit which does not affect the main signal light propagating in the optical fiber transmission line, an optical amplifier repeater using the same, and a monitoring system therefor. It is in.

[0012]

In order to achieve the above object, the present invention has, as a first feature, a 2 × 2 first optical coupler provided on a first optical transmission line; The first optical transmission line is a 2 × 2 second optical coupler provided in a second optical transmission line in which the signal light flows in the opposite direction, and one output port of the first optical coupler is connected to the second optical coupler. A third optical transmission line connected to one output port of the second optical coupler, a first reflection unit provided at the other output port of the first optical coupler, and having a first reflection wavelength; It is an object of the present invention to provide a supervisory signal light bypass circuit, comprising: a second reflection means provided at the other output port of the second optical coupler and having a second reflection wavelength. Here, the third optical transmission line is not limited to the one described in the embodiment, and the ports of the first and second optical couplers may be directly connected.

According to a second aspect of the present invention, there is provided a 2 × 2 first optical coupler provided in a first optical transmission line, wherein the first optical transmission line includes Is a 2 × 2 second optical transmission line provided in the second optical transmission line in which the signal light flow is in the opposite direction.
An optical coupler, a first reflection means provided at one output port of the first optical coupler, having a first reflection wavelength, and having been subjected to a non-reflection termination process, and an optical coupler of the second optical coupler. A first monitoring signal light bypass circuit provided at one of the output ports, the second monitoring signal light bypass circuit having a second reflection wavelength and a non-reflection terminated second reflection means; and the first optical transmission line A 2 × 2 third optical coupler provided in the second optical transmission line, and a 2 × 2 fourth optical coupler provided in the second optical transmission line;
A third reflection means provided at one output port of the third optical coupler and having the first reflection wavelength and subjected to non-reflection termination processing; and one output port of the fourth optical coupler. A second monitoring signal light bypass circuit comprising: a fourth reflecting means having a second reflection wavelength and having been subjected to non-reflection terminating processing; and a first monitoring signal light bypass circuit. First and second optical amplifiers respectively inserted in the first and second optical transmission lines located between the second supervisory signal optical bypass circuits, and one output of the first optical coupler First connection means for connecting a port to one output port of the second optical coupler or the fourth optical coupler; one output port of the third optical coupler to the fourth optical coupler; One output port of the two optical couplers; To provide an optical amplifier repeater, characterized by having, a second connection means for connecting.

According to a third aspect of the present invention, there is provided an optical terminal device for transmitting and receiving signal light, and a first optical transmission line connected to the optical terminal device. A second optical transmission line through which signal light is transmitted in a direction opposite to the first optical transmission line; and the first and second optical transmission lines provided in the middle of the first and second optical transmission lines. And at least one optical amplifying repeater having a set of optical amplifiers for amplifying the signal light passing through each of the optical transmission lines, wherein the optical terminal device transmits the main signal light An optical transmitter for outputting, an optical receiver for receiving signal light from the second optical transmission line, a transmission line monitoring circuit for transmitting and receiving supervisory signal light, the main signal light and the supervisory signal light Optical multiplexing means for multiplexing and transmitting the signal to the first optical transmission line;
Light separating means for separating a main signal light and a monitor signal light received from the second optical transmission line, wherein the optical amplification repeater converts the monitor signal light from the first optical transmission line A monitoring signal optical bypass circuit for bypassing to the second optical transmission line, wherein the transmission line monitoring circuit of the optical terminal device is configured to transmit the second signal via the monitoring signal optical bypass circuit of the optical amplification repeater; The monitoring signal light returned from the optical transmission line is received, and the optical transmission is performed based on the monitoring signal light transmitted from the optical terminal device and the intensity amplitude, phase, frequency, and time difference information of the received monitoring signal light. It is to provide a monitoring method characterized by monitoring a road.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of a supervisory signal light bypass circuit according to the present invention. Here, (a) ~
(D) shows four types of supervisory signal light bypass circuits. Each monitoring signal light bypass circuit is composed of two 2 ×
It is composed of two optical couplers and two optical fiber gratings. In the figure, UP indicates upward, and DOWN indicates downward. IN indicates an input, and OUT indicates an output. (A) is a circuit capable of bypassing the backscattered light of the monitoring light input λsv2 from the upstream optical fiber transmission line 21a, (b) is a circuit capable of bypassing the backscattered light from the downstream optical fiber transmission line 21b, c), (d)
Is a circuit for bypassing only the supervisory signal light λsv1 transmitted from the optical terminal equipment. Here, the monitoring signal light is modulated by any of optical pulse modulation, light intensity modulation, light frequency modulation, and light phase modulation.

In the monitoring signal light bypass circuit 20A shown in FIG. 1A, an optical coupler 22a is provided in the middle of the upstream optical fiber transmission line 21a, and an optical coupler 22b is provided in the middle of the downstream optical fiber transmission line 21b. ing. Optical coupler 22
An optical fiber 23 as a third optical transmission path is connected between the input end of the optical coupler 22a and the output end of the optical coupler 22b. An optical fiber grating 24a is connected to the output side end of the optical coupler 22a, and an optical fiber grating 24b is connected to the output side end of the optical coupler 22b. Here, the reflection wavelength of the optical fiber grating 24a is set to the monitoring signal light λsv1, and the reflection wavelength of the optical fiber grating 24b is set to the monitoring signal light λsv2. Therefore, the optical fiber gratings 24a and 24b cannot reflect signal light having a wavelength other than the set wavelength.

The monitoring signal light bypass circuit 20B shown in FIG. 1B has a configuration in which the arrangement of the optical fiber 23 and the optical fiber gratings 24a and 24b in FIG. Also in this configuration, the reflection wavelength of the optical fiber grating 24a is set to the monitoring signal light λsv1, and the reflection wavelength of the optical fiber grating 24b is set to the monitoring signal light λsv2.

The monitoring signal light bypass circuit 20C shown in FIG. 1C has the same configuration of the upstream optical fiber transmission lines 21a and 21b and the optical couplers 22a and 22b, but the optical fiber grating 24a is connected to the input of the optical coupler 22a. The optical fiber grating 24b is connected to the output side end of the optical coupler 22b.
Are connected between the output-side ends of the optical couplers 22a and 22b. The monitoring signal light bypass circuit 20D shown in FIG. 1D has a configuration in which the arrangement of the optical fiber 23 and the optical fiber gratings 24a and 24b in FIG. 1C is switched between input and output.

FIG. 2 shows the path of the supervisory signal light of the supervisory signal light bypass circuits 20A to 20D having the configuration of FIG. In the monitoring signal light bypass circuit 20A shown in FIG.
Assuming that .about..lambda.4 and the supervisory signal light .lambda.sv1 are transmitted from the terminal equipment (not shown) to the upstream optical fiber transmission line 21a, the supervisory signal light .lambda. Incident on the down optical fiber transmission line 21b through the optical fiber 23,
Further, the light passes through the downstream optical fiber transmission line 21b and is transmitted to the input side of the downstream optical fiber transmission line 21b. The backscattered light generated when the monitor signal light λsv1 propagates through the downstream optical fiber transmission line 21b is returned to the transmitting terminal device.

The backscattered light of the supervisory signal light λsv2 transmitted from the terminal equipment (generated when the supervisory signal light propagates along the optical fiber transmission line) is transmitted through the optical coupler 22a and then transmitted to the upstream optical fiber. It scatters in the road 21a and goes backwards,
The light is branched by the optical coupler 22a, enters the optical fiber grating 24b through the optical fiber 23, and is reflected and returned to the terminal device that transmitted through the downstream optical fiber transmission line 21b and transmitted. As described above, the transmission line monitoring device of the terminal station device can monitor the optical bypass circuit. Moreover, there is no influence on the main signal light propagating through the optical fiber transmission line.

The supervisory signal light bypass circuit 2 shown in FIG.
In the case of 0B, when the main signal light and the supervisory signal light λsv1 are transmitted from the terminal equipment (not shown) to the upstream optical fiber transmission line 21a, the supervisory signal light λsv1 arriving downstream after passing through the optical coupler 22a is scattered. The scattered light generated returns to the upstream optical fiber transmission line 21a, and is returned to the terminal device that transmitted via the optical coupler 22a → the optical fiber grating 24a → the optical fiber 23 → the optical coupler 22b → the downstream optical fiber transmission line 21b. Further, the monitoring signal light λsv2 is branched by the optical coupler 22a, and the optical fiber 23 → optical coupler 22b → optical fiber grating 24b → optical coupler 22b → optical fiber transmission line 21b (reverse direction) → scattering → optical fiber transmission line 21b (forward direction). Is returned to the terminal station device that transmitted the route. As described above, the transmission line monitoring device of the terminal station device can monitor the optical bypass circuit. Moreover, there is no influence on the main signal light propagating through the optical fiber transmission line.

The monitor signal light bypass circuit 2 shown in FIG.
In the case of 0C, when the main signal light and the supervisory signal light λsv1 are transmitted from the terminal equipment (not shown) to the upstream optical fiber transmission line 21a, the supervisory signal light λsv1 is branched by the optical coupler 22a, and the optical fiber 23 → the optical coupler. The path follows the path of 22b → optical fiber grating 24b → optical coupler 22b → downward optical fiber transmission line 21b (forward direction), and is returned to the transmitting terminal apparatus. As described above, the transmission line monitoring device of the terminal station device can monitor the optical bypass circuit. Moreover, there is no influence on the main signal light propagating through the optical fiber transmission line.

Next, in the case of the monitoring signal light bypass circuit 20D shown in FIG. 1D, when the main signal light and the monitoring signal light λsv1 are transmitted from the terminal equipment (not shown) to the upstream optical fiber transmission line 21a, The monitoring signal light λsv1 is branched by the optical coupler 22a, and the optical fiber grating 24a → the optical coupler 22
The signal is returned to the transmitting terminal device through the path of a → optical fiber 23 → optical coupler 22b → downward optical fiber transmission line 21b (forward direction). As described above, the transmission line monitoring device of the terminal station device can monitor the optical bypass circuit. Moreover, there is no influence on the main signal light propagating through the optical fiber transmission line.

Next, an optical amplifying repeater of the present invention constituted by using the supervisory signal light bypass circuit shown in FIG. 1 will be described. FIG. 3 shows a basic configuration of an optical amplification repeater equipped with the monitor signal bypass circuit of the present invention. The optical amplification repeater 30 in FIG. 3 includes a monitoring signal light bypass circuit having the configuration shown in FIG. 1B, a monitoring signal light bypass circuit having the configuration shown in FIG. 1A, and light provided in the upper and lower optical fiber transmission lines. It is configured by a combination with an amplifier.

The optical amplifying repeater 30 is provided with supervisory signal light bypass circuits 32 and 33 interposed between the upstream optical fiber transmission line 31a and the downstream optical fiber transmission line 31b. Bypass circuit 33
The optical amplifiers 34a and 34b are provided between them. The optical amplifier 34a is provided on the upstream optical fiber transmission line 31a,
The optical amplifier 34b is provided on the downstream optical fiber transmission line 31b.

The monitoring signal light bypass circuit 32 includes a 2 × 2 optical coupler 32 provided on the upstream optical fiber transmission line 31a.
a, an optical fiber 32c provided between one end of the 2 × 2 optical coupler 32b provided on the downstream optical fiber transmission line 31b and one end of the 2 × 2 optical coupler 32a and another end of the 2 × 2 optical coupler 32a. An optical fiber grating 32d connected to the end, an optical fiber grating 32e connected to the other end of the 2 × 2 optical coupler 32b, and an anti-reflection terminal 32 provided at an end of the optical fiber grating 32d
f, a non-reflection terminal 32g provided at the end of the optical fiber grating 32e. Each non-reflection end absorbs the signal light passing through the optical fiber grating and prevents reflection toward the optical fiber grating.

The monitoring signal light bypass circuit 33 includes a 2 × 2 optical coupler 33a provided on the upstream optical fiber transmission line 31a on the output side of the optical amplifier 34a, and a downstream optical fiber transmission line 31b.
2 × 2 optical coupler 33b, 2 × 2 optical coupler 3
An optical fiber 33c provided between one end of 3a and one end of 33b, an optical fiber grating 33d connected to the other end of the 2 × 2 optical coupler 33a, and a 2 × 2 optical coupler 33
optical fiber grating 33 connected to the other end of b
e, an anti-reflection terminal 33f provided at an end of the optical fiber grating 33d, and an optical fiber grating 3
It comprises a non-reflection end 33g provided at the end of 3e.

The monitoring light is bypassed before and after the optical amplifiers 34a and 34b as described with reference to FIGS.
Since the signal is returned to the transmitting terminal device, the transmission path monitoring device of the terminal device can monitor the optical bypass circuit. Moreover, there is no influence on the main signal light propagating through the optical fiber transmission line. Then, both the main signal light and the monitor signal light passing through the optical amplifiers 34a and 34b are
The signal is amplified by the a and b, and the function as the optical amplification repeater 30 is exhibited. The optical amplification repeater 30 in FIG. 3 can be used as one device of an optical transmission system.
Hereinafter, an optical fiber transmission system according to the present invention will be described.

FIG. 4 shows a first embodiment of the optical fiber transmission system of the present invention. The optical fiber transmission system 40 shown in FIG.
a, 41b, optical terminal units 42a, 42b connected to both sides of the optical fiber transmission lines 41a, 41b, and optical amplification repeaters 30a, 30b. The optical amplification repeaters 30a and 30b have the same configuration and are as shown in FIG. The optical fiber transmission lines 41a and 41b and the optical amplifier repeaters 30a and 30b can transmit both the main signal light and the monitor signal light having different wavelengths. Optical terminal units 42a and 42b and optical amplification repeaters 30a and 30b
Are provided with a monitoring signal light bypass circuit, but are provided so that only the monitoring signal light can flow between the upstream optical fiber transmission line 41a and the downstream optical fiber transmission line 41b.

The optical terminal unit 42a includes an optical transmitter (OS) 4
3a, an optical receiver (OR) 44a, an optical multiplexing means 45a, an optical demultiplexing means (MON) 46a, a transmission line monitoring circuit 47a, and a monitoring signal light bypass circuit 48a. Similarly, the optical terminal device 42b includes an optical transmitter (OS)
43b, an optical receiver (OR) 44b, an optical multiplexing means 45b,
A light separating means (MON) 46b, a transmission line monitoring circuit 47b,
And a monitoring signal light bypass circuit 48b. The monitoring signal light bypass circuit 48a (48b)
The supervisory signal light enters the optical multiplexing means 45a (45b),
The monitoring signal light is obtained from the light separating means 46a (46b). The optical multiplexing means 45a (45b) includes an optical transmitter 43a.
(43b) and the transmission line monitoring circuit 47a (47b) are connected, and the optical receiver 4a is connected to the optical separation means 46a (46b).
4a (44b) and the light separating means 46a (46b) are connected. Further, a monitoring signal light bypass circuit 48a (48b) is connected to the optical multiplexing means 45a (45b) and the light separating means 46a (46b), and the monitoring signal light bypass circuit 48a (48b) is connected to the optical fiber transmission line 4.
1a and 41b are connected.

FIG. 5 shows the path of the monitor signal light of wavelength λsv1 in the optical amplification repeater 30a of the optical fiber transmission system 40 shown in FIG. That is, the wavelength λ is transmitted from the optical terminal unit 42a to the optical amplification repeater 30a to the optical fiber transmission line 41a.
The monitoring operation when the sv1 monitoring signal light is transmitted is shown. The optical signal transmitted through the optical fiber transmission line 41a is optically amplified by the upstream optical amplifier 34a in the optical amplification repeater 30a, and is output to the optical coupler 33a of the optical fiber transmission line 41a. From the optical fiber transmission line 41a, the backscattered light of the optical signal passing through the optical coupler 33a is transmitted to the optical amplification repeater 3.
Returning to 0a, the signal is branched by the optical coupler 33a and bypassed to the downstream optical fiber transmission line 41b. After the backward scattered light of the optical signal bypassed to the downstream side passes through the optical coupler 33b, only the wavelength component of the monitoring signal light is reflected by the optical fiber grating 33e. 41b. Thus, the backscattered light of the monitoring signal light (wavelength λsv1) from the upstream optical fiber transmission line 41a is
b is returned to the optical terminal unit 42a. Accordingly, the transmission line monitoring circuit 47a can monitor the monitoring signal light bypass circuit 33.

FIG. 6 shows the path of the supervisory signal light of wavelength λsv2 in the optical amplification repeater 30a of the optical fiber transmission system 40 shown in FIG. That is, the monitoring operation when the monitoring signal light of the wavelength λsv2 is transmitted from the optical terminal unit 42a to the optical fiber transmission line 41a to the optical amplification repeater 30a shown in FIG. The monitoring signal light λsv2 is generated by the transmission line monitoring circuit 47a, multiplexed with the main signal by the optical multiplexing means 45a in the optical terminal unit 42a, and transmitted to the optical fiber transmission line 41a. Optical fiber transmission line 41a
Is transmitted by the optical coupler 33a in the optical amplifying repeater 30a, and then only the monitoring signal light λsv2 is reflected by the optical fiber grating 33d (reflection wavelength: λsv2), and passes through the optical coupler 33a again. Then, the signal is bypassed to the downstream optical fiber transmission line 41b. The bypassed supervisory signal light λsv2 is coupled to the downstream optical fiber transmission line 41b by the optical coupler 33b.
The signal propagates in the direction opposite to the direction of the main signal b. This monitoring signal light λ
Backscattered light generated when sv2 propagates through the optical fiber transmission line 41b is transmitted to the optical terminal device 42a together with the main signal of the optical fiber transmission line 41b.

Here, since the reflection wavelength bandwidth of the optical fiber grating can be designed to be a very narrow value, the main signal can be sufficiently removed even if the wavelength interval between the monitor signal light and the main signal light is narrowed. Only the supervisory signal light component can be coupled to the downstream optical fiber transmission line 41b.

The supervisory signal light λsv2 returned from the optical fiber transmission line 41b is separated from the main signal light by the optical separation means 46a and input to the transmission line monitoring circuit 47a. Thereby, the transmission line monitoring circuit 47a, based on the intensity amplitude, phase, frequency, and time difference information of the transmitted monitoring signal light and the received monitoring signal light, transmits the optical amplification repeaters 34a and 34b and the optical fiber transmission lines 41a and 41b. Can be observed whether or not the state is normal.

In order to observe the backscattered light from the optical fiber transmission lines 41a and 41b, an optical pulse modulation signal is generally used, and a similar signal format is used for the monitoring signal light of the present invention. Can be. As the modulation format of the light pulse, the one that changes the light intensity is the mainstream,
A method of changing the optical frequency and performing coherent detection can also be used.

FIG. 7 shows the results of observation of the optical fiber transmission system observed along the paths shown in FIGS.
(A) shows the flow of the monitoring signal light, and the optical terminal devices 42a to 42a to
42b, three optical amplification repeaters (30a, 30b, 3)
0c) is provided. (B) shows a time change of the monitor signal light λsv1, and (c) shows a time change of the monitor signal light λsv2. As is apparent from FIG. 7, by using two monitoring signals (λsv1 and λsv2) having different wavelengths, the upper and lower optical fiber transmission lines 41 are provided on one optical terminal apparatus side.
Both a and 41b can be observed simultaneously.

Next, a description will be given of a second embodiment of the optical amplifier according to the present invention. FIG. 8 shows another embodiment of the optical amplifying repeater having the supervisory signal light bypass circuit of the present invention. In FIG. 8, the same reference numerals are used for the same components as those in FIG. The optical amplifying repeater 80 of FIG. 8 includes an optical coupler 32a and an optical coupler 33b.
Are connected by an optical fiber 81, and one ends of the optical coupler 33a and the optical coupler 32b are connected by an optical fiber 82, thereby forming monitoring signal light bypass circuits 83 and 84.

FIG. 9 shows the path of the supervisory signal light of wavelength λsv1 in the optical amplifying repeater of FIG. The supervisory signal light λsv1 transmitted from the transmission path monitoring circuit 47a and the main signal lights λ1 to λ4 transmitted from the optical transmitter 43a are transmitted through the optical fiber transmission path 41a and branched by the optical coupler 32a. The branched monitor signal light λsv1 reaches the optical coupler 33b via the optical fiber 81, is reflected by the optical fiber grating 33e, passes through the optical coupler 33b to the optical fiber transmission path 41b, and is optically amplified by the optical amplifier 34b. Thereafter, the signal is returned to the terminal device that transmitted the signal through the optical coupler 32b, and the transmission path monitoring circuit 47a can monitor the optical bypass circuit 83.

Further, by monitoring with the monitoring signal light λsv1, the monitoring signal light λsv1 having a light intensity proportional to the optical input level on the upstream side of the optical amplifying repeater 80 is output.
Since the signal propagates through 1b and returns to the optical terminal device 42a, if the intensity of the supervisory signal light λsv1 received by the transmission line monitoring circuit 47a is adjusted, it is determined whether the optical input level to the downstream optical amplifier 34b is appropriate. Can be monitored.

In the configuration of FIG. 9, the monitoring optical signal bypass circuits 32 and 33 are housed in the optical amplifying repeater 80, but may be inserted in the upstream optical fiber transmission lines 31a and 31b.

FIG. 10 shows an optical amplifying repeater 8 having the configuration of FIG.
The path of the monitoring signal light when monitoring the 0 optical bypass circuit 84 is shown. The supervisory signal light λsv2 transmitted from the transmission line monitoring circuit 47a and the main signal light (λ1 to λ4) transmitted from the optical transmitter 43a are transmitted through the optical fiber transmission line 41a and transmitted to the optical coupler 32a and the optical amplifier 34a. The light passes through the optical coupler 33b, and is branched by the optical coupler 33b. The main signal light is transmitted to the optical terminal device 42b as it is. The branched monitor signal light λsv2 is supplied to the optical coupler 33a.
The optical fiber 82 → the optical coupler 32b → the optical fiber transmission line 41b → the optical terminal device 42a is followed, and is returned to the transmission line monitoring circuit 47a. In this way, the optical bypass circuit 84 can be monitored.

Also, by monitoring with the monitoring signal light λsv2, the monitoring signal light λsv2 having a light intensity proportional to the optical output level on the upstream side of the optical amplifying repeater 80 is output.
Since the signal propagates through 1b and returns to the optical terminal unit 42a, if the intensity of the supervisory signal light λsv2 received by the transmission line supervisory circuit 47a is adjusted, the optical output level from the upstream optical amplifier 34a is normal. Can be monitored.

As shown in FIGS. 9 and 10, the optical amplifying repeater 80 of the present invention can change the bypass path to the input side or the output side by changing the wavelength of the supervisory signal light. It is possible to separately monitor the optical input level or optical output level of the amplifier repeater.

FIG. 11 shows the results of observation of the optical fiber transmission system observed along the paths shown in FIGS.
(A) shows the flow of the monitoring signal light, and the optical terminal devices 42a to 42a to
42b, three optical amplification repeaters (30a, 30b, 3)
0c) is provided. (B) shows a time change of the monitor signal light λsv1, and (c) shows a time change of the monitor signal light λsv2. As is clear from FIG. 11, by using two monitor signals (λsv1 and λsv2) having different wavelengths, both the optical input level and the optical output level of the upstream optical amplifying repeater can be determined from the upstream optical terminal equipment side. It can be observed at the same time.

FIG. 12 shows a third embodiment of the optical amplifying repeater of the present invention. In this embodiment, an optical attenuator is provided in each of the optical fibers and the optical fiber gratings of the monitoring signal light bypass circuits 32 and 33 of the optical amplifying repeater 30 shown in FIG. There are features. In the monitoring signal light bypass circuit 32, the optical attenuator 51a is connected in series with the optical fiber grating 32d, the optical attenuator 51b is provided in the optical fiber 32c, and the optical attenuator 51c is provided in series with the optical fiber grating 32e.
Are provided respectively. In the monitoring signal light bypass circuit 33, the optical fiber grating 33
An optical attenuator 52a is provided in series with d, and an optical attenuator 52b is provided in the optical fiber 33c in series with the optical fiber grating 33e. By providing the optical attenuators 51a to 51c and 52a to 52c, the loss amount can be set, and the bypass amount of the monitoring signal light can be set arbitrarily.

In the above-described embodiment, a generally widely known optical fiber coupler or the like can be used as the optical coupler.

When an optical fiber grating is used as the optical grating in the above embodiment, low loss can be obtained.
A highly reliable bypass circuit can be realized. Further, an optical waveguide type can be used as the optical grating.

[0048]

As described above, according to the supervisory signal light bypass circuit of the present invention, an optical signal is branched by an optical coupler.
By reflecting only the supervisory signal light by the light reflecting means and multiplexing it to the opposite line, the supervisory signal light can be transferred without affecting the main signal light propagating through the optical fiber transmission line.

According to the optical amplifying repeater of the present invention, a monitoring signal light bypass circuit is provided in each of the upstream and downstream optical transmission lines, and the monitoring signal light bypass circuit includes two upper and lower optical couplers, Light reflecting means is provided at one end of each output port,
Since the bypass path is formed between the optical couplers, monitoring can be performed without affecting the main signal light propagating through the optical fiber transmission line. Further, since the main signal is not deteriorated, it is not necessary to widen the amplification wavelength band of the optical amplifier.

Further, according to the monitoring method of the present invention, since the optical amplification repeater having the monitoring signal light bypass circuit having the above-described configuration is provided in the optical transmission line, the monitoring in the optical relay transmission system is performed by the optical fiber transmission. This can be performed without affecting the main signal light propagating in the path.

Further, since the light reflecting means using the optical fiber grating can narrow the reflection wavelength band, the monitoring signal light can be adjacent to the main signal light, and the amplification wavelength band of the optical amplification repeater is relatively narrow. There is an advantage that you can.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating an example of a supervisory signal light bypass circuit according to the present invention.

FIG. 2 is an explanatory diagram showing a path of a monitoring signal light of each monitoring signal light bypass circuit having the configuration of FIG. 1;

FIG. 3 is a connection diagram showing a basic configuration of an optical amplification repeater equipped with a monitoring signal bypass circuit of the present invention.

FIG. 4 is a connection diagram showing a first embodiment of the optical fiber transmission system of the present invention.

FIG. 5 is an explanatory diagram showing a path of a first supervisory signal light in the optical amplification repeater of the optical fiber transmission system shown in FIG.

FIG. 6 is an explanatory diagram showing a path of a second supervisory signal light in the optical amplification repeater of the optical fiber transmission system shown in FIG.

FIG. 7 is a waveform chart showing observation results of the optical fiber transmission system observed along the paths shown in FIGS. 5 and 6.

FIG. 8 is a connection diagram showing a second embodiment of the optical amplification repeater having the supervisory signal light bypass circuit of the present invention.

FIG. 9 shows a wavelength λsv in the optical amplifying repeater of FIG.
FIG. 3 is an explanatory diagram showing a path of a supervisory signal light.

10 is an explanatory diagram showing a path of a monitoring signal light when monitoring an optical bypass circuit of the optical amplification repeater having the configuration of FIG.

FIG. 11 is a waveform chart showing observation results of the optical fiber transmission system observed along the paths shown in FIGS. 9 and 10;

FIG. 12 is a connection diagram showing a third embodiment of the optical amplifying repeater of the present invention.

FIG. 13 is a connection diagram showing a conventional optical amplification repeater that can be monitored by a monitoring signal light from a terminal device.

FIG. 14 is an explanatory diagram showing a path of supervisory signal light in the optical amplifying repeater of FIG.

FIG. 15 is a connection diagram showing a configuration of another conventional optical amplification repeater.

FIG. 16 is an explanatory diagram showing a path of a supervisory signal light in the optical amplifying repeater of FIG.

[Explanation of symbols]

1 Optical amplification repeater 2, 34a, 34b Optical amplifier 3, 22a, 22b, 32a, 32b, 33a, 33b
Optical coupler 4 Optical attenuator 5, 24a, 24b Optical fiber grating 6 Non-reflection termination 7 Monitoring signal light bypass circuit 8 Optical terminal unit 9, 21a, 21b Optical fiber transmission line 20A, 20B, 20C, 83, 84 Monitoring signal light Bypass circuit 23, 32c, 33c, 81 Optical fiber 30, 30a, 30b, 30c, 80, 100 Optical amplification repeater 31a, 32b, 41a, 41b Optical fiber transmission line 32, 33, 48a, 48b Monitoring signal light bypass circuit 32d , 32e, 33d, 33e Optical fiber grating 32f, 32g, 33f, 33g Non-reflection termination 40 Optical fiber transmission system 42a, 42b Optical terminal device 43a, 43b Optical transmitter (OS) 44a, 44b Optical receiver (OR) 45a , 45b Optical combining means 46a, 46b Optical separating means (MO ) 47a, 47b line monitoring circuit 51 a - 51 c, 52 a - 52 c optical attenuator

Claims (11)

[Claims] 1. A 2 × 2 first optical coupler provided on a first optical transmission line, and a second optical transmission line having a signal light flowing in a direction opposite to that of the first optical transmission line. A 2 × 2 second optical coupler provided; a third optical transmission line connecting one output port of the first optical coupler to one output port of the second optical coupler; A first reflection means provided at the other output port of the first optical coupler and having a first reflection wavelength; and a first reflection means provided at the other output port of the second optical coupler and having a second reflection wavelength A monitor signal light bypass circuit, comprising: a second reflection unit. 2. The supervisory signal light according to claim 1, wherein the third optical transmission line is connected so that only signal light having a wavelength matching the first reflection wavelength passes. Bypass circuit. 3. The third optical transmission line is connected so that only signal light having a wavelength that matches any of the first and second reflection wavelengths passes therethrough. 2. The monitoring signal light bypass circuit according to claim 1. 4. The apparatus according to claim 1, wherein said first and second reflection means are optical fiber gratings.
The monitoring signal light bypass circuit according to any one of the preceding claims. 5. A 2 × 2 first optical coupler provided in a first optical transmission line and a second optical transmission line having a signal light flowing in a direction opposite to that of the first optical transmission line. A 2 × 2 second optical coupler provided, and a first reflection means provided at one output port of the first optical coupler and having a first reflection wavelength and subjected to non-reflection termination processing And a second reflection means provided at one output port of the second optical coupler and having a second reflection wavelength and subjected to non-reflection termination processing. A 2 × 2 third optical coupler provided on the first optical transmission line, a 2 × 2 fourth optical coupler provided on the second optical transmission line, and the third A third reflection means provided at one output port of the optical coupler, having a first reflection wavelength, and having been subjected to non-reflection termination processing; A second supervisory signal light bypass circuit provided at one output port of the fourth optical coupler and having fourth reflection means having the second reflection wavelength and having been subjected to non-reflection termination processing; First and second optical amplifiers respectively inserted in the first and second optical transmission lines located between the first monitoring signal light bypass circuit and the second monitoring signal light bypass circuit; First connection means for connecting one output port of the first optical coupler to one output port of the second optical coupler or the fourth optical coupler; and one of the third optical couplers And a second connecting means for connecting the output port of the second optical coupler to one of the output ports of the fourth optical coupler or the second optical coupler. 6. The optical amplifying repeater according to claim 5, wherein each of said first and second connection means and said first to fourth reflection means is provided with an optical attenuator. . 7. An optical terminal device for transmitting and receiving signal light, a first optical transmission line connected to the optical terminal device,
A second optical transmission path through which signal light is transmitted in a direction opposite to the first optical transmission path; and the first and second optical paths provided in the middle of the first and second optical transmission paths. An optical repeater transmission system comprising at least one optical amplification repeater having a set of optical amplifiers for amplifying signal light passing through each of the transmission lines, wherein the optical terminal device outputs a main signal light An optical transmitter, and an optical receiver for receiving signal light from the second optical transmission line;
A transmission line monitoring circuit for transmitting and receiving a monitoring signal light;
An optical multiplexing unit that multiplexes the main signal light and the monitoring signal light and sends the multiplexed signal to the first optical transmission line; and separates the main signal light and the monitoring signal light received from the second optical transmission line. The optical amplification repeater, wherein the optical amplification repeater converts a part of the monitoring signal light into the first signal.
A monitoring signal light bypass circuit for bypassing the optical transmission line to the second optical transmission line, wherein the transmission line monitoring circuit of the optical terminal device passes through the monitoring signal light bypass circuit of the optical amplification repeater. And the second
Receiving the supervisory signal light returned from the optical transmission line of the optical terminal, and based on the intensity amplitude, phase, frequency, and time difference information of the supervisory signal light transmitted from the optical terminal apparatus and the received supervisory signal light, the respective optical signals are received. A monitoring method characterized by monitoring a transmission path. 8. The monitoring signal light bypass circuit of the optical amplification repeater has a function of bypassing a part of backscattered light generated when the monitoring signal light propagates through an optical fiber transmission line. The monitoring method according to claim 7, wherein 9. The 2 × 2 first optical coupler provided on the first optical transmission line, and the 2 × 2 first optical coupler provided on the second optical transmission line. A second optical coupler; a third optical transmission line connecting one output port of the first optical coupler to one output port of the second optical coupler; and the other of the first optical coupler. A first reflection means provided at an output port of the second optical coupler and having a first reflection wavelength; and a second reflection means provided at the other output port of the second optical coupler and having a second reflection wavelength. The monitoring method according to claim 7, wherein the monitoring method is provided. 10. The monitoring signal light bypass circuit according to claim 1,
A 2 × 2 first optical coupler provided in the optical transmission line of the second optical transmission line, and a 2 × 2 optical coupler provided in the second optical transmission line in which the flow of the signal light is opposite to the first optical transmission line. A second optical coupler, a first reflecting means provided at one output port of the first optical coupler, having a first reflection wavelength, and having been subjected to a non-reflection termination process; A first supervisory signal light bypass circuit provided at one output port of the coupler and having second reflection means having a second reflection wavelength and having been subjected to non-reflection termination processing; A 2 × 2 third optical coupler provided on the transmission line, a 2 × 2 fourth optical coupler provided on the second optical transmission line, and one output port of the third optical coupler A third reflection means having the first reflection wavelength and being subjected to a non-reflection termination process; A second monitoring signal light bypass circuit, provided at one of the output ports, having a fourth reflection means having the second reflection wavelength and having been subjected to non-reflection termination processing; and First and second optical amplifiers respectively inserted into the first and second optical transmission lines located between the signal light bypass circuit and the second monitoring signal light bypass circuit; and the first light First connecting means for connecting one output port of the coupler to one output port of the fourth optical coupler; and one output port of the third optical coupler and one output of the second optical coupler. The monitoring method according to claim 7, further comprising: a second connection unit that connects to the port. 11. The third optical transmission line, the first connection unit, the second connection unit, and each of the first to fourth reflection units may be provided with an optical attenuator. The monitoring method according to claim 9 or 10, wherein