Abstract: One aspect of the present invention is a communication system for a passive optical network that includes: an OLT system including a first OLT (Optical Line Terminal), a second OLT, and an OLT control apparatus that controls the first OLT and the second OLT; a plurality of splitters that are connected between the first OLT and the second OLT using optical communication channels; and ONU systems that are connected to the respective splitters using optical communication channels, and each include a first session establishing unit that establishes a session with the first OLT, a second session establishing unit that establishes a session with the second OLT, and a signal processing unit that executes signal processing of an ONU (Optical Network Unit) based on an optical signal output from the first session establishing unit or the second session establishing unit.

Abstract: Provided is a radio over fiber (RoF)-based distributed antenna system (DAS) structure that cost-effectively provides a fifth generation (5G) mobile communication service guaranteeing a quality of service (QoS) with high bandwidth and low latency characteristics without radio shadowing in an indoor environment.

Abstract: Coherent optical multiplexing 1+1 protection disclosed herein uses multiplexers, each having multiplexing and demultiplexing sub-units. Relay ports of a node are connected with the multiplexers, and each relay port is configured to input and output optical signals with the corresponding multiplexer. Two transmission ports of the node are connected with disjoint paths and are configured to input and output optical signals therewith. The node includes: a first optical splitter having input ports connected with the relay ports and two output ports connected with the two transmission ports; an optical switch connected with the transmission ports respectively via two input interfaces; a second optical splitter, which is a 1×N optical splitter, having one input port connected with an output interface of the optical switch and having output ports connected with the relay ports. The solution is reliable in implementation, has low insertion loss, and has good transmission performance.

Abstract: Device cost and electric power consumption are reduced. Nodes 11a to 11d as optical add/drop multiplexers each include AWGs 24a and 24b connected between light transmission paths as optical fibers 12 and 13 and transponders 25a to 25n and configured to output optical signals from the light transmission paths to the transponders 25a to 25n through ports and transmit optical signals from the transponders 25a to 25n to the light transmission paths through ports, and an optical coupler 24c configured to connect ports of the AWGs 24a and 24b to the transponders 25a to 25n through coupling or bifurcation. The channel interval of ports of the AWGs 24a and 24b is multiple times larger than the channel interval of ports of the transponders 25a to 25n, and transponder signals of a plurality of different wavelengths to and from one or a plurality of the transponders 25a to 25n can pass through ports of the AWGs 24a and 24b.

Abstract: A memory device includes a first memory die of a plurality of memory dies, the first memory die comprising a first memory array and a first power management component, wherein the first power management component is configured to send a first test value to one or more other power management components on one or more other memory dies of the plurality of memory dies during a first power management cycle of a first power management token loop.

Abstract: Coherent optical multiplexing 1+1 protection disclosed herein uses multiplexers, each having multiplexing and demultiplexing sub-units. Relay ports of a node are connected with the multiplexers, and each relay port is configured to input and output optical signals with the corresponding multiplexer. Two transmission ports of the node are connected with disjoint paths and are configured to input and output optical signals therewith. The node includes: a first optical splitter having input ports connected with the relay ports and two output ports connected with the two transmission ports; an optical switch connected with the transmission ports respectively via two input interfaces; a second optical splitter, which is a 1×N optical splitter, having one input port connected with an output interface of the optical switch and having output ports connected with the relay ports. The solution is reliable in implementation, has low insertion loss, and has good transmission performance.

Abstract: Coherent optical multiplexing 1+1 protection disclosed herein uses multiplexers, each having multiplexing and demultiplexing sub-units. Relay ports of a node are connected with the multiplexers, and each relay port is configured to input and output optical signals with the corresponding multiplexer. Two transmission ports of the node are connected with disjoint paths and are configured to input and output optical signals therewith. The node includes: a first optical splitter having input ports connected with the relay ports and two output ports connected with the two transmission ports; an optical switch connected with the transmission ports respectively via two input interfaces; a second optical splitter, which is a 1×N optical splitter, having one input port connected with an output interface of the optical switch and having output ports connected with the relay ports. The solution is reliable in implementation, has low insertion loss, and has good transmission performance.

Abstract: An object is to provide a dispersion compensating system with a large amount of dispersion compensation and reduced operation costs. Disclosed is a dispersion compensating system in which a core node and an access node are connected through a ring network, the access node includes a delay measurement unit configured to receive delay measurement signals from the core node to measure a delay between the core node and the access node, an average dispersion amount calculation unit configured to calculate an amount of dispersion compensation to be applied to an optical burst signal prior to transmission to the ring network, based on the delay thus measured, and a real-part inverse dispersion application unit configured to perform pre-equalization on a waveform of the optical burst signal prior to the transmission, based on the calculated amount of dispersion compensation.

Abstract: Techniques for identifying service paths for satisfying a service demand in a data communication network are disclosed. Aspects include identifying a plurality of vertices in a communications route cycle, the communications route cycle alternating through the plurality of vertices and a plurality of edges in a sequence; identifying a plurality of internal paths in the communications route cycle, each of the plurality of internal paths is disjoint to the plurality of edges; identifying a first internal path and a second internal path among the plurality of internal paths as a crossing pair of internal paths; detecting a failure of at least two edges among the plurality of edges; and identifying, based on the communications route cycle and the identified crossing pair of internal paths, a service path that satisfies the service demand in response to detecting the failure of the at least two edges.

Abstract: A system and method for of pre-provisioning recovery paths in a mesh network including creating i) a working path between a head end NE and a tail end NE of the mesh network and ii) a recovery path between the head end NE and the tail end NE, wherein the working path and the recovery path include one or more intermediate NEs; provisioning the working path in an activated state, including establishing cross connects of each of the NEs of the working path; provisioning the recovery path in a pending state, including establishing cross connects of each of the NEs of the recovery path; after provisioning the recovery path, detecting a failure along the working path, and in response, allocating and reserving link resources along the recovery path; and activating, by the NEs along the recovery path, cross connects of the recovery path into respective hardware associated with the NEs.

Abstract: A satellite payload system is presented. The system includes plurality of optical processing modules, including a plurality of ring-connected optical processing modules and at least one inter-satellite optical processing module, and at least one optical fiber ring communicatively coupled to each of the ring-connected optical processing modules. At least one of the ring-connected optical processing modules is configured to provide on-board signal processing of signals conveyed on the at least one optical fiber ring. At least one of the ring-connected optical processing modules is communicatively coupled to a respective inter-satellite optical processing module. Each inter-satellite optical processing module is configured to optically communicatively couple to a respective remote satellite.

Abstract: According to the present invention, there is provided apparatus for providing protection of an optical link. The apparatus comprises a first port for coupling to the optical link and a second port for coupling to a further optical link. The apparatus further comprises a third port configured to receive an upstream optical signal to be transmitted over the optical link, and to output a downstream optical signal received over the optical link. The apparatus further comprises protection switching apparatus operable to selectively couple the third port to the first port or to the second port. The apparatus further comprises modifying apparatus configured to modify the upstream optical signal, received at the third port, before it is output from the first port, such that the switching upstream optical signal has a distinctive physical characteristic.

Abstract: An Ethernet-based optical transmission system, and particularly, an apparatus and method for controlling a remote optical Ethernet device. An optical Ethernet apparatus includes a system recovery processor configured to output a system reset signal or a system power ON/OFF control signal and a system recovery controller configured to detect a system recovery command that occurs when a predetermined signal pattern is repeated the designated number of times for a designated period of time, and to control the system recovery processor using the detected system recovery command.

Abstract: An optical network is configured to optimize network resources. The optical network includes multiple optical nodes, light paths between the multiple optical nodes, and a network monitoring device. The network monitoring device monitors the optical network to identify a failure in the optical network. When the failure is a fiber failure, light paths are re-routed around the fiber failure while maintaining the required bandwidth for the optical network. When the failure is a transponder card failure within one of the multiple nodes, a floating spare card may be provisioned to service a particular light path associated with the transponder card failure. When the failure is a node failure, transponder cards in some of the multiple optical nodes are provisioned to reconfigure some of the plurality of light paths to route traffic around the failed node.

Abstract: A network management device monitors an optical network that is configured for a required bandwidth. The optical network includes multiple optical nodes and a plurality of light paths between the multiple optical nodes. The multiple optical nodes include transport cards with a majority of the transport cards provisioned as active cards to receive a traffic load of up to full capacity of the transport cards, and with a minority of the transport cards provisioned as floating spare cards for the active cards. The network management device identifies an unused first floating spare card and an unused second floating spare card in a pair of the multiple optical nodes and automatically provisions, by the network management device, the first floating spare card and the second floating spare card to service a light path for best-effort traffic between the pair of the multiple optical nodes.

Abstract: Example embodiments of the present invention relate to an optical node comprising of at least two degrees, a plurality of directionless add/drop ports, a plurality of primary WDM transmitters and receivers, and at least one protection WDM transmitter and receiver, wherein the at least one protection WDM transmitter and receiver can transmit and receive in place of any of the plurality of primary WDM transmitters and receivers.

Abstract: Disclosed herein are optical distribution networks and corresponding methods for providing physical-layer redundancy. Example embodiments include a head-end passive optical splitter-combiner (OSC) to split optical signals from an Optical Line Terminal (OLT) onto primary and secondary optical paths for redundant distribution to optical network terminal(s) (ONTs), a passive access OSC for tapping the redundant signals, and an optical switch for selecting between the redundant signals and providing an ONT access to the selected signal. Example optical distribution networks and corresponding methods provide multiple drop points, a fully cyclical path, and autonomous protection switching, all at low cost. A further advantage of these networks and methods is that where faults may occur, maintenance may not be required for a certain time.

Abstract: A device may include a component, a first switch, a repeater, and a second switch. The component may configure optical paths between ports. The component may comprise a first pair of optical ports connected to a first pair of optical fibers, and a second pair of optical ports connected to a second pair of optical fibers. The first switch may be configured to output one of two optical signals received by the first pair of optical ports from the first pair of optical fibers. The repeater may reshape or amplify the outputted optical signal. The second switch may be configured to direct the reshaped or amplified signal to one of the second pair of optical ports.

Abstract: A node of an optical transport network system transmits optical wavelengths to an adjacent node through an operational line. An apparatus for protection switching of the optical transport network system transmits only an optical channel with a fault among a plurality of optical channels composed of flexible optical channel data units in an optical wavelength of the operational line, via a reserve line.

Abstract: A method for shared mesh restoration includes configuring a switch to allow sharing of a plurality of backup line cards across a plurality of node degrees associated with a reconfigurable optical add/drop multiplexer (ROADM). The switch is communicatively coupled to the ROADM. The method further includes configuring a number of backup line cards coupled to the switch. The number of backup line cards is based on determining a number of active backup lightpaths for each of a plurality of network failures associated with each of the plurality of node degrees of the ROADM, identifying which node degree and failure has the largest number of active backup lightpaths for all of the plurality of node degrees of the ROADM and for each of the plurality of network failures, and determining the number of backup line cards to configure based on the identified largest number of active backup lightpaths.

Abstract: A node device in an optical transport ring network including plural node devices connected in a ring form using plural optical transmission paths so that optical transport frames of a working line and a protection line are transmitted using the plural optical transmission paths, includes a control information transmitter, when a failure occurs in the optical transmission paths, transmitting the optical transport frame to an opposing node device as a transmission destination node in the optical transmission paths, the optical transport frame including switching control information; and a switcher receiving the optical transport frame including switching control information, the optical transport frame being transmitted to the node device as the transmission destination node, forming a loop back to fold a transmission path between the plural optical transmission paths, and switching the optical transmission path from the work line to the protection line.

Abstract: A method, a network, and a node each implement the transmission of Automatic Protection Switching (APS) switching coordination bytes across an OTN network. A working signal and a protection signal are received, one of which is designated as an active signal. The active signal is encapsulated in an Optical channel Data Unit (ODU) signal. APS switching coordination bytes from the working and protection signals are placed in an overhead segment of the ODU signal. The ODU signal is transmitted into and received from an Optical Transport Network (OTN) network. The working and protection signals are recreated based on the active signal encapsulated in the ODU signal and the APS switching coordination bytes in the overhead segment. The recreated working and protection signals are transmitted. In this manner, a single ODU signal may be used to transmit both the working and protection signals.

Abstract: An approach is provided for performing fault recovery using composite transport groups (CTGs). A first logical channel is established within a composite transport group, wherein the first logical channel is established over a first link associated with a first service provider to a customer premise equipment (CPE) node configured to transport packets. A second logical channel is established within the composite transport group, wherein the second logical channel is established over a second link associated with a second service provider to an optical node. Packets are received over the first logical channel. Packets are received over the second logical channel if the first logical channel experiences a fault condition, wherein switching to the second logical channel is transparent to the CPE node.

Abstract: A method for realizing an automatic protection switching of a transmission device is provided, and the method includes that: according to a received automatic protection switching trigger condition and information of each line sub-card, which are transmitted by a cross sub-card via a Time Division Multiplexing Fabric to Framer Interface (TFI5) frame, a control sub-card determines to execute protection switching, and sends a protection switching command to the cross sub-card; and the cross sub-card completes the protection switching action. A system for realizing an automatic protection switching of a transmission device is also provided. According to the technical solution of the present invention, the automatic protection switching of the transmission device in an Optical Transport Network (OTN) is achieved conveniently.

Abstract: Switching architectures for WDM mesh and ring network nodes are presented. In mesh networks, the switching architectures have multiple levels—a network level having wavelength routers for add, drop and pass-through functions, an intermediate level having device units which handle add and drop signals, and a local level having port units for receiving signals dropped from the network and transmitting signals to be added to the network. The intermediate level device units are selected and arranged for performance and cost considerations. The multilevel architecture also permits the design of reconfigurable optical add/drop multiplexers for ring network nodes, the easy expansion of ring networks into mesh networks, and the accommodation of protection mechanisms in ring networks.

Abstract: An optical network and method of protection switching between first and second transceivers where dispersion compensation is effected electrically in the transmitters. The method includes detecting, at the second transceiver, a signal failure of a signal transmitted from the first transceiver and, upon detecting the signal failure, signaling the first transceiver to change its compensation function. The signaling can be done by encoding overhead bits in a signal transmitted from the second to the first transceiver. Another method of protection switching includes both transceivers toggling alternate reception paths upon detecting a signal failure and changing their dispersion compensation function to that of their respective alternate path.

Abstract: Optical safety functions are incorporated into protection switching modules which maintain redundant pathways to avoid interruptions in optical network connections. The optical safety functions which lower optical power levels upon interruptions of optical connections are effectively combined with protection switching procedures which are also triggered by interruptions in optical network connections. The interoperation of protection and safety processes keep optical power levels below hazardous levels at system points which might be accessible to human operators.

Abstract: Methods and systems for automatically recovering from a failure event in one or more nodes of a redundant ring network are provided. An indication is received at a first ring of nodes that an associated second ring of nodes has failed. A probing token is circulated around the second ring of nodes while a probing timer is started. The injecting a probing token and starting a probing timer are repeated if the probing timer expires before the probing token circulates completely around the second ring of nodes. A recovery token is circulated around the second ring of nodes to enable each node of the second ring of nodes and to disable the probing timer if the probing token circulates completely around the second ring of nodes.

Abstract: Optical network protection devices and protection methods including: a working line; a protection line; a determination module configured to determine the protection type of optical network; a first judgment module configured to judge whether the working line is normal according to performance parameter values of service signal in the working line and switching conditions configured for multiplexing section protection when the protection type of optical network is the multiplexing section protection; a second judgment module, configured to judge whether the working line is normal according to performance parameter values of service signal in the working line and switching conditions configured for channel section protection when the protection type of optical network is the channel section protection; a switching module, configured to take the service signal in the protection line as an output signal when working line is abnormal.

Abstract: This concerns a protected long-reach PON having a plurality of terminals connected to a distribution network that is fed by both a main and back up feed, each feed including a head end and a repeater. The back up head end had access to a ranging table with data previously obtained by the main head end, thereby speeding up the switch over in the event of a fault with the main feed. In one embodiment, the repeater has a virtual ONU therein, allowing the back up repeater to be ranged by the back up head end, thereby yet further speeding up the ranging procedure. The main and back up repeaters are sufficiently equidistant from the distribution network to allow the back up head to perform normal scheduling without performing a ranging operation on each of the terminals, even if the different terminals transmit at slightly different wavelengths. This is achieved using the ranging information obtained with regard to the back up repeater.

Abstract: A method for realizing interaction of optical channel data unit (ODUk) protection tangent rings are provided. A node used for protection of the ODUk and a receiving unit, a sending unit, a protected receiving unit and a protected sending unit on the node are selected. A connection between a receiving service unit and the protected sending unit with the same transmission direction on the node is established, or a connection between a sending service unit and the protected receiving unit with the same transmission direction on the node is established. Two virtual nodes are established on the node if the node is an intersection node, and connections between the receiving service unit and the protected sending unit, and between the sending service unit and the protected receiving unit are established respectively in each direction of both directions through one of the virtual nodes.

Abstract: Systems and methods for distributing signals in an optical network are disclosed. In accordance with one embodiment of the present disclosure a method for distributing signals in an optical network comprises combining input signals into one or more output signals, determining, an availability status of optical lanes for carrying the output signals and distributing the output signals to optical transmitters associated with the optical lanes if the availability status indicates that the optical lanes are available.

Abstract: A PON ring system and a method for realizing primary and backup link protection in a passive optical network (PON) are provided. A PON ring is established between at least two optical line terminations (OLTs) through at least two user side edge nodes or network side edge nodes. Each of the OLTs is coupled to any other OLT through the at least two edge nodes. Two links respectively in a clockwise direction and a counterclockwise direction exist in the PON ring, in which one link is a primary link and the other is a backup link. Node of the links adopt the transmission mode of “multiple sending and selective receiving”. Therefore, the present invention reduces the impact on the PON caused by single link failure in the network.

Abstract: The present invention provides for a method for reserving spare bandwidth for a link in a communication network including a plurality of links. The method provides for monitoring the volume of traffic routed through each link of the communication network. A single link failure for each link is then simulated and the volume of traffic which would be rerouted through each link for maintaining communication and the volume of traffic removed from each link are determined for each simulated single link failure. The difference between the volume of traffic which would need to be rerouted through each link and the corresponding volume of traffic removed from each link is then computed, and a maximum difference value is determined for each link for all simulated single link failures. An amount of spare bandwidth equivalent to the determined maximum difference is then reserved for each link.

Abstract: N optical transceivers are each connected to a respective electronic module in one-to-one relation such that a respective one electronic module controls a respective one optical transceiver. An electronic switch matrix provides cross-connect capability between the P redundant electronic modules and N electronic modules to the N optical transceivers. A system controller determines when an active N electronic module has failed, and configures the electronic switch matrix to switch a P redundant electronic module into the optical transceiver to which the failed electronic module was connected. A system switch module redirects traffic and routing information, under the direction of the system controller, from the failed module to the newly activated redundant module so that the redundant module assumes the functionality of the failed module.

Abstract: An optical communications system includes a MSAP and an optical transceiver mounted at the MSAP that communicates over an optical network to at least one optical network terminal (ONT). A first electronic module is operatively connected to the optical transceiver and configured to control the optical transceiver and mounted at the MSAP separate from the optical transceiver. A redundant second electronic module is supported within the MSAP and mounted separate from the optical transceiver. A Mux/Demux module interconnects and supports the first and second electronic modules to form an integral unit and mounted at the MSAP separate from the optical transceiver. The Mux/Demux module is configured to switch the second electronic module into communication with the optical transceiver upon failure of the first electronic module.

Abstract: In accordance with embodiments of the present disclosure, a method for demand aggregation is provided. The method may include routing demands in a ring network such that a length for each routed demand does not exceed a route length maximum, and a load imbalance at each node in the ring network is minimized. The method may also include maximizing optical line card sharing by assigning routed demands sharing common ends to the same wavelength.

Abstract: An optical ring network has one or more working wavelengths and multiple protection wavelengths adapted to support the working wavelength(s). Routing tables may be used in network nodes to assign traffic of a failed working wavelength to a protection wavelength. The protection technique may be applied to networks employing, for example, Dense Wave Division Multiplexing (DWDM).

Abstract: Delivering multicast data traffic over a communication network includes a first network node delivering multicast data traffic to second network nodes. The first and second network nodes are connected by a transmission network in a ring architecture and implement a point-to-multipoint layer 2 protocol. A method includes at the first network node: collecting alarms signals indicative of a failure along the whole ring and of the second network nodes. Based on a current state of the alarm signals, delivering the multicast data traffic either in a first delivery direction along the ring, or in a second delivery direction along the ring opposite to the first delivery direction, or in both the first and second delivery directions. At each of the second network nodes: collecting alarm signals indicative of a failure of the transmission network locally to the second network node and of the second network node.

Abstract: Optical networks occasionally experience a fault along a communications path. Service providers prefer to have an alternative communications path available to enable users to still communicate in a seamless manner. Accordingly, a method and corresponding apparatus for providing path protection for dedicated paths in an optical network is provided.

Abstract: An optical ring network has one or more working wavelengths and multiple protection wavelengths adapted to support the working wavelength(s). Routing tables may be used in network nodes to assign traffic of a failed working wavelength to a protection wavelength. The protection technique may be applied to networks employing, for example, Dense Wave Division Multiplexing (DWDM).

Abstract: A system for serving N optical communication lines by a redundant set of modules in an optical network; where the set of modules comprises N>1 main modules and one backup module, N optical splitters, 2N fiber connections and a control means. In the system, each of the N optical splitters is connected to two different modules of the set by two respective fiber connections out of the 2N connections, while each of the N optical splitters is also coupled to one of the N optical communication lines. The arrangement is such that the control means selectively activates/inactivates any of the fiber connections for respectively enabling/blocking transfer of data there-along; the control means thus ensures that each specific line of the N optical communication lines is always served by either one or another of two different modules.

Abstract: The present invention relates to the field of optical communication and provides a method and system for arranging link resource fragments. The method comprises: configuring cascade services in a link in advance; generating a preset arrangement method according to an initial channel number of occupied channel(s) in the link and a cascade number of service born in the channel(s) (S210); a local end node that initiates a link resource arrangement notifying an opposite end node to arrange link resource fragments (S220); the local end node and the opposite end node reconfiguring a cross connection according to the preset arrangement method (S230). The method and system of the present invention can re-arrange the channel resources within one link, and integrate the scattered channel resource fragments into complete and available resources with a broader bandwidth, thus achieving the maximum utilization of the link bandwidth resources.

Abstract: An optical ring network has one or more working wavelengths and multiple protection wavelengths adapted to support the working wavelength(s). Routing tables may be used in network nodes to assign traffic of a failed working wavelength to a protection wavelength. The protection technique may be applied to networks employing, for example, Dense Wave Division Multiplexing (DWDM).

Abstract: An amplifier node, in an optical network, includes a first switch connected to a working path from which network traffic is received; a second switch connected to the working path to which the network traffic is transmitted; and two amplifiers that interconnect the first switch and the second switch, where the network traffic travels from the first switch to the second switch via a first amplifier. The amplifier node also includes a controller to receive an instruction to switch the network traffic from the first amplifier to a second amplifier that enables the first amplifier to be repaired; send, to the first switch and the second switch, another instruction to switch the network traffic from the first amplifier to the second amplifier; receive an indication that the network traffic is traveling via the second amplifier; and send a notification that the first amplifier can be repaired based on the indication.

Abstract: Systems, methods, and devices are disclosed for monitoring optical communications between a managed location and a remote location. In particular, an optical signal is transmitted over an optical fiber and passed-through a test device. A portion of the optical signal is filtered from the original optical signal and passed to a monitoring unit. The monitoring unit may instruct one or more switches in the test device to loop the optical signal back toward the managed location. Subsequently, testing and monitoring may be performed at the managed location. The device may provide a test output or may transmit the information to the managed location.

Abstract: First and second switching device are connected by a number of signal paths. The first switching device receives an instruction to switch from a first one of the signal paths to a second one of the signal paths. The first switching device performs, in response to the received instruction, a first switching operation to connect the first path, at an input of the first switching device, to the second path, at an output of the first switching device. The second switching device receives the instruction to switch from the first path to the second path and detects a loss of signal on the first path as a result of the first switching operation performed by the first switching device. The second device performs, in response to detecting the loss of signal on the first path, a second switching operation to connect the first path, at an output of the second switching device, to the second path, at an input of the second switching device.

Abstract: An optical communication network node apparatus is provided that considerably reduces the node apparatus in scale, especially, a switch device in scale relative to increase in the number of wavelength multiplexes.

Abstract: Schemes are provided for starting up optical transmission links where, after a link interruption, endpoints switch into a startup mode original detection state, and a query-transmit pulse goes out at both end points at given time intervals. In a “TRANSMITTED” handshake mode, in a loop to be passed through n times, and at least once, after the transmission of a transmit pulse, it is detected whether a received pulse is received within a given time span. If no received pulse is received, then the mode is ended and the system is returned to the original detection state. If a received pulse is received, it is answered with another transmit pulse. After the last transmit pulse, if another received pulse occurs within a given time span, the link is activated. If not, the “TRANSMITTED” handshake mode ends and the system enters the original detection state.

Abstract: An optical transmission apparatus connected to an optical ring network stores identification information of an optical transmission apparatus as a communication partner predetermined on a communication path. Each optical transmission apparatus includes self identification information in header information of an optical signal having a working wavelength used in normal operation, and transmits the optical signal to one of the two optical ring networks transferring optical signals in mutually opposite directions. The optical transmission apparatus determines whether the identification information included in the header information of the received optical signal having the working wavelength matches pre-stored identification information. The optical transmission apparatus thus detects a fault that occurs by the communication path.