JP5849032B2 - Redundant optical transmission line and duplexing method - Google Patents

Description

  The present invention relates to an optical transmission line duplexing apparatus having a duplex line and a duplexing method thereof, and compensates for a transmission time difference caused by a difference in optical path length when duplexing communication light, and provides a communication service while continuing a transmission logical link. The present invention relates to an optical transmission line duplexing technique for transferring a signal on an active line to a detour line without interruption.

  In recent years, with the spread of services such as video and optical telephones, services that require real-time performance and services with high added value are also spreading in optical access networks. In the past, there were cases where the communication route was forced to change due to road widening work, bridge replacement work, or other equipment work (new construction or repair of electricity, water, etc.) for off-site optical line equipment. It has occurred (hereinafter referred to as troubled relocation work). In such a situation, when trouble relocation work occurs in the communication equipment that supports the service as described above, a large amount of traffic is stopped at a time, which affects many users. In order to reduce the impact, facilities have been operated with inefficiencies, such as by dividing the construction period or performing switching work in a time zone where the amount of traffic is small, for example, from midnight to early morning.

  Under such circumstances, a tool for shortening the optical line switching connection time as much as possible and shortening the communication recovery time has been commercialized (for example, see Patent Document 1). However, even with a system that shortens the switching connection time of the optical line as much as possible, transmission is possible due to the temporary disconnection of the optical line and the difference in the line length between the working line and the detour path (difference in arrival time of the transmission signal). There was a problem that data loss and transmission logical link mismatch could not be avoided. Therefore, it is inevitable that the construction period is distributed so as to minimize the influence on the user (service degradation), and the midnight work is further prolonged.

  In view of the above circumstances, as a conventional optical transmission line duplication technology, by adjusting the line length (optical path length), creating a duplex line having the same optical path length, and adjusting the phase of the transmission signal, There is a method for avoiding a mismatch of transmission logical links (see, for example, Non-Patent Document 1 and Non-Patent Document 2). This makes it possible to carry out obstacle relocation work without stopping the service.

Japanese Patent No. 3573606

Higashi et al .: Basic study on optical access media switching system -Service uninterrupted optical media switching system-, IEICE Technical OFT2008-52, pp.27-31, 2008 Tanaka et al .: Improving the reliability of optical fiber switching technology without service interruption, Science technique OFT2010-18, pp.11-16, 2010.

  However, in the conventional optical transmission line duplexing technology as described above, since the existing off-site optical line equipment is operated by the tape core wire, the switching of the optical line at a time is performed by four or eight optical lines. It is necessary to switch. In order to realize them, there is a problem that the number of optical transmission line duplexing devices corresponding to the number of optical lines to be switched at one time is required, and the device becomes large.

  Therefore, in order to solve the above-described problem, the present invention can share an optical path length adjusting unit for each core wire, and thereby can reduce the size of the duplexed portion and a duplexing method thereof The purpose is to provide.

The duplexed optical transmission line according to the present invention has the following configuration.
(1) A subscriber-side transmission device and a station-side transmission device that are opposed to each of the cores of the tape core are used in an optical communication system in which signal light is transmitted and received via the working line. In an optical transmission line duplexing device that forms a detour path between two optical branching couplers in the working line with respect to a core line, and duplexes communication with respect to each core line of the tape core line, An optical path length difference detection light source for generating test light for detecting an optical path length difference from the detour path, an upstream signal light emitted from the subscriber side transmission apparatus, and a downstream signal light emitted from the station side transmission apparatus And a wavelength division multiplexing (WDM) coupler that multiplexes and demultiplexes the test light emitted from the optical path length difference detection light source for each wavelength, an optical branch coupler for upstream signal light that multiplexes and demultiplexes the upstream signal light, and And the upstream signal light wavelength converter for converting the wavelength of the signal light Ri,
An upstream optical signal variable delay device that delays the upstream optical signal; an upstream optical signal amplifier that amplifies the optical power of the upstream optical signal; an upstream optical signal blocker that selects a communication path for the upstream optical signal; An optical branching coupler for downstream signal light that multiplexes and demultiplexes the signal light, a downstream signal light wavelength converter that converts the wavelength of the downstream signal light, a downstream signal light variable delay device that delays the downstream signal light, and the downstream A downlink signal optical amplifier that amplifies the optical power of the signal light, a downlink signal light blocker that selects a communication path of the downlink signal light, a test light variable delay device that delays the test light, and an optical power of the test light A wavelength division multiplexing coupler for a shared optical variable delay device that collectively multiplexes / demultiplexes the wavelength-converted upstream signal light, downstream signal light, and test light with respect to each core of the tape core; ,Previous The optical fiber variable delay device that collectively delays the wavelength-converted upstream signal light, downstream signal light, and test light for each core of the tape core, and the test light that has propagated through the working line and the detour path are combined. An optical path length detector that detects the optical path length difference between the working line and the detour path from the received light signal, and a core wire that switches the test light incident on the optical path length difference detector for each core wire The switch includes a switching device, and a control device that monitors the optical path length difference and controls the delay time of the variable delay device.

(2) In (1), the test optical variable delay device and the test optical amplifier are installed in only one of the detour paths.
(3) In (1) or (2), the shared optical variable delay device has a delay amount of the uplink signal variable delay device and the downlink signal variable delay device.

  (4) In (1) or (2), a part of the uplink signal variable delay device and the downlink signal variable delay device is configured so that an optical path length of each path of the uplink signal light, downlink signal light, and test light of the detour path The aspect is used to compensate for the difference and the optical path length difference between the two optical branching couplers in the working line with respect to each core of the tape core.

The duplexing method for optical transmission lines according to the present invention has the following configuration.
(5) A subscriber-side transmission device and a station-side transmission device that are opposed to each of the cores of the tape core are used in an optical communication system in which signal light is transmitted and received via the working line. In the optical transmission path duplexing method, in which a detour path is formed between two optical branching couplers in the working line with respect to the core wire, and communication is duplexed with respect to each core wire of the tape core wire, Test light for detecting the optical path length difference from the detour path is generated, and the upstream signal light emitted from the subscriber side transmission apparatus, the downstream signal light emitted from the station side transmission apparatus, and the optical path length difference detection light source The test light to be emitted is multiplexed / demultiplexed for each wavelength by a wavelength division multiplexing (WDM) coupler, the upstream signal light is multiplexed / demultiplexed by an optical branch coupler for upstream signal light, and the wavelength of the upstream signal light is changed. The upstream signal light is converted by an upstream signal light wavelength converter, the upstream signal light is delayed by an upstream signal light variable delay device, the optical power of the upstream signal light is amplified by an upstream signal optical amplifier, and the upstream signal light communication path is Selected by a signal light breaker, the downstream signal light is multiplexed / demultiplexed by an optical branch coupler for downstream signal light, the wavelength of the downstream signal light is converted by a downstream signal light wavelength converter, and the downstream signal light is converted into a downstream signal Delayed by an optical variable delay device, amplified optical power of the downstream signal light by a downstream signal optical amplifier, selected a communication path of the downstream signal light by a downstream signal light circuit breaker, and configured the test light to be a test light variable delay device The optical power of the test light is amplified by a test optical amplifier, and the wavelength-converted upstream signal light, downstream signal light, and test light for each of the tape cores can be shared light. The wavelength division multiplexing coupler for the delay unit collectively multiplexes and demultiplexes, and the wavelength-converted upstream signal light, downstream signal light, and test light for each of the tape cores are collectively delayed by the shared optical variable delay unit. The optical path length difference detector detects the optical path length difference between the active line and the detour path from the received light signal by combining the test light propagating through the working line and the detour path, and receiving the optical path length difference. The test light incident on the detector is switched for each core by a core switch, and the optical path length difference is monitored and the delay time of the variable delay is controlled by a control device.

(6) In (5), the test optical variable delay device and the test optical amplifier are installed in only one of the detour paths.
(7) In (5) or (6), the shared optical variable delay device has delay amounts of the uplink signal variable delay device and the downlink signal variable delay device.

  (8) In (5) or (6), a part of the uplink signal variable delay device and the downlink signal variable delay device is connected to the optical path length of each path of the uplink signal light, downlink signal light, and test light of the detour path. The aspect is used to compensate for the difference and the optical path length difference between the two optical branching couplers in the working line with respect to each core of the tape core.

  According to the present invention, the wavelength of the test signal emitted from the upstream signal light emitted from the subscriber side transmission device of each core wire, the downstream signal light emitted from the station side transmission device, and the optical path length difference detection light source by the tape core wire. By converting to a different wavelength, the optical path length adjustment unit can be used in common for each of the cores of the tape core, and a duplex optical transmission path apparatus that supports multi-core tape cores can be provided. Further, it is possible to provide an optical transmission line duplexing device that is smaller than the conventional system in which the optical duplexing device is installed in parallel by the number of tape cores.

It is a block diagram which shows the structure of the optical transmission line duplication apparatus corresponding to multi-core of embodiment which concerns on this invention. FIG. 2 is a block diagram showing a specific configuration of the shared optical variable delay device shown in FIG. 1. In FIG. 1, it is a block diagram which shows the structure in the case of installing the means to detect an optical path length difference only in the core line of any one path | route of a detour path. In FIG. 1, it is a block diagram which shows a structure in case a common optical variable delay device comprises the variable delay device in each path | route of a detour route.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.
FIG. 1 is a block diagram showing a configuration of a multi-core optical transmission line duplexing apparatus according to this embodiment. Here, an example of a two-core tape core wire is shown.

In Figure 1, the downstream signal light having a wavelength lambda _DOWN1 sent from Tsubonegawa transmission apparatus 1-1 is branched at the top optical coupler 3-1, each active optical fiber ribbon 5 and the upper bypass optical fiber 26-1 Divided. The downstream signal light having the wavelength λ _Down1 propagated through the upper bypass optical fiber 26-1 is demultiplexed by the upper WDM coupler 9-1 and incident on the downstream signal light wavelength converters 17-1 and 17-3. _Are converted into the downstream wavelength conversion signal light 30-1 having the wavelength λa _Down1 and the downstream wavelength conversion signal light 30-3 having the wavelength λb _Down1 , respectively. The downlink wavelength conversion signal light 30-1 and the downlink wavelength conversion signal light 30-3 are transmitted after the delay times set by the downlink signal variable delay units 15-1 and 15-3, respectively.

  The delayed downstream wavelength conversion signal light 30-1 and downstream wavelength conversion signal light 30-3 are passed through the upper optical WDM couplers 11-1 and 12-1 for the shared optical variable delay device, respectively. It is transmitted after the delay time set by 13-2. The delayed downstream wavelength converted signal light 30-1 and downstream wavelength converted signal light 30-3 are transmitted through the shared optical variable delay lower WDM couplers 11-2 and 12-2, respectively, and downstream optical signal amplifiers 19-1 and 19-2, respectively. -3, where the optical power is amplified.

The amplified downstream amplified signal light 31-1 and the downstream amplified signal light 31-3 are combined by the lower WDM coupler 10-1 through the downstream signal light blockers 14-1 and 14-3, respectively, and are used for bypassing the lower light. Through the fiber 27-1, the lower optical branching coupler 4-1 is combined with the downstream signal light having the wavelength λ _Down1 propagated from the station side transmission apparatus 1-1 to the working optical fiber tape 5, and then the subscriber side transmission apparatus 2 Reach -1. Downstream signal light reaching the optical path length difference detecting light source 8-1 from the lower optical branching coupler 4-1 is blocked by the signal light blocking filter 29-1.

Similarly, the downstream signal light having a wavelength lambda _DOWN2 sent from Tsubonegawa transmission apparatus 1-2 is branched at the top optical coupler 3-2, divided into each active optical fiber ribbon 5 and the upper bypass optical fiber 26-2 It is done. The downstream signal light having the wavelength λ _Down2 propagated through the upper bypass optical fiber 26-2 is demultiplexed by the upper WDM coupler 9-2 and incident on the downstream signal light wavelength converters 17-5 and 17-7. They are converted into downstream wavelength conversion signal light 30-5 having wavelength λa _Down2 and downstream wavelength conversion signal light 30-7 having wavelength _λbDown2 . The downlink wavelength conversion signal light 30-5 and the downlink wavelength conversion signal light 30-7 are transmitted after the delay time set by the downlink signal variable delay devices 15-5 and 15-7, respectively.

  The delayed downstream wavelength conversion signal light 30-5 and downstream wavelength conversion signal light 30-7 are respectively transmitted through the shared optical variable delay device 13-1 through the upper WDM couplers 11-1 and 12-1 for the shared optical variable delay device. And 13-2 are transmitted after the delay time set by 13-2. The delayed downstream wavelength converted signal light 30-5 and the downstream wavelength converted signal light 30-7 are respectively transmitted through the lower WDM couplers 11-2 and 12-2 for the shared optical variable delay device and the downstream optical signal amplifier 19-5 and 19-7, where the optical power is amplified.

The amplified downstream amplified signal light 31-5 and the downstream amplified signal light 31-7 are combined by the lower WDM coupler 10-2 through the downstream signal light blockers 14-5 and 14-7, respectively, and the lower optical bypass is performed. The optical fiber 27-2 is combined with the downstream signal light having the wavelength λ _Down2 propagated from the station side transmission apparatus 1-2 through the working optical fiber tape 5 by the lower optical branching coupler 4-2, and then the subscriber side transmission apparatus. Reach 2-2. Downstream signal light that reaches the optical path length difference detection light source 8-2 from the lower optical branching coupler 4-2 is blocked by the signal light blocking filter 29-2.

The upstream signal light of wavelength λ _Up1 transmitted from the subscriber side transmission device 2-1 is branched by the lower optical coupler 4-1, and is divided into the working optical fiber tape 5 and the lower bypass optical fiber 27-1. The upstream signal light having the wavelength λ _Up1 propagated through the lower bypass optical fiber 27-1 is demultiplexed by the lower WDM coupler 10-1, and incident on the upstream signal light wavelength converters 17-2 and 17-4. They are converted into upstream wavelength conversion signal light 30-2 having wavelength λa _Up1 and upstream wavelength conversion signal light 30-6 having wavelength λb _Up1 , respectively. The upstream wavelength conversion signal light 30-2 and the upstream wavelength conversion signal light 30-6 are transmitted after the delay time set by the upstream signal variable delay devices 15-2 and 15-4, respectively.

  The delayed upstream wavelength conversion signal light 30-2 and upstream wavelength conversion signal light 30-6 are respectively transmitted through the shared optical variable delay device 13-1 through the lower WDM couplers 11-2 and 12-2 for the shared optical variable delay device. And 13-2 are transmitted after the delay time set by 13-2. The delayed upstream wavelength conversion signal light 30-2 and upstream wavelength conversion signal light 30-6 are passed through upper WDM couplers 11-1 and 12-1 for shared optical variable delay devices, respectively, and upstream optical signal amplifier 19-2 and 19-4, where the optical power is amplified.

The amplified upstream amplified signal light 31-2 and upstream amplified signal light 31-6 are combined by the lower WDM coupler 9-1 through the upstream signal light blockers 14-2 and 14-4, respectively, and the upper bypass optical fiber 26-1 is combined with the upstream signal light having the wavelength λ _Up1 propagated from the subscriber-side transmission device 2-1 through the working optical fiber tape 5 by the upper optical branching coupler 3-1 to be combined with the station-side transmission device 1- 1 is reached. Upstream signal light reaching the optical path length difference detector 24 from the upper optical branching coupler 3-1 is blocked by the signal light blocking filter 28.

Similarly, the upstream signal light _having the wavelength λ _Up2 transmitted from the subscriber-side transmission device 2-2 is branched by the lower optical coupler 4-2, and is split into the working optical fiber tape 5 and the lower bypass optical fiber 27-2, respectively. Divided. The upstream signal light _having the wavelength λ _Up2 propagated through the lower bypass optical fiber 27-2 is demultiplexed by the lower WDM coupler 10-2 and incident on the upstream signal light wavelength converters 17-6 and 17-8. _These are converted into upstream wavelength conversion signal light 30-6 _having wavelength λa _Up2 and upstream wavelength conversion signal light 30-8 having wavelength λb _Up2 . The upstream wavelength conversion signal light 30-6 and the upstream wavelength conversion signal light 30-8 are transmitted after the delay times set by the upstream signal variable delay units 15-6 and 15-8, respectively.

  The delayed upstream wavelength conversion signal light 30-6 and upstream wavelength conversion signal light 30-8 are passed through the shared optical variable delay device lower WDM couplers 11-2 and 12-2, respectively, It is transmitted after the delay time set by 13-2. The delayed upstream wavelength conversion signal light 30-6 and upstream wavelength conversion signal light 30-8 are passed through the upper WDM couplers 11-1 and 12-1 for shared optical variable delay devices, respectively, and upstream optical signal amplifier 19-6 and 19-8, where the optical power is amplified.

The amplified upstream amplified signal light 31-6 and the upstream amplified signal light 31-8 are combined by the lower WDM coupler 9-2 through the upstream signal light blockers 14-6 and 14-8, respectively, and the upper detour light Through the fiber 26-2, the upper optical branching coupler 3-2 is combined with the upstream signal light _having the wavelength λ _Up2 propagated from the subscriber side transmission device 2-2 through the working optical fiber tape 5 to be combined with the station side transmission device 1 Reach -2. The upstream signal light reaching the optical path length difference detector 24 from the upper optical branching coupler 3-2 is blocked by the signal light blocking filter 28.

  Since the shared optical variable delay devices 13-1 and 13-2 can multiplex optical signals, the downstream optical signal wavelength converters 17-1, 17-3, 17-5 and 17-7 and the upstream optical signal wavelength The converters 17-2, 17-4, 17-6 and 17-8 convert the wavelength of the signal light into different wavelengths, respectively, so that the upper WDM couplers 11-1 and 12-1 for the shared optical variable delay device The shared optical variable delay devices 13-1 and 13-2 between the lower WDM couplers 11-2 and 12-2 for the shared optical variable delay device can be used in common for optical signals of different wavelengths.

In order to detect whether or not the signal propagation times of the signal light propagated through the working optical fiber tape 5 and the detour path between transmission apparatuses match, the upstream of the wavelength λ _Up from the optical path length difference detection light source 8-1 is detected. Test light having a wavelength λ _sense different from the signal light and the downstream signal light having the wavelength λ _Down is transmitted. The transmitted test light having the wavelength λ _sense is distributed to the working optical fiber tape 5 and the lower bypass optical fiber 27-1 in the lower optical branching coupler 4-1. The test optical signal having the wavelength λ _sense propagated through the lower bypass optical fiber 27-1 is demultiplexed by the lower WDM coupler 10-1, and is incident on the test optical amplifier 18-1 to amplify the optical power. The amplified test light is transmitted after a delay time set by the test light variable delay device 16-1.

The delayed test light having the wavelength λ _sense is transmitted after the delay time set by the shared optical variable delay device 13-2 through the lower WDM coupler 12-2 for the shared optical variable delay device. The delayed test light having the wavelength λ _sense is incident on the test optical amplifier 20-1 through the upper WDM coupler 12-1 for the shared optical variable delay device, where the optical power is amplified. The amplified wavelength λ _sense test light passes through the lower WDM coupler 9-1, the upper bypass optical fiber 26-1, and the upper optical branching coupler 3-1, from the optical path length detection light source 8-1 to the working optical fiber tape. 5 is combined with the test light having the wavelength λ _sense that has propagated through the optical fiber 5, and reaches the optical path length difference detector 24 through the core line switch 25.

  In the control device 22, the test light propagated through the working optical fiber tape 5 from the optical path length difference detection light source 8-1 through the detection signal line 23 and the lower bypass optical fiber 27-1 from the optical path length difference detection light source 8-1. The optical path length difference between the working path and the detour path detected by the optical path length difference detector 24 from the test light combined by the upper optical branching coupler 3-1 is transmitted through the upper detour optical fiber 26-1. Can be confirmed. Therefore, the delay times when the optical path length differences are matched by changing the delay times of the test optical variable delay device 16-1 and the shared optical variable delay device 13-2 by the control lines 21-1, 21-2 and 21-3. Are used to set the delay times of the downstream variable signal delay units 15-1 and 15-3 and the upstream variable signal delay units 15-2 and 15-4. As a result, the optical transmission line can be duplexed between the station side transmission apparatus 1-1 and the subscriber side transmission apparatus 2-1.

In this embodiment, the subscriber side transmission apparatus 2-1 and the subscriber side transmission apparatus respectively propagating wavelength lambda _Up1 and wavelength lambda _Up2 of the upward optical signal active optical fiber ribbon 5 from 2-2 2-1 and 2- upstream signal wavelength [lambda] a _Up1 and the wavelength [lambda] b _Up1 and wavelength [lambda] a _Up2 and wavelength [lambda] b _Up2 from 2 propagating bypass line respectively are multiplexed by the upper light branching coupler 3-1 and 3-2, respectively, Tsubonegawa transmission device 1 Light is received at 1 and 1-2. However, since all upstream signals have different wavelengths, no optical interference occurs.

Similarly, the wavelength lambda _DOWN1 and wavelength lambda _DOWN2 of the downstream signal light and the local side transmission apparatus 1-1 and 1-2 from the bypass line to propagate the active optical fiber ribbon 5 from Tsubonegawa transmission apparatus 1-1 and 1-2 respectively the downstream signal wavelength [lambda] a _DOWN1 and the wavelength [lambda] b _DOWN1 and wavelength [lambda] a _DOWN2 and wavelength [lambda] b _DOWN2 propagating respectively are multiplexed by the upper light branching coupler 4-1 and 4-2, respectively, the subscriber side transmission apparatus 2-1 and 2 -2 is received. However, since all downstream signals have different wavelengths, no optical interference occurs.

  In the present embodiment, the upstream signal variable delay units 15-2, 15-4, 15-6 and 15-8, the upstream signal light blockers 14-2, 14-4, 14-6 and 14-8, and the downstream signal variable. Delay devices 15-1, 15-3, 15-5 and 15-7, downstream optical signal blockers 14-1, 14-3, 14-5 and 14-7, test optical variable delay devices 16-1 and 16- 2. The shared optical variable delay devices 13-1 and 13-2 are controlled by the control device 22 through control lines 21-1, 21-2, and 21-3. By ON / OFF control of the upstream signal light blockers 14-2, 14-4, 14-6 and 14-8 and the downstream signal light blockers 14-1, 14-3, 14-5 and 14-7, The downlink signal and the uplink signal can select a path that passes through the shared optical variable delay device 13-1, a path that passes through the shared optical variable delay device 13-2, a path that passes both, or a path that does not pass both. is there.

The upper optical branching couplers 3-1 and 3-2 and the test light reflection filters 7-1 and 7-2 are installed in advance for searching the fault location of the line equipment before the service starts.
The lower WDM couplers 10-1 and 10-2 and the upper WDM couplers 9-1 and 9-2 detect upstream signal light emitted from the subscriber side transmission apparatus, downstream signal light emitted from the station side transmission apparatus, and optical path length difference detection. The test light emitted from the light source is multiplexed / demultiplexed, the upstream signal is multiplexed / demultiplexed, and the downstream signal is multiplexed / demultiplexed. To satisfy the above characteristics, the upstream signal light emitted from the subscriber side transmission device, the downstream signal light emitted from the station side transmission device, the test light emitted from the optical path length difference detection light source, the upstream optical signal amplifier, and the downstream optical signal A WDM coupler that multiplexes and demultiplexes the wavelengths of the upstream and downstream signal lights transmitted from the amplifier, an upstream optical branching coupler that multiplexes and demultiplexes the upstream signal light in the detour line, and the downstream in the detour line This can be realized by combining with a signal optical branching coupler.

The core wire switch 25 connects any of the core wires of the working optical fiber tape 5 to the optical path length difference detector 24, and can be realized by either an optical switch or an optical fiber selector. .
The upstream signal light blockers 14-2, 14-4, 14-6 and 14-8, and the downstream signal light blockers 14-1, 14-3, 14-5 and 14-7 block the passage and blocking of the signal light. A switch that can be switched from the downstream optical signal amplifiers 19-1, 19-3, 19-5, and 19-7 and the upstream optical signal amplifiers 19-2, 19-4, 19-6, and 19-8. Receiving light from the leaked light transmission device is prevented. The upstream signal light blockers 14-2, 14-4, 14-6 and 14-8, and the downstream signal light blockers 14-1, 14-3, 14-5 and 14-7 are optical switches with one input and one output. It can be realized by an optical signal switching device using, or an electrical signal switching device using a 1-input 1-output electrical switch. When using an electrical switch with 1 input and 1 output, the optical signal is converted into an electrical signal by opto-electrical conversion, and the changed electrical signal is switched between passing and shutting off with the electrical switch with 1 input and 1 output, and the electricity passed through the electrical switch This can be realized by converting the signal into an optical signal by an electro-optical converter.

FIG. 2 is a block diagram showing a specific configuration of the shared optical variable delay devices 13-1 and 13-2.
The shared optical variable delay devices 13-1 and 13-2 are realized by m 2-input 2-output optical switches 41 and a delay optical fiber 40. By connecting m number of 2-input 2-output optical switches 41 in series and switching the paths of m number of 2-input 2-output optical switches 41, it is possible to produce 2 m power paths. Become. The delay time of the shared optical variable delay devices 13-1 and 13-2 is adjusted to the length of the delay optical fiber 40, and the optical path length is different by the length of the delay optical fiber 40. This can be realized by manufacturing a path having an optical path length. Since the shared optical variable delay devices 13-1 and 13-2 can realize the entire optical signal path with an optical fiber, the upstream optical signal wavelength converters 17-1, 17-3, 17-5 and 17-7, Downlink optical signal wavelength converters 17-2, 17-4, 17-6 and 17-8 convert all of the shared optical variable delay devices 13-1 and 13-2 by converting the wavelengths of the optical signals to different wavelengths. Can be used as a common variable delay device.

The minimum change time of the variable delay time of the common optical variable delay 13-1 and 13-2 as a [Delta] T, the fixed delay time of the two inputs and two outputs of the optical switch 41 as Delta] t _s, fixed delay time of the delay optical fiber 40 Is Δt _f , the variable delay time T of the shared optical variable delay devices 13-1 and 13-2 is:
T = (2 ^m −1) × ΔT (1)
It becomes. The overall fixed delay time t is
t = Δt _s + (Δt _s + Δt _f ) × (m−1) (2)
It becomes.
However, the fixed delay time t is a delay time of the shared optical variable delay devices 13-1 and 13-2 that is generated when a path having the shortest optical path length is selected from 2 m optical path length paths. Also, ΔT must be equal to or less than the propagation time α that does not affect the upstream and downstream signal lights, with the minimum change time of the variable delay time of the shared optical variable delay devices 13-1 and 13-2.

The duplexing process 100 using the optical transmission line duplexing apparatus of this embodiment will be described.
While changing the delay time of the shared optical variable delay device 13-2, the presence or absence of the optical path length difference in the optical path length difference detector 24 is confirmed, and the delay time when the optical path length difference disappears is measured.
First, the delay time
T = 0 (3)
far. Next, the presence or absence of an optical path length difference is confirmed from the detection signal from the optical path length difference detector 24. If there is an optical path length difference, the delay time T is set.
T = T + α (4)
And repeat the above steps. However, α is a propagation time that does not affect the upstream and downstream signal lights, and the bit codes match when the upstream and downstream signal lights that have passed through the shared optical variable delay devices 13-1 and 13-2 are combined. It is also a range. Repeat these operations to determine the delay time when it is determined that the optical path length difference is gone.
Td = T (5)
And

Next, the delay time changing process 101 of the shared optical variable delay devices 13-1 and 13-2 when the communication between the transmission apparatuses is performed using only the detour path will be described.
The initial state is that the upstream signal light blockers 14-2 and 14-6, the downstream signal light blockers 14-1 and 14-5 pass, the upstream signal light blockers 14-4 and 14-8, and the downstream signal light blocker 14 An example will be described in which −3 and 14−7 are cut off.

First, assuming that the delay time T2 of the shared optical variable delay device 13-2 is the delay time T1 of the shared optical variable delay device 13-1,
T2 = T1 + α (6)
Set to. Next, the upstream signal light blockers 14-4 and 14-8 and the downstream signal light blockers 14-3 and 14-7 are passed, and then the upstream signal light blockers 14-2 and 14-6, the downstream signal light Breakers 14-1 and 14-5 are turned off. Next, the delay time T1 of the shared optical variable delay device 13-1 is calculated.
T1 = T2 + 2 × α (7)
Set to. Next, the upstream signal light blockers 14-2 and 14-6 and the downstream signal light blockers 14-1 and 14-5 are passed, and then the upstream signal light blockers 14-4 and 14-8, Breakers 14-3 and 14-7 are turned off. The above steps are repeated to a desired length so that the difference between the delay time T2 of the shared optical variable delay device 13-2 and the delay time T1 of the shared optical variable delay device 13-1 is always maintained at α.

  The minimum change time ΔT of the variable delay time of the shared optical variable delay devices 13-1 and 13-2 is determined by the upstream variable signal delay devices 15-2, 15-4, 15-6 and 15-8 in the optical transmission line duplexer. When the downstream signal variable delay units 15-1, 15-3, 15-5 and 15-7 and the test optical variable delay units 16-1 and 16-2 are provided, the upstream signal variable delay unit 15-2 , 15-4, 15-6 and 15-8, downlink signal variable delay units 15-1, 15-3, 15-5 and 15-7, and test optical variable delay units 16-1 and 16-2. It is possible to set a time within a variable delay time range that is a variable delay amount range. In that case, upstream signal variable delay units 15-2, 15-4, 15-6 and 15-8, downstream signal variable delay units 15-1, 15-3, 15-5 and 15-7, test light variable The minimum change time ΔTc of the variable delay time of the delay units 16-1 and 16-2 must be less than the propagation time α that does not affect the upstream and downstream signal lights.

  Also, upstream signal variable delay devices 15-2, 15-4, 15-6 and 15-8, downstream signal variable delay devices 15-1, 15-3, 15-5 and 15-7, test optical variable delay device 16 -1 and 16-2 are upstream signal variable delay units 15-2, 15-4, 15-6 and 15-8, downstream signal variable delay units 15-1, 15-3, 15-5 and 15-7, A part of the variable delay time of the test optical variable delay devices 16-1 and 16-2 is compensated to match the optical path length of each path of the detour path, the optical path length variation of each path of the detour path, and the upper light. It can be used to compensate for the optical path length difference of each core of the working optical fiber tape 5 between the branching couplers 3-1 and 3-2 and the lower optical branching couplers 4-1 and 4-2.

FIG. 4 is a block diagram showing a configuration in the case where the shared optical variable delay device includes the variable delay device in each route of the detour route.
The working optical fiber between the upper optical branching couplers 3-1 and 3-2 and the lower optical branching couplers 4-1 and 4-2 is in a range where the optical path lengths of the respective paths of the detour paths are equal or the bit codes are equal. When the optical path lengths of the respective core wires of the tape 5 coincide with each other or the bit codes coincide with each other, the upstream variable signal delay units 15-2, 15-4, 15-6 and 15-8 as shown in FIG. Downstream signal variable delay units 15-1, 15-3, 15-5 and 15-7, and test optical variable delay units 16-1 and 16-2 are configured as upstream signal variable delay units 15-2, 15-4, 15-. 6 and 15-8, downstream signal variable delay units 15-1, 15-3, 15-5 and 15-7, and test optical variable delay units 16-1 and 16-2 are shared optical variable delay unit 13- It is good also as a structure included in 1 and 13-2.

  Compensation for making the optical path lengths of the detour paths coincide with each other is performed in advance by using the shared optical variable delay units 13-1 and 13-2 and the upstream signal variable delay units 15-2, 15-4, 15-6, and 15-. 8. Downlink signal variable delay units 15-1, 15-3, 15-5 and 15-7, and test optical variable delay units 16-1 and 16-2 are each changed from 0 to the maximum delay time. Variable signal delays 15-2, 15-4, 15-6 and 15-8, downlink signal variable delays 15-1, 15-3, 15-5 and 15-7, so that the signal changes linearly This can be realized by setting the delay time of the optical variable delay devices 16-1 and 16-2 and storing the delay time value at this time in the control device 22 as an adjustment delay time.

  Upstream signal variable delay devices 15-2, 15-4, 15-6 and 15-8, Downstream signal variable delay devices 15-1, 15-3, 15-5 and 15-7, Test optical variable delay device 16-1 And 16-2 can be realized by an optical variable delay device similar to the shared optical variable delay devices 13-1 and 13-2 or an electric variable delay device using a semiconductor variable delay line. When a semiconductor variable delay line is used, an optical signal is converted into an electric signal by an opto-electric converter, the converted electric signal is passed through the semiconductor variable delay line, the delay time is changed, and the delay time is changed. Is converted into an optical signal by an electro-optical converter. By connecting the semiconductor variable delay lines in series, the variable delay time can be increased. However, it is considered that the waveform of the electric signal after passing through the semiconductor variable delay lines is destroyed when the number of serial connection is increased. At that time, by shaping the waveform of the electric signal after passing through the semiconductor variable delay line and performing timing reproduction and identification reproduction, it becomes possible to increase the variable delay time while maintaining the waveform. Waveform shaping, timing recovery, and identification recovery can be realized by performing a regenerative repeater or clock data recovery.

  Upstream signal light wavelength converters 17-1, 17-3, 17-5 and 17-7, and downstream signal light wavelength converters 17-2, 17-4, 17-6 and 17-8 are respectively connected to upstream signals and downstream signals. It has a function of converting the wavelength of the signal. Upstream signal light wavelength converters 17-1, 17-3, 17-5 and 17-7, and downstream signal light wavelength converters 17-2, 17-4, 17-6 and 17-8 A combination of optical amplifiers, cross-gain modulation using frequency shifters and semiconductor optical amplifiers, optical-to-optical converters using cross-phase modulation, and optical signals are converted to electrical signals using PDs (photo diodes) that are optical-electrical converters. This can be realized by a configuration in which the converted electric signal is converted into an optical signal by an LD (Laser Diode) which is an electro-optical converter.

  Upstream signal optical amplifiers 19-1, 19-3, 19-5 and 19-7, downstream signal optical wavelength converters 19-2, 19-4, 19-6 and 19-8 are connected to test optical amplifiers 18-1, 18-2, 20-1 and 20-2 have a function of amplifying an optical signal, a function of compensating a line loss of a detour line, and a function of expanding a dynamic range of the optical transmission line duplexer. Upstream signal optical amplifiers 19-1, 19-3, 19-5 and 19-7, downstream signal optical wavelength converters 19-2, 19-4, 19-6 and 19-8 are connected to test optical amplifiers 18-1, Reference numerals 18-2, 20-1, and 20-2 convert semiconductor optical amplifiers or optical fiber amplifiers that are optical amplifiers or optical signals into electrical signals by PDs (photo diodes) that are photoelectric converters, and the converted electrical signals. It is realizable with the structure which converts into an optical signal with LD (Laser Diode) which is an electro-optical converter.

As means for detecting the optical path length difference, there are a method using light interference and a method for detecting an error signal of clock data recovery.
In the system using light interference, the optical path length difference detection light sources 8-1 and 8-1 have a function of transmitting test chirped pulse light. Only the combined test chirp pulse light obtained by combining the test chirp pulse light propagated through the working line and the detour path by the wavelength selection filter 28 that passes only the wavelength of the test chirp pulse light is transmitted, and the combined test chirp pulse light that is transmitted is transmitted. Is received by the optical-electrical converter, the received combined test chirp pulse light is converted into an electrical signal, and the frequency principal component detector which is the optical path length difference detector 24 is detected from the converted electrical signal. It becomes possible. The optical path length difference detection light sources 8-1 and 8-1 can be realized by a pulse test light transmitter having a configuration in which pulse light is transmitted by a direct drive LD (Laser Diode). The frequency principal component detector which is the optical path length difference detector 24 can be realized by performing a fast Fourier transform on the interference waveform obtained with an oscilloscope. The closer the obtained frequency principal component is to 0 Hz, the smaller the optical path length difference between the working line and the detour path. Further, by providing a frequency shifter in the detour path, the frequency main component of the interference waveform when the optical path length difference between the working line and the detour path detected by the optical path length difference detector 24 is 0 can be shifted from 0 Hz. Good.

  In the method of detecting an error signal of clock data recovery, the optical path length difference detection light sources 8-1 and 8-1 have a function of transmitting a test optical signal having a communication speed equal to or higher than that of the transmission device. . In this function, the test optical signal propagated through the working line through the wavelength selection filter 28 that allows only the wavelength of the test optical signal to pass through, and the detour path, and the test optical amplifiers 20-1, 18-1, 20-2, or 18 The test optical signal wavelength-converted in -1 is multiplexed, only the test chirped pulse light generated by this multiplexing is transmitted, and the transmitted combined test optical signal is received by the photoelectric converter, The received combined test optical signal is converted into an electrical signal, a clock is extracted from the converted electrical signal, and an error at the time of extraction can be detected by a clock data recovery-error detector which is an optical path length difference detector 24 It is what. The optical path length difference detection light sources 8-1 and 8-1 can be realized by a test optical signal transmitter configured to transmit a test optical signal by a direct drive LD (Laser Diode). The clock data recovery-error detector which is the optical path length difference detector 24 can be realized by using a clock data recovery device. In the range where no error is detected from the clock data recovery device, the optical path length difference between the working line and the detour line is close to zero. Further, as the optical path length difference detection light sources 8-1 and 2-2, the downstream signal light transmitted from the station side transmission apparatuses 1-1 and 1-2 is converted into an electrical signal by the photoelectric converter and converted. It is good also as a structure which converts an electrical signal into the light of the wavelength of a test optical signal with an electro-optical converter. Moreover, it is good also as a structure which uses the upstream signal light transmitted from a subscriber side transmission apparatus as a test optical signal.

The test light is received by the test light reflection filters 6-1, 6-2, 7-1, and 7-2 to the station side transmission devices 1-1 and 1-2 and the subscriber side transmission devices 2-1 and 2-2 Is cut off.
FIG. 3 is a block diagram showing a configuration of an optical transmission line duplexing apparatus in the case where a means for detecting a difference in optical path length is installed only on the core of one of the detour paths.

  The working optical fiber between the upper optical branching couplers 3-1 and 3-2 and the lower optical branching couplers 4-1 and 4-2 is in a range where the optical path lengths of the respective paths of the detour paths are equal or the bit codes are equal. When the optical path lengths of the respective core wires of the tape 5 are in the same range or the bit codes are in the same range, the means for detecting the optical path length difference is one of the detour paths as shown in FIG. It is good also as a structure installed only in a core wire.

  Needless to say, the present invention is not limited to the above-described embodiment as it is, and can be used as a single-core optical transmission line duplexer. In the implementation stage, the constituent elements can be modified and embodied without departing from the spirit of the invention. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some configurations may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different example embodiments may be combined as appropriate.

1-1, 1-2 ... Station side transmission device 2-1, 2-2 ... Subscriber side transmission device 3-1, 3-2 ... Upper optical branching coupler 4-1, 4-2 ... Lower optical branching coupler 5 ... Active optical fiber tapes 6-1 and 6-2 ... Test light reflection filters 7-1 and 6-2 ... Test light reflection filters 8-1 and 8-1 ... Light path length detection light sources 9-1 and 9-2 ... Upper WDM coupler 10-1, 10-2 ... Lower WDM coupler 11-1, 11-2 ... Upper WDM coupler for shared optical variable delay device 12-1, 12-2 ... Lower WDM coupler for shared optical variable delay device 13-1 , 13-2 ... Shared optical variable delay devices 14-1, 14-3, 14-5, 14-7 ... Downstream signal light blockers 14-2, 14-4, 14-6, 14-8 ... Upstream signal light Circuit breakers 15-1, 15-3, 15-5, 15-7 ... Downstream signal variable delay devices 15-2, 15-4, 15-6, 15-8 ... Upstream signal variable delay devices 16-1, 16- 2 ... Test light variable delay devices 17-1, 17-3, 17-5, 17-7 ... Downstream signal light wavelength converters 17-2, 17-4, 17-6, 17-8 ... Upstream signal light wavelength converters 18 -1, 18-2 ... test optical amplifiers 19-1, 19-3, 19-5, 19-7 ... downstream optical signal amplifiers 19-2, 19-4, 19-6, 19-8 ... upstream optical signal amplifiers 20-1, 20-2 ... test optical amplifiers 21-1, 21-2, 21-3 ... control line 22 ... control device 23 ... detection signal line 24 ... optical path length difference detector 25 ... core line switch 26-1 , 26-2, upper detour optical fibers 27-1, 27-2, lower detour optical fibers 28, signal light blocking filters 29-1, 29-2, signal light blocking filters 30-1, 30-3, 30 -5, 30-7 ... Downlink wavelength conversion signal light 30-2, 30-4, 30-6, 30-8 ... Uplink wavelength conversion signal light 31-1, 31-3, 31-5, 31-7 Downstream amplified signal light 31-2,31-4,31-6,31-8 ... upstream amplifying signal light 40 ... optical delay fiber 41 ... 2 input 2 output optical switch

Claims (8)

Used in an optical communication system in which each subscriber side transmission apparatus opposing against core and Tsubonegawa transmission device ribbon to transmit and receive signal light via the working line, each core wire of the ribbon the periphrastic between the optical branching coupler at two positions in the working line forming the line path, in the optical transmission path duplex system for duplex communication with the respective cores of the ribbon for,
An upper wavelength division multiplexing coupler that is provided for each detour path and is connected to an upper optical branching coupler closer to the station-side transmission device among the two optical branching couplers;
A lower wavelength division multiplex coupler that is provided for each detour path and is connected to a lower optical branch coupler closer to the subscriber-side transmission device among the two optical branch couplers;
An upper wavelength division multiplex coupler for a shared optical variable delay device; and
Lower wavelength division multiplex coupler for shared optical variable delay,
A shared optical variable delay device provided between an upper wavelength division multiplexing coupler for the shared optical variable delay device and a lower wavelength division multiplexing coupler for the shared optical variable delay device;
An upstream signal light wavelength converter for converting the wavelength of the upstream signal light generated from the subscriber side transmission device, which is input from the lower wavelength division multiplexing coupler;
An upstream signal light variable delay device for delaying the upstream signal light converted by the upstream signal light wavelength converter ;
An upstream optical amplifier for amplifying the optical power of the upstream optical signal delayed by the upstream optical signal variable delay device ;
An upstream signal optical circuit breaker that selects a communication path of upstream signal light amplified by the upstream signal optical amplifier ;
Downlink signal light wavelength converter for converting the wavelength of the downlink signal light generated from the station side transmission device, which is input from the upper wavelength division multiplexing coupler,
Downlink signal light variable delay device for delaying the downlink signal light converted by the downlink signal light wavelength converter ,
A downlink signal optical amplifier that amplifies the optical power of the downlink signal light delayed by the downlink signal light variable delay device ; and
A downlink signal light breaker that selects a communication path of the downlink signal light amplified by the downlink signal optical amplifier ;
Optical path length difference detection that generates test light for detecting an optical path length difference between the working line and the detour path, and transmits the test light to the active line and the detour path via the lower optical branching coupler. A light source for
A test optical variable delay device;
A test optical amplifier;
The test light propagated through the working line and the test light propagated through the detour path, which are output from the upper optical branching coupler, are combined and received, and from the received light signal, the working line and the detour path An optical path length difference detector for detecting an optical path length difference;
A cord switch for switching test light incident on the optical path length difference detector for each cord; and
A controller for monitoring the optical path length difference and controlling a delay time of the variable delay device ,
The upstream signal light converted by the upstream signal light wavelength converter of each of the detour paths is a lower wavelength division multiplexing coupler for the shared optical variable delay device, the shared optical variable delay device, and an upper wavelength for the shared optical variable delay device. Propagated to the upper optical branching coupler via the division multiplexing coupler and the upper wavelength division multiplexing coupler for each detour path,
Downlink signal light converted by the downlink signal light wavelength converter of each detour path is an upper wavelength division multiplexing coupler for the shared optical variable delay device, the shared optical variable delay device, and a lower wavelength for the shared optical variable delay device. Propagated to the lower optical branching coupler through the division multiplexing coupler and the lower wavelength division multiplexing coupler for each detour path,
The test light transmitted to each detour path includes the lower wavelength division multiplex coupler for each detour path, the lower wavelength division multiplex coupler for the shared optical variable delay device, the shared optical variable delay device, and the shared optical variable delay device. Is propagated to the upper optical branching coupler via the upper wavelength division multiplexing coupler, and the upper wavelength division multiplexing coupler for each detour path,
The test optical amplifier amplifies the optical power of the test light transmitted to the detour path, and the test light variable delay device delays the test light transmitted to the detour path. Duplex device.   2. The optical transmission line duplication apparatus according to claim 1, wherein the test optical variable delay device and the test optical amplifier are installed only in any one of the detour paths.   3. The optical transmission line duplication apparatus according to claim 1, wherein the shared optical variable delay device has delay amounts of the upstream signal variable delay device and the downstream signal variable delay device.   The upstream signal variable delay unit and a part of the downstream signal variable delay unit are configured such that the optical path length difference between the upstream signal light, the downstream signal light, and the test light of the detour path and the optical fiber of the tape core 3. The optical transmission line duplication apparatus according to claim 1, wherein the optical transmission line duplication apparatus is used to compensate for an optical path length difference between two optical branching couplers on an active line. Used in an optical communication system in which each subscriber side transmission apparatus opposing against core and Tsubonegawa transmission device ribbon to transmit and receive signal light via the working line, each core wire of the ribbon in the periphrastic between the optical branching coupler at two positions in the working line to form a line path, the optical transmission path duplexing method for duplicating communications for each of the core wire of the ribbon for,
An upper wavelength division multiplexing coupler that is provided for each detour path and is connected to an upper optical branching coupler closer to the station-side transmission device among the two optical branching couplers;
A lower wavelength division multiplex coupler that is provided for each detour path and is connected to a lower optical branch coupler closer to the subscriber-side transmission device among the two optical branch couplers;
An upper wavelength division multiplex coupler for a shared optical variable delay device; and
Lower wavelength division multiplex coupler for shared optical variable delay,
A shared optical variable delay device provided between an upper wavelength division multiplexing coupler for the shared optical variable delay device and a lower wavelength division multiplexing coupler for the shared optical variable delay device;
An upstream signal light wavelength converter for converting the wavelength of the upstream signal light generated from the subscriber side transmission device, which is input from the lower wavelength division multiplexing coupler;
An upstream signal light variable delay device for delaying the upstream signal light converted by the upstream signal light wavelength converter ;
An upstream optical amplifier for amplifying the optical power of the upstream optical signal delayed by the upstream optical signal variable delay device ;
An upstream signal optical circuit breaker that selects a communication path of upstream signal light amplified by the upstream signal optical amplifier ;
Downlink signal light wavelength converter for converting the wavelength of the downlink signal light generated from the station side transmission device, which is input from the upper wavelength division multiplexing coupler,
Downlink signal light variable delay device for delaying the downlink signal light converted by the downlink signal light wavelength converter ,
A downlink signal optical amplifier that amplifies the optical power of the downlink signal light delayed by the downlink signal light variable delay device ; and
A downlink signal light breaker that selects a communication path of the downlink signal light amplified by the downlink signal optical amplifier ;
Optical path length difference detection that generates test light for detecting an optical path length difference between the working line and the detour path, and transmits the test light to the active line and the detour path via the lower optical branching coupler. A light source for
A test optical variable delay device;
A test optical amplifier;
The test light propagated through the working line and the test light propagated through the detour path, which are output from the upper optical branching coupler, are combined and received, and from the received light signal, the working line and the detour path An optical path length difference detector for detecting an optical path length difference;
A cord switch for switching test light incident on the optical path length difference detector for each cord; and
A controller for monitoring the optical path length difference and controlling a delay time of the variable delay device ,
The upstream signal light converted by the upstream signal light wavelength converter of each of the detour paths is a lower wavelength division multiplexing coupler for the shared optical variable delay device, the shared optical variable delay device, and an upper wavelength for the shared optical variable delay device. Propagated to the upper optical branching coupler via the division multiplexing coupler and the upper wavelength division multiplexing coupler for each detour path,
Downlink signal light converted by the downlink signal light wavelength converter of each detour path is an upper wavelength division multiplexing coupler for the shared optical variable delay device, the shared optical variable delay device, and a lower wavelength for the shared optical variable delay device. Propagated to the lower optical branching coupler through the division multiplexing coupler and the lower wavelength division multiplexing coupler for each detour path,
The test light transmitted to each detour path includes the lower wavelength division multiplex coupler for each detour path, the lower wavelength division multiplex coupler for the shared optical variable delay device, the shared optical variable delay device, and the shared optical variable delay device. Is propagated to the upper optical branching coupler via the upper wavelength division multiplexing coupler, and the upper wavelength division multiplexing coupler for each detour path,
The test optical amplifier amplifies the optical power of the test light transmitted to the detour path, and the test light variable delay device delays the test light transmitted to the detour path. Duplexing method.   6. The optical transmission path duplexing method according to claim 5, wherein the test optical variable delay device and the test optical amplifier are installed in only one of the detour paths.   7. The optical transmission path duplexing method according to claim 5, wherein the shared optical variable delay device is provided with delay amounts of the upstream signal variable delay device and the downstream signal variable delay device.   The upstream signal variable delay unit and a part of the downstream signal variable delay unit are configured such that the optical path length difference between the upstream signal light, the downstream signal light, and the test light of the detour path and the optical fiber of the tape core 7. The method for duplicating an optical transmission line according to claim 5, wherein the optical transmission line duplexing method is used to compensate for an optical path length difference between two optical branching couplers on the working line.

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