JP2020182120A - Optical repeater and fiber optic transmission system - Google Patents

Abstract

To provide a technology that enables an optical amplification repeater to switch the direction of a fiber path even after an optical fiber transmission line is laid in order to make the communication capacity of an optical fiber transmission line asymmetric between directions in an optical fiber transmission system.SOLUTION: An optical repeater includes variable isolators and an EDF 11 connected between the variable isolators that amplify optical signals. The variable isolator propagates through a specific fiber path (FB3, FB4) and passes an optical signal input from one of input/output ports 1 and 2 of the optical repeater and output from the other port in only one direction. Further, the variable isolator can switch a direction in which the optical signal is passed between a WE direction and an EW direction. An optical SW controller controls the variable isolator such that the optical signal passes in the WE direction or the EW direction on the basis of the detection result of the optical signals input from the input/output port 1 and 2, respectively to make the direction of the specific fiber path variable.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical repeater in an optical fiber transmission system such as an optical submarine cable system, and an optical fiber transmission system.

In an optical fiber transmission system such as an optical submarine cable system, an optical fiber transmission line is generally configured for bidirectional communication in fiber pair (FP) units in which two optical fibers are paired (for example). , Patent Document 1). Therefore, the communication capacity in one direction and the communication capacity in the opposite direction are the same. Further, it is common to provide a plurality of FPs in one cable.

However, in an optical fiber transmission system, the amount of communication traffic may differ significantly in each communication direction. In this case, even if the communication traffic volume reaches the optical fiber communication capacity for one-way communication, the communication traffic volume does not reach the optical fiber communication capacity for reverse communication with less communication traffic. Become. Nevertheless, if a new optical fiber transmission line is laid in FP units in response to an increase in communication traffic demand, the optical fiber corresponding to the communication direction with a small amount of communication traffic will not be effectively used, and the laying cost will be wasted. Occurs. Therefore, it is necessary to realize an optical fiber transmission system that flexibly corresponds to the amount of communication traffic to be carried by making the communication capacity asymmetrical between the opposite roads.

Therefore, as a technique for making the communication capacity asymmetric between opposite directions in an optical fiber transmission system, there is a technique for reversing the communication direction (direction) of the optical fiber transmission line. For example, Patent Document 2 discloses a technique for switching the direction of optical reproduction relay for some optical fibers among a plurality of optical fibers in an optical relay device provided in the middle of an optical fiber transmission line. ing.

Special Table 2007-531476 Gazette Japanese Unexamined Patent Publication No. 63-074221

However, in recent optical fiber transmission systems, optical amplification relay is the mainstream instead of optical reproduction relay as a relay method for optical signals. In the optical amplification repeater used for the optical amplification relay, the input / output direction is generally defined in one direction. Therefore, in order to realize the reversal of the route in the optical amplification repeater in response to the demand for information traffic, a mechanism different from that of the optical reproduction repeater as in the above-mentioned prior art is required.

The present invention has been made in view of the above-mentioned problems. In the present invention, in order to make the communication capacity of the optical fiber transmission line asymmetric between the directions in the optical fiber transmission system, the direction of the fiber path is switched by the optical amplification repeater even after the optical fiber transmission line is laid. The purpose is to provide the technology that makes it possible.

The optical repeater according to one aspect of the present invention is an optical repeater of an optical fiber transmission system arranged in the middle of an optical fiber transmission line composed of a plurality of parallel fiber paths, and the plurality of fiber paths. An optical signal that is arranged in a specific fiber path, propagates through the specific fiber path, is input from one of the first input / output port and the second input / output port of the optical repeater, and is output from the other. An optical amplifier having a first optical element and a second optical element that pass through only in one direction, and an amplification medium that is connected between the first optical element and the second optical element and amplifies an optical signal. In the first optical element and the second optical element, the directions through which the optical signals pass are opposite to the first direction from the first input / output port to the second input / output port and the first direction. The first direction is based on the detection results of the optical amplifier and the optical signals input from the first input / output port and the second input / output port, which are switchable between the second direction and the second direction. Alternatively, it is characterized by including a controller that changes the direction of the specific fiber path by controlling the first optical element and the second optical element so that an optical signal passes in the second direction. To do.

According to the present invention, in an optical fiber transmission system, it is possible to switch the direction of the fiber path with an optical amplification repeater even after the optical fiber transmission line is laid.

The figure which shows the configuration example of an optical fiber transmission system. The figure which shows the configuration example of an optical repeater. The figure which shows the configuration example of the optical repeater for monitoring the output of an optical repeater by a monitoring device. The figure which shows the configuration example of the optical repeater for monitoring the output of an optical repeater by a monitoring device. The figure which shows the configuration example of the optical repeater for monitoring the state of a fiber path by a monitoring device. The figure which shows the configuration example of the optical repeater for monitoring the state of a fiber path by a monitoring device. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the configuration example of the optical repeater for monitoring by a monitoring device. The figure which shows the configuration example of the optical repeater for monitoring by a monitoring device. The figure which shows the example of the propagation path of a monitoring signal. The figure which shows the example of the propagation path of a monitoring signal. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the example of the propagation path of a monitoring signal. The figure which shows the example of the propagation path of a monitoring signal. The figure which shows the example of the propagation path of a monitoring signal. The figure which shows the example of the propagation path of a monitoring signal and Rayleigh scattered light. The figure which shows the configuration example of the optical repeater for monitoring by a monitoring device. The figure which shows the configuration example of the optical repeater for monitoring by a monitoring device. The figure which shows the structural example of the optical repeater provided with GFF.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. Further, the same or similar configurations will be given the same reference number, and duplicate description will be omitted.

[Example 1]
First, Example 1 of the present invention will be described with reference to FIGS. 1 to 5.

<Optical fiber transmission system>
FIG. 1 is a diagram showing a configuration example of an optical fiber transmission system according to a first embodiment of the present invention. The optical fiber transmission system shown in FIG. 1 includes an end station device 100 and an end station device 300, and the end station device 100 and the end station device 300 are connected via an optical fiber transmission line. Further, an optical amplification repeater (hereinafter referred to as "optical repeater") 200 (200-1,2,3) is arranged in the middle of the optical fiber transmission line. In this embodiment, an optical submarine cable system is assumed as the optical fiber transmission system, the terminal station device 100 corresponds to the land equipment on the west side, and the terminal station device 300 corresponds to the land equipment on the east side. In addition, a part of the optical fiber transmission line will be laid on the seabed between the land equipment on the west side and the land on the east side.

As shown in FIG. 1, the optical fiber transmission lines between the terminal devices 100 and 300 are the first fiber path (FB1), the second fiber path (FB2), the third fiber path (FB3), and the fourth fiber path. It is composed of (FB4), that is, it is composed of a plurality of parallel fiber paths. In this embodiment, among FBs 1 to 4, the directions of the optical fiber transmission lines are fixed for FB1 and FB2. On the other hand, for FB3 and FB4, the direction of the optical fiber transmission line can be switched (inverted) by the optical repeater 200, that is, the direction setting is variable. The reversal of the direction of the optical fiber transmission line is realized by an optical amplifier (reversible optical amplifier) that can reverse the direction provided in the optical repeater 200. By making the direction of one or more fiber paths out of a plurality of fiber paths constituting the optical fiber transmission line variable, the communication capacity of the optical fiber transmission line can be made asymmetrical between the directions.

In the example of FIG. 1, the direction from the terminal station device 100 to the terminal station device 300 (west to east direction, hereinafter referred to as “WE direction”) is preset with respect to FB1. For FB2, the direction from the terminal station device 300 to the terminal station device 100 (the direction from east to west, hereinafter referred to as “EW direction”) is preset. Further, as an example, assuming that the amount of information traffic transmitted in the EW direction is larger than the amount of information traffic transmitted in the WE direction, a route in the EW direction is set for FB3 and FB4. ing.

The optical fiber transmission line is configured by connecting an optical fiber and an optical repeater 200 in a longitudinal manner for each fiber path. As a submarine facility between the terminal devices 100 and 300, a plurality of optical repeaters 200 are arranged in a vertically connected state via an optical fiber included in the cable. In the example of FIG. 1, three optical repeaters 200-1, 2, and 3 are vertically connected in an optical fiber transmission line. The optical repeaters 200 provided in the same span in each fiber path are included in the same repeater housing. Similarly, optical fibers provided in the same span are included in the same cable.

A plurality of higher-level communication devices (CE) are connected to the terminal devices 100 and 300, respectively. Information traffic is transmitted and received between each higher-level CE connected to the terminal station device 100 and the corresponding higher-level CE connected to the terminal station device 300. The terminal device 100 converts a client signal including information traffic received from each higher-level CE into an optical signal on the line side. At that time, the terminal device 100 aggregates the client signals received from the plurality of higher-level CEs according to the number of FBs that can be used for transmission in the WE direction to generate a line-side optical signal. The terminal station device 100 transmits the generated line-side optical signal to the terminal station device 300 via the FB (FB1 in the example of FIG. 1) in which the direction in the WE direction is set among FB1 to FB4.

The line-side optical signal output from the terminal station device 100 propagates through the optical fiber (fiber path) toward the opposite terminal station device 300. The line-side optical signal propagating in the fiber path is amplified each time it reaches the optical repeater 200, so that the attenuation compensation by the optical fiber is repeated and arrives at the terminal device 300, which is a land facility on the opposite side.

The terminal device 300 extracts a client signal from the line side optical signal received via the FB1 in which the direction in the WE direction is set. The terminal device 300 transmits the extracted client signal to the corresponding higher-level CE. In this way, information traffic is transmitted from each higher-level CE connected to the western terminal station device 100 to the corresponding higher-level CE connected to the eastern terminal station device 300. Information traffic is similarly transmitted from each upper CE connected to the eastern terminal device 300 to the corresponding upper CE connected to the western terminal device 100. In the example of FIG. 1, FB2 to FB4 are used for transmitting the line side optical signal from the terminal station device 300 to the terminal station device 100.

<Optical repeater>
As described above, in the optical fiber transmission system of FIG. 1, FB3 and FB4 are configured as fiber paths with variable route settings. In this embodiment, each optical repeater 200 is routed according to the control signals from the terminal devices 100 and 300 so that the route of the fiber path can be easily switched even after the optical fiber transmission path is laid. It consists of an optical amplification repeater that can be switched between. Hereinafter, an example of a specific configuration and operation of the optical repeater 200 of this embodiment will be described.

FIG. 2A is a diagram showing a configuration example of the optical repeater 200 of this embodiment, and shows a configuration example for FB3 and FB4 which are fiber paths with variable directions. The optical repeater 200 shown in FIG. 2A includes an optical amplifier 10, an optical tap 21, an optical tap 22, and an optical SW controller 23 that amplify an input optical signal. The optical tap 21 is connected to the terminal device 100 side (west side) of the optical amplifier 10 on the fiber path. The optical tap 22 is connected to the terminal device 300 side (east side) of the optical amplifier 10 on the fiber path. Further, the optical taps 21 and 22 are connected to the optical SW controller 23. The optical repeater 200 has an input / output port 1 on the west side and an input / output port 2 on the east side.

The optical amplifier 10 is a reversible optical amplifier arranged in a specific fiber path (FB3, FB4) among a plurality of fiber paths. The optical amplifier 10 is an optical amplifier including a rare earth-added fiber, and in this example, an erbium-added fiber amplifier (EDFA) including an erbium-added fiber (EDF) 11. The optical amplifier 10 includes an EDF 11, variable isolators 12 and 13, an excitation light source 14, an isolator 15, and a WDM coupler 16. The EDF 11 is an amplification medium for amplifying an optical signal, in which a WDM coupler 16 is arranged between the variable isolator 12 and the variable isolator 13 on a fiber path and a WDM coupler 16 is arranged between the variable isolator 12 and the EDF 11. The excitation light source 14 inputs the excitation light to the WDM coupler 16 via the isolator 15 to supply the excitation light propagating in the WE direction to the EDF 11 via the WDM coupler 16. That is, in the optical amplifier 10 of FIG. 2A, forward excitation is performed when the optical signal passes through the EDF 11 in the WE direction, and backward excitation is performed when the optical signal passes through the EDF 11 in the opposite EW direction. Is done.

Generally, the EDFA has an isolator in at least one of the front and rear stages of the EDF, and the direction is fixed. On the other hand, in this embodiment, the directions of FB3 and FB4 can be switched (inverted) by using isolators (variable isolators 12 and 13) having variable directions for the optical amplifier 10. For the road-fixed FB1 and FB2 shown in FIG. 1, a general directional optical amplifier that amplifies the optical signal passing from the input side to the output side is used.

The variable isolators 12 and 13 are directionally variable isolators that can switch (invert) the direction in which light passes by a control signal from the outside. In this embodiment, the variable isolators 12 and 13 propagate through specific fiber paths (FB3, FB4), are input from one of the input / output ports 1 and the input / output ports 2 of the optical repeater 200, and are output from the other. Pass the optical signal in only one direction. Further, the variable isolators 12 and 13 have the directions in which the optical signal is passed, the WE direction from the input / output port 1 to the input / output port 2 (first direction) and the EW direction opposite to the WE direction (second direction). ) Can be switched between.

In this embodiment, the directions of the variable isolators 12 and 13 are switched by the control signal from the optical SW controller 23. As will be described later, the optical SW controller 23 is a variable isolator that allows the optical signal to pass in the first or second direction based on the detection results of the optical signals input from the input / output port 1 and the input / output port 2, respectively. By controlling 12 and 13, the direction of a specific fiber path is made variable.

The variable isolators 12 and 13 are configured so that the directionality can be switched by, for example, switching the direction of the applied electric field. Since the isolator is realized by the magneto-optical effect, the variable isolators 12 and 13 are directional by reversing the position of the magnet by 180 ° or by reversing the current direction of the electromagnet and reversing the direction of its magnetic field. May be switchable.

In the optical repeater 200, the optical tap 21 branches a part of the light input from the west side of the optical repeater 200 and propagating in the WE direction to the optical SW controller 23. The optical tap 22 branches a part of the light propagating in the EW direction, which is input from the east side of the optical repeater 200, to the optical SW controller 23.

The optical SW controller 23 measures the power of each optical signal received via the optical taps 21 and 22. That is, the optical SW controller 23 monitors the optical signals branched from the optical taps 21 and 22. The optical SW controller 23 has a function of setting the directions of the variable isolators 12 and 13 according to the measured power. The optical SW controller 23 controls the switching of the directions of the variable isolators 12 and 13 by the control signals output to the variable isolators 12 and 13.

For example, when the optical SW controller 23 detects the light from the terminal device 100 side (west side) and does not detect the light from the terminal device 300 side (east side), the light passes in the WE direction. The directions of the variable isolators 12 and 13 are set as described above. On the other hand, when the optical SW controller 23 detects the light from the terminal device 300 side (east side), the optical SW controller 23 sets the directions of the variable isolators 12 and 13 so that the light passes in the EW direction.

In this way, when the optical SW controller 23 detects the optical signal input from the input / output port 1 of the optical repeater 200 and does not detect the optical signal input from the input / output port 2, The variable isolators 12 and 13 are controlled so that the optical signal passes in the WE direction (first direction). On the other hand, when the optical SW controller 23 detects an optical signal input from the input / output port 2 of the optical repeater 200, the variable isolators 12 and 13 pass the optical signal in the EW direction (second direction). To control.

In this embodiment, an example in which the optical amplifier 10 includes the variable isolators 12 and 13 has been described, but the optical amplifier 10 may include a variable circulator instead of the variable isolators 12 and 13. That is, the optical amplifier 10 can transmit (pass) light in only one direction and switch the input / output direction of light (the direction in which light passes) from the outside by a control signal like a variable isolator and a variable circulator. It is realized by using various optical elements.

As described above, the optical repeater 200 of this embodiment includes an optical amplifier 10 arranged in a specific fiber path (FB3, FB4) among a plurality of fiber paths. The optical amplifier 10 is an EDF 11 (EDF 11) that amplifies an optical signal connected between a variable isolator 12 (first optical element) and a variable isolator 13 (second optical element) and between the first optical element and the second optical element. Amplification medium) and. The variable isolators 12 and 13 propagate through a specific fiber path and pass an optical signal input from one of the input / output ports 1 and the input / output port 2 of the optical repeater 200 and output from the other in only one direction. Further, the variable isolators 12 and 13 have a first direction (WE direction) from the input / output port 1 to the input / output port 2 and a direction opposite to the first direction (WE direction) in which the optical signals are passed. It is possible to switch between two directions (EW direction). The optical SW controller 23 controls the variable isolators 12 and 13 so as to pass the optical signal in the first direction or the second direction based on the detection results of the optical signals input from the input / output port 1 and the input / output port 2, respectively. By doing so, the direction of a specific fiber path is made variable.

As described above, in this embodiment, the optical SW controller 23 monitors the light output from the terminal devices 100 and 300, respectively, and switches the directions of the variable isolators 12 and 13 based on the detection result of the light. .. As a result, the directions of the fiber paths (FB3 and FB4) can be reversed. Therefore, according to this embodiment, it is possible to realize an optical fiber transmission system in which the direction of the fiber path can be easily switched even after the optical fiber transmission line is laid.

[Example 2]
In the optical amplifier 10 of the first embodiment, forward excitation is performed when the optical signal passes through the EDF 11 in the WE direction, and backward excitation is performed when the optical signal passes through the EDF 11 in the WE direction in the opposite direction. Therefore, the gain characteristic of the optical amplifier 10 may change due to the switching of the fiber path. Therefore, in the second embodiment, the optical amplifier is configured so that the gain characteristics of the optical amplifier are the same regardless of the direction of the fiber path. In the following, the points different from the first embodiment will be mainly described, and the common points with the first embodiment will be omitted.

FIG. 2B is a diagram showing a configuration example of the optical repeater 200 of the present embodiment of the present embodiment. The difference from the configuration of the first embodiment (FIG. 2A) lies in the configuration of the optical amplifier 10, specifically, WDM couplers and excitation light sources are provided on both sides of the EDF 11 on the fiber path. .. In this embodiment, in addition to the same excitation light source 14, isolator 15, and WDM coupler 16 as in Example 1, the excitation light source 17, isolator 18, and is between the eastern variable isolator 13 and EDF 11 on the fiber path. A WDM coupler 19 is provided.

Similar to the first embodiment, the excitation light source 14 inputs the excitation light to the WDM coupler 16 via the isolator 15 to supply the excitation light propagating in the WE direction to the EDF 11 via the WDM coupler 16. The excitation light source 17 inputs the excitation light to the WDM coupler 19 via the isolator 18 to supply the excitation light propagating in the EW direction to the EDF 11 via the WDM coupler 19. As a result, bidirectional excitation is performed in the optical amplifier 10, and the gain characteristics of the optical amplifier can be made equal regardless of the direction of the fiber path.

The configuration of FIG. 2B is only an example, and various modifications are possible. For example, the excitation light output from one excitation light source may be branched into two systems by an optical splitter, and the branched light may be input to the WDM couplers 16 and 19, respectively. Alternatively, optical relay so that the optical SW controller 23 can select whether to perform forward excitation, backward excitation, or bidirectional excitation in the optical amplifier 10 according to the setting of the route of the fiber path. It is also possible to configure the vessel 200. For example, when either forward excitation or backward excitation can be selected, the output destination of the excitation light from one excitation light source can be switched between the WDM coupler 16 and the WDM coupler 19 by an optical switch. May be good. In that case, the switching of the optical switch is controlled by the optical SW controller 23. Further, the optical SW controller 23 may be able to individually switch on and off of the feeding circuit for the excitation light sources 14 and 17 shown in FIG. 2 (B). In that case, the optical SW controller 23 can select whether to perform forward excitation, backward excitation, or bidirectional excitation in the optical amplifier 10 by controlling the on and off of each feeding circuit.

According to such a modification, it becomes possible to select and use forward excitation, backward excitation, and bidirectional excitation in the optical amplifier 10 as necessary. For example, it is possible to control the optical amplifier 10 so that forward excitation or backward excitation is always performed regardless of the setting of the route of the fiber path.

[Example 3]
In the third embodiment, in an optical fiber transmission system including one or more fiber paths with variable directions, an example in which an end station device (monitoring device) monitors an optical repeater in each fiber path will be described. In the following, the points different from the above-described embodiment will be mainly described, and the points common to the above-described embodiment will be omitted.

First, as a premise of this embodiment, a method for monitoring an optical repeater in an optical fiber transmission system using a fiber pair composed of two fiber paths having fixed routes as shown in FB1 and FB2 in FIG. An example will be described.

Specifically, an optical signal (monitoring signal) for monitoring is output from the terminal device (monitoring device) to one fiber path, passes through the loopback path of the optical repeater to be monitored, and the other fiber path. The output power of the optical repeater is monitored by measuring the power of the monitoring signal returned via. In the optical repeater, the light is branched on the output side of the optical amplifier on one fiber path, and the branched light is passed through only the wavelength λ _{1 of the} monitoring signal, and the light on the other fiber path is passed through. A loopback path for inputting to the combiner provided on the input side of the amplifier is provided. As a result, the monitoring signal of wavelength λ ₁ transmitted from the monitoring device via one fiber path can be received by the source monitoring device via the loopback path of the optical repeater and the other fiber path.

Further, when a plurality of optical repeaters are connected in cascade as shown in FIG. 1, when a pulse signal having a short existence time is transmitted as a monitoring signal having a wavelength of λ ₁ , the distance from the monitoring device to each optical repeater is obtained. The reciprocating time of the pulse signal between the monitoring device and the optical repeater differs depending on the device. Therefore, by measuring the round-trip time of the pulse signal, it is possible to determine which of the optical repeaters the pulse signal that has passed through the loopback path and returned has been received. Further, when the power of the returned pulse signal is constantly or periodically measured and a decrease in the measured power is detected, it can be determined that the output power of the optical repeater is decreased. In this way, the monitoring device can remotely monitor the output power of the optical repeater via the optical fiber transmission line.

The above-mentioned monitoring method requires a fiber pair of a fiber path for unidirectional transmission and a fiber path for transmission in the opposite direction (that is, a fiber pair for bidirectional transmission). However, in this embodiment, as in the above-described embodiment, it is premised that the number of fiber paths for transmission in each direction is different by providing the fiber paths with variable directions. Therefore, the above-mentioned monitoring method premised on the use of a fiber pair cannot be directly applied to this embodiment.

Therefore, in this embodiment, an example of monitoring the optical repeater 200 in the fiber path with variable directions in the optical fiber transmission system will be described.

FIG. 3 is a diagram showing a configuration example of the optical repeater 200 having a configuration for monitoring the optical repeater 200 by the monitoring devices 110 and 310 arranged in the terminal station devices 100 and 300. Similar to the first embodiment, of the fiber paths (FB1 to FB4) constituting the optical fiber transmission, the routes are fixed for FB1 and FB2. For FB1, a route is set in the WE direction, and for FB2, a route is set in the EW direction. Further, FB3 and FB4 are fiber paths whose directions can be switched by the optical repeater 200. Further, FIG. 4 shows a part of the configuration of the optical repeater 200, and shows only the configuration necessary for the explanation of the present embodiment in the configuration of FIG.

The monitoring device 110 arranged in the terminal station device 100 on the west side uses a monitoring signal having a wavelength of λ ₂ as an optical signal used for monitoring the optical repeater 200 in each fiber path. On the other hand, the monitoring device 310 arranged in the terminal device 300 on the east side uses a monitoring signal having a wavelength of λ ₁ as an optical signal used for monitoring the optical repeater 200 in each fiber path. As each monitoring signal, as described above, a short pulse pulse signal can be used.

Hereinafter, the configuration of the optical repeater 200 and the monitoring method of the optical repeater 200 in each fiber path will be described with reference to FIG.

Monitoring of the optical repeater 200 in FB1 and FB2 is performed in the same manner as the above-mentioned monitoring method using FB1 and FB2 as a fiber pair. Specifically, in the monitoring of the optical repeater 200 in the FB ₁ , the monitoring signal of the wavelength λ ₂ output from the monitoring device 110, propagating the FB 1 in the WE direction and passing through the optical amplifier 40a is branched by the optical tap 42. Will be done. After that, the monitoring signal passes through the optical filter 36 through which the optical signal having the wavelength λ ₂ is passed through the combiner 34, and is input to the optical coupler 44 on the input side of the optical amplifier 40b on the FB2.

In this way, the monitoring signal that has passed through the optical amplifier 40a on the FB1 is in the reverse direction (EW direction) via the loopback path composed of the optical tap 42, the combiner 34, the optical filter 36, and the optical coupler 44. ) Is input to FB2 as an optical signal propagating. The monitoring signal input to the FB2 passes through the optical amplifier 40b, propagates through the FB2, and is received by the monitoring device 110. The monitoring device 110 can monitor the output power of each optical repeater 200 in the FB 1 based on the measurement result of the power of the monitoring signal of wavelength λ ₂ received from each optical repeater 200.

Further, in the monitoring of the optical repeater 200 in the FB 2, the monitoring signal of the wavelength λ ₁ output from the monitoring device 310, propagating the FB 2 in the EW direction and passing through the optical amplifier 40b is branched by the optical tap 43. After that, the monitoring signal passes through the optical filter 35 that passes the optical signal of wavelength λ ₁ through the combiner 33, and is input to the optical coupler 41 on the input side of the optical amplifier 40a on the FB1.

In this way, the monitoring signal that has passed through the optical amplifier 40b on the FB2 is in the opposite direction (WE direction) via the loopback path composed of the optical tap 43, the combiner 33, the optical filter 35, and the optical coupler 41. ) Is input to FB1 as an optical signal propagating. The monitoring signal input to the FB1 passes through the optical amplifier 40a, propagates through the FB1, and is received by the monitoring device 310. The monitoring device 310 can monitor the output power of each optical repeater 200 in FB2 based on the measurement result of the power of the monitoring signal of wavelength λ ₁ received from each optical repeater 200.

Next, monitoring of the optical repeater 200 in FB3 will be described. Since the monitoring of the optical repeater 200 in FB4 is the same as that in FB3, the description thereof will be omitted.

On the FB3, optical taps (optical taps 31c, 32c) are provided on both the terminal device 100 side (west side) of the optical amplifier 10c and the terminal device 300 side (east side) of the optical amplifier 10c. As a result, the monitoring signal output from any of the monitoring devices 110 and 310 is branched into a loopback path for guiding the monitoring signal in the direction opposite to that of the FB3 to the fiber path (FB1 or FB2) in which the direction is set.

When the route of FB3 is set in the WE direction, the optical repeater 200 is monitored as follows. In this case, the monitoring signal of wavelength λ ₂ output from the monitoring device 110, propagating the FB 3 in the WE direction and passing through the optical amplifier 10c is branched by the optical tap 32c. After that, the monitoring signal passes through the optical filter 36 via the combiner 34 and is input to the optical coupler 44 on the input side of the optical amplifier 40b on the FB2 fixed in the direction opposite to the FB3. ..

In this way, the monitoring signal that has passed through the optical amplifier 10c on the FB3 is in the opposite direction (EW direction) via the loopback path composed of the optical tap 32c, the combiner 34, the optical filter 36, and the optical coupler 44. ) Is input to FB2 as an optical signal propagating. The monitoring signal input to the FB2 passes through the optical amplifier 40b, propagates through the FB2, and is received by the monitoring device 110. The monitoring device 110 can monitor the output power of each optical repeater 200 in the FB 3 based on the measurement result of the power of the monitoring signal of wavelength λ ₂ received from each optical repeater 200.

On the other hand, when the route of FB3 is set in the EW direction, the optical repeater 200 is monitored as follows. In this case, the monitoring signal of wavelength λ ₁ output from the monitoring device 310, propagating the FB 3 in the EW direction and passing through the optical amplifier 10c is branched by the optical tap 31c. After that, the monitoring signal passes through the optical filter 35 via the combiner 33 and is input to the optical coupler 41 on the input side of the optical amplifier 40a on the FB1 fixed in the direction opposite to the FB3. ..

In this way, the monitoring signal that has passed through the optical amplifier 10c on the FB3 is in the opposite direction (WE direction) via the loopback path composed of the optical tap 31c, the combiner 33, the optical filter 35, and the optical coupler 41. ) Is input to FB1 as an optical signal propagating. The monitoring signal input to the FB1 passes through the optical amplifier 40a, propagates through the FB1, and is received by the monitoring device 310. The monitoring device 310 can monitor the output power of each optical repeater 200 in the FB 3 based on the measurement result of the power of the monitoring signal of wavelength λ ₁ received from each optical repeater 200.

As described above, according to the configuration of the optical repeater 200 of this embodiment, the terminal devices 100, 300 (monitoring devices 110, 310) monitor the optical repeater 200 in the fiber path with variable directions. Becomes possible.

There is no limit to the number of fiber paths that make up the optical fiber transmission line, and of the M fiber paths (M is an integer of 1 or more), (M-2) fiber paths are variable directions. It can be configured as a route. That is, leaving a fiber pair (FB1 and FB2) of a fiber path fixed in one direction and a fiber path fixed in the opposite direction, the remaining arbitrary number of fiber paths can be changed. It is possible to use a fiber path. In this case, the number of inputs of the combiners 33 and 34 is M, which is equal to the number of fiber paths.

[Example 4]
In the fourth embodiment, in an optical fiber transmission system including one or more fiber paths with variable directions, an end station device (monitoring device) monitors the state of each fiber path (detects the occurrence of a break and a break point). Will be described. In the following, the points different from the above-described embodiment will be mainly described, and the points common to the above-described embodiment will be omitted.

First, as a premise of this embodiment, monitoring of the state of the fiber path in the optical fiber transmission system using a fiber pair composed of two fiber paths having fixed directions as shown in FB1 and FB2 in FIG. An example of the method will be described.

Specifically, in order to detect a break point generated in the middle of the fiber path, for example, a coherent-optical time domain reflectometry (C-OTDR) is used. For example, when a short pulse pulse signal is output from a monitoring device (C-OTDR device) located at an end station device to one fiber path of a fiber pair, Rayleigh scattered light generated at every position on the fiber path is reversed. Come back in the direction. This scattered light is guided to the other fiber path through the return path (scattered light path) provided in the optical repeater. This causes Rayleigh scattered light to reach the monitoring device at the source of the pulse signal through the other fiber path.

Rayleigh scattering occurs everywhere in the longitudinal direction of the fiber path. Therefore, by measuring the time from when the pulse signal is transmitted until the Rayleigh scattered light returns to the transmission source, it is determined at which position on the fiber path the received scattered light is the scattered light. it can. Since the power of light propagating in the optical fiber is attenuated according to the propagation distance, the power is continuously attenuated according to the propagation distance under normal conditions. That is, if the position where the scattered light is rapidly attenuated can be determined, it can be estimated that the optical fiber is broken at that position.

The above-mentioned monitoring method requires a fiber pair of a fiber path for unidirectional transmission and a fiber path for transmission in the opposite direction (that is, a fiber pair for bidirectional transmission). However, in this embodiment, as in the above-described embodiment, it is premised that the number of fiber paths for transmission in each direction is different by providing the fiber paths with variable directions. Therefore, the above-mentioned monitoring method premised on the use of a fiber pair cannot be directly applied to this embodiment.

Therefore, in this embodiment, an example of monitoring the state of each fiber path in an optical fiber transmission system including one or more fiber paths with variable directions will be described.

FIG. 5 shows a configuration example of the optical repeater 200 having a configuration for monitoring each fiber path (occurrence of breakage and detection of break point) by the monitoring devices 110 and 310 arranged in the terminal station devices 100 and 300. It is a figure which shows. Note that FIG. 5 shows an example in which the optical repeater 200 has a configuration for monitoring the state of each fiber path in addition to the configuration for monitoring the optical repeater 200 (Example 3). Similar to the above-described embodiment, of the fiber paths (FB1 to FB4) constituting the optical fiber transmission, the routes are fixed for FB1 and FB2. For FB1, a route is set in the WE direction, and for FB2, a route is set in the EW direction. Further, FB3 and FB4 are fiber paths whose directions can be switched by the optical repeater 200. Further, FIG. 6 shows a part of the configuration of the optical repeater 200, and shows only the configuration necessary for the explanation of the present embodiment in the configuration of FIG.

The monitoring device 110 arranged in the terminal station device 100 on the west side uses a monitoring signal having a wavelength of λ ₄ as an optical signal used for monitoring the state of each fiber path. On the other hand, the monitoring device 310 arranged in the terminal device 300 on the east side uses a monitoring signal having a wavelength of λ ₃ as an optical signal used for monitoring the optical repeater 200 in each fiber path. As each monitoring signal, as described above, a short pulse pulse signal can be used.

The monitoring of the state of each fiber path in FB1 and FB2 is performed in the same manner as the above-mentioned monitoring method using FB1 and FB2 as a fiber pair. Specifically, in monitoring the state of the fiber path in the FB 1, as shown in FIG. 7, the monitoring signal of the wavelength λ ₄ output from the monitoring device 110 propagates in the FB 1 in the WE direction and passes through the optical amplifier 40a. Then, it is output from the optical repeater 200 to the east side. Rayleigh scattered light generated on the east side of the optical repeater 200 returns to the optical repeater 200 through the FB1. The Rayleigh scattered light input to the optical repeater 200 from the east side is branched by the optical tap 62. After that, the Rayleigh scattered light passes through the optical filter 56 that passes an optical signal having a wavelength of λ ₄ through the combiner 54, and is input to the optical coupler 64 on the input side of the optical amplifier 40b on the FB2.

In this way, the Rayleigh scattered light returned to the optical repeater 200 through the FB1 passes through a return path (scattered light path) composed of the optical tap 62, the combiner 54, the optical filter 56, and the optical coupler 64. , Is input to FB2 as light propagating in the opposite direction (EW direction). The Rayleigh scattered light input to the FB2 passes through the optical amplifier 40b, propagates through the FB2, and is received by the monitoring device 110. The monitoring device 110 can detect (estimate) a breaking point on the FB1 based on the reception result of the Rayleigh scattered light.

Further, in monitoring the state of the fiber path in the FB 2, as shown in FIG. 8, the monitoring signal of the wavelength λ ₃ output from the monitoring device 310 propagates in the FB 2 in the EW direction and passes through the optical amplifier 40b. It is output from the optical repeater 200 to the west side. When a break occurs in the fiber path on the west side of the optical repeater 200, the Rayleigh scattered light generated at the break point returns to the optical repeater 200 through the FB2. The Rayleigh scattered light input to the optical repeater 200 from the west side is branched by the light tap 63. After that, the Rayleigh scattered light passes through the optical filter 55 that passes an optical signal having a wavelength λ ₃ via the combiner 53, and is input to the optical coupler 61 on the input side of the optical amplifier 40a on the FB1.

In this way, the Rayleigh scattered light that has returned to the optical repeater 200 through the FB2 is in the opposite direction (WE) via the return path composed of the optical tap 63, the combiner 53, the optical filter 55, and the optical coupler 61. It is input to FB1 as light propagating in the direction). The Rayleigh scattered light input to the FB1 passes through the optical amplifier 40a, propagates through the FB1, and is received by the monitoring device 310. The monitoring device 310 can detect (estimate) a breaking point on the FB2 based on the reception result of the Rayleigh scattered light.

Next, monitoring of the state of the fiber path in FB3 will be described. On the FB3, optical taps (optical taps 51c and 52c) are provided on both the terminal device 100 side (west side) of the optical amplifier 10c and the terminal device 300 side (east side) of the optical amplifier 10c. As a result, the Rayleigh scattered light generated on the FB3 is branched into a return path for guiding the Rayleigh scattered light generated on the FB3 to a fiber path (FB1 or FB2) in which a direction opposite to the FB3 is set.

When the direction of FB3 is set in the WE direction, the state of FB3 is monitored as follows. As shown in FIG. 9, the monitoring signal of wavelength λ ₄ output from the monitoring device 110 propagates through the FB 3 in the WE direction, passes through the optical amplifier 10c, and is output from the optical repeater 200 to the east side. Rayleigh scattered light generated on the east side of the optical repeater 200 returns to the optical repeater 200 through the FB3. The Rayleigh scattered light input to the optical repeater 200 from the east side is branched by the optical tap 52c. After that, the Rayleigh scattered light passes through an optical filter 56 that passes an optical signal having a wavelength of λ ₄ through a combiner 54, and is an optical amplifier on FB2 fixed in a direction opposite to FB3. It is input to the optical coupler 64 on the input side of 40b.

In this way, the Rayleigh scattered light that has returned to the optical repeater 200 through the FB3 is in the reverse direction (EW) via the return path composed of the optical tap 52c, the combiner 54, the optical filter 56, and the optical coupler 64. It is input to FB2 as light propagating in the direction). The Rayleigh scattered light input to the FB2 passes through the optical amplifier 40b, propagates through the FB2, and is received by the monitoring device 110. The monitoring device 110 can detect (estimate) a breaking point on the FB3 based on the reception result of the Rayleigh scattered light.

On the other hand, when the route of FB3 is set in the EW direction, the state of FB3 is monitored as follows. As shown in FIG. 10, the monitoring signal of wavelength λ ₃ output from the monitoring device 310 propagates through the FB _{3 in} the EW direction, passes through the optical amplifier 10c, and is output from the optical repeater 200 to the west side. Rayleigh scattered light generated on the west side of the optical repeater 200 returns to the optical repeater 200 through the FB3. The Rayleigh scattered light input to the optical repeater 200 from the west side is branched by the optical tap 51c. After that, the Rayleigh scattered light passes through an optical filter 55 that passes an optical signal having a wavelength of λ ₃ through a combiner 53, and is an optical amplifier on FB1 fixed in a direction opposite to FB3. It is input to the optical coupler 61 on the input side of 40a.

In this way, the Rayleigh scattered light that has returned to the optical repeater 200 through the FB3 is in the opposite direction (WE) via the return path composed of the optical tap 51c, the combiner 53, the optical filter 55, and the optical coupler 61. It is input to FB1 as light propagating in the direction). The Rayleigh scattered light input to the FB1 passes through the optical amplifier 40a, propagates through the FB1, and is received by the monitoring device 310. The monitoring device 310 can detect (estimate) a breaking point on the FB3 based on the reception result of the Rayleigh scattered light.

The monitoring of the fiber path in FB4 is the same as that in FB3 as illustrated in FIGS. 11 and 12, and the description thereof will be omitted.

As described above, according to the configuration of the optical repeater 200 of the present embodiment, in the optical fiber transmission system including one or more fiber paths with variable directions, the terminal devices 100, 300 (monitoring devices 110, 310). ) Can monitor the condition of each fiber path (occurrence of fracture and detection of fracture point).

There is no limit to the number of fiber paths that make up the optical fiber transmission line, and of the M fiber paths (M is an integer of 1 or more), (M-2) fiber paths are variable directions. It can be configured as a route. That is, leaving a fiber pair (FB1 and FB2) of a fiber path fixed in one direction and a fiber path fixed in the opposite direction, the remaining arbitrary number of fiber paths can be changed. It is possible to use a fiber path. In this case, the number of inputs of the combiners 53 and 54 is M, which is equal to the number of fiber paths.

[Example 5]
In the fourth embodiment described above, the wavelength of the monitoring signal used by the western monitoring device 110 to monitor the state of each fiber path is λ ₄ , and the wavelength of the monitoring signal used by the eastern monitoring device 310 to monitor the state of each fiber path. The wavelength λ ₃ is used as. On the other hand, in the fifth embodiment, the state of each fiber path is monitored by using an arbitrary wavelength that can be relay-transmitted by the optical repeater 200 (however, the wavelength for monitoring the optical repeater 200 is excluded). An example to be performed will be described. In the following, the points different from the above-described embodiment will be mainly described, and the points common to the above-described embodiment will be omitted.

FIG. 13 is a diagram showing a configuration example of the optical repeater 200 of this embodiment. The difference from the fourth embodiment (FIG. 5) is that the optical switches (SW) 57c and 57d are provided between the optical taps 51c and 51d on the FB3 and FB4, which are fiber paths with variable directions, and the combiner 53. It is provided, and there is no optical filter 55. Further, the optical SW 58c and 58d are provided between the optical taps 52c and 52d on the FB3 and FB4 and the combiner 54, and the optical filter 56 is not provided. The optical SW 57c, 57d and the optical SW 58c, 58d can be switched on / off according to an instruction signal from the optical SW controllers 23c, 23d. Each optical SW transmits light when it is on and blocks light when it is off.

For example, when the direction of FB3 is set in the WE direction, the optical SW controller 23 turns off the optical SW57c and turns on the optical SW58c. As a result, the Rayleigh scattered light returning from the terminal device 300 side (east side) is sent to the FB2 via the return path composed of the light tap 52c, the light SW58c, and the combiner 54, as in the fourth embodiment. It is possible to guide. Further, even if the optical filter 55 does not exist, the optical signal input to the optical repeater 200 from the terminal device 100 side (west side) is input to the FB1 by being blocked by the optical SW57c. Can be prevented. Therefore, as in the fourth embodiment, the monitoring device 110 can estimate the breaking point on the FB3 based on the reception result of the Rayleigh scattered light in the FB2.

On the other hand, when the direction of FB3 is set in the EW direction, the optical SW controller 23 turns on the optical SW57c and turns off the optical SW58c. As a result, the Rayleigh scattered light returning from the terminal device 100 side (west side) is sent to the FB1 via the return path composed of the light tap 51c, the light SW57c, and the combiner 53, as in the fourth embodiment. It is possible to guide. Further, even if the optical filter 56 does not exist, the optical signal input to the optical repeater 200 from the terminal device 300 side (east side) is input to the FB2 by being blocked by the optical SW58c. Can be prevented. Therefore, as in the fourth embodiment, the monitoring device 310 can estimate the breaking point on the FB3 based on the reception result of the Rayleigh scattered light in the FB1.

Since the monitoring of the fiber path in FB4 is the same as that in FB3, the description thereof will be omitted.

According to the present embodiment, as in the fourth embodiment, in the optical fiber transmission system including one or more fiber paths with variable directions, the terminal devices 100, 300 (monitoring devices 110, 310) are in the state of each fiber path. Can be monitored (occurrence of fracture and detection of fracture point).

[Example 6]
In Examples 1 to 5 described above, the configuration in which the optical amplifier 10 in the optical repeater 200 includes a variable isolator has been described. In the sixth embodiment, an example will be described in which a variable circulator is provided in the optical amplifier 10 instead of the variable isolator, and monitoring of a fiber path with a variable direction is realized without using another fiber path as in the above embodiment. To do. In the following, the points different from the above-described embodiment will be mainly described, and the points common to the above-described embodiment will be omitted.

FIG. 14 is a diagram showing a configuration example of the optical repeater 200 of this embodiment. The optical amplifier 10 shown in FIG. 14 includes variable circulators 71 and 72 in place of the variable isolators 12 and 13 in the configuration shown in FIG. Note that in FIG. 14, the configuration related to excitation in the optical amplifier 10 (excitation light source 14, isolator 15, WDM coupler 16, etc. in FIG. 2) is not shown. The optical amplifier 10 further includes optical taps 73, 74, optical filters 75, 76, optical coupler splitters 77, 78, and optical filters 79, which are arranged on variable-direction fiber paths (FB3 and FB4). Equipped with 80.

The directional settings of the variable circulators 71 and 72 are switched by the optical Sw controller 23. Specifically, the variable circulators 71 and 72 output the light input from the port 1 from the port 2 and the light input from the port 2 to the port 3 when the route of the fiber path is set in the WE direction. It is set to output from the port 1 and output the light input from the port 4 from the port 1. That is, the variable circulators 71 and 72 transmit light propagating in the direction from port 1 to port 2 when the direction of the fiber path is set in the WE direction, but in the opposite direction (from port 2 to port 1). It is common with the variable isolators 12 and 13 (FIG. 2) in that it blocks the light propagating in the direction), but differs in that the light input from the port 2 is output to the port 3.

On the other hand, when the direction of the fiber path is set in the EW direction, the variable circulators 71 and 72 output the light input from the port 2 from the port 1 and output the light input from the port 2 as shown in FIG. 18 (B) described later. It is set so that the light input from 3 is output from port 2 and the light input from port 3 is output from port 2. That is, the variable circulators 71 and 72 transmit light propagating in the direction from port 2 to port 1 when the direction of the fiber path is set in the EW direction, but in the opposite direction (from port 1 to port 2). It is common with the variable isolators 12 and 13 (FIG. 2) in that it blocks the light propagating in the direction), but differs in that the light input from the port 1 is output to the port 4.

As shown in FIG. 14, the port 3 of the variable circulator 71 is connected to the common port of the optical coupler splitter 77, and an optical filter 79 is provided between the port 4 of the variable circulator 71 and the port 2 of the optical coupler splitter 77. Be connected. Further, an optical filter 75 is connected between the port 1 of the optical coupler splitter 77 and the optical tap 73. Further, the port 4 of the variable circulator 72 is connected to the common port of the optical coupler splitter 78, and the optical filter 80 is connected between the port 3 of the variable circulator 72 and the port 2 of the optical coupler splitter 78. Further, an optical filter 76 is connected between the port 1 of the optical coupler splitter 78 and the optical tap 74.

The optical coupler splitters 77 and 78 branch and output the light input to the common port to the port 1 and the port 2, output the light input to the port 1 to the common port, and output the light input to the port 2. Operates to output to a common port. The optical filter 75 passes an optical signal of wavelength λ ₂ and the optical filter 76 passes an optical signal of wavelength λ ₁ . Further, the optical filters 79 and 80 pass optical signals having wavelengths λ ₁ , λ ₂ and λ ₃ .

Next, monitoring of the output of the optical repeater 200 and monitoring of the state of the fiber path in the fiber path (FB3 and FB4) with variable directions will be described. Hereinafter, FB3 will be described, but the same applies to FB4. When the route in the WE direction is set with respect to the FB 3, the monitoring device 110 monitors the optical repeater 200 by using the monitoring signal having the wavelength λ ₁ . On the other hand, when the route in the EW direction is set with respect to the FB 3, the monitoring device 310 monitors the optical repeater 200 by using the monitoring signal having the wavelength λ ₂ . Further, both the monitoring devices 110 and 310 use a monitoring signal having a wavelength of λ ₃ to monitor the state of the FB ₃ . Although the optical signal for carrying the information traffic is not shown in FIGS. 14 and 15 to 21, which will be described later, the optical signal of the variable circulators 71 and 72 depends on the setting of the route with respect to the FB3. It is transmitted from port 1 to port 2 or from port 2 to port 1.

(Monitoring of the optical repeater 200 by the monitoring device 110)
Next, the monitoring of the optical repeater 200 by the monitoring device 110 when the direction in the WE direction is set with respect to the FB3 will be described. In the following, as shown in FIG. 15A, an example of monitoring the optical repeater 200-3 by the monitoring device 110 using the monitoring signal of the wavelength λ ₁ will be described. The monitoring device 110 actually monitors all the optical repeaters 200.

As shown in FIG. 15B, the monitoring signal output from the monitoring device 110 in the terminal station device 100 on the west side and propagating on the FB3 is input to the optical repeater 200-3 from the west side. The monitoring signal input to the optical amplifier 10 of the optical repeater 200-3 passes through the optical tap 73, the variable circulator 71, the EDF, and the variable circulator 72, and reaches the optical tap 74. The monitoring signal branches so that a part of the monitoring signal goes to the optical repeater 200-4 on the downstream side in the WE direction and a part of the monitoring signal goes to the optical filter 76 at the optical tap 74. As shown in FIG. 15B, each optical repeater 200 is provided with a loopback path for propagating a monitoring signal having a wavelength of λ _{1 in} the opposite direction (EW direction) starting from the optical tap 74. There is.

The monitoring signal branched from the optical tap 74 in the direction of the optical filter 76 passes through the optical filter 76 that allows light of wavelength λ ₁ to pass through, is input to the optical coupler splitter 78 from port 1, and is output from the common port. Next, the monitoring signal is input to the variable circulator 72 from the port 4 and output from the port 1, so that the monitoring signal travels in the EW direction opposite to the WE direction, which is the original propagation direction.

After that, the monitoring signal passes through the EDF, is input to the variable circulator 71 from the port 2 and is output from the port 3, is further input to the optical coupler splitter 77 from the common port, and is output from the ports 1 and 2. The monitoring signal output from the port 1 is blocked by the optical filter 75 that allows light of wavelength λ ₂ to pass through. On the other hand, the monitoring signal output from the port 2 passes through the optical filter 79, is input to the variable circulator 71 from the port 4, is output from the port 1, and is input to the optical tap 73. A part of the optical tap 73 branches toward the optical repeater 200-2 on the upstream side in the WE direction, and a part of the optical tap 73 branches toward the optical filter 75. The monitoring signal input to the optical filter 75 that allows light of wavelength λ ₂ to pass through is blocked by the optical filter 75.

As shown in FIG. 16, the monitoring device output from the optical repeater 200-3 to the upstream side (west side) in the WE direction is located between the optical repeater 200-3 and the monitoring device 110. It passes through the optical repeaters 200-2 and 200-1 in order.

Specifically, the monitoring signal of wavelength λ ₁ input to the optical repeater 200-2 from the east side passes through the optical tap 74, is input to the variable circulator 72 from port 2, and is output from port 3. Next, the monitoring signal passes through the optical filter 80, is input to the optical coupler splitter 78 from the port 2 and is output from the common port, is further input to the variable circulator 72 from the port 4, and is output from the port 1. After that, the monitoring signal passes through the EDF and is output from the optical repeater 200 to the west side in the same manner as the above-mentioned optical repeater 200-3. The monitoring signal also passes through the optical repeater 200-1 and is finally received by the monitoring device 110.

The monitoring device 110 can monitor the output power of each optical repeater 200 in the FB 3 based on the measurement result of the power of the monitoring signal of wavelength λ ₁ received from each optical repeater 200.

(Monitoring of fiber path status by monitoring device 110)
Next, as shown in FIG. 17 (A), the monitoring device 110 monitors the state of the FB ₃ using the monitoring signal of the wavelength λ ₃ with the fiber path having a variable direction (FB3 in this example) as the monitoring target. An example will be described. In this example, it is assumed that a break occurs in the section between the optical repeater 200-3 and the optical repeater 200-4 of the FB3.

As shown in FIG. 17B, the monitoring signal output from the monitoring device 110 in the western end station device 100 and propagating through the FB3 passes through each optical repeater 200. Specifically, the monitoring signal of wavelength λ ₃ input to the optical repeater 200 from the west side passes through the optical tap 73, the variable circulator 71, EDF, the variable circulator 72, and the optical tap 74, and passes through the optical repeater. It is output to the east side of 200. The monitoring signal branched in the direction of the optical filter 76 by the optical tap 74 is blocked by the optical filter 76 that allows light having a wavelength λ ₁ to pass through.

As shown in FIG. 17B, the Rayleigh scattered light generated on the FB3 returns through the FB3 in the direction opposite to the propagation direction (WE direction) of the monitoring signal, and is input to the optical repeater 200 from the east side. To. The monitoring signal of wavelength λ ₃ is output to the west side of the optical repeater 200 in the optical repeater 200 through the same path as the monitoring signal of wavelength λ ₁ shown in FIG. 16 (B).

In this way, the Rayleigh scattered light output from each optical repeater 200 to the upstream side (west side) in the WE direction passes through the other optical repeaters 200 between the monitoring device 110 in the same manner, and finally. Is received by the monitoring device 110. The monitoring device 110 can estimate the breaking point on the FB3 based on the reception result of the Rayleigh scattered light on the FB3.

(Monitoring of the optical repeater 200 by the monitoring device 310)
Next, the monitoring of the optical repeater 200 by the monitoring device 310 when the route in the EW direction is set with respect to the FB3 will be described. FIG. 18 shows the setting of the directions of the variable circulators 71 and 72 in each optical repeater 200 when the direction in the EW direction is set with respect to the FB3. In the following, as shown in FIG. 18A, an example of monitoring the optical repeater 200-3 by the monitoring device 310 using the monitoring signal of the wavelength λ ₂ will be described. The monitoring device 310 actually monitors all the optical repeaters 200.

As shown in FIG. 19B, the monitoring signal of wavelength λ ₂ output from the monitoring device 310 in the terminal device 300 on the east side and propagating on the FB 3 is input to the optical repeater 200-3 from the east side. .. Each optical repeater 200 is provided with a loopback path for propagating a monitoring signal having a wavelength of λ _{2 in} the opposite direction (WE direction) starting from the optical tap 73. Since this loopback path has symmetry with the loopback path for the monitoring signal of wavelength λ ₁ shown in FIG. 15 (B), the description thereof will be omitted.

As shown in FIG. 20, the monitoring signal output from the optical repeater 200-3 to the west side is the optical repeater 200-4, 200-5, which is located between the optical repeater 200-3 and the monitoring device 310. Go through .. in order. Since the propagation path of the monitoring signal in each optical repeater 200 has symmetry with the propagation path shown in FIG. 16, the description thereof will be omitted. The monitoring signal passes through each optical repeater 200 in order, and is finally received by the monitoring device 310.

The monitoring device 310 can monitor the output power of each optical repeater 200 in the FB 3 based on the measurement result of the power of the monitoring signal of the wavelength λ ₂ received from each optical repeater 200.

(Monitoring of fiber path status by monitoring device 310)
Next, as shown in FIG. 21 (A), the monitoring device 310 monitors the state of the FB ₃ using the monitoring signal of the wavelength λ ₃ with the fiber path having a variable direction (FB3 in this example) as the monitoring target. An example will be described. In this example, it is assumed that a break occurs in the section between the optical repeater 200-3 and the optical repeater 200-4 of the FB3.

As shown in FIG. 21 (B), the monitoring signal output from the monitoring device 310 in the terminal station device 300 on the east side and propagating through the FB 3 passes through each optical repeater 200. Since the propagation path of the monitoring signal in each optical repeater 200 has symmetry with the propagation path shown in FIG. 17, the description thereof will be omitted. The Rayleigh scattered light generated in the FB3 and propagating in the WE direction opposite to the EW direction passes through each optical repeater 200 in order and is finally received by the monitoring device 310. The monitoring device 310 can estimate the breaking point on the FB3 based on the reception result of the Rayleigh scattered light on the FB3.

As described above, according to the present embodiment, monitoring of the optical repeater in the fiber path having a variable direction and monitoring of the state of the fiber path are performed without using another fiber path as in the above-described embodiment. Will be able to do.

[Example 7]
In the seventh embodiment, as a modification of the sixth embodiment, the monitoring signal or Rayleigh scattered light returning to the optical amplifier 10 in the optical repeater 200 in the direction opposite to the propagation direction of the monitoring signals from the monitoring devices 110 and 310. An example of providing an EDF (amplification medium) for amplifying the light will be described. In the following, the points different from the sixth embodiment will be mainly described, and the points common to the sixth embodiment will be omitted.

22 and 23 are diagrams showing a configuration example of the optical repeater 200 of this embodiment. FIG. 22 shows the fiber path, and FIG. 23 shows the fiber path when the direction of the fiber path is set to the WE direction. It shows the case where the direction is set in the WE direction. Compared with the sixth embodiment (FIGS. 14 to 21), the EDF2 is connected between the common port of the optical coupler splitter 77 and the common port of the optical coupler splitter 78. As a result, in the monitoring of the optical repeater 200, the monitoring signals output from the monitoring devices 110 and 310 pass through the EDF 2 while propagating in the opposite direction through the loopback path. Further, in monitoring the state of the fiber paths (FB3 and FB4) having variable directions, the Rayleigh scattered light of the monitoring signals output from the monitoring devices 110 and 310 passes through the EDF2 while propagating in the opposite direction through the return path.

In the sixth embodiment described above, since the monitoring signal and the monitoring signal or Rayleigh scattered light returning in the opposite direction pass through the same EDF1 in both directions, the optical amplifier 10 may not obtain the desired amplification gain. .. On the other hand, according to the present embodiment, the optical repeater 200 is configured so that the monitoring signal or Rayleigh scattered light returning in the opposite direction passes through EDF2 different from EDF1 to provide a desired amplification gain. Becomes possible.

[Example 8]
The gain characteristics of the optical amplifier 10 in Examples 1 to 9 described above may have wavelength dependence. In the eighth embodiment, a configuration example for compensating for the wavelength dependence of the gain characteristic of the optical amplifier 10 will be described. In the following, the points different from the above-described embodiment will be mainly described, and the points common to the above-described embodiment will be omitted.

FIG. 24 is a diagram showing a configuration example of the optical repeater 200 of this embodiment. Note that FIG. 24 shows a simplified configuration of the optical amplifier 10. In this embodiment, with respect to the configuration shown in FIG. 2, between the optical amplifier 10 and the optical tap 21 on the fiber path (FB3 and FB4) with variable directions (the terminal device 100 side (west side) of the optical amplifier 10). ), The optical circulator 91 is added. Further, an optical circulator 91 is added between the optical amplifier 10 and the optical tap 22 (on the terminal device 300 side (east side) of the optical amplifier 10) on the fiber path (FB3 and FB4) with variable directions.

As shown in FIG. 24, ports 1 and 2 of the optical circulator 91 are connected to the fiber path, and a gain equalization filter (GFF) 93 is connected between the port 3 and the port 4. In this connected state, the optical circulator 91 outputs the light input from the port 1 from the port 2, outputs the light input from the port 2 from the port 3, and outputs the light input from the port 4 from the port 1. Is set to. Further, ports 1 and 2 of the optical circulator 92 are connected to the fiber path, and GFF 93 is connected between the port 3 and the port 4. In this connected state, the optical circulator 91 outputs the light input from the port 2 from the port 1, outputs the light input from the port 3 from the port 2, and outputs the light input from the port 1 from the port 4. Is set to.

In the configuration shown in FIG. 24, the optical circulator 91 propagates the fiber path in the WE direction to transmit the optical signal input to the optical amplifier 10, while propagating the fiber path in the EW direction and being output from the optical amplifier 10. The optical signal is guided to pass through GFF93. The optical circulator 92 propagates the fiber path in the EW direction and transmits the optical signal input to the optical amplifier 10, while propagating the fiber path in the WE direction and transmitting the optical signal output from the optical amplifier 10 to the GFF 94. Guide them to pass.

As described above, in this embodiment, the optical signal passes through the GFF only after passing through the optical amplifier 10 regardless of whether the optical signal propagates in the WE direction or the EW direction through the variable-direction fiber path (FB3 and FB4). The optical repeater 200 is configured to do so. This makes it possible to compensate for the wavelength dependence of the gain characteristic of the optical amplifier 10 regardless of the direction in which the optical signal travels. As a result, it is possible to give a desired gain characteristic to the optical signal amplified by the optical amplifier 10.

[Example 9]
In the ninth embodiment, the multi-core fiber is applied to the optical fiber transmission system of each of the above-described embodiments. In each of the above-described embodiments, the optical fiber used as the fiber path of the optical fiber transmission line may be composed of a multi-core fiber having a plurality of cores through which an optical signal passes. In this case, the M optical fibers in the cable of the optical fiber transmission line in each of the above-described embodiments correspond to the multi-core fibers having M cores.

Further, the optical amplifier in the optical repeater 200 may be a multi-core EDF having a plurality of cores. In the above embodiment, the number of fiber paths or the number of optical fiber cores is 4 (M = 4), but a multi-core fiber can be applied to an optical fiber transmission system having 3 or more fiber paths. ..

The invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the gist of the invention.

100, 300: Terminal equipment 200 (200-1,2,3, ...): Optical repeater 110, 310: Monitoring device 10, 40: Optical amplifier

Claims (26)

An optical repeater for an optical fiber transmission system, which is arranged in the middle of an optical fiber transmission line composed of a plurality of parallel fiber paths.
It is arranged in a specific fiber path among the plurality of fiber paths, propagates through the specific fiber path, is input from one of the first input / output port and the second input / output port of the optical repeater, and is output from the other. A first optical element and a second optical element that allow the optical signal to pass through in only one direction, and an amplification medium that amplifies the optical signal and is connected between the first optical element and the second optical element. The first optical element and the second optical element of the optical amplifier have the first direction from the first input / output port to the second input / output port and the first direction through which an optical signal is passed. The optical amplifier, which can be switched between the second direction opposite to the one direction,
Based on the detection results of the optical signals input from the first input / output port and the second input / output port, the first optical element and the first optical element so as to allow the optical signal to pass in the first direction or the second direction. A controller that changes the direction of the specific fiber path by controlling the second optical element,
An optical repeater characterized by being equipped with. The controller
When the optical signal input from the first input / output port is detected and the optical signal input from the second input / output port is not detected, the optical signal is passed in the first direction. Controls the first optical element and the second optical element,
When an optical signal input from the second input / output port is detected, the first optical element and the second optical element are controlled so that the optical signal passes in the second direction. The optical repeater according to claim 1. A first optical tap provided between the first input / output port and the first optical element and branching a part of an optical signal propagating in the first direction along the specific fiber path to the controller.
A second optical tap provided between the second input / output port and the second optical element and branching a part of an optical signal propagating in the second direction along the specific fiber path to the controller. Further prepare
The optical repeater according to claim 1 or 2, wherein the controller monitors an optical signal branched from the first optical tap and the second optical tap. The optical repeater according to any one of claims 1 to 3, wherein the first optical element and the second optical element are directionally variable isolators. The optical repeater according to any one of claims 1 to 3, wherein the first optical element and the second optical element are circulators having variable directionality. The optical repeater according to any one of claims 1 to 5, wherein the amplification medium is an erbium-added fiber (EDF). The optical amplifier
A first light source that is coupled to the specific fiber path between the first optical element and the amplification medium and outputs excitation light that passes through the amplification medium in the first direction.
A second light source that is coupled to the specific fiber path between the second optical element and the amplification medium and outputs excitation light that passes through the amplification medium in the second direction.
The optical repeater according to any one of claims 1 to 6, further comprising. The controller has the first light source and the first light source so that the front excitation or the rear excitation is performed in both the case where the optical signal passes through the amplification medium in the first direction and the case where the optical signal passes in the second direction. 2. The optical repeater according to claim 7, wherein the on and off of the light source is controlled. The optical amplifier
A light source that outputs excitation light supplied to the amplification medium, and
Whether the excitation light output from the light source is input and the excitation light is input to the amplification medium in the first direction or the excitation light is input to the amplification medium in the second direction. Further equipped with an optical switch for switching between
The controller controls switching of the optical switch so that forward excitation or backward excitation is performed in both the case where the optical signal passes through the amplification medium in the first direction and the case where the optical signal passes in the second direction. The optical repeater according to any one of claims 1 to 6, wherein the optical repeater is characterized. The plurality of fiber paths include a first fiber path having a fixed route in the first direction, a second fiber path having a fixed route in the second direction, and the specific fiber path having a variable direction. Including at least a third fiber path that is
The optical fiber transmission system includes a first monitoring device and a second monitoring device connected to the optical fiber transmission line.
The first monitoring device is arranged on the first input / output port side of the optical repeater, and monitors the second wavelength when the route in the first direction is set with respect to the third fiber path. The signal is output to the third fiber path,
The second monitoring device is arranged on the second input / output port side of the optical repeater, and monitors the first wavelength when the second direction route is set with respect to the third fiber path. The signal is output to the third fiber path,
The optical repeater
When the route in the first direction is set with respect to the third fiber path, the monitoring signal of the second wavelength output from the first monitoring device and propagating through the third fiber path is transmitted. A first loopback path that leads from the third fiber path to the second fiber path after passing through the optical amplifier, of the second wavelength received by the first monitoring device via the second fiber path. The first loopback path that monitors the output power of the optical repeater based on the measurement result of the power of the monitoring signal, and the first loopback path.
When the route in the second direction is set with respect to the third fiber path, the monitoring signal of the first wavelength output from the second monitoring device and propagating through the third fiber path is transmitted. A second loopback path that leads from the third fiber path to the first fiber path after passing through the optical amplifier, and is of the first wavelength received by the second monitoring device via the first fiber path. The second loopback path that monitors the output power of the optical repeater based on the measurement result of the power of the monitoring signal, and the second loopback path.
The optical repeater according to any one of claims 1 to 9, further comprising. In the first loopback path, an optical tap that branches a part of an optical signal propagating in the third fiber path in the first direction to the first loopback path and the branched optical signal are input. It includes a first optical filter that passes an optical signal of the second wavelength and an optical coupler that inputs an optical signal that has passed through the first optical filter into the second fiber path.
In the second loopback path, an optical tap that branches a part of an optical signal propagating in the second direction along the third fiber path into the second loopback path and the branched optical signal are input. 10. The aspect of claim 10 is characterized by including a second optical filter that passes an optical signal of the first wavelength and an optical coupler that inputs an optical signal that has passed through the second optical filter into the first fiber path. The optical repeater described. The plurality of fiber paths include a plurality of third fiber paths, each of which is a variable-direction specific fiber path.
The first loopback path further includes a combiner that combines optical signals branched from each of the plurality of third fiber paths and outputs them to the first optical filter.
11. The second loopback path further includes a combiner that combines optical signals branched from each of the plurality of third fiber paths and inputs the optical signals to the second optical filter. The optical repeater described in. The plurality of fiber paths include a first fiber path fixed to a road in the first direction, a second fiber path fixed to a road in the second direction, and the specific fiber path having a variable direction. Including at least a third fiber path that is
The optical fiber transmission system includes a first monitoring device and a second monitoring device connected to the optical fiber transmission line.
The first monitoring device outputs a monitoring signal of the fourth wavelength to the third fiber path when the route in the first direction is set with respect to the third fiber path.
The second monitoring device outputs a monitoring signal of a third wavelength to the third fiber path when the route in the second direction is set with respect to the third fiber path.
The optical repeater
It is output from the first monitoring device, is generated from the monitoring signal of the fourth wavelength that has passed through the optical repeater in the first direction in the third fiber path, and returns to the second direction to the optical repeater. It is a first return path that guides the input Rayleigh scattered light from the third fiber path to the second fiber path, and the first monitoring device determines the reception result of the Rayleigh scattered light in the second fiber path. Based on the first return path, which detects a break point on the third fiber path,
It is output from the second monitoring device, is generated from the monitoring signal of the third wavelength that has passed through the optical repeater in the second direction in the third fiber path, and returns to the first direction to the optical repeater. It is a second return path that guides the input Rayleigh scattered light from the third fiber path to the first fiber path, and the second monitoring device receives the Rayleigh scattered light in the first fiber path. Based on the second return path, which detects a break point on the third fiber path,
The optical repeater according to any one of claims 1 to 12, further comprising. In the first return path, an optical tap that branches a part of an optical signal propagating in the third fiber path in the second direction to the first return path and the branched optical signal are input, and the first return path is described. It includes a third optical filter that passes an optical signal of four wavelengths and an optical coupler that inputs an optical signal that has passed through the third optical filter into the second fiber path.
In the second return path, an optical tap that branches a part of an optical signal propagating in the first direction of the third fiber path to the second return path and the branched optical signal are input, and the second return path is described. 13. The thirteenth aspect of claim 13, wherein a fourth optical filter that passes an optical signal of three wavelengths and an optical coupler that inputs an optical signal that has passed through the fourth optical filter into the first fiber path are included. Optical repeater. In the first return path, an optical tap that branches a part of an optical signal propagating in the third fiber path in the second direction to the first return path, and the branched optical signal are input, and the input It includes a first optical switch capable of switching whether or not to transmit the optical signal, and an optical coupler that inputs an optical signal transmitted through the first optical switch to the second fiber path.
In the second return path, an optical tap that branches a part of an optical signal propagating in the first direction of the third fiber path to the second return path and the branched optical signal are input, and the input It is characterized by including a second optical switch capable of switching whether or not to transmit the optical signal, and an optical coupler that inputs an optical signal transmitted through the second optical switch to the first fiber path. The optical repeater according to claim 13. The plurality of fiber paths include a first fiber path fixed to a road in the first direction, a second fiber path fixed to a road in the second direction, and the specific fiber path having a variable direction. Including at least a third fiber path that is
The optical fiber transmission system includes a first monitoring device and a second monitoring device connected to the optical fiber transmission line.
The first monitoring device is arranged on the first input / output port side of the optical repeater, and monitors the first wavelength when the route in the first direction is set with respect to the third fiber path. The signal is output to the third fiber path,
The second monitoring device is arranged on the second input / output port side of the optical repeater, and monitors the second wavelength when the direction in the second direction is set with respect to the third fiber path. The signal is output to the third fiber path,
The optical repeater
A first circulator having a variable directionality is provided as the first optical element.
A second circulator with variable directionality is provided as the second optical element.
A first optical tap provided between the second circulator and the second input / output port and branching a part of an optical signal propagating in the first direction,
A first filter in which an optical signal branched from the first optical tap is input and the optical signal of the first wavelength is passed through,
A second optical tap provided between the first circulator and the first input / output port and branching a part of an optical signal propagating in the second direction,
A second filter to which an optical signal branched from the second optical tap is input and the optical signal of the second wavelength is passed is further provided.
When the route in the first direction is set with respect to the third fiber path,
In the optical repeater, after the monitoring signal of the first wavelength propagating in the first direction passes through the first circulator, the amplification medium, and the second circulator in order, the first optical tap and the first. A route is set which is input to the second circulator via one filter and is output to the third fiber path so as to propagate from the second circulator toward the first monitoring device in the second direction.
The first monitoring device monitors the output power of the optical repeater based on the measurement result of the power of the monitoring signal of the first wavelength received via the third fiber path.
When the route in the second direction is set with respect to the third fiber path,
In the optical repeater, the monitoring signal of the second wavelength propagating in the second direction passes through the second circulator, the amplification medium, and the first circulator in order, and then the second optical tap and the second. A route that is input to the second circulator through the two filters and output from the second circulator to the third fiber path is set so as to propagate in the second direction.
The claim is characterized in that the second monitoring device monitors the output power of the optical repeater based on the measurement result of the power of the monitoring signal of the second wavelength received via the third fiber path. The optical repeater according to any one of 1 to 9. The first circulator is connected to a third filter that passes optical signals of the first wavelength and the second wavelength.
The second circulator is connected to a fourth filter that passes optical signals of the first wavelength and the second wavelength.
The first circulator outputs a monitoring signal of the first wavelength output from the second circulator in the second direction when a route in the first direction is set with respect to the third fiber path. It is set to guide to the third filter and output the monitoring signal of the first wavelength that has passed through the third filter to the third fiber path in the second direction.
The second circulator outputs a monitoring signal of the second wavelength output from the first circulator in the first direction when a route in the second direction is set with respect to the third fiber path. 16. The claim 16 is characterized in that the monitoring signal of the second wavelength that has passed through the fourth filter is set to be guided to the fourth filter and output to the third fiber path in the first direction. The optical repeater described in. When the route in the first direction is set with respect to the third fiber path,
The second circulator guides the monitoring signal of the first wavelength, which is input from the second input / output port and propagates in the second direction, to the fourth filter, and passes through the fourth filter of the first wavelength. Is set to output the monitoring signal of the above to the third fiber path in the second direction.
The first circulator guides the monitoring signal of the first wavelength propagating in the second direction, which is output from the second circulator, to the third filter, and monitors the first wavelength that has passed through the third filter. The optical repeater according to claim 17, wherein the signal is set to be output to the third fiber path in the second direction. When the route in the second direction is set with respect to the third fiber path,
The first circulator guides a monitoring signal of the second wavelength, which is input from the first input / output port and propagates in the first direction, to the third filter, and passes through the third filter of the second wavelength. Is set to output the monitoring signal of the above to the third fiber path in the first direction.
The second circulator guides the monitoring signal of the second wavelength propagating in the first direction, which is output from the first circulator, to the fourth filter, and monitors the second wavelength that has passed through the fourth filter. The optical repeater according to claim 17 or 18, wherein the signal is set to be output to the third fiber path in the first direction. The first monitoring device further outputs a monitoring signal of a third wavelength to the third fiber path when the route in the first direction is set with respect to the third fiber path.
The second monitoring device further outputs a monitoring signal of a third wavelength to the third fiber path when the direction in the second direction is set with respect to the third fiber path.
The third filter and the fourth filter pass optical signals of the first wavelength, the second wavelength, and the third wavelength.
When the route in the first direction is set with respect to the third fiber path,
In the optical repeater, it is output from the first monitoring device, is generated from the monitoring signal of the third wavelength that has passed through the optical repeater in the first direction in the third fiber path, and returns to the second direction. A path is set to guide the Rayleigh scattered light input to the optical repeater in the second direction toward the first monitoring device via the third filter and the fourth filter.
The first monitoring device detects a breaking point on the third fiber path based on the reception result of the Rayleigh scattered light in the third fiber path.
When the route in the second direction is set with respect to the third fiber path,
In the optical repeater, it is output from the second monitoring device, is generated from the monitoring signal of the third wavelength that has passed through the optical repeater in the second direction in the third fiber path, and returns to the first direction. A path is set to guide the Rayleigh scattered light input to the optical repeater toward the second monitoring device via the fourth filter and the third filter in the first direction.
Any one of claims 17 to 19, wherein the second monitoring device detects a breaking point on the third fiber path based on the reception result of the Rayleigh scattered light in the third fiber path. The optical repeater described in the section. The optical repeater
A first amplification medium provided between the first circulator and the second circulator in the third fiber path, and
A monitoring signal directed toward the first monitoring device or the second monitoring device or a second amplification medium for amplifying Rayleigh scattered light is provided.
When the route in the first direction is set with respect to the third fiber path, the monitoring signal of the first wavelength output from the first filter in the optical repeater is the second amplification medium. The route that passes through and is input to the second circulator is set.
When the second direction route is set with respect to the third fiber path, the monitoring signal of the second wavelength output from the second filter in the optical repeater is the second amplification medium. The optical repeater according to claim 16, wherein a route is set to pass through the first circulator and be input to the first circulator. The optical repeater
A first amplification medium provided between the first circulator and the second circulator in the third fiber path, and
A monitoring signal directed toward the first monitoring device or the second monitoring device or a second amplification medium for amplifying Rayleigh scattered light is provided.
When the route in the first direction is set with respect to the third fiber path, the Rayleigh scattered light of the third wavelength output from the third filter in the optical repeater is the second. A path that passes through the amplification medium and is input to the fourth filter is set.
When the second direction route is set with respect to the third fiber path, the Rayleigh scattered light of the third wavelength output from the fourth filter in the optical repeater is the second. The optical repeater according to claim 20, wherein a path that passes through the amplification medium and is input to the third filter is set. A third circulator with variable directionality arranged between the first input / output port and the optical amplifier,
A directionally variable fourth circulator arranged between the second input / output port and the optical amplifier,
The first gain equalization filter connected to the third circulator,
A second gain equalization filter connected to the fourth circulator is further provided.
The controller
When the route in the first direction is set for the specific fiber path, the optical signal propagating in the first direction does not pass through the first gain equalization filter, and the light The third circulator and the fourth circulator are set so as to pass through the second gain equalization filter after passing through the amplifier.
When the second direction route is set for the specific fiber path, the optical signal propagating in the second direction does not pass through the second gain equalization filter, and the light The optical relay according to any one of claims 1 to 22, wherein the third circulator and the fourth circulator are set so as to pass through the first gain equalization filter after passing through the amplifier. vessel. The optical repeater according to any one of claims 1 to 23, wherein the plurality of fiber paths are composed of a multi-core fiber. First terminal station device and
A second terminal station apparatus connected to the first terminal station apparatus via an optical fiber transmission line composed of a plurality of parallel fiber paths, and a second terminal station apparatus.
The optical repeater according to any one of claims 1 to 9 and 23, which is arranged in the middle of the optical fiber transmission line and includes an optical amplifier for amplifying an optical signal transmitted through each fiber path.
An optical fiber transmission system characterized by comprising. The first terminal station device including the first monitoring device and
A second terminal station device including the second monitoring device, which is connected to the first terminal station device via an optical fiber transmission line composed of a plurality of parallel fiber paths.
The optical repeater according to any one of claims 10 to 22, comprising an optical amplifier arranged in the middle of the optical fiber transmission line and amplifying an optical signal transmitted through each fiber path.
An optical fiber transmission system characterized by comprising.

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