Optical transmission system and optical transmission method

[Problem] whether optical input interruption detected by an OXC device is due to an external failure from an upstream side or an internal failure of the OXC device in a transponder device connected to the OXC device using an optical transmission line, and this determination is implemented at low cost.[Solution] An optical transmission system (10A) is configured by connecting a plurality of OXC devices (14A) using optical fibers (16) between transponder devices (15A1) that relay optical signals transmitted to/from terminals (19a, 19b). The OXC device (14A) includes an OSC part (4d1) and a monitoring control part (4e1). The OSC part (4d1) outputs wavelength information on an optical signal in which optical input interruption has occurred and path information on a path of an optical fiber (16) in which the optical input interruption has occurred, at the time of detecting the optical input interruption from the optical fiber (16). In accordance with the wavelength information and the path information that have been output as above, the OXC device (14A) includes an AIS generation part (4j) that generates an AIS signal including both pieces of information on the wavelength and the path of the optical signal relating to the optical input interruption and alarm information relating to both the pieces of information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/JP2020/005650, having an International Filing Date of Feb. 13, 2020, which claims priority to Japanese Application Serial No. 2019-033359, filed on Feb. 26, 2019. The disclosure of the prior application is considered part of the disclosure of this application, and is incorporated in its entirety into this application.

TECHNICAL FIELD

The present invention relates to an optical transmission system and an optical transmission method having a disaggregated configuration. In the disaggregated configuration, transponder devices and optical cross connect (OXC) devices are connected using an optical fiber cable and aggregated.

BACKGROUND ART

FIG.8illustrates a block diagram of a conventional optical transmission system10. In the optical transmission system10, a plurality of OXC devices12,13, and14are connected using optical fiber cables (also referred to as “optical fibers”)16between a transponder device11and a transponder device15that are distant from each other (hereinafter referred to as “transponder devices11and15”). In addition, an element management system (EMS) device17is cable-connected to the transponder devices11and15using optical fibers, conductive cables, and the like. An EMS device18is cable-connected to the OXC devices12to14. Terminals19and20as communication devices such as personal computers, routers, or the like are respectively connected to the transponder devices11and15.

This optical transmission system10shows an aspect in which the transponder devices11and15have a same configuration, the OXC devices12to14also have a same configuration, and a signal is transmitted from the terminal19to the terminal20. For this reason, a multiplexer (MUX)12cthat multiplexes optical signals having a plurality of wavelengths is provided in the OXC device12disposed on a transmission side, and a demultiplexer (DMUX)14cthat demultiplexes optical signals having a plurality of wavelengths is provided in the OXC device14disposed on a reception side.

Note that the OXC device13connected between the OXC device12and the OXC device14that are placed on both sides of the OXC device13relays optical signals transmitted between the OXC device12and the OXC device14on both sides.

The transponder devices11and15relay optical signals transmitted between the terminal19and the terminal20. The OXC devices12to14switch multi-way wavelength paths using optical fibers16. The EMS device17monitors and controls processes for relaying communication in the transponder devices11and15, and the EMS device18monitors and controls processes for switching multi-way wavelength paths in the OXC devices12to14.

FIG.9illustrates, as a representative example, the OXC device14and the transponder device15connected to the OXC device14. The OXC device14includes an optical amplifier4a, an optical switch (SW)4b, a DMUX4c, an optical supervisory channel (OSC) part4d, a monitoring control part4e, an alarm indication signal (AIS) generation part4f, and a communication processing part4g. The EMS device18is connected to the monitoring control part4e, and the EMS device18receives monitoring information from the monitoring control part4e.

The transponder device15includes a plurality of (one or more) transponders5a1and5a2, a communication processing part5g, an AIS receiving part5h, and a monitoring control part5e. The communication processing part5gof the transponder device15and the communication processing part4gof the OXC device14are cable-connected using LAN cables or the like. The EMS device17is connected to the monitoring control part5e, and the EMS device17receives the monitoring information from the monitoring control part5e. Note that both the AIS receiving part5hand the monitoring control part5econstitute a second control part described in the claims.

In such a configuration, when optical signals of wavelengths λ1to λn that have been transmitted through the optical fiber16are input to the OXC device14, the optical signals are amplified by the optical amplifier4aand are input to the DMUX4cthrough the optical SW4b. The DMUX4cdemultiplexes the optical signals of the wavelengths λ1to λn and transmits the optical signals of the wavelengths λ1and λ2to the transponder device15through the optical fiber16.

In the transponder device15, one transponder5a1relays an optical signal of the wavelength λ1to transmit to the terminal20a1, and the other transponder5a2relays an optical signal of the wavelength λ2to transmit to the terminal20a2. Information relating to the relay processes of the transponders5a1and5a2is notified to the monitoring control part5eand detected.

The OSC part4dof the OXC device14monitors an alarm signal from an upstream device of the optical fiber16. When the alarm signal indicating a failure of the upstream device is detected, the OSC part4doutputs the alarm signal to the monitoring control part4e. In addition, also when optical input interruption due to a fault of the optical fiber16is detected by the optical amplifier4a, information about the optical input interruption is output to the monitoring control part4e.

When the optical input interruption information is detected, the monitoring control part4eoutputs fault information to the AIS generation part4f. The AIS generation part4fgenerates an AIS signal (alarm display signal) in accordance with input fault information and transmits this AIS signal to the communication processing part5gof the transponder device15through the communication processing part4g. This transmitted AIS signal is received by the AIS receiving part5hand is notified to the monitoring control part5e. The monitoring control part5edetects that optical input interruption has occurred in the OXC device14in accordance with detection of the AIS signal.

As such optical transmission system, Patent Literature 1 discloses a method for enhancing a fault section rating for a fault of a wavelength multiplexing section in an optical multiplexing network. Further, Non Patent Literature 1 describes a device capable of reducing a device cost and reducing power consumption by causing a wavelength multiplexing device not to perform electrical termination processing, and the device exchanges an alarm in an optical wavelength multiplexing section using an OSC separately from a main signal. Furthermore, Non Patent Literature 2 describes a configuration of an optical multiplexing transmission system in which a transponder part and a wavelength multiplexing part are configured in separate systems such as an open reconfigurable optical add/drop multiplexer (ROADM) or an open line system.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2012-015966 A

Non Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

Meanwhile, in the optical transmission system10described above, as illustrated inFIG.8, for example, it is assumed that a failure21has occurred in the optical fiber16between the OXC device12and the OXC device13. In this case, in the OXC device13disposed on a downstream side of the failure21, optical input interruption is detected as denoted by a circle21a, and an AIS signal is generated as denoted by a white circle21b. Failure position information indicating the occurrence of the failure21in the optical fiber16between the OXC devices12and13is superimposed on this AIS signal. The AIS signal is detected by the OXC device14disposed further downstream as denoted by a circle21c. This detected AIS signal cannot be detected by the transponder device15.

In the transponder device15, an optical signal related to the failure21is in an interruption state, and thus optical input interruption is detected by the transponders5a1and5a2as denoted by a circle21d. In other words, optical input interruption due to an external failure occurred on an upstream side can be detected by the transponders5a1and5a2.

However, the transponders5a1and5a2have optical input interruption due to a failure on an upstream side of the OXC device14in addition to optical input interruption due to failures occurring in a section from the transponder device15to the OXC device14, and there is a problem in that it is difficult to determine which of the above two factors has caused the optical input interruption.

If the determination cannot be made as described above, a maintenance operator of the transponder device15cannot quickly determine whether a failure is self-responsibility (responsibility of own device) or the other responsibility (responsibility of other devices), and unnecessary maintenance work and the like may be performed.

This type of problem also occurs in case of Patent Literature 1 and Non Patent Literatures 1 and 2. In the technology disclosed in Patent Literature 1, information, in other words, fault information from an optical node device (corresponding to a MUX) to an optical path termination device is not notified. In the technology described in Non Patent Literature 1, no OSC part is provided between a wavelength multiplexing part of an endpoint device and a transponder part, and no alarm transmission is performed. In the technology described in Non Patent Literature 2, an EMS that operates a communication device is separately provided in a wavelength multiplexing part and a transponder part, and it is necessary to acquire information about both an EMS for the transponder part and an EMS for the wavelength multiplexing part so as to acquire a state of an optical transmission network. In this configuration, an alarm transmitting/receiving means is not provided between the transponder part and the wavelength multiplexing part, and thus, a maintenance operator of the transponder cannot quickly determine whether an optical channel failure detected by the transponder part is due to self-responsibility or another responsibility.

FIG.9illustrates a configuration in which one transponder device15is connected to one OXC device14in the optical transmission system10. However, practically, a plurality of transponder devices15is connected in parallel with one OXC device14. In this case, in order to transmit an AIS signal generated by the OXC device14to each of the transponder devices15, the same number of LAN cables as that of the transponder devices15is necessary, and there is a problem that the facility costs increase as the number of transponder devices15increases.

The present invention has been made in view of such circumstances, and an objective thereof is to provide an optical transmission system and an optical transmission method capable of appropriately determining whether optical input interruption detected by an OXC device is due to an external failure from an upstream side or due to an internal failure of the OXC device in a transponder device connected to the OXC device using an optical transmission line and implementing this determination at low cost.

Means for Solving the Problem

As a means for solving the problem described above, the disclosure according to a first aspect is an optical transmission system. The optical transmission system connects, using an optical transmission path, and aggregates a plurality of optical cross connect (OXC) devices that switches wavelength paths of optical signals between transponder devices that relays optical signals transmitted to and from a communication device. The OXC device includes: a first control part, when optical input interruption in which an optical signal input from the optical transmission line is interrupted is detected, configured to output wavelength information indicating a wavelength of the optical signal in which the optical input interruption has occurred, and path information on a path of the optical transmission line in which the optical input interruption has occurred; and a generation part configured to generate an alarm signal in accordance with the wavelength information and the path information output from the first control part, the alarm signal including both pieces of information on the wavelength and the path of the optical signal relating to the optical input interruption and alarm information relating to the both pieces of information. The transponder device includes a second control part configured to notify of an external failure of the transponder device based on the both pieces of information and the alarm information included in the generated alarm signal.

In the disclosure according to a fourth aspect, an optical transmission method of an optical transmission system that connects, using an optical transmission line, and aggregates a plurality of optical cross connect (OXC) devices that switches wavelength paths of optical signals between transponder devices that relays optical signals transmitted to and from a communication device, the optical transmission method including: in the OXC device, when the optical input interruption in which an optical signal input from the optical transmission line is unconnected is detected, outputting wavelength information indicating a wavelength of the optical signal in which optical input interruption has occurred and path information on a path of the optical transmission line in which the optical input interruption has occurred, and generating an alarm signal in accordance with the output wavelength information and the output path information, the alarm signal including both pieces of information on the wavelength and the path of the optical signal relating to the optical input interruption and alarm information relating to the both pieces of information; and in the transponder device, notifying of an external failure of the transponder device based on the both pieces of information and the alarm information included in the generated alarm signal.

According to the configuration of the first aspect and the method of the fourth aspect, in the OXC device, an alarm signal is generated. The alarm signal includes both pieces of information on a wavelength of an optical signal relating to optical input interruption from an optical transmission line and information on a path of the optical transmission line in which the optical signal is transmitted and alarm information relating to the both pieces of information, and this alarm signal is notified from the OXC device to the transponder device. The transponder device can detect an external failure of the transponder device based on the both pieces of information and alarm information included in the notified alarm signal. For this reason, in the transponder device connected to the OXC device using an optical transmission line, it is possible to appropriately determine whether the optical input interruption detected by the OXC device is due to an external failure on an upstream side or an internal failure of the OXC device.

In the disclosure according to a second aspect, in the optical transmission system according to the first aspect, an optical coupler is inserted into an optical transmission line coupling the OXC device and the transponder device, and the alarm signal generated by the generation part is transmitted from the OXC device to the transponder device through the optical coupler.

According to this configuration, an alarm signal can be transmitted to the transponder device using an existing optical transmission line coupling the OXC device and the transponder device through the optical coupler. For this reason, a high-cost configuration is not necessary, in which an alarm signal is transmitted by cable-connecting an OXC device and a transponder device using a LAN cable or the like other than an optical transmission line as in a conventional configuration. In other words, a configuration in which the transponder device can appropriately determine whether optical input interruption of the OXC device is due to an external failure or an internal failure can be realized at low cost.

In a disclosure according to a third aspect, in the optical transmission system according to the first or second aspect, the transponder device includes a first database (DB) storing information on a path number that is a number of a path of the optical transmission line, information on an accommodation wavelength that is a wavelength of an optical signal accommodated in the path, information on device identifications (IDs) that are unique information on a transmitting device and a destination device of the signal, and information on a transponder ID. The OXC device includes a second DB in which each piece of the information stored in the first DB is registered and stored. The transponder device determines recovery from the optical input interruption when a state is changed from a state of being unconnected to the OXC device to a state of being connected through the optical transmission line and, after this determination, the transponder device superimposes each piece of the information read from the first DB on a control signal that has been changed to a unique specific wavelength, and transmits a resultant control signal to the OXC device, and the OXC device receives the transmitted control signal and registers and stores the information superimposed on the received control signal in the second DB in accordance with control of the second control part.

According to this configuration, when the OXC device is connected to the transponder device for the first time, each piece of information on the accommodation wavelength, the device ID, and the transponder ID stored in the first DB of the transponder device can be registered and stored in the second DB of the OXC device. After storing, an occurrence of an external failure relating to optical input interruption of the OXC device can be notified to the transponder device using each piece of information stored in the second DB.

Effects of the Invention

The present disclosure provides an optical transmission system and an optical transmission method capable of appropriately determining, at low cost, whether optical input interruption detected by an OXC device is due to an external failure from an upstream side or an internal failure of the OXC device in a transponder device coupled to the OXC device using an optical transmission line.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, in all the drawings of the present specification, components having corresponding functions are denoted by the same reference signs and description thereof will be appropriately omitted.

Configuration of Embodiment

FIG.1is a block diagram illustrating a configuration of an optical transmission system according to an embodiment of the present invention. In an optical transmission system10A illustrated inFIG.1, one OXC device14A and a plurality of transponder devices15A1to15An connected to the OXC device14A using optical fibers16are illustrated.

One OXC device14A and a plurality of transponder devices15A1to15An respectively correspond to an optical cross connection (OXC) device14and a transponder device15on a right end side of the optical transmission system10illustrated inFIG.8. Thus, the overall connection configuration of the optical transmission system10A illustrated inFIG.1corresponds to that of the optical transmission system10.

The OXC device14A includes an optical amplifier4a, an optical SW4b, a DMUX4c, an optical monitoring channel (OSC) part4d1, a monitoring control part4e1, an accommodation information management part4i, an AIS generation part4j, electrical/optical (E/O) conversion parts4k1and4kn, and optical couplers4l1to4ln. In addition, a form in which a first path16aand a second path16bare connected to the OXC device14A using the optical fibers16is also illustrated. Note that the optical fibers16constitute an optical transmission line described in the claims. Both the OSC part4dand the monitoring control part4e1constitute a first control part described in the claims. The AIS generation part4jconstitutes a generation part described in the claims.

The transponder devices15A1to15An have the same configuration. The transponder device15A1includes two transponders5a1and5a2, an optical coupler5l1, an optical/electrical (O/E) conversion part5k1, an AIS receiving part5h1, a monitoring control part5e1, and an accommodation information management part5i1. A terminal20a1is connected to one transponder5a1, and a terminal20a2is connected to the other transponder5a2.

Similarly, the transponder device15An includes two transponders5n1and5n2, an optical coupler5ln, an O/E conversion part5kn, an AIS receiving part5hn, a monitoring control part5en, and an accommodation information management part5in. A terminal20n1is connected to one transponder5n1, and a terminal20n2is connected to the other transponder5n2.

Here, the optical coupler4l1(or the optical coupler4ln) of the OXC device14A and the optical coupler5l1(or the optical coupler5ln) of the transponder device15A1are connected using an optical fiber16.

In such a configuration, when optical signals of respective wavelengths λ1to λn that have been transmitted through the first path16aare input to the OXC device14A, the optical signals are amplified by the optical amplifier4aand are input to the DMUX4cthrough the optical SW4b. The DMUX4cdemultiplexes the optical signals of respective wavelengths λ1to λn. The optical signals of the wavelengths λ1and λ2that have been demultiplexed are transmitted to the transponder device15A1through the optical fiber16. In addition, the optical signals of the wavelengths λm and λn that have been demultiplexed by the DMUX4care transmitted to the transponder device15An through the optical fiber16. In this way, the wavelengths λ1, λ2, . . . , λm, and λn of the optical signals accommodated in the respective transponder devices15A1to15An are different.

In the transponder device15A1, one transponder5a1transmits an optical signal of the wavelength λ1to the terminal20a1by relaying the optical signal, and the other transponder5a2transmits an optical signal of the wavelength λ2to the terminal20a2by relaying the optical signal. Information relating to the relay process of each of the transponders5a1and5a2is notified to the monitoring control part5e1and is detected.

Similarly, in the transponder device15An, one transponder5n1transmits an optical signal of the wavelength λm to the terminal20n1by relaying the optical signal and the other transponder5n2transmits an optical signal of the wavelength λn to the terminal20n2by relaying the optical signal. Information relating to the relay process of each of the transponders5n1and5n2is notified to the monitoring control part5e1and is detected.

Next, a configuration for detecting a failure will be described. In the OXC device14A, the OSC part4d1monitors the optical signals of the wavelengths λ1to λn that are input into the OXC device14A from an upstream side of the first path16a. In this monitoring, when an interruption state (optical input interruption) of an optical signal is detected, the OSC part4d1outputs, to the monitoring control part4e, optical input interruption information including wavelength information on wavelengths (for example, λ1and λ2) of the optical signal in which optical input interruption has occurred and path information on a path (for example, the first path) of this optical signal. Note that the optical input interruption may be detected by the optical amplifier4aand may be notified to the monitoring control part4e1.

When an AIS signal generated due to a failure on an upstream side by the OXC device placed on the upstream side is detected, the OSC part4d1outputs this detected AIS signal to the monitoring control part4e1. In addition, in a case where optical input interruption due to an internal failure of the OXC device14A is detected, the OSC part4d1outputs optical input interruption information to the monitoring control part4e. The AIS signal notified from outside and the optical input interruption information relating to an internal failure are notified to the transponder devices15A1to15An as they are.

When the optical input interruption information including the information on the wavelengths λ1and λ2of the optical signal is input from the OSC part4d1, the monitoring control part4e1outputs the information on the wavelengths λ1and λ2of the optical signals in which optical input interruption has occurred and the information on the first path of this optical signal in the optical input interruption information to the AIS generation part4j.

Here, the accommodation information management part4istores and manages information on an optical signal input to the OXC device14A and accommodation information on each of the transponder devices15A1to15An in a database (DB)4ia. As illustrated inFIG.2, each piece of information on a channel number, a path number, an accommodation wavelength, a destination device identification (ID), and a transponder ID are stored in the DB4ia.

The channel number is a number that is used for distinguishing between the transponder devices15A1to15An, for example, “1” is a number relating to the transponder device15A1, and “n” (here, n is a natural number other than 1 and 2) is a number relating to the transponder device15An.

The path number is the number of a path according to the optical fiber16on an input side of the OXC device14A, “01” is the number of the first path16a(FIG.1), and “02” is the number of the second path16b(FIG.1).

The accommodation wavelength represents the wavelengths of optical signals accommodated in a path, and “λ1” and “λ2” represent the wavelengths of the optical signals accommodated in the first path16a. “λm” and “λn” represent the wavelengths of the optical signals accommodated in the first path16a.

The destination device ID is the ID of one of the transponder devices15A1to15An that is a destination of the AIS signal, “TP1” is the ID of the transponder device15A1, and “TPn” is the ID of the transponder device15An.

The transponder ID is a transponder-specific ID in each of the transponder devices15A1to15An, “Ta1” is the ID of transponder5a1of the transponder device15A1, and “Ta2” is the ID of the transponder5a2in the transponder device15A1. “Tj1” is the ID of a transponder in a transponder device not illustrated in the drawing. “Tn1” is the ID of the transponder5n1in the transponder device15An, and “Tn2” is the ID of the transponder5n2in the transponder device15An.

When the information of the wavelengths λ1and λ2of optical signals and the information on the first path of these optical signals are input from the monitoring control part4e1, the AIS generation part4jof the OXC device14A illustrated inFIG.1generates an AIS signal31having a format illustrated inFIG.3in accordance with the DB4ia(seeFIG.2) included in the accommodation information management part4i. The format of the AIS signal31is composed of information (format information) of a packet header, a transmitting device ID, a destination device ID, a transponder ID, a wavelength number, an AIS alarm, and the like in order from the top inFIG.3. Note that both the transmitting device ID and the destination device ID constitute a device ID described in the claims. In addition, the AIS signal31constitutes an alarm signal described in the claims.

The packet header is header information used for identifying a start of a packet of the packetized AIS signal31. The transmitting device ID is an ID of the OXC device14A as a device that transmits the AIS signal31. The destination device ID is selected from the destination device IDs (FIG.3) stored in the DB4iaand is inserted into the format information.

The transponder ID is selected from the transponder IDs stored in the DB4iaand is inserted into the format information.

The wavelength number is a number corresponding to a wavelength selected from the wavelength information stored in the DB4ia.

The AIS alarm is alarm information that notifies of a failure that has occurred in the optical fiber16and a failure that has occurred in the OXC device connected to the optical fiber16.

Here, the information on the destination device ID, the transponder ID, and the wavelength number, which are illustrated inFIG.3, stored in the DB4iais selected in accordance with accommodation wavelengths corresponding to the wavelengths λ1and λ2of the optical signals input from the monitoring control part4e1to the AIS generation part4jor the path number corresponding to the first path of the optical signals.

The AIS generation part4jillustrated inFIG.1reads and superimposes each piece of information from the DB4iaof the accommodation information management part4iin accordance with the information on the wavelengths λ1and λ2of the optical signals from the monitoring control part4e1and the information on the first path in which these optical signals are transmitted to generate an AIS signal31. In this generation, two signals are generated; an AIS signal on which a path number “01” of the first path16a, an accommodation wavelength “λ1”, a destination device ID “TP1”, and a transponder ID “Ta1” are superimposed, and an AIS signal on which a path number “01”, an accommodation wavelength “λ2”, a destination device ID “TP1”, and a transponder ID “Ta2” are superimposed.

The two AIS signals are transmitted to a control channel (for example, a first channel) connected to the destination transponder device15A1. At this time, the two AIS signals are converted from electrical signals to optical signals by the E/O conversion part4k1and are input from the optical coupler4l1to the optical coupler5l1of the transponder device15A1through the optical fiber16.

After the optical signals are converted into electrical signals by the O/E converter5k1, the two AIS signals input to the optical coupler5l1are received by the AIS receiving part5h1and are input to the monitoring control part5e1. The monitoring control part5e1notifies a monitoring device such as the EMS device17(seeFIG.9) connected to the transponder devices15A1to15An of the occurrence of a failure of the first path16aaccording to the two AIS signals and the occurrence of a failure of the optical signals of the wavelengths λ1and λ2transmitted to the first path16ato recognize the failures as external failures.

AIS Signal Transmitting and Receiving Operation

Here, operations performed when an AIS signal generated by the OXC device14A is transmitted and is received by the transponder device15A1will be described with reference to a flowchart illustrated inFIG.4.

In step S1illustrated inFIG.4, the monitoring control part4e1of the OXC device14adetermines whether or not the optical input interruption information has been input from the OSC part4d1. As a result, it is assumed that the optical input interruption information has been input, and the optical input interruption includes the wavelength information on the wavelengths λ1and λ2of optical signals in which the optical input interruption has occurred and the path information on the first path16aof these optical signals.

In this case, in step S2, the monitoring control part4e1outputs both pieces of information on the wavelengths λ1and λ2of the optical signals and the first path16aincluded in the optical input interruption information to the AIS generation part4j.

In step S3, the AIS generation part4jreads each piece of information on the DB4iaof the accommodation information management part4iin accordance with both the pieces of information described above and generates the AIS signal31in the predetermined format (FIG.3). In this case, two AIS signals are generated.

For example, a first AIS signal is formed from information on a format of a packet header “H1”, a transmitting device ID “14A”, a destination device ID “TP1”, a transponder ID “Ta1”, a wavelength number “λ1”, and an AIS alarm “failure”.

For example, a second AIS signal is formed from information on a format of a packet header “H2”, a transmitting device ID “14A”, a destination device ID “TP1”, a transponder ID “Ta2”, a wavelength number “λ2”, and an AIS alarm “failure”.

In step S4, the two AIS signals generated in such a format are output from the AIS generator4jand are converted from electrical signals to optical signals by the E/O conversion part4k1and then are transmitted from the optical coupler4l1to the transponder device15A1through the optical fiber16.

In step S5, the two AIS signals that have been transmitted are converted from optical signals to electrical signals by the O/E conversion part5k1through the optical coupler5l1of the transponder device15A1and then are received by the AIS receiving part5h1and are input to the monitoring control part5e1. The monitoring control part5e1notifies a monitoring device such as the EMS device17(seeFIG.9) of an occurrence of an external failure of the transponder device15A1in accordance with the two AIS signals.

Pre-registration Process for OXC Device DB

Next, a pre-registration process of accommodation information for the DB4iaincluded in the accommodation information management part4iof the OXC device14A will be described with reference toFIGS.5and6.FIG.5is a block diagram illustrating a configuration of the OXC device14A and the transponder device15A1for a pre-registration process of accommodation information for the DB4iaof the accommodation information management part4i.FIG.6is a flowchart illustrating a process of pre-registering accommodation information in the DB4ia.

An OXC device14A illustrated inFIG.5includes a MUX4o, an optical SW4p, an optical coupler4q, O/E conversion parts4rand4s, E/O conversion parts4tand4u, an optical coupler4v, and an optical amplifier4xin addition to the components of the OXC device14A (FIG.1) described above. In addition, a transponder device15A1includes an accommodation information management part5i1having a DB5iain addition to the components of the transponder device15A1(FIG.1) described above.

The optical coupler4vis connected between the optical amplifier4aand DMUX14c. The MUX4ohas an input end connected to the transponder15a1through an optical fiber16and an output end connected to the optical SW4p. The optical SW4pis connected to the optical amplifier4xand the O/E conversion part4sthrough the optical coupler4q.

The O/E conversion part4sand the O/E conversion part4rare connected to an input end of the monitoring control part4e1. The E/O conversion parts4tand4uare connected to an output end of the monitoring control part4e1, and the E/O conversion part4tis connected to the optical coupler4v.

The basic operation of these components will be described. The MUX4omultiplexes an optical signal from the transponder15a1with optical signals from other transponders not illustrated in the drawing and outputs a multiplexed optical signal to the optical coupler4qthrough the optical SW4p. The optical coupler4qoutputs the multiplexed optical signal to the first path16athrough the optical amplifier4xand outputs the multiplexed optical signal to the monitoring control part4e1through the O/E conversion part4s. The E/O conversion part4tconverts the electrical signal from the monitoring control part4e1into an optical signal and outputs the converted optical signal to the optical coupler4v, and the optical coupler4voutputs the optical signal to the optical SW4b.

In the transponder device15A1, similar to the DB4iaillustrated inFIG.2, the DB5iaof the accommodation information management part5i1stores each piece of information on a channel number, a path number, an accommodation wavelength, a destination device ID, and a transponder ID.

Next, a pre-registration process of accommodation information for the DB4iaof the OXC device14A will be described with reference to a flowchart ofFIG.6. This pre-registration process starts when the OXC device14A and the transponder device15A1are connected for the first time.

In step S11illustrated inFIG.6, when an input of a main signal, which is an optical signal of the wavelength λ1from the OXC device14A, is detected, the transponder5a1of the transponder device15A1determines that the optical input interruption is recovered, and this recovery information is output to the monitoring control part5e1.

The recovery determination function of the optical input interruption of the transponder15a1described above operates when optical input interruption under monitoring is recovered, and operates also when the OXC device14A and the transponder device15A1are connected for the first time. The OXC device14A and the transponder device15A1are unconnected before this first connection, and thus, the transponder device15A1is in a state in which optical input interruption is detected. For this reason, when the transponder15a1or15a2(the transponder device15A1) is connected to the OXC device14A for the first time, and an optical signal is transmitted, the transponder determines recovery from the optical input interruption.

In step S12, when information on the optical input interruption recovery is input, the monitoring control part5e1detects this recovery and returns this response to the transponder15a1. When returning the response, the monitoring control part5e1notifies the transponder15a1of each piece of information on the channel number, the path number, the accommodation wavelength, the destination device ID (for example, the ID of the OXC device14A), and the transponder ID that have been stored in the DB5iaof the accommodation information management part5i1.

In step S13, the transponder15a1that has received the response of step S12described above changes the wavelength of a laser (laser wavelength), which is not illustrated, mounted in the transponder15a1to a unique specific wavelength (for example, λc). Thereafter, the transponder15a1generates a control signal that is an optical signal of the specific wavelength λc using the laser. At the time of this generation, the transponder15a1superimposes format information on the packet header, the transmitting device ID, the destination device ID (the ID of the OXC device14A), the transponder ID, the wavelength number, and the like illustrated inFIG.7on a control signal used for performing pre-registration in accordance with the information on the DB5ianotified from the monitoring control part5e1.

In step S14, the transponder15a1transmits the control signal on which the format information is superimposed to the OXC device14A of the destination. The OXC device14A receives the control signal and inputs the control signal to the optical coupler4qthrough the MUX4oand the optical SW4p. The optical coupler4qseparates the control signal and an optical signal other than an optical signal of the specific wavelength λc of the control signal from each other and outputs only the control signal to the monitoring control part4e1.

In step S15, the monitoring control part4e1superimposes path information (path information such as the first path16a, the second path16b, and the like) according to the optical fiber16connected to the OXC device14A on the input control signal and inputs a resultant signal to the accommodation information management part4i.

In step S16, as illustrated inFIG.2, the accommodation information management part4iwrites and stores (registers) the format information and the path information superimposed on the control signal into corresponding fields of the DB4iaas accommodation information.

In step S17, the monitoring control part4e1superimposes the ID of the OXC device14A (the OXC device ID) on the control signal of the specific wavelength λc and transmits a resultant signal to the transponder15a1through E/O conversion part4t, the optical coupler4v, the optical SW b, and the DMUX4c.

In step S18, in a case where the received signal is a control signal of the specific wavelength λc, the transponder15a1outputs the OXC device ID superimposed on the control signal to the monitoring control part5e1.

In step S19, the monitoring control part5e1outputs the input OXC device ID to the accommodation information management part5i1. The accommodation information management part5i1links the OXC device ID to each piece of information notified to the transponder15a1at the time of response in Step S12and store the information in DB5ia.

In step S20, when the storage is completed, the monitoring control part5e1sends an ACK signal, which is a response signal, to the OXC device14A. After this transmission, the subsequent steps S21and S22are processed in parallel, and the pre-registration operation ends after these processes.

In other words, in step S21, when an ACK signal is received through the MUX4oand the optical SW4p, the OXC device14A switches the optical SW4pto a selection mode of an optical signal that is a main signal.

In step S22, the transponder15a1switches the laser wavelength (the specific wavelength λc), which has been changed in step S13described above, to a wavelength for the main signal before change.

Effects of Embodiment

Effects of the optical transmission system10A according to this embodiment will be described. This optical transmission system10A connects, using an optical fiber16, and aggregates a plurality of OXC devices14A using an optical fiber16which switches wavelength paths of optical signals between transponder devices (for example, the transponder device15A1) that relays optical signals transmitted to and from the terminals19aand19bas communication devices.

Next, features of the configuration of this embodiment will be described.

(1) The OXC device14A is provided with a first control part including both an OSC part4d1and a monitoring control unit4e1. The OSC part4d1, when the optical input interruption in which an optical signal input from the optical fiber16is interrupted is detected, outputs wavelength information indicating a wavelength of an optical signal in which optical input interruption has occurred and path information on a path of the optical fiber16in which the optical input interruption has occurred. In addition, the OXC device14A includes an AIS generation part4j. The AIS generation part4jgenerates an AIS signal (alarm signal) including both pieces of information on the wavelength and the path of the optical signal relating to the optical input interruption and alarm information relating to both the pieces of information, in accordance with the wavelength information and the path information that have been output from the first control part.

The transponder device15A1is provided with a second control part including an AIS receiving part5h1and a monitoring control part5e1. The AIS receiving part5h1notifies an external failure on an upstream side of the transponder device15A1based on both information and alarm information included in the above-described generated AIS signal.

According to this configuration, in the OXC device14A, an AIS signal is generated, and this AIS signal is notified to the transponder device15A1from the OXC device14A. The AIS signal includes information on the wavelength of the optical signal according to the optical input interruption from the optical fiber16and information on the path of the optical fiber16through which the optical signal is transmitted and alarm information relating to the both pieces of information. The transponder device15A1can detect an external failure on an upstream side of the transponder device15A1based on the both pieces of information and the alarm information included in the notified AIS signal. For this reason, it is possible to appropriately determine in the transponder device15A1connected to the OXC device14A using the optical fiber16whether the optical input interruption detected by the OXC device14A is due to an external failure from the upstream side or an internal failure.

(2) The optical couplers4I1and5I1are inserted into the optical fiber16connecting the OXC device14A and the transponder device15A1, and the AIS signal generated by the AIS generation part4jis transmitted from the OXC device14A1to the transponder device15A1through the optical couplers4I1and5I1.

According to this configuration, an AIS signal can be transmitted to the transponder device15A1through the optical couplers4I1and5I1using an existing optical fiber16connecting the OXC device14A and the transponder device15A1. For this reason, a high-cost configuration is not necessary, in which an AIS signal is transmitted by cable-connecting the OXC device14A and the transponder device15A1using a LAN cable or the like other than the optical fiber16. In other words, a configuration in which the transponder device15A1can appropriately determine whether optical input interruption of the OXC device14A is due to an external failure or an internal failure can be realized at low cost.

(3) The transponder device15A1includes a DB5iastoring each piece of information on a path number that is a number of a path of the optical fiber16, an accommodation wavelength that is a wavelength of an optical signal accommodated in the path, device IDs that are a transmitting device ID and a destination device ID of the signal, and a transponder ID. The OXC device14A includes a DB4iain which each piece of information stored in the DB5iais registered and stored. The transponder device15A1determines recovery from the optical input interruption at the time of transition from a state of being unconnected from the OXC device14A to a connected state through the optical fiber16and, after this determination, superimposes each piece of information read from the DB5iaon a control signal that has been changed to a unique specific wavelength, and transmits a resultant control signal to the OXC device14A. The OXC device14A receives the control signal that has been transmitted and registers and stores each piece of information superimposed on the received control signal in the DB4iain accordance with control of the second control part.

According to this configuration, when the OXC device14A is connected to the transponder device15A1for the first time, each piece of information on the accommodation wavelength, the device ID, and the transponder ID stored in the DB5iaof the transponder device15A1can be registered and stored in the DB4iaof the OXC device14A. After the storage, the occurrence of an external failure relating to optical input interruption of the OXC device14A can be notified to the transponder device15A1using each piece of information stored in the DB4ia.

In addition, a specific configuration can be appropriately changed without departing from the gist of the present invention.

REFERENCE SIGNS LIST