Abstract: A system and method for multiple-channel line card. The system includes a first photonic integrated device configured to receive a first optical signal and output a first plurality of electrical signals for a first plurality of channels respectively. The first plurality of channels corresponds to a first plurality of wavelength ranges associated with the first optical signal. Additionally, the system includes a first clock and recovery device configured to receive the first plurality of electric signals and retime the first plurality of electric signals, and a first switch coupled to the first clock and recovery device, a first interface, and a second interface. Moreover, the system includes the first interface configured to output a second plurality of electrical signals to another system for multiple-channel line card, and the second interface configured to couple with one or more plugged first channel devices.

Abstract: The present invention provides a WDM optical system that includes a tunable filter for selecting one or more optical channels from a WDM optical signal. A portion of a WDM signal enters a first optical filter stage that exhibits a periodic transmission spectrum and possesses individually tunable filter elements. A second optical filter stage receives throughput from the first filter stage and has a periodic transmission spectrum and individually tunable filter elements. A controller electrically communicates with the optical filter to select individual optical channels from the portion of the wavelength division multiplexed optical signal received through the filter input port; each selected optical channel is output via a filter throughput port. In an exemplary embodiment, each tunable filter element is a micro-ring resonator and the micro-ring resonators in the first filter stage have a different free spectral range (FSR) than the micro-ring resonators of the second filter stage.

Abstract: A core unit arranged in a transmission path includes a through path for causing an input signal to an input port to pass through to an output port, a drop-side port 25a that drops the input signal having a predetermined wavelength, and an add-side port 25b that adds channel having a predetermined wavelength to the input light.

Abstract: A WDM optical cross-connect has input and output channels for through traffic. A first group of matrices connects the input channels to the output channels. Each input channel is connected to an input of a matrix of the first group and each output channel is connected to an output of the matrix. Input/output channels are provided for adding/dropping traffic. Each add/drop channel is connected to an input/output of a second group of matrices. The outputs/inputs of the second group of matrices are connected to inputs of a third group of matrices or outputs of a fourth group of matrices and the outputs/inputs of the third/fourth group of matrices are connected to inputs/outputs of the first group of matrices such that the matrices of the second, third and first groups of the first, fourth and second groups each form a Clos network.

Abstract: By using wavelength division multiplexing technologies, redundant star topology network is constructed on a ring-shaped optical fiber network. Edge-switches 5a, 5b, 5c, and 5d are connected to client station groups 6a, 6b, 6c, and 6d are connected, respectively. The edge-switches 5a, 5b, 5c, and 5d are connected to edge optical transport device 2a, 2b, 2c, and 2d. Core-switches 4a and 4b are connected to a core optical transport device 1. The edge optical transport device 2a, 2b, 2c, 2d, and the core optical transport device 1 are connected to a ring-shaped single optical fiber 3. A communication circuit 7 is formed among core optical transport device 1, edge optical transport devices 2a, 2b, 2c, and 2d, by using wavelength division multiplexing technologies.

Abstract: Systems and methods for unidirectional communication in an optical network employing bidirectional transponders are provided. The modulation and amplification capabilities of the bidirectional transponder are used to forward information to the next node. In this way a highly cost-effective “drop and continue” architecture is provided. In one implementation, the client-side output of the bidirectional transponder is looped back to the client-side input using, e.g., a Y-cable fiber. In this way, a unidirectional signal present on a network-side input wavelength to the transponder is presented both on a network-side output wavelength of the transponder and at the same time to a client. The modulation and amplification capabilities of the bidirectional transponder are thus exploited in forwarding the unidirectional signal to the next node.

Abstract: A system and method for limiting the impact of an unstable wavelength on other wavelengths in a reconfigurable optical add/drop multiplexer (ROADM) network are disclosed. The method generally comprises measuring optical channel power at prescribed time intervals; for each measurement of channel power falling outside a predefined threshold, recording a threshold crossing event; comparing the recorded threshold crossing events to stored criteria indicative of an unstable wavelength channel; and removing an unstable wavelength from the ROADM network if the threshold crossing events exceed the stored criteria.

Abstract: A system and method for dynamically adding/dropping wavelengths in a reconfigurable optical add-drop multiplexer (ROADM) transport network is disclosed. The system includes a plurality of M×N wavelength selective switches (WSS) for locally dropping selected wavelengths at a node, where each M×N WSS has M inputs connected to optical fan-out devices in each of M network degrees, and a plurality of M×N wavelength selective switches for locally adding selected wavelengths to a node, where each M×N WSS has M outputs connected to optical fan-in devices in each of M network degrees. Several expedients of M×N wavelength selective switches comprising M switching elements for use in the system are also disclosed.

Abstract: Systems, apparatus and methods for implementing single-fiber optical ring networks based on double side band modulation.

Abstract: In an optical transmission network of the present invention, an optical signal output from a CWDM unit is combined on an optical transmission path of a DWDM network via a multiplexing filter arranged on a light output terminal of a DWDM unit adjacent to the CWDM unit. Furthermore, an optical signal propagated on an optical transmission path is branched from the DWDM light by a de-multiplexing filter provided on a light input terminal of an adjacent DWDM unit, and applied to a CWDM unit adjacent to the DWDM unit. As a result, it is possible to mutually connect a plurality of CWDM networks, using an optical transmission path of a DWDM network, and it is possible to realize a longer distance for CWDM networks.

Abstract: Multiplex-demultiplex (mux/demux) “groups” multiplex and demultiplex a predetermined maximum number of optical wavelengths. A method for assigning wavelengths of fiber links and mux/demux groups to given traffic (or traffic segments) in an optical communications network, minimizes over all terminals a total number of mux/demux groups required. The method (FIG. 5) involves (510) sorting the terminals in order of size of load. Further, for each traffic segment between pairs of first and second terminals, the method involves (516) assigning a smallest wavelength that is available between the first and second terminals and that is available on the segment path between the terminals; and in the terminals, (518) deploying mux/demux groups supporting the assigned wavelengths. A modified method (FIGS. 6A, 6B), as well as a method for dynamically assigning and deploying newly arriving traffic segments (FIG. 7), are also provided.

Abstract: An optical system with a first and second network tiers. The first network tier includes a plurality of major nodes optically interconnected by at least one transmission path. The second network tier includes a plurality of minor nodes disposed along the transmission path and the minor nodes are connected to at least one of the major nodes. The minor node is configured to transmit all traffic to an adjacent major node, and the major nodes are configured to transmit to and receive information from other major nodes and minor nodes on transmission paths connected to the major node.

Abstract: An optical ring network architecture including a number (N) of multi-add/drop filters, such as filters formed using symmetrical pairs of frequency routers. Each multi-add/drop filter is coupled to two other multi-add/drop filters using N?2 transmission media, such as optical fibers, to form a ring. The network also includes a number (N) of terminal stations associated with the multi-add/drop filters. A terminal station (p) is coupled with, and receives information from, its associated multi-add/drop filter (p) through a single optical fiber. In addition, the terminal station p is coupled with, and transmits information in a first direction around the ring to, a multi-add/drop filter p+1 through a single optical fiber. Communications from terminal station p to each other terminal station in the first direction are assigned one of N?1 wavelengths such that no two wavelengths on a given optical fiber are associated with communications between terminal stations in the same direction.

Abstract: The present disclosure provides high-degree reconfigurable optical add-drop multiplexing (ROADM) systems using bi-directional wavelength selective switches (WSSs) and optical circulators. A single WSS is utilized on each degree of a node in a bi-directional manner, i.e. both ingress and egress share the same WSS. Advantageously, the present invention eliminates conventional splitters/combiners thereby capping intra-node insertion loss to a certain value regardless of the number of degrees. More importantly, the present invention reduces noise penalty associated with high-degree nodes while minimizing cost.

Abstract: A traffic signal node cross scheduling method includes: decomposing a multi-wavelength signal into multiple first single-wavelength signals; decomposing a first single-wavelength signal into multiple small-granularity wavelength signals; scheduling the multiple small-granularity wavelength signals; and converging the multiple small-granularity wavelength signals after scheduled into a second single-wavelength signal. A traffic signal node cross scheduling system is also provided by the embodiments of the present invention. According to the traffic signal node cross scheduling method and system provided by the embodiments of the present invention, one scheduling matrix may be used to implement the scheduling of the wavelength and sub-wavelength traffics, which improves the integration of the network node cross scheduling system and the utilization rate of the scheduling matrix, and reduces the hardware cost of the network node cross scheduling system.

Abstract: An optical transmission equipment includes an optical amplifier that is coupled to an optical transmission path and amplifies a first optical signal which is received from the optical transmission path, a first controller that controls the optical amplifier depending on a first optical power of output light from the optical amplifier and a second optical power of reflecting light to the optical amplifier, an optical coupler that branches a second optical signal from the optical amplifier into a first output and a second output, an optical demultiplexer that demultiplexes the first output of the optical coupler, an optical switch or attenuator that receives the second output of the optical coupler, and a second controller that controls the optical switch or attenuator depending on a third optical power of output light from the optical switch or attenuator and a fourth optical power of reflecting light to the optical switch or attenuator.

Abstract: A Centralized Resource Management (CRM) system that supports the sharing of all the transponders in a WXC node, i.e., any spare transponder can be reconfigured to accommodate any drop channel, regardless of wavelength or input port. Consequently, network restoration in case of network failures is supported as well as the ability to reconfigure as a result of dynamic traffic requirements in the network. CRM advantageously is applied to conventional WXC node as well as WSS-based WXC nodes in the WDM networks. Three CTM schemes which manage the transponders in the WSS-based WXC node are described along with reconfiguration algorithms for an optical switchless CRM solution.

Abstract: There is provided a WDM transmission apparatus including a calculator being operable to calculate an optical signal level of a wavelength after wavelength demultiplexing based on information of OSNR, an amplifier controller being operable to compensate for the optical signal levels of all the wavelengths after wavelength demultiplexing to become a target level based on an optical signal level calculated by the calculator, and an deviation corrector being operable to correct a deviation of an optical signal level between each wavelength based on the optical signal level calculated by the calculator.

Abstract: In an optical data transmission system, one channel is removed from a group of wavelength division multiplexed optical channels and another channel carrying different information at the same wavelength is inserted in its place. The process occurs by adding an optical signal whose electric field is the difference between the electric field of the new and old channels. The difference calculation takes into account the phase of the incoming WDM channel and phase of the laser source of the difference signal. The method has applications in optical transmission networks as add-drop nodes and optical regenerators, for generation of high bandwidth optical signals, and for secret optical communications.

Abstract: If opening and deleting of arbitrary optical pathways are repeated in a configuration where plural OADM nodes are connected to each other in a ring manner, empty waves in the ring are fragmented, and thus, it is necessary to optimize the optical pathways. When an optical pathway is opened from an OADM node to a different OADM node, transponders capable of connecting two routes to the OADM nodes and of setting different wavelengths for two routes are mounted in a state where there are no empty waves on a part of the route, so that an already-opened optical pathway is detoured to a detour route or a different wavelength in the OADM ring, and continuous empty waves are produced in a section to be opened so as to open a new optical pathway.

Abstract: A system and method for dynamically adding/dropping wavelengths in a reconfigurable optical add-drop multiplexer (ROADM) transport network is disclosed.

Abstract: The present invention provides a colorless multiplexing system and method for detecting new optical channels at power levels below that which would cause data errors in existing traffic, and on top of background light, thus, overcoming a known risk inherent in colorless multiplexing—that a channel of the same wavelength as an existing channel is incorrectly added to the original working, traffic-carrying, channel's path.

Abstract: A communication system between head-ends and end-users is provided which expands bandwidth and reliability. A concentrator receives communication signals from a head-end and forwards the received communication signals to one or more fiber nodes and/or one or more mini-fiber nodes. The concentrator demultiplexes/splits received signals for the mini-fiber nodes and the fiber nodes and forwards demultiplexed/split signals respectively. The mini-fiber nodes may combine signals received from the head-end with loop-back signals used for local medium access control prior to forwarding the signals to the end-users. Upstream data are received by the mini-fiber nodes and/or fiber node and transmitted to the concentrator. The concentrator multiplexes/couples the mini-fiber node and the fiber node upstream signals and forwards multiplexed/coupled signals to the head-end.

Abstract: The present disclosure provides optimized configurations for a directionless reconfigurable optical add/drop multiplexer application. The present invention includes an add module with improved optical signal-to-noise through placing amplifiers prior to a multi-cast optical switch. The present invention includes various drop module configurations utilizing distributed gain, channel selective filters, and bi-directional configurations to reduce power consumption and complexity. Additionally, the present invention includes an integrated broadcast and select architecture.

Abstract: In an optical transmission device, when wavelength division multiplexed light formed from signals of a plurality of wavelengths are received, an optical signal of one wavelength comprised in this wavelength division multiplexed light is planarized and non-signal light of the same wavelength is reproduced. The reproduced light is modulated with a transmission data string, an optical signal is generated, and a wavelength division multiplexed light comprising the generated optical signal is transmitted.

Abstract: An optical transmission apparatus has a first wavelength selective switch (WSS) for route switching, provided with respect to each route, to selectively output signal light from a first input route to second through Nth output routes and to selectively output signal lights from second through Nth input routes to a first output route, for every wavelength, a second WSS for add and drop, to selectively output a signal light from an add port to the first through Nth output routes via the first WSS for every wavelength, and to selectively output the signal lights from the first through Nth input routes to a drop port via the first WSS for every wavelength, and an optical coupler to multiplex each of the signal lights output from the first WSS to the output routes and each of the signal lights output from the second WSS to the output routes, for every route, and to send multiplexed signal light to a first WSS of an other route, and to branch and supply multiplexed signal light input from said other route to the fi

Abstract: To provide a node (an optical transmission apparatus) enabling expanding the upper limit of the number of nodes capable of automatically forming a squelch table generated in advance in a BLSR system. For the above purpose, when generating a squelch table, hop counts counted from an add node or a drop node are used in place of a node ID of the own, as information of the add node, the drop node, etc. to be transmitted and received using a squelch data link. Thus, it becomes unnecessary to transmit and receive two information sets, a source node ID and a destination node ID, as conventionally required. By this, the number of bits available for identifying nodes can be expanded, enabling expansion of the number of nodes for which a squelch table can be formed automatically.

Abstract: The present disclosure is directed to a light source distributor for use in an injection-locked WDM-PON (wavelength division multiplexed-passive optical network). The light source distributor receives an A band and a B band injection optical signals through a single optical terminal from an injection light source for outputting both the A band and the B band injection optical signals; transmits the A band injection optical signal to a first optical multiplexer/demultiplexer of a central office and the B band injection signal to a second optical multiplexer/demultiplexer of a remote node; transmits a wavelength-locked A band optical signal received from the first optical multiplexer/demultiplexer to the second optical multiplexer/demultiplexer; and transmits a wavelength-locked B band optical signal received from the second optical multiplexer/demultiplexer to the first optical multiplexer/demultiplexer.

Abstract: In accordance with the teachings of the present invention, wavelength selective switch (WSS) design configurations for mesh light-trails are provided. In a particular embodiment, a node included in an optical network comprises a first light access unit operable to add or drop local traffic and a first WSS assembly communicatively coupled to the first light access unit and comprising at least four WSSs, at least two input ports, and at least four output ports, the four WSSs configured to direct any input traffic in any wavelength received at one of the input ports to the first light access unit and/or to any of the output ports.

Abstract: Techniques are disclosed for generating a hitless migration plan to optimal state, given an optimal routing and wavelength assignment for demands. For example, a technique for use in performing a circuit transition in accordance with an optical ring-based network comprises obtaining a first (e.g., initial) circuit layout and a second (e.g., final) circuit layout for a given set of demands to be routed on the optical ring-based network. The technique then comprises calculating a transition sequence plan useable to transition the network from the first circuit layout to the second circuit layout such that substantially no network service disruption occurs due to the circuit transition. The transition sequence plan is calculated by determining a minimum set of circuits that when moved from first positions in the first circuit layout result in a feasible transition sequence for remaining circuits in the first circuit layout.

Abstract: A communication network comprising first and second communication paths, and nodes coupled therethrough. Each node comprises first and second switches, each having a first terminal coupled to an end of a first communication path, and a second terminal coupled to an end of a second communication path. Third terminals of the first and second switches are coupled together through at least one third communication path. A Wavelength-Division-Multiplexed device of the node is coupled to an external communication node and a fourth terminal of each switch. A node controller responds to an applied input by controlling at least one switch to cause selective coupling of at least one of (a) first and second nodes together via at least one of the paths, and (b) the external communication node and at least one of the first and second nodes via at least one of the paths.

Abstract: A relay node used in a WDM optical network is disclosed. The relay node includes: a high-speed side port configured to send and receive a high-speed signal; a low-speed side port configured to send and receive a low-speed signal; a unit configured to generates a checking message for requesting another node to report constraint information of a low-speed side port of the another node, wherein the constraint information relates to adding an optical signal from the low-speed side port to a high-speed side port of the another node or dropping an optical signal from the high-speed side port to the low-speed side port of the another node; a unit configured to generate a response message including the constraint information of the own node in response to receiving the checking message sent from the another node; and a storing unit configured to store at least the constraint information of the another node.

Abstract: The invention provides a unified optical network architecture for metro and access communication networks, wherein a metro ring network interfaces access PONs through one or more reconfigurable Optical Add/Drop Multiplexers to provide wavelength-reconfigurable all-optical transmission of communication signals from the metro ring network to designated optical network units associated with the end-users, and wherein one metro hub located in the metro ring network is utilized to set transmission wavelengths and timing for both downstream and upstream signal transmission for multiple access PONs.

Abstract: Optical node (1) comprising at least one input port (PA, PC, PE) and a plurality of output ports (PB, PD, PF), at least one add unit (3B, 3D, 3F) for adding at least one signal on an output port (PB, PD, PF), a broadcasting unit (8) for broadcasting on at least two output ports (PB, PD, PF) the express traffic received on an input port (PA, PC, PE), characterized in that the broadcasting unit (8) is configured for broadcasting at least one added signal on at least two output ports (PB, PD, PF).

Abstract: Consistent with the present invention, tunable demultiplexers are provided in WSS-based add/drop multiplexer. The tunable demultiplexers are modular and thus allow the add/drop multiplexer to be readily expandable, and facilitate flexible add/drop capabilities whereby a channel present on any input line to the WSS can be dropped and supplied to one or more desired outputs of the tunable demultiplexer. Similar flexibility can be achieved on the add-side of the WSS. Moreover, the demultiplexers and the WSS are remotely configurable, thus obviating the need to manually disconnect and connect demultiplexers to a router. In a particular embodiment, multicast switches are provided that permit the same channel, for example, to be provided to one or more outputs of the add/drop multiplexer, such that copy of the channel can carry working traffic while the other copy carries protection traffic. As a result, 1+1 and 1:N optical layer protection can be achieved.

Abstract: An optical add-drop function part of an optical add-drop multiplexer has an output end of transmitted light signal in which an optical termination mechanism formed by an optical detector for detecting open of an optical fiber, an optical switch, and an optical terminator are mounted. Further, a reflection level calculation circuit, a reflection warning determination circuit, and an optical switch selection circuit are mounted to perform laser safety in the optical add-drop function part as well. The laser safety part in the optical add-drop function part is operated earlier than the laser safety part in an optical amplification function part.

Abstract: A tunable optical filter comprises an optical switch having a single first optical port and a plurality of second optical ports; a plurality of band pass filters, each one of the band pass filters optically coupled to a respective second optical port; and an optical multiplexer having a plurality of inputs and a single output, each input optically coupled to a respective band pass filter, wherein the optical switch delivers a plurality of optical channels to a selected one of the band pass filters, the selected band pass filter transmitting a single selected optical channel to an input of the optical multiplexer. Alternatively, the multiplexer may be substituted by a second optical switch. Optionally, the band pass filters may reflect other channels back to the plurality of second optical ports.

Abstract: The relative launch power of signals at an add/drop node transponder is controlled to maximize available power. Known values of signal bandwidth and likely noise in the signal path, for example, derived from the system manager, are used to control the launch power into the optical amplifier, in order to optimize the launch power accordingly.

Abstract: A reconfigurable optical add-drop multiplexer (ROADM) and a method of passing at least one optical channel through the multiplexer. In one embodiment, the multiplexer includes: (1) a main input port, (2) a main output port, (3) an add input port, (4) a drop output port, (5) dispersive optics configured spatially to spread and recombine optical spectra containing optical channels and (6) a spatial light modulator having an integral, lateral-gradient volume Bragg grating and configured to assume a bar state in which at least one of the optical channels is passed from the main input port to the main output port and at least another of the optical channels is passed from the add input port to the drop output port and a cross state in which the integral, lateral-gradient volume Bragg grating is transmissive with respect to the channels.

Abstract: Optical communication networks often incorporate fiber rings or fiber mesh topologies for interconnecting its nodes. Both of these topologies can contain closed optical loops at one or more wavelengths within the optical spectrum. In amplified optical systems, the inherent loss of these optical loops is counteracted by the amplifier gain. Thus, the optical loop may have a net loss that is too low to prevent excessive noise buildup resulting in a lasing fiber loop. The noise that builds up within such amplified systems is dominated by the Amplified Spontaneous Emission (ASE) noise resulting in ASE loops. Such loops can have a serious impact on all wavelengths carried by the fiber and lead to a partial or complete loss of end to end communication due to a severe degradation in signal to noise ratio. This invention provides an effective method and system for avoiding ASE loops in optical communication networks.

Abstract: An optical network includes an optical ring that is capable of transmitting, between two or more nodes, a plurality of working traffic streams that include traffic transmitted in one of a plurality of wavelengths. A node is capable of transmitting, in a first wavelength, a first protection traffic stream associated with a first working traffic stream, in response to an interruption of the first working traffic stream. A node is also capable of transmitting, in a second wavelength, a second protection traffic stream associated with a second working traffic stream, in response to an interruption of the second working traffic stream. The optical network also includes a regeneration element capable of selectively regenerating the first protection traffic stream. The regeneration element is also capable of tuning the regeneration element to receive traffic in the second wavelength and of selectively regenerating the second protection traffic stream.

Abstract: Providing bandwidth expansion in existing HFC infrastructures. A break in a fiber ring is established. A temperature hardened demultiplexer is coupled at the break to an input side of the fiber ring. A temperature hardened multiplexer is coupled at the break to an output side of the fiber ring. The temperature hardened demultiplexer is configured to pass-through a first predetermined wavelength to the temperature hardened multiplexer and to drop out a second predetermined wavelength. The second predetermined wavelength is extended from the demultiplexer for providing a first predetermined wavelength to an expansion node. The temperature hardened multiplexer is configured to receive the first predetermined wavelength from the temperature hardened demultiplexer and to receive the second predetermined wavelength from the expansion node.

Abstract: At a WDM add/drop node of an optical fiber, an add/drop multiplexer system with opto-electric components in the through channel path has an optical switch connected in parallel with an add/drop multiplexer. Upon a power loss to the add/drop multiplexer, the optical switch bypasses the add/drop multiplexer so that WDM channel signals pass through the WDM add/drop node without interference from the unpowered add/drop multiplexer. Loss of through channels at the node is prevented. Upon a return of power, the optical switch reroutes the WDM signals on the optical fiber to the add/drop multiplexer but after the add/drop multiplexer is fully operational.

Abstract: To provide a technology of preventing an optical signal from being mistakenly recognized as an optical noise even when a surge occurs. A control device of a node that transfers signal light monitors inputted light, determines, when power of the inputted light reaches a saturation level of a monitor unit as a result of monitoring, that the inputted light is signal light, further determines based on a spectral line shape of the inputted light, when the power thereof does not reach the saturation level, whether the inputted light is the signal light or ASE light; and stops a transfer of the ASE light if determined to be the ASE light.

Abstract: The present invention relates to a communication path calculation method and module. More particularly, the present invention provides a communication path calculation method and module that are implemented or incorporated in a transmission apparatus including a ROADM or the like which performs WDM communication, advertises information on a wavelength which can be added or dropped, as information on a link, and uses the information to autonomously calculate a communication path. Optical transmission equipment that is accommodated in a WDM network over which a wavelength-division multiplexed signal is transferred includes a reconfigurable OADM module. For calculation of a communication path, the OADM module creates a link table listing clients of the own equipment and connected WDMs, and advertises the link table to the other pieces of equipment accommodated by the network as pieces of information on restrictions to be imposed on routing from the own equipment.

Abstract: In an optical add/drop multiplexer dropping and inserting a light of a specific wavelength for a WDM signal light and an optical network system utilizing the same, a wavelength selective switch selects a part of WDM signal lights inputted as lights of drop wavelengths and outputting other lights, and a reject/add filter terminates lights of same wavelengths as add wavelengths among output lights from the wavelength selective switch and multiplexes other lights than the terminated lights and lights of the add wavelengths to be outputted. At this time, the drop wavelengths are made to include all of the add wavelengths.

Abstract: A device (D) dedicated to optical switching in a switching node (NC) comprises at least one first switching matrix (MC1) and one second switching matrix (MC2) coupled to each other and each comprising i) a first stage including Ni diffusion modules each having a first input and Mi first outputs and ii) a second stage including Ni fusion modules each having Ni second inputs each coupled to one of the Mi first outputs of one of the Ni diffusion modules via an optical line, at least one third input and one second output. The second stage of at least one of the matrices comprises at least one additional fusion module having Ni second inputs adapted to apply optical power adjustment and one second output. At least one optical line (LS1) couples the second output of an additional fusion module of one of the matrices (MC1) to a third input of each of the Ni fusion modules of the other matrix (MC2).

Abstract: Part of an inputted optical add signal 118 is reflected by a mirror 117, and is thereby inputted into an optical wavelength multiplexer 105 in the reverse direction so that the optical add signal is returned to paths 115-1 through 115-16 corresponding to wavelengths ?1 through ?16. If the returned optical add signal is an optical add signal having a correct wavelength, the optical signal enters its corresponding backward direction optical detector 113-16. Accordingly, it is possible to check whether or not a wavelength of the optical add signal is correct.

Abstract: An optical transmission apparatus includes a demultiplexing unit that demultiplexes a light input to the optical transmission apparatus into a plurality of lights; an optical attenuator that adjusts an output level of a light within a band that includes a signal light from among demultiplexed lights; a bypass unit that bypasses a light outside the band from among demultiplexed lights; a multiplexing unit that multiplexes adjusted light and the light from the bypass unit; and an optical amplifier that amplifies input light. The optical amplifier is provided at least one of a stage prior to the demultiplexing unit and a stage subsequent to the multiplexing unit.

Abstract: Heretofore, it was necessary to individually locate an optical switch, an optical switch control circuit, and the like, before and after an optical transceiver that performs optical protection. As a result, costs and the space for implementation increase, and a delay in services is also caused, which were the problems. For the purpose of solving the above problems, the present invention provides a simple optical protection method used in an optical add-drop multiplexer. Add switches 105-1 through 105-N and drop switches 103-1 through 103-N for optical signals corresponding to each wavelength in an optical add-drop multiplexer 100 are made controllable independently of one another. Add switches and drop switches of the active-side and backup-side optical add-drop multiplexers are switched by optical switch control circuits 106-1 through 106-N respectively to make a detour around a failure so that the optical protection is achieved.