JP5070597B2 - Optical transmission system, optical transmission method, optical switch device, center device, optical coupler device, subscriber device, and optical communication system - Google Patents

Description

  The present invention relates to an optical transmission system, an optical transmission method, an optical switch device, a center device, an optical coupler device, a subscriber device, and an optical communication system. For example, an optical transmission line using an FTTH (Fiber To The Home) system or the like is provided. The present invention relates to an optical transmission system, an optical transmission method, an optical switch device, a center device, an optical coupler device, a subscriber device, and an optical communication system having a redundant configuration.

  In an optical transmission system, an optical fiber is used as a transmission line, and a signal is converted into light intensity and transmitted. That is, at the transmission end, for example, information such as telephone, data, and facsimile is replaced with an electric signal by a transmission circuit that performs conversion and modulation, and the intensity of light is further increased by an electric / optical conversion circuit (E / O conversion circuit). And sent to the optical fiber cable. On the other hand, at the receiving end, the optical signal sent from the optical fiber cable is returned to the electrical signal by the optical / electrical conversion circuit (O / E conversion circuit), and is returned to the original signal through the receiving circuit.

  In such an optical transmission system, an optical fiber cable laid as a downstream transmission line from the transmission end may be physically damaged due to external factors. As a countermeasure against this, the optical transmission system is configured as a line redundancy system that switches from a normal optical fiber route to a spare optical fiber route. The switching of the optical fiber route is generally performed by detecting an abnormality in the light receiving level with an optical switch device installed on the transmission line or in the sub-center station. In this case, in order to detect physical damage of the optical fiber cable by the optical fiber itself, it is necessary to provide the optical switch device with a function of detecting the light reception level and a function of switching the optical transmission line, and these functions are realized. In order to do so, an active device is required. However, the active device requires periodic maintenance and inspection, and its reliability as a component is low. For this reason, there exists a problem that the structure of the whole optical transmission system is complicated, and its reliability is low.

As this type of related technology, for example, there is a CATV transmission route redundant system described in Patent Document 1.
In the redundant system described in the prior art of the same document, in the CATV (Community Antenna Television, television broadcasting joint reception equipment) transmission route and HFC (Hybrid Fiber Coax, cable television equipment combining optical fiber and coaxial cable) system The optical transmission route portion is made redundant as follows. That is, in the downlink direction, the optical signal output from the E / O converter of the center device is branched by the optical coupler and transmitted through both the downlink normal route and the downlink redundant route, and the two O / E converters of the node device are transmitted. Are individually converted into electrical signals. In the upstream direction, the upstream optical signal output from the E / O converter of the node device is branched by the optical coupler of the same device and transmitted through the upstream normal route and the upstream redundant route, and the two O / Es of the center device are transmitted. Individually converted into electrical signals by the converter.

  However, in the transmission by the FTTH system such as a PON (Passive Optical Network, an optical network that does not use an active component such as an amplifier) system, a downstream O / E converter and an upstream E / O converter in the transmission path are unnecessary. In order to perform redundancy on the receiving side of the optical transmission route as in the topology according to the above-described prior art, an optical switch or the like is mounted on the node device and the light reception level of the optical switch is monitored, and switching is performed based on the monitoring result. It is necessary to carry out, and it is necessary to provide an active device on the transmission line.

  Further, in the redundant system described in the embodiment of Patent Document 1, an LD (laser diode) that outputs an optical signal to the center device side, an O / E conversion unit that converts an upstream optical signal into an electrical signal, A detection unit for detecting an upstream electrical signal, a wavelength control unit for switching the oscillation wavelength of the LD based on detection by the detection unit, and when the optical signal has a predetermined wavelength, the optical signal is sent to the downstream normal route and other wavelengths. In this case, a down route switching unit for outputting to the down redundant route is provided. Also, on the node device side, an LD that outputs an upstream optical signal, an O / E converter that converts the optical signal into an electrical signal, and an optical monitor that monitors the level of the optical signal input to the O / E converter An oscillation unit that generates a carrier wave input to the LD, an oscillation control unit that controls on / off of the oscillation unit based on a monitoring result of the optical monitor unit, and an LD of the LD based on on / off of the oscillation unit A wavelength control unit that switches the oscillation wavelength, and an upstream route switching unit that outputs the optical signal to the upstream normal route when the upstream optical signal has a predetermined wavelength, and to the upstream redundant route when the upstream optical signal has a wavelength other than that, Yes. In addition, at least one of the downlink route switching unit and the uplink route switching unit includes a WDM (Wavelength Division Multiplexing) multiplexer / demultiplexer.

  Further, in the optical transmission line switching system described in Patent Document 2, when an optical transmission line between two optical transmission devices is duplexed by a regular transmission line and a backup transmission line, and a failure occurs in the regular transmission line, Bidirectional communication is continued using the backup transmission path.

In the bidirectional optical transmission device described in Patent Document 3, an electrical signal input to the E / O converter is converted into an optical signal and output from the transmission end. This output signal is sent to one optical fiber line via the 1 × 2 optical switch and propagated to the 2 × 1 optical coupler. The 2 × 1 optical coupler outputs the input propagation signal from the other terminal and transmits it to the receiving end of the O / E converter. The O / E converter converts the input optical signal into an electrical signal and outputs it. When the optical fiber line is disconnected for some reason, this disconnection is detected by the control device, and the connection state of the 1 × 2 optical switch is switched. As a result, the output signal of the E / O converter is transmitted to another optical fiber line, and is propagated to the receiving end of the O / E converter via the 2 × 1 optical coupler.
JP 2003-304200 A (second page, abstract, FIG. 2, FIG. 1) Japanese Patent Laying-Open No. 2003-046413 (second page, FIG. 4) JP 09-008729 A (page 3, FIG. 1)

However, the techniques described in the above documents have the following problems.
That is, in the redundant system described in the embodiment of Patent Document 1, it is necessary to provide an active device in the center device and the node device, and the downlink route switching unit and the uplink route switching unit are configured by WDM multiplexers / demultiplexers. Therefore, there is a problem that the configuration of the redundant system is complicated and has low reliability.

  In the optical transmission line switching system described in Patent Document 2, when a failure occurs in the regular transmission line, communication is continued using the spare transmission line, but the configuration is different from that of the present invention. The configuration for detecting a failure that occurred in is unknown.

  In the bidirectional optical transmission device described in Patent Document 3, when a failure occurs in one optical fiber line, communication is continued through the other optical fiber line, but the configuration is different from the present invention. The configuration for detecting a failure occurring in the optical fiber line is unknown.

  The present invention has been made in view of the above-described circumstances. An optical transmission path is configured without using an active device, and a highly reliable optical transmission system, optical transmission method, optical An object of the present invention is to provide a switch device, a center device, an optical coupler device, a subscriber device, and an optical communication system.

In order to solve the above-described problems, the first configuration of the present invention is configured to transmit a first optical transmission line, a second optical transmission line, and an optical signal transmitted from a predetermined optical signal transmission unit to the first optical transmission line. An optical switch that selectively transmits to an optical transmission line or the second optical transmission line, and a predetermined optical signal reception of the optical signal transmitted through the first optical transmission line or the second optical transmission line And an optical transmission system having an optical coupler for sending to the optical signal, wherein the optical coupler sends the optical signal to the optical signal receiving means and outputs a branched light branched from the optical signal, A return optical coupler is provided for branching and outputting the branched light output from the optical coupler into a first return light and a second return light, and the first optical transmission line transmits the optical signal. is configured to transmit the first folded optical and conveyed, prior to The second optical transmission path, is configured to transmit the second folded optical as well as transmitting the optical signal, the optical switch, the first of said first folded transmitted through the optical transmission line The optical signal is received when light is received and the second return light transmitted through the second optical transmission line is received, and the light reception level of the first return light is equal to or greater than a predetermined first threshold. while sending the to the first optical transmission path, the first light receiving level of the folded light rather smaller than the first threshold and the second folded optical second threshold light level is predetermined The optical signal is sent to the second optical transmission line at the above time.

According to a second configuration of the present invention, a first optical transmission line, a second optical transmission line, and an optical signal transmitted from a predetermined optical signal transmission unit are used as the first optical transmission line or the second optical transmission line. An optical switch for selectively sending out to an optical transmission line; and an optical coupler for sending out the optical signal transmitted through the first optical transmission line or the second optical transmission line to a predetermined optical signal receiving means. relates to an optical transmission method for use in an optical transmission system with, the optical coupler, sends out the optical signal to the optical signal receiving means, and configured to output the split lights split from the optical signal, said optical coupler A branching optical coupler for branching and outputting the branched light output from the first folded light and the second folded light, and transmitting the optical signal through the first optical transmission line, a configuration for transmitting the first folded optical, and said second An optical transmission path, the transmitting the optical signal Leave configured to transmit the second folded optical, the optical switch, the first said transmitted through the optical transmission path of the first light-receiving a folded optical And receiving the second return light transmitted through the second optical transmission path, and receiving the optical signal when the light reception level of the first return light is not less than a predetermined first threshold value. while delivering 1 to the optical transmission line, the first folded optical light receiving level rather smaller than the first threshold value, and when said second folded optical light receiving level is more than a predetermined second threshold The optical signal is transmitted to the second optical transmission line.

  According to the configuration of the present invention, since the subsequent stage of the optical switch is composed of only passive components, no active components are required, periodic maintenance and inspection can be eliminated, and a relatively simple configuration and high reliability. An optical transmission system can be constructed.

  The optical coupler is configured to send an optical signal to the optical signal receiving means and to output a branched light branched from the optical signal. The branched light output from the optical coupler is converted into a first folded light and a second reflected light. A folding optical coupler is provided that diverges and outputs the reflected light. The first optical transmission line is configured to transmit the optical signal and the first return light, and the second optical transmission path transmits the optical signal and the second return light. It is configured. The optical switch receives the first return light transmitted through the first optical transmission path and receives the second return light transmitted through the second optical transmission path. An optical signal is sent to the first optical transmission line when the light reception level of the return light is greater than or equal to a predetermined first threshold, while the light reception level of the first return light is smaller than the first threshold and An optical transmission system configured to send an optical signal to a second optical transmission line when the light receiving level of the folded light of 2 is equal to or higher than a second threshold and an optical transmission method used in the optical transmission system are provided. .

  In the present invention, the first optical transmission line is constituted by a first multi-core optical fiber cable that transmits the optical signal and transmits the first return light, and the second optical transmission line is the optical signal. And a second multi-core optical fiber cable that transmits the second folded light.

  According to the present invention, the optical switch includes a first optical / electrical converter that converts the first folded light transmitted through the first optical transmission line into a first electrical signal, and a second optical transmission. A second optical / electrical converter for converting the second folded light transmitted through the path into a second electrical signal, and an active mode control signal when the first electrical signal is greater than or equal to the first threshold value. A control unit that outputs a non-active mode control signal when the first electrical signal is smaller than the first threshold and the second electrical signal is equal to or greater than the second threshold. A switch unit for sending an optical signal to the first optical transmission line when the control signal is in the active mode, and sending the optical signal to the second optical transmission line when the control signal is in the non-active mode; It has.

According to the present invention, the optical switch device includes an optical switch unit that selectively sends an input optical signal to the first optical transmission line or the second optical transmission line, and the input from the first optical transmission line. A control unit that detects the light reception level of the first return light and the light reception level of the second return light input from the second optical transmission line, and controls the optical switch unit based on the respective light reception levels And. The control unit causes the optical switch unit to send the optical signal to the first optical transmission line when the light receiving level of the first return light is equal to or higher than a predetermined first threshold value. When the received light level of the first return light is smaller than the first threshold value and the received light level of the second return light is equal to or higher than a predetermined second threshold value, the optical signal is sent to the second optical transmission line. It is configured to be sent out.

According to the present invention, the center device converts the input transmission electric signal into an optical signal, and the optical signal input from the electric / optical signal conversion unit is first optically transmitted. An optical switch unit that selectively transmits to the optical path or the second optical transmission line, a light receiving level of the first return light input from the first optical transmission line, and an input from the second optical transmission line A control unit that detects a light reception level of the second return light and controls the optical switch unit based on each light reception level. The control unit causes the optical switch unit to send the optical signal to the first optical transmission line when the light receiving level of the first return light is equal to or higher than a predetermined first threshold value. When the received light level of the first return light is smaller than the first threshold value and the received light level of the second return light is equal to or higher than a predetermined second threshold value, the optical signal is sent to the second optical transmission line. It is configured to be sent out.

According to the present invention, the optical coupler device receives the first optical signal transmitted from the first optical transmission line and the second optical signal transmitted from the second optical transmission line, and receives the received optical signal. And a first coupler that outputs return light, a second coupler that branches the return light into first return light and second return light, and the first return light to the first optical transmission. First return light output means for outputting to the path, and second return light output means for outputting the second return light to the second optical transmission line.

According to the present invention, the subscriber unit inputs the first optical signal transmitted from the first optical transmission line and the second optical signal transmitted from the second optical transmission line, and receives the received optical signal. And a first coupler that outputs return light, a second coupler that branches the return light into first return light and second return light, and the first return light to the first optical transmission. A first return light output means for outputting to the path; a second return light output means for outputting the second return light to the second optical transmission line; and the output from the first optical coupler. And an optical receiver that receives the received optical signal and converts the received optical signal into a received electrical signal.

According to the present invention, an optical communication system includes a first optical transmission line, a second optical transmission line, an electric / optical signal converter that converts an input transmission electric signal into an optical signal, An optical switch that selectively sends the optical signal input from the optical signal converter to the first optical transmission line or the second optical transmission line; and an optical switch that is input from the first optical transmission line. A control unit that detects a light reception level of one return light and a light reception level of the second return light input from the second optical transmission line, and controls the optical switch unit based on the light reception levels; A first coupler that inputs a first optical signal transmitted from a first optical transmission line and a second optical signal transmitted from the second optical transmission line, and outputs a received optical signal and return light A second coupler for branching the return light into a first return light and a second return light; and the first coupler A first return beam output means for outputting the return light to the first optical transmission line above, and the second return light output means for outputting said second return beam to said second optical transmission line, said first And an optical receiver that receives the received optical signal output from one optical coupler and converts the received optical signal into a received electrical signal. The control unit causes the optical switch unit to send the optical signal to the first optical transmission line when a light receiving level of the first return light is equal to or higher than a predetermined first threshold, When the received light level of the first return light is smaller than the first threshold value and the received light level of the second return light is equal to or higher than a predetermined second threshold value, the optical signal is sent to the second optical transmission line. It is configured to be sent out.

FIG. 1 is a diagram showing a configuration of a main part of an optical transmission system according to an embodiment of the present invention and an environment in which the system is used.
In the environment of this example, as shown in the figure, for example, the input side of the optical transmission line 20 is connected to the center apparatus 10 provided in a telephone carrier or the like, and the user's house is connected to the output side of the optical transmission line 20, for example. Etc. are connected to the subscriber unit 30. The optical transmission line 20 is provided outdoors, for example, and includes a normal transmission line 21, a backup transmission line 22, and a closure 23.

  The normal transmission path 21 is composed of a multi-core optical fiber cable, and transmits the optical signal pad and the return light pau. The backup transmission line 22 is composed of a multi-core optical fiber cable, and transmits the optical signal pbd and transmits the return light pbu. An optical coupler 24 and an optical coupler 25 are accommodated in the closure 23. The optical coupler 24 is configured as a 2-input × 1-output port type, but has an empty port terminated in addition to an output port normally used. This empty port is used as an output terminal when the terminal is removed. As a result, the optical coupler 24 sends the optical signal pad transmitted through the normal transmission path 21 or the optical signal pbd transmitted through the backup transmission path 22 to the subscriber device 30 as the optical signal pm. The branched light pn branched from the pad or the optical signal pbd is output. The optical coupler 25 branches the branched light pn output from the optical coupler 24 into a folded light pau and a folded light pbu and outputs the branched light pau.

  The center device 10 is provided with an optical transmitter 11 and an optical switch (optical SW) 12. The optical transmitter 11 converts the electrical signal ei for transmission into an optical signal pi and sends it out. The optical switch 12 selectively transmits the optical signal pi transmitted from the optical transmitter 11 to the normal transmission path 21 or the backup transmission path 22. In particular, in this embodiment, the optical switch 12 receives the return light pau transmitted through the normal transmission path 21, receives the return light pbu transmitted through the backup transmission path 22, and receives the return light pau. When the level is equal to or higher than a predetermined first threshold value, the optical signal pi is sent as the optical signal pad to the normal transmission path 21, while the light reception level of the same return light pau is smaller than the first threshold value and the same return light. When the light reception level of pbu is equal to or higher than a predetermined second threshold, the optical signal pi is sent to the backup transmission line 22 as the optical signal pbd. The first threshold value is set to a value that can determine whether the normal transmission path 21 is good or bad, and the second threshold value is set to a value that can determine whether the backup transmission line 22 is good or bad.

  The subscriber device 30 has an optical receiver 31. The optical receiver 31 converts the optical signal pm sent from the optical coupler 24 into a receiving electric signal ej and sends it to a telephone (not shown). The optical switch 12 and the optical transmission line 20 constitute an optical transmission system.

FIG. 2 is a configuration diagram of the optical switch 12 in FIG.
As shown in FIG. 2, the optical switch 12 includes an optical / electrical converter (O / E) 41, an optical / electrical converter (O / E) 42, a controller 43, and a switch 44. It is configured. The optical / electrical converter 41 converts the folded light pau transmitted through the normal transmission path 21 into an electrical signal ea. The optical / electrical converter 42 converts the return light pbu transmitted through the backup transmission path 22 into an electrical signal eb. The control unit 43 outputs an active mode control signal ct when the electrical signal ea is equal to or greater than the first threshold, while the electrical signal ea is smaller than the first threshold and the electrical signal eb is the second threshold. The control signal ct in the non-active mode is output when the threshold value is exceeded. The switch unit 44 sends the optical signal pi as the optical signal pad to the normal transmission path 21 when the control signal ct is in the active mode, while the optical signal pi is sent to the standby transmission path when the control signal ct is in the non-active mode. 22 is transmitted as an optical signal pbd.

FIG. 3 is a flowchart for explaining the operation of the optical switch 12.
With reference to this figure, the processing content of the optical transmission method used for the optical transmission system of this example is demonstrated.
In this optical transmission system, the optical signal pi sent from the optical transmitter 11 is sent to the normal transmission path 21 as an optical signal pad via the optical switch 12. The optical signal pad transmitted through the normal transmission path 21 is transmitted to the optical receiver 31 of the subscriber unit 30 as the optical signal pm through the optical coupler 24 and is branched by the optical coupler 24 as the branched light pn. Is output. The branched light pn is branched by the optical coupler 25, and the return light pau and the return light pbu are output from the optical coupler 25.

  The return light pau is transmitted to the optical switch 12 via the normal transmission path 21, and the return light pbu is transmitted to the optical switch 12 via the backup transmission path 22. In the optical switch 12, the return light pau is received and the return light pbu is received. When the received light level of the return light pau is equal to or higher than the first threshold value, the optical signal pi continues as the optical signal pad in the normal transmission path 21. Is sent to. On the other hand, when the light reception level of the return light pau becomes smaller than the first threshold due to the occurrence of a failure or the like in the normal transmission path 21, if the light reception level of the return light pbu is equal to or higher than the second threshold, The optical signal pi is sent to the backup transmission line 22 as the optical signal pbd.

  In this case, in the optical switch 12, as shown in FIG. 3, the return light pau transmitted through the normal transmission path 21 is converted into an electrical signal ea by the optical / electrical converter 41 (step A1, first optical signal). / Folded light pbu transmitted through the backup transmission line 22 is converted into an electric signal eb by the optical / electrical converter 42 (step A2, second optical / electrical conversion process). The control unit 43 outputs an active mode control signal ct when the electrical signal ea is equal to or higher than the first threshold, while the electrical signal ea is smaller than the first threshold and the electrical signal eb is the second threshold. The control signal ct in the non-active mode is output when the threshold value is equal to or greater than the threshold value (step A3, mode control process). In the switch unit 44, when the control signal ct is in the active mode, the optical signal pi is transmitted as the optical signal pad to the normal transmission path 21 (step A4a, optical signal transmission processing), while the control signal ct is in the inactive mode. Sometimes the optical signal pi is sent to the backup transmission line 22 as the optical signal pbd (step A4b, optical signal sending process).

  The optical signal pbd transmitted through the backup transmission line 22 is transmitted to the optical receiver 31 of the subscriber unit 30 as the optical signal pm through the optical coupler 24, and is branched by the optical coupler 24 as the branched light pn. Is output.

  As described above, in this embodiment, the optical transmission system includes the optical switch 12 and the optical transmission path 20, and the optical transmission path 20 includes the normal transmission path 21, the standby transmission path 22, and the optical coupler 24 in the closure 23. In addition, since it is composed of only passive components of the optical coupler 25 and does not require active components, periodic maintenance and inspection of the optical transmission line 20 is unnecessary, and a highly reliable optical transmission system is constructed with a relatively simple configuration. Is done.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiment, and even if there is a design change without departing from the gist of the present invention, Included in the invention.
For example, the optical coupler 25 is omitted, the branched light pn from the optical coupler 24 is sent to the optical / electrical converter 41 via the normal transmission path 21, and the electrical signal eb of the optical / electrical converter 42 is sent to the second By setting the threshold value or more, a failure on the backup transmission line 22 side is not detected, but substantially the same operation and effect as in the above embodiment can be obtained (claims 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, and 21). Further, when the control signal ct of the control unit 43 is in the non-active mode, that is, when the optical signal pi is sent to the spare transmission line 22 as the optical signal pbd, display means such as an LED (Light Emitting Diode). You may make it display with. Thereby, even if a failure occurs in the normal transmission path 21, the person in charge of maintenance can quickly move to the maintenance work.

  The present invention can be applied to all redundant optical transmission systems that transmit information converted into optical signals.

It is a figure which shows the structure of the principal part of the optical transmission system which is one Example of this invention, and the environment where this system is used. It is a block diagram of the optical switch 12 in FIG. 3 is a flowchart for explaining the operation of the optical switch 12;

Explanation of symbols

10 center device 11 optical transmitter (optical signal transmission means, electrical / optical signal converter, part of center device)
12 Optical SW (optical switch, optical switch part, part of optical switch device, part of center device)
20 Optical transmission line (part of optical transmission system)
21 Normal transmission line ( first optical transmission line )
22 Backup transmission line ( second optical transmission line )
23 Closure (return light output means, first return light output means, second return light output means, part of optical coupler device)
24 Optical coupler (first coupler, part of optical coupler device)
25 Optical coupler (Folding optical coupler, second coupler, return light output means, first return light output means, second return light output means, part of optical coupler device)
30 subscriber apparatus 31 optical receiver (optical signal receiving means, optical receiver, part of subscriber apparatus)
41 Optical / electrical converter (O / E) (part of optical switch)
42 Optical / electrical converter (O / E) (part of optical switch)
43 Control unit (part of optical switch, part of optical switch device, part of center device)
44 Switch part (part of optical switch)

Claims (16)

The first optical transmission path, the second optical transmission path, and the optical signal transmitted from the predetermined optical signal transmission means are selectively transmitted to the first optical transmission path or the second optical transmission path. An optical transmission system comprising: an optical switch; and an optical coupler that sends the optical signal transmitted through the first optical transmission path or the second optical transmission path to a predetermined optical signal receiving means,
The optical coupler is
The optical signal is sent to the optical signal receiving means, and the branched light branched from the optical signal is output.
A folding optical coupler for branching and outputting the branched light output from the optical coupler into a first folded light and a second folded light;
The first optical transmission line is:
The optical signal is transmitted and the first folded light is transmitted.
The second optical transmission line is:
The optical signal is transmitted and the second folded light is transmitted.
The optical switch is
Receiving the first return light transmitted through the first optical transmission path, receiving the second return light transmitted through the second optical transmission path, and receiving the first return light; The optical signal is sent to the first optical transmission line when the received light level is equal to or higher than a predetermined first threshold, while the received light level of the first return light is smaller than the first threshold, and An optical transmission system configured to transmit the optical signal to the second optical transmission line when a light receiving level of the second return light is equal to or greater than a predetermined second threshold. The first optical transmission line is:
A first multi-core optical fiber cable that transmits the optical signal and transmits the first folded light;
The second optical transmission line is:
The optical transmission system according to claim 1, characterized in that it is constituted by a second multi-fiber optical fiber cable for transmitting the second folded optical with transmitting the optical signal. The optical switch is
A first optical / electrical converter that converts the first folded light transmitted through the first optical transmission path into a first electrical signal;
A second optical / electrical converter that converts the second folded light transmitted through the second optical transmission path into a second electrical signal;
An active mode control signal is output when the first electrical signal is greater than or equal to the first threshold, while the first electrical signal is less than the first threshold and the second electrical signal is A control unit that outputs a control signal in a non-active mode when the second threshold value or more;
A switch for sending the optical signal to the first optical transmission line when the control signal is in an active mode, and sending the optical signal to the second optical transmission line when the control signal is in a non-active mode The optical transmission system according to claim 1 or 2, further comprising: The first optical transmission path, the second optical transmission path, and the optical signal transmitted from the predetermined optical signal transmission means are selectively transmitted to the first optical transmission path or the second optical transmission path. An optical transmission used in an optical transmission system having an optical switch and an optical coupler for sending the optical signal transmitted through the first optical transmission path or the second optical transmission path to a predetermined optical signal receiving means. A method,
The optical coupler is configured to send the optical signal to the optical signal receiving means and to output a branched light branched from the optical signal,
A folding optical coupler for branching and outputting the branched light output from the optical coupler into a first folded light and a second folded light;
The first optical transmission path is configured to transmit the optical signal and the first return light, and the second optical transmission path transmits the optical signal and the second optical transmission path. As a configuration to transmit the return light,
The optical switch receives the first return light transmitted through the first optical transmission path and receives the second return light transmitted through the second optical transmission path; The optical signal is sent to the first optical transmission line when the light reception level of the first return light is greater than or equal to a predetermined first threshold, while the light reception level of the first return light is the first threshold. And transmitting the optical signal to the second optical transmission line when the light receiving level of the second folded light is equal to or greater than a predetermined second threshold. The first optical transmission line is constituted by a first multi-core optical fiber cable that transmits the optical signal and transmits the first folded light,
5. The optical transmission method according to claim 4, wherein the second optical transmission line is constituted by a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light. With the optical switch,
A first optical / electrical conversion process for converting the first folded light transmitted through the first optical transmission path into a first electrical signal;
A second optical / electrical conversion process for converting the second folded light transmitted through the second optical transmission path into a second electrical signal;
An active mode control signal is output when the first electrical signal is greater than or equal to the first threshold, while the first electrical signal is less than the first threshold and the second electrical signal is A mode control process for outputting a control signal of a non-active mode when the second threshold value or more;
Light that transmits the optical signal to the first optical transmission line when the control signal is in the active mode, and transmits the optical signal to the second optical transmission line when the control signal is in the non-active mode. 6. The optical transmission method according to claim 4, wherein signal transmission processing is performed. An optical switch unit that selectively sends an input optical signal to the first optical transmission line or the second optical transmission line;
A light reception level of the first return light input from the first optical transmission path and a light reception level of the second return light input from the second optical transmission path are detected, and based on the respective light reception levels A control unit for controlling the optical switch unit,
The control unit
The optical switch unit is configured to send the optical signal to the first optical transmission line when a light receiving level of the first return light is equal to or higher than a predetermined first threshold, The optical signal is transmitted to the second optical transmission line when the light reception level is lower than the first threshold and the light reception level of the second return light is equal to or higher than a predetermined second threshold. An optical switch device. The first optical transmission line is:
A first multi-fiber cable that transmits the optical signal and transmits the first return light;
The second optical transmission line is:
8. The optical switch device according to claim 7, comprising a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light. An electrical / optical signal converter for converting an input transmission electrical signal into an optical signal;
An optical switch unit that selectively transmits the optical signal input from the electrical / optical signal conversion unit to the first optical transmission line or the second optical transmission line;
A light reception level of the first return light input from the first optical transmission path and a light reception level of the second return light input from the second optical transmission path are detected, and based on the respective light reception levels A control unit for controlling the optical switch unit,
The control unit
The optical switch unit is configured to send the optical signal to the first optical transmission line when a light receiving level of the first return light is equal to or higher than a predetermined first threshold, The optical signal is transmitted to the second optical transmission line when the light reception level is lower than the first threshold and the light reception level of the second return light is equal to or higher than a predetermined second threshold. The center apparatus characterized by the above-mentioned. The first optical transmission line is:
A first multi-fiber cable that transmits the optical signal and transmits the first return light;
The second optical transmission line is:
10. The center apparatus according to claim 9, wherein the center apparatus is configured by a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light. A first coupler that inputs a first optical signal transmitted from a first optical transmission line and a second optical signal transmitted from a second optical transmission line, and outputs a received optical signal and return light; ,
A second coupler for branching the return light into a first return light and a second return light;
First return light output means for outputting the first return light to the first optical transmission line;
An optical coupler apparatus comprising: second return light output means for outputting the second return light to the second optical transmission line. The first optical transmission line is:
A first multi-fiber cable that transmits the optical signal and transmits the first return light;
The second optical transmission line is:
12. The optical coupler apparatus according to claim 11, comprising a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light. A first coupler that inputs a first optical signal transmitted from a first optical transmission line and a second optical signal transmitted from a second optical transmission line, and outputs a received optical signal and return light; ,
A second coupler for branching the return light into a first return light and a second return light;
First return light output means for outputting the first return light to the first optical transmission line;
Second return light output means for outputting the second return light to the second optical transmission line;
A subscriber unit comprising: an optical receiving unit that receives the received optical signal output from the first optical coupler and converts the received optical signal into a received electrical signal. The first optical transmission line is:
A first multi-fiber cable that transmits the optical signal and transmits the first return light;
The second optical transmission line is:
14. The subscriber unit according to claim 13, comprising a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light. A first optical transmission line, a second optical transmission line,
An electrical / optical signal converter for converting an input transmission electrical signal into an optical signal;
An optical switch for selectively sending out the optical signal input from the electrical / optical signal converter to the first optical transmission line or the second optical transmission line;
A light reception level of the first return light input from the first optical transmission path and a light reception level of the second return light input from the second optical transmission path are detected, and based on the respective light reception levels A control unit for controlling the optical switch unit;
A first optical signal transmitted from the first optical transmission line and a second optical signal transmitted from the second optical transmission line are input, and a received optical signal and return light are output. A coupler,
A second coupler for branching the return light into a first return light and a second return light;
First return light output means for outputting the first return light to the first optical transmission line;
Second return light output means for outputting the second return light to the second optical transmission line ;
An optical receiver that receives the received optical signal output from the first optical coupler and converts the received optical signal into a received electrical signal;
The controller is
The optical switch unit is configured to send the optical signal to the first optical transmission line when a light receiving level of the first return light is equal to or higher than a predetermined first threshold, The optical signal is transmitted to the second optical transmission line when the light reception level is lower than the first threshold and the light reception level of the second return light is equal to or higher than a predetermined second threshold. An optical communication system. The first optical transmission line is:
A first multi-fiber cable that transmits the optical signal and transmits the first return light;
The second optical transmission line is:
16. The optical communication system according to claim 15, comprising a second multi-core optical fiber cable that transmits the optical signal and transmits the second return light.

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