Optical transponder

An optical transmitter includes: a plurality of client ports configured to receive a client signal from an end user device; a plurality of line ports configured to generate a line signal in which the client signal is stored, and transmit the line signal to an optical receiver; a switch configured to connect the plurality of client ports with the plurality of line ports; and a label provider configured to provide the client signal with a label for identifying a transmission destination in the optical receiver.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2019/011630 filed on Mar. 20, 2019, claiming priority based on Japanese Patent Application No. 2018-066355 filed Mar. 30, 2018, the disclosure of which is incorporated herein in its entirely by reference.

TECHNICAL FIELD

The present invention relates to an optical transmission system, and particularly relates to an optical transmitter, an optical receiver, and an optical transponder that are used in a terminal station of an optical transmission system.

BACKGROUND ART

An optical transceiver included in a terminal station used in an optical submarine cable system has a function of processing a client signal to be input, and outputting a line signal. The client signal is a signal to be transmitted and received between an end user device and the terminal station. The line signal is a signal for transmitting and receiving the client signal to and from another terminal station via a submarine transmission path. PTL 1 describes a configuration of an optical transceiver included in a terminal station.

FIG. 9is a diagram illustrating a configuration example of an optical transceiver (optical transponder, hereinafter, referred to as a “transponder”) included in a general terminal station. A transponder900includes a client port901, a cross connect unit902, and a line port903. The terminal station transmits and receives a client signal to and from the end user device via the client port901. The terminal station transmits and receives a line signal to and from another terminal station connected with a submarine transmission path via the line port903. The cross connect unit902is a cross connect switch for connecting the client port901with the line port903.

In association with the present invention, further, PTL 2 describes a technique relating to a correspondence between each channel before and after multiplexing, and each channel after demultiplexing in a multiplexing transmission system. PTL 3 describes a technique for outputting a signal separated from a time-division multiplex signal with a desired channel arrangement.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In a general optical transmission system for connecting terminal stations, by registering cross-connect information common to an station and an opposite station, a client signal is communicated between an end user device connected to the station, and an end user device connected to the opposite station. In such a configuration, a system administrator needs to constantly administer cumbersome cross-connect information of each terminal station in addition to use information of each port. For example, when a port for outputting a signal is changed by changing a specification of the system, it is necessary to update port information of an input port on a reception side according to a change in port information of an output port on a transmission side. Therefore, there is a problem that administration becomes cumbersome to the system administrator.

The present invention provides an optical transmitter, an optical receiver, and an optical transponder that facilitate port administration for inputting and outputting a client signal.

Solution to Problem

An optical transmitter according to the present invention includes:

a plurality of client ports for receiving a client signal from an end user device;

a plurality of line ports for generating a line signal in which the client signal is stored, and transmitting the line signal to an optical receiver;

a switch for connecting the plurality of client ports with the plurality of line ports; and

a label providing means for providing the client signal with a label for identifying a transmission destination in the optical receiver.

An optical receiver according to the present invention includes:

a plurality of line ports for receiving a line signal in which a client signal is stored from an optical transmitter, and outputting the client signal;

a label terminating means for extracting, from a label included in the client signal, information for identifying a transmission destination of the client signal;

a switch for connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal; and

a plurality of client ports for transmitting the client signal to an end user device.

An optical transponder according to the present invention includes:

a plurality of client ports for transmitting and receiving a client signal between an end user device and the optical transponder;

a plurality of line ports for transmitting and receiving a line signal in which the client signal is stored to and from a communication device;

a label providing means for providing the client signal to be transmitted from the end user device to the communication device, with a first label for identifying a transmission destination in the communication device;

a label terminating means for extracting, from a second label included in the client signal received from the communication device, information for identifying a transmission destination of the client signal stored in the line signal received from the communication device; and

a switch for connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal.

An optical transmission method according to the present invention includes:

receiving a client signal from an end user device at a plurality of client ports;

transmitting a line signal in which the client signal is stored to an optical receiver at a plurality of line ports;

connecting the plurality of client ports with the plurality of line ports; and

providing the client signal to be transferred from any one of the plurality of client ports to any one of the plurality of line ports, with a label for identifying a transmission destination in the optical receiver.

An optical reception method according to the present invention includes:

transmitting a client signal to an end user device at a plurality of client ports;

receiving a line signal in which the client signal from an optical transmitter is stored at a plurality of line ports;

extracting, from a label included in the client signal, information for identifying a transmission destination of the client signal; and

connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal.

Advantageous Effects of Invention

An optical transmitter, an optical receiver, and an optical transponder according to the present invention facilitate port administration for inputting and outputting a client signal.

EXAMPLE EMBODIMENT

First Example Embodiment

FIG. 1is a diagram illustrating a configuration example of an optical transmission system1according to a first example embodiment of the present invention. The optical transmission system1includes terminal stations11and21, end user devices13and23, and an optical transmission path51. A client signal is bidirectionally transmitted between the end user device13and the end user device23via the terminal stations11and21, and the optical transmission path51.

The end user devices13and23are communication devices of a user of the optical transmission system1, and, for example, general transmission devices or servers. The end user devices13and23transmit and receive, to and from the terminal station11or21, a client signal to be transmitted to and from a communication destination.

The terminal station11includes n transponders111to11n(n is a natural number). The terminal station11converts a client signal transmitted by the end user device13into a line signal, and outputs the line signal to a wavelength multiplexing unit121. The line signal is an optical signal to be transmitted between the terminal station11and the terminal station21, and in which the client signal is stored. The wavelength multiplexing unit121wavelength-multiplexes line signals input from the transponders111to11nand having different wavelengths, and outputs a wavelength-multiplexed signal to the optical transmission path51as a wavelength division multiplexing (WDM) signal. Further, the terminal station11wavelength-demultiplexes a WDM signal received from the terminal station21in the wavelength multiplexing unit121, and outputs demultiplexed line signals to the transponders111to11nas line signals. The transponders111to11nconvert the line signals into client signals, and outputs the client signals transmitted by the end user device23to the end user device13.

The terminal station21has a configuration and a function similar to those of the terminal station11. Specifically, the terminal station21includes n transponders211to21n(n is a natural number). The terminal station21converts a client signal transmitted by the end user device23into a line signal, and outputs the line signal to a wavelength multiplexing unit221. The wavelength multiplexing unit221wavelength-multiplexes line signals input from the transponders211to21n, and outputs a wavelength-multiplexed line signal to the optical transmission path51as a WDM signal. Further, the terminal station21wavelength-demultiplexes a WDM signal received from the terminal station11in the wavelength multiplexing unit221, and outputs demultiplexed line signals to the transponders211to21n. The transponders211to21nconvert the line signals into electric signals, and output client signals transmitted by the end user device13to the end user device23. In this way, both of the wavelength multiplexing units121and221play a role of a wavelength multiplexing/demultiplexing means having a wavelength multiplexing function and a wavelength demultiplexing function.

The optical transmission system1is applicable not only to a land optical transmission system but also to a submarine optical transmission system. For example, the optical transmission path51is a submarine transmission path, and the terminal stations11and21installed on a land terminate the submarine transmission path. The optical transmission path51may also include an optical amplifier, an optical repeater, and an optical add/drop multiplexer (OADM), regardless of an installation configuration thereof.

FIG. 2is a diagram illustrating a configuration example of the transponder110according to the present example embodiment. The transponder110is a generic term of the transponders111to11nand211to21nillustrated inFIG. 1. The transponder110has a configuration and a function common to the transponders111to11nand211to21n. InFIG. 2and thereafter, an arrow appended between blocks indicates an example of a direction of a signal for description, and does not limit the direction of the signal.

The transponder110includes a client port115, a cross connect unit116, and a line port117. The client port115is an interface of a client signal opposed to the end user device13or23. The line port117is an interface of a line signal, opposed to the wavelength multiplexing unit121or221. Each of the client port115and the line port117is provided in plural.

The cross connect unit116includes a label providing unit161, a switch162, and a label terminating unit163. The label providing unit161provides a client signal to be transferred from any one of the client ports115to any one of the line ports117with a label for identifying a client port included in a transponder of a terminal station being a transmission destination of the client signal. The label terminating unit163extracts, from a label included in a client signal to be output from the line port117to the switch162, information for identifying any one of the client ports115being a transmission destination of the client signal. The switch162connects a client port115being a transmission destination of a client signal, with a line port117that has received a line signal including the client signal, based on the information extracted by the label terminating unit163. Each of the label providing unit161and the label terminating unit163plays a role of a label providing means or a label terminating means in the transponder110.

A line signal to be transmitted and received to and from an outside of the transponder110by the line port117is an optical signal. Allowing each of the plurality of line ports117included in the terminal stations11and21to transmit and receive an optical signal having a different wavelength in the wavelength multiplexing unit121or221enables wavelength demultiplexing in the wavelength multiplexing unit121or221. Inside the cross connect unit116according to the present example embodiment, a client signal is an electric signal. Therefore, the line port117performs conversion between a client signal (electric signal) and a line signal (optical signal). However, the client signal is not limited to an electric signal.

FIG. 3is a diagram describing transmission of a client signal, when the transponder110is opposed. InFIG. 3, a transmission source of the client signal is described as the transponder110, and a transmission destination of the client signal is described as the transponder210. In the following, description is made for a case where a client signal is transmitted from a client port A (115A) of the transponder110to a client port A (215A) of the transponder210. A configuration and a function of the transponder210are similar to those of the transponder110.

The client port A (115A) receives a client signal from the end user device13inFIG. 1. The client port A outputs the client signal to the label providing unit161. The label providing unit161provides the client signal with a label. The label is information capable of uniquely identifying the client signal output by the client port A. For example, the label may be information automatically generated from a mounting position or a port administration number of the client port A. Alternatively, when the terminal stations11and21are configured in such a way that a blade is mounted on a chassis, a value generated from a mounting slot position of the blade on which a hardware of a client port is mounted, and a port administration number on the blade may be set as the label. This value is also a value capable of uniquely identifying the client port. The label may be wavelength information at the time of converting the client signal into a line signal, or an identifier for identifying an end user device being a transmission destination or a transmission source of the client signal. The label providing unit161outputs, to the switch162, the client signal provided with the label. In the following, a label to be provided to a client signal to be transmitted from the client port A (115A) to the client port A (215A) is described as a “label A”. A client signal provided with the label A is described as a “client signal A”, and a line signal in which the client signal A is stored is described as a “line signal A”.

The switch162outputs the client signal A to any one of the line ports117. On the other hand, as described later, the transponder210that has received the client signal A transfers the client signal A to the client port A (215A), based on the label A provided to the client signal A. Therefore, in the optical transmission system1, it is not necessary to administer a correspondence between the line port117on a transmission side where the client signal A is processed, and a line port217where the line signal A is received. Accordingly, the switch162is able to select the line port117freely for outputting the client signal A within a range allowable for a resource of the optical transmission system1. The selected line port117converts the client signal A into the line signal A, and transmits the line signal A from the transponder110to the transponder210.

The line signal A is received by the line port217of the transponder210via the optical transmission path51. The transponders110and210may include a plurality of line ports117and217, and store another client signal in an optical signal having a different wavelength for transmission. In this case, for example, as illustrated inFIG. 1, the wavelength multiplexing unit121is disposed between the transponder110and the optical transmission path51, and the wavelength multiplexing unit221is disposed between the optical transmission path51and the transponder210. By the wavelength multiplexing units121and221, it is possible to transmit a WDM signal among the plurality of line ports117and217. The WDM signal may include a line signal other than the line signal A in which the client signal A for connecting the client ports A (115A and215A) is stored. The wavelength multiplexing units121and221, and the optical transmission path51are configured in such a way that the line port217receives a line signal transmitted by the line port117.

The line signal A transmitted from the client port A (115A) via the line port117and the optical transmission path51is received by the line port217of the transponder210. The line port217converts the received line signal A into the client signal A, and outputs the client signal A to the label terminating unit263.

The label terminating unit263extracts the label A provided to the client signal A, and outputs the client signal A and the label A to the switch262. The switch262selects one of the ports for outputting the client signal A, based on the label A. For example, the switch262holds, in a table, information on a transmission destination of the client A included in the label A, and information on an output port of the switch262, associated with the transmission destination, and selects an output port for outputting the client signal by referring to the table. When the label A is extracted in the label terminating unit263, a transmission destination of the client signal A is the client port A (215A). Therefore, the switch262reads, from the table, a port connected to the client port A (215A) associated with the label A. Then, the switch262connects an input port with an output port of the switch262in such a way that the client signal A is output from the read port. As described above, information on a transmission destination of the client signal A is information for uniquely identifying the client signal A, and may be information capable of identifying a transmission destination of the client signal A, based on the information.

In this way, the transponder110provides a client signal with information (label) capable of uniquely identifying a client port being a transmission destination of the client signal. Then, the transponder210selects a client port for outputting the client signal, based on the label information. Therefore, it is not necessary to administer information on from which one of line ports of the transponder110, a line signal is transmitted, and by which one of line ports of the transponder210, the line signal is received. Specifically, in the optical transmission system1, it is possible to transmit a client signal without being conscious of cross-connect information within the transponders110and210, and it is possible to facilitate port administration in the cross connect unit116for inputting and outputting a client signal.

Both of the transponders110and210include the label providing unit161and the label terminating unit163. Therefore, also when a client signal is transmitted from the transponder210to the transponder110, a similar advantageous effect is acquired by an operation similar to the above.

Second Example Embodiment

FIG. 4is a diagram illustrating a configuration example of a transponder110A according to a second example embodiment of the present invention. Compared to the transponder110according to the first example embodiment, the transponder110A according to the present example embodiment includes a line port117A, in place of the line port117. The transponder110A may be used as the transponder110inFIGS. 2 and 3according to the first example embodiment.

The line port117A includes an FEC processing unit164, in addition to a function of the line port117. The FEC processing unit164performs forward error correction (FEC) processing to a client signal passing through the line port117A. Specifically, the FEC processing unit164performs error correction encoding processing to a client signal input from a switch162, adds an error correction frame (FEC frame) to the client signal, and transmits the client signal, as a line signal. The FEC processing unit164performs error correction code decoding processing of a client signal converted from a received line signal.

At the time of transmitting a line signal, the FEC processing unit164inserts a label provided by a label providing unit161into a free area of an FEC frame of a client signal, and converts the client signal into a line signal. At the time of decoding an FEC frame of a client signal converted from a received line signal, the FEC processing unit164extracts a label inserted into a free area of the FEC frame, and outputs the label together with the client signal to the label terminating unit163.

The transponder110A according to the second example embodiment provides, in addition to an advantageous effect according to the first example embodiment, an advantageous effect that it is possible to suppress an increase in a size of a client signal and a line signal resulting from providing a label, by inserting the label into a free area of the FEC frame.

Third Example Embodiment

FIG. 5is a diagram illustrating a configuration example of a transponder110B according to a third example embodiment of the present invention. The transponder110B according to the present example embodiment includes a line port117B, in place of the line port117A. The transponder110B may be used as the transponder110inFIGS. 2 and 3according to the first example embodiment.

The line port117B includes a failure detection unit165, in addition to an FEC processing unit164. The FEC processing unit164included in the line port117B applies processing to a client signal passing through the line port117B similarly to the FEC processing unit164according to the second example embodiment.

The failure detection unit165generates information (failure information) indicating an anomaly at the time of detecting an anomaly of the line port117B, and transmits the failure information to an opposing transponder (e.g., the transponder210inFIG. 3). Failure information may be generated not only at the time of failure of the line port117B, but also when an anomaly is present in a line signal received from the optical transmission path51by the line port117B, or in a client signal included in the line signal. The FEC processing unit164included in the line port117B stores the failure information in a free area of an FEC frame, and transmits the failure information to an opposing transponder. The opposing transponder examines whether the failure information is stored in a free area of an FEC frame of a line signal received from the transponder110B. When the failure information is stored, the opposing transponder eliminates, from a transmission destination of the line signal, a line port of the transponder110B in which the failure information is detected. Then, the opposing transponder transmits the line signal to a line port other than the line port in which the failure information is detected. Therefore, also when the line port117B of the transponder110fails, it is possible to suppress lowering of transmission quality of a line signal. Also, as compared with a case where an anomaly of a client signal is detected in an end user device, it is possible to discover a failure of the client signal at an earlier stage, and it is easy to specify a place where an anomaly occurs.

First Modification Example of Third Example Embodiment

In the transponder110B illustrated inFIG. 5, a priority may be set for each of a plurality of client ports115. At the time of transmitting failure information to an opposing transponder, the FEC processing unit164may also transmit a priority of each of the client ports115in the transponder110B. Thus, the opposing transponder is able to allocate a line signal to a line port in such a way that communication with a client port115notified from the transponder110B and having a high priority is prioritized, and transmit the line signal to the transponder110B. Consequently, also when it is not possible to transmit and receive a client signal by using all line ports117B due to a failure of any one of the line ports117B in the transponder110B, it becomes possible to protect a client signal having a high priority.

Second Modification Example of Third Example Embodiment

FIG. 6is a diagram illustrating a configuration example of a transponder110C being a second modification example according to the third example embodiment. The transponder110C includes a line port117B having a failure detection unit165similarly to the transponder110B. The transponder110C achieves a redundancy switching function by making a total of transmission capacities of line ports117B greater than a total of transmission capacities of client ports115. For example, when a transmission capacity of one client port115, and a transmission capacity of one line port115B are the same, the number of the line ports117B may be set greater than the number of the client ports115. Thus, when a line port117B has failed, it is possible to allow a redundant line port117B to substitute the function of the line port117B. Generally, setting a sum of transmission capacities of the line ports117B greater than a sum of transmission capacities of the client ports115allows another line port117B to process a part or the entirety of a client signal to be transmitted and received by the failed line port117B. Switching the line port117B in the transponder110C, and allocating a capacity of a line signal to be transmitted to the line port117B may be controlled, based on failure information by a transponder opposing to the transponder110C.

Fourth Example Embodiment

FIG. 7is a diagram illustrating a configuration example of an optical transmitter300according to a fourth example embodiment. According to the first example embodiment, a configuration in which a client signal is transmitted between the transponder110and the opposing transponder210, and an advantageous effect thereof have been described. An advantageous effect to be acquired by the transponder110is also acquired by the following optical transmitter300.

The optical transmitter300includes a client port115, a label providing unit161, a switch162, and a line port117. The label providing unit161provides a client signal to be transferred from any one of the client ports115to any one of the line ports117with a label for identifying a transmission destination of the client signal. The switch connects a client port115that has received a client signal from an end user device, and a line port117for transmitting the client signal. It is possible to employ the optical transmitter300as the transponder110inFIG. 3. Further, the optical transmitter300may employ the line port117A illustrated inFIG. 4or the line port117B illustrated inFIG. 5, in place of the line port117.

The optical transmitter300having a configuration as described above provides a client signal with a label for identifying a transmission destination of the client signal. Thus, a transponder being a transmission destination of a client signal is able to discriminate a port being an output destination of the client signal by label information, and select a port for transferring the client signal. Consequently, it is possible to transmit a client signal without being conscious of cross connect of any one of transponders being a transmission source and a transmission destination of the client signal. Specifically, the optical transmitter300is able to facilitate port administration in a cross-connect function of inputting and outputting a client signal.

Fifth Example Embodiment

FIG. 8is a diagram illustrating a configuration example of an optical receiver400according to a fifth example embodiment. An advantageous effect to be acquired by the transponder210according to the first example embodiment is also acquired by the following optical receiver400.

The optical receiver400includes a client port115, a switch162, a label terminating unit163, and a line port117. The optical receiver400may be used in place of the transponder210inFIG. 3. The label terminating unit163extracts, from a label included in a line signal received by the line port117, information for identifying a transmission destination of a client signal. The switch162connects, based on the information, the client port115being a transmission destination of a client signal, with the line port117that has received a line signal including the client signal.

The optical receiver400having a configuration as described above discriminates a port being an output destination of a client signal, based on information included in a label provided to the client signal by a transponder being a transmission source of the client signal. Then, the optical receiver400controls the switch162in such a way that the client signal is transferred to the port. Consequently, it is possible to transmit a client signal, without being conscious of cross connect of any one of transponders being a transmission source and a transmission destination of the client signal. Specifically, the optical receiver400is able to facilitate port administration in a cross-connect function of inputting and outputting a client signal.

It is also possible to configure the transponders110,110A,110B,110C, and210described in the first to third example embodiments, based on an optical transponder having both of a configuration of the optical transmitter300according to the fourth example embodiment, and a configuration of the optical receiver400according to the fifth example embodiment. The example embodiments of the present invention may also be described as the following supplementary notes, but are not limited to these supplementary notes.

An optical transmitter including:

a plurality of client ports for receiving a client signal from an end user device;

a plurality of line ports for generating a line signal in which the client signal is stored, and transmitting the line signal to an optical receiver;

a switch for connecting the plurality of client ports with the plurality of line ports; and

a label providing means for providing the client signal with a label for identifying a transmission destination in the optical receiver.

The optical transmitter according to supplementary note 1, wherein

each of the plurality of line ports includes a forward error correction processing means for performing error correction processing on the client signal, and storing the label in a free area of an error correction frame of the client signal.

The optical transmitter according to supplementary note 1 or 2, wherein

the label providing means is disposed between any one of the plurality of client ports and the switch.

An optical receiver including:

a plurality of line ports for receiving a line signal in which a client signal is stored from an optical transmitter, and outputting the client signal;

a label terminating means for extracting, from a label included in the client signal, information for identifying a transmission destination of the client signal;

a switch for connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal; and

a plurality of client ports for transmitting the client signal to an end user device.

The optical receiver according to supplementary note 4, wherein

each of the plurality of line ports includes a forward error correction processing means for performing error correction processing on the client signal, and extracting the label from an error correction frame of the line signal and outputting the label to the label terminating means.

The optical receiver according to supplementary note 4 or 5, wherein

the label terminating means is disposed between any one of the plurality of line ports and the switch.

An optical transmission system configured in such a way that the optical transmitter according to any one of supplementary notes 1 to 3, and the optical receiver according to any one of supplementary notes 4 to 6 are opposed to each other and transmit the client signal.

An optical transponder including:

a plurality of client ports for transmitting and receiving a client signal between an end user device and the optical transponder;

a plurality of line ports for transmitting and receiving a line signal in which the client signal is stored to and from a communication device;

a label providing means for providing the client signal to be transmitted from the end user device to the communication device, with a first label for identifying a transmission destination in the communication device;

a label terminating means for extracting, from a second label included in the client signal received from the communication device, information for identifying a transmission destination of the client signal stored in the line signal received from the communication device; and

a switch for connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal.

The optical transponder according to supplementary note 8, wherein

a sum of transmission capacities of the plurality of line ports is greater than a sum of transmission capacities of the plurality of client ports.

The optical transponder according to supplementary note 8 or 9, further including

a wavelength multiplexing/demultiplexing means for wavelength-demultiplexing the line signal to be transmitted and received to and from the communication device at each of the plurality of line ports.

An optical transponder including

a plurality of the optical transponders according to supplementary note 10, wherein

the wavelength multiplexing/demultiplexing means further wavelength-demultiplexes the line signal to be transmitted and received to and from the communication device by each of a plurality of the optical transponders.

An optical transmission system configured in such a way that the optical transponder according to any one of supplementary notes 8 to 11, and the communication device including the optical transponder according to any one of supplementary notes 8 to 11 are communicably connected via an optical transmission path.

The optical transmission system according to supplementary note 12, wherein,

when an anomaly is detected in any one of the plurality of line ports, a line port in which the anomaly is detected transmits information indicating that the anomaly is detected, to the communication device.

The optical transmission system according to supplementary note 13, wherein,

when receiving information indicating that the anomaly is detected, the communication device suppresses transmission of the line signal to the line port in which the anomaly is detected.

The optical transmission system according to supplementary note 13 or 14, wherein

information indicating that the anomaly is detected is stored in a free area of a forward error correction frame of the line signal.

The optical transmission system according to supplementary note 14 or 15, wherein

the communication device preferentially transmits the client signal having a high priority being set associated with the first label of the client signal received from the optical transmission path via the line port other than a line port in which the anomaly is detected.

The optical transmission system according to supplementary note 16, wherein

the priority is stored in a free area of a forward error correction frame of the line signal.

An optical transmission method including:

receiving a client signal from an end user device at a plurality of client ports;

transmitting a line signal in which the client signal is stored, to an optical receiver at a plurality of line ports;

connecting the plurality of client ports with the plurality of line ports; and

providing the client signal to be transferred from any one of the plurality of client ports to any one of the plurality of line ports, with a label for identifying a transmission destination in the optical receiver.

An optical reception method including:

transmitting a client signal to an end user device at a plurality of client ports;

receiving a line signal in which the client signal from an optical transmitter is stored at a plurality of line ports;

extracting, from a label included in the client signal, information for identifying a transmission destination of the client signal; and

connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal.

An optical transmission and reception method including:

transmitting and receiving a client signal to and from an end user device at a plurality of client ports;

transmitting and receiving a line signal in which the client signal is stored to and from a communication device at a plurality of line ports;

providing the client signal to be transmitted from the end user device to the communication device, with a first label for identifying a transmission destination in the communication device;

extracting, from a second label included in the line signal received from the communication device, information for identifying a transmission destination of the client signal; and

connecting any one of the plurality of client ports with any one of the plurality of line ports that receives the line signal, based on information for identifying a transmission destination of the client signal.

While the invention has been particularly shown and described with reference to example embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirt and scope of the present invention as defined by the claims. For example, each of the structure of the embodiments may be applied to other embodiments unless they conflict with each other. This application is based upon and claims the benefit of priority from Japanese patent application No. 2018-066355, filed on Mar. 30, 2018, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST