Abstract: One embodiment of the present invention provides a system that facilitates discovery of remote nodes in EPONs. The system includes a central node and at least one remote node. During operation, the system first receives a solicitation message from the central node, wherein the solicitation message includes a time stamp indicating the solicitation message's transmission time and assigns a starting time and size for a discovery slot in which the remote node is allowed to transmit a response message to the central node for registration. The system then sets a local time at the remote node according to the received time stamp. After a random delay starting from the beginning of the assigned discovery slot, the system transmits the response message to the central node during the discovery slot with a response transmission probability that is less than or equal to one.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: A method and system provide capacity-efficient restoration within an optical fiber communication system. The system includes a plurality of nodes each interconnected by optical fibers. Each optical fiber connection between nodes includes at least three channel groups with different priority levels for restoration switching in response to a connection failure. The system maintains and restores full-capacity communication services by switching at least a portion of the channel groups from a first optical fiber connection to a second optical fiber connection system based on the priority levels assigned to the channel groups. Service reliability is effectively maintained without incurring additional costs for dedicated spare optical fiber equipment by improving idle capacity utilization.

Abstract: In a method and device which can quickly detect a fiber misconnection without setting an expected value, a node identifier of source node and an identifier of an interface for inputting/outputting a signal are set in a predetermined first field of a header to be transmitted to a destination node, and when both identifiers set in the first field are received from the destination node, both identifiers are set in a predetermined second field of the header to be transmitted and stored with the first field. When the identifiers set in the first and second fields are received and the identifiers of the second field among the identifiers are consistent with the identifiers of the first field stored at the second step (means), a connection is determined to be correct.

Abstract: A wavelength-division multiplexed self-healing passive optical network is capable of detecting cut-off and deterioration of feeder fiber and distribution fiber and restoring a network with a star structure. The network includes a central office, a remote node, and a plurality of subscriber units. Working and protection feeder fibers connect the central office to the remote node. A reflection unit at an end of the remote node connects to the central office for reflecting a monitoring optical signal transmitted from the central office. An output monitor stage at an end of the central office connects to the remote node for detecting the reflected monitoring optical signal and generating a control signal based on the presence of abnormality of the working and protection feeder fibers.

Abstract: A method and apparatus is provided for installing an optical cable link between first and second communication access points is provided. The method begins by securing a first end of an optical cable to the first communication access point to establish optical connectivity therebetween. A second end of the optical cable is secured to the second communication access point to establish optical connectivity therebetween. Prior to securing the second end of the optical cable, an optical probe signal is launched into the first or second end of the optical cable. A portion of the optical probe signal is received which has traversed at least a part of the cable and in which information concerning optical characteristics of the optical cable is embodied. An alert indicative of cable tampering is generated if the received portion of the optical probe signal changes beyond a threshold limit.

Abstract: Two multiplexing/demultiplexing sections of working and protection sides are prepared for each of a plurality of optical transmission devices which constitute a system, and the optical transmission devices are synchronized with each other to execute switching between the working and protection sides so that one of the working and protection sides can be selected for the entire system. Each expansion device collects optical line trouble information for each of the working and protection sides, and transmits to a main device. The main device integrates the information with trouble information transmitted from expansion devices per expansion device. The main device converts the integrated trouble information into point information, totals for each of the working and protection sides, compares, and decides which of the working and protection sides is to be selected.

Abstract: An optical network includes an optical ring and at least three subnets. Each subnet includes a plurality of add/drop nodes coupled to the optical ring. The add/drop nodes are operable to passively add a first traffic stream in a first direction on the optical ring and a second traffic stream in a second direction on the optical ring. The first traffic stream comprises different content than the second traffic stream, and the first traffic stream and the second traffic stream are transmitted on the same wavelength. The network also includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and are operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets.

Abstract: An optical network includes a plurality of subnets. The subnets each include a plurality of add/drop nodes coupled to the optical ring and operable to passively add and drop traffic to and from the optical ring. The network further includes a plurality of gateway nodes. The gateway nodes are each coupled to the optical ring at a boundary between neighboring subnets and operable to selectively pass and terminate wavelengths between subnets to allow wavelength reuse in the subnets and to provide protection switching.

Abstract: The present invention provides a method and system for monitoring composite optical signals carried over plural fiber-optic lines within an optical network. Methods and systems in accordance with the present invention each utilize a single OPM to monitor each one of a set of sample proportions of composite signals split off from respective fiber-optic lines. In one embodiment, an optical performance monitoring system comprises a plurality of fiber-optic lines, each fiber-optic line carrying a respective composite optical signal, a plurality of optical taps, each optical tap being optically coupled to a respective one of the fiber-optic lines and splitting a portion of the composite optical signal thereof, a plurality of optical switches, each optical switch being optically coupled to a respective one of the optical taps and comprising either an Open configuration and a Closed configuration, an optical coupler, and an Optical Performance Monitor (OPM).

Abstract: A network is protected against interruption of service while one or more faulty switches or optical fiber transmission lines are repaired or replaced, by an interconnecting configuration of small N×N optical input/output switches, where N is 2 or greater than 2. The switches are configured among protection and working transmission lines. The small number of fibers for each switch improves repair and installation connection reliability and permits configurations that flexibly meet differing requirements. Also the fault is monitored with a fault check signal.

Abstract: A light detection device for detecting an optical path position of invisible light. The detection device includes a main body and a light guide. The light guide includes a distal end functioning as a light incident portion through which the detected light enters and a light radiation portion from which visible light is emitted. A drive mechanism reciprocates the light guide in an X-direction while vibrating the light guide in a perpendicular Y-direction. The distal end of the light guide rod moves within a light detection area in an XY plane. A visible light-emitting unit radiates visible light from the distal end when the detected light enters the distal end. The visible light-emitting unit includes a photo-detector for detecting the detected light and a light-emitting element for generating the visible light when the photo-detector detects the detected light.

Abstract: Optical amplifier which can eliminate the need for an optical detection section before an external attenuating medium, can prevent SN degradation, and can reduce power required for pumping light. An attenuation amount detection section detects an amount of signal light attenuation caused by a variable optical attenuator and the external attenuating medium connected in series, by means of a front optical detection section provided before the variable optical attenuator and the external attenuating medium and a back optical detection section provided thereafter. An attenuation amount control section controls the variable optical attenuator such that the amount of signal light attenuation detected by the attenuation amount detection section is kept constant. A connection detection section detects a connection or disconnection of the external attenuating medium in accordance with the amount of signal light attenuation obtained when the amount of attenuation caused by the variable optical attenuator is minimized.

Abstract: The invention describes methods and systems for monitoring the performance of an optical network by marking a group of optical signals with a set of identification tags which are unique to network characteristics. In the preferred embodiments, fiber identification (FID) and bundle identification (BID) tags are encoded into optical signals by marking an optical signal with low frequency dither tones whose frequencies are unique to the fiber section and to a bundle of fibers respectively. Detecting of the FID and BID tones provides more effective and accurate monitoring of performance of the optical network and allows determining of the network topology, e.g. paths of optical channels and traffic load through different fiber sections in the network. Other sets of hierarchically arranged identifiers encoded into optical signals have also been proposed, including band, conduit, city, region, country, etc. identifiers, as well as identifiers related to network security and service characteristics.

Abstract: The spectrum of a received WDM band or subband is analyzed to detect failure of, e.g., fiber or amplifiers along a line. In one implementation, measurements are taken within the optical spectrum at locations of expected data-carrying optical signals and at two locations just outside the wavelength range occupied by these signals. Magnitudes of adjacent measurements are compared to obtain differences. If none of the differences exceed a threshold, a fault may be determined.

Abstract: A transmission system is provided that recognizes occurrence of a fault efficiently so that the workability and quality of service can be improved. An optical amplifier part amplifies an optical main signal. A fault occurrence recognizing part detects a pump light used for an opposing device via an optical fiber transmission line to which an optical main signal is sent by the repeater. If the pump light is not detected, the fault occurrence recognizing part recognizes occurrence of a fault. A light cutoff control part stops the optical amplifying part outputting an amplified signal so that the light cutoff control in only one of two directions is performed when a fault occurs.

Abstract: A link based network protection path calculation mechanism wherein a protection route is calculated that is guaranteed not to traverse the link it is intended to protect. The mechanism takes advantage of the fact that the same color cannot pass twice through the same optical fiber. The protection path is determined by eliminating all colors from the logical topology of the network except for the color corresponding to the link to be protected before executing the search algorithm. This serves to guarantee that the protection path calculated will not traverse the same physical fiber as the link to be protected. Virtual colors can be assigned to the links running through fiber bundles such that they do not pass through the same fiber/bundle twice.

Abstract: The present invention discloses an optical transmission line constructing method comprising the steps of connecting a plurality of optical fibers differing from each other in terms of a transmission characteristic; making inspection light incident on an entrance end of the connected plurality of optical fibers; detecting, on the entrance end side, respective return light components of the inspection light occurring at individual positions of the plurality of optical fibers in its longitudinal direction; evaluating a characteristic information distribution of return light in the longitudinal direction of the plurality of optical fibers; and constructing an optical transmission line according to a result of the evaluation.

Abstract: Polarization effects are managed to provide differential timing information for localizing disturbances affecting two or more counter-propagating light signals on one or more optical waveguides passing through a detection zone. Activity can be localized to a point for a security perimeter. Events causing optical disturbance can be mapped to points along a straight line, a perimeter or arbitrary pattern or an array. Events cause local changes in optical properties in the optical waveguide, in particular an optical fiber. Short term local changes are distinguishable from phase changes of light travel in the waveguide by managing the polarization state of input and output beams.

Abstract: A method and system of intrusion detection system for a multimode fiber optic cable. A light signal is launched into the cable fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes arriving at the remote end of the cable is sampled and monitored for transient changes in the mode field power distribution. The power distribution changes with physical disturbance of the cable. When those changes are detected as being characteristic of fiber intrusion, the system activates an alarm. This method can sense and alarm any attempt to access the optical fibers in a fiber optic communication cable. In preferred embodiments, the active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion.

Abstract: The detector comprises a loopback unit 10 which is connected to a connector formed at one end of an optical camera cable, an optical loop fiber 11 connecting a first optical fiber 31 and a second optical fiber 32, and a short-circuit wiring 12 which short-circuits plural electric lines of the optical camera cable. The detector also comprises a measuring unit 40 comprising a transmission loss measuring part which is connected to a connector formed at the other end of the optical camera cable and measures transmission loss between the first optical fiber and the second optical fiber, a resistivity measuring part which measures resistivity between electric lines, a disconnection detecting part which detects connection or disconnection of electric lines by using measured resistivity, and a display part, which displays the result of transmission loss measured by the transmission loss measuring part and connection or disconnection detected by the disconnection detecting part.

Abstract: A wavelength division multiplex transmission system with substantial functions for avoidance of defects is provided. The system comprises an optical transmission device and an optical receiving device. The optical transmission device comprises an operating-system optical transmission unit and a standby-system optical transmission unit, and distributes transmission signals to be transmitted among a plurality of wavelength components, converts the signals into WDM signals, and transmits the WDM signals to a WDM transmission network. The optical receiving device comprises an operating-system optical receiving unit and a standby-system optical receiving unit, and restores WDM signals from the WDM transmission network into transmission signals.

Abstract: An autoprotected optical communication ring network includes a first and a second optical carrier having opposite transmission directions and a plurality of optically reconfigurable nodes optically connected along the first and the second optical carrier and adapted to communicate in pairs on links susceptible to failure, the ring network having a normal operative condition in which the nodes of each pair are optically configured so as to exchange optical signals on a working arc path at a respective first wavelength (?x) on the first carrier and at a respective second wavelength (?y) different from the first wavelength (?x) on the second carrier, the working path having a complementary arc path defining a protection arc path in which the first wavelength (?x) on the first carrier and the second wavelength (?y) on the second carrier can be used for further links.

Abstract: The invention describes methods and systems for monitoring the performance of an optical network by introducing a fiber identification (FID) tag and/or bundle identification (BID) tag which are unique to the fiber section and to the bundle of fibers respectively. The FID tag is introduced by marking an optical signal, traveling through a section of fiber, with a low frequency dither tone whose frequency is unique to the fiber section. Similarly, the BID tag is introduced by marking an optical signal, traveling through a section of fiber in a bundle of fibers, with another low frequency dither tone whose frequency is unique to the bundle section. Detecting of the FID and BID tones either alone or along with an optionally introduced channel identification (CID) tone is provided.

Abstract: The detection light reflection function is given to PLC type LD, PD or LD/PD modules having light guides and optoelectronic chips (LD, LED, PD or APD) by forming a grating on the light guides which selectively reflects only the detection light.

Abstract: An autoprotected optical communication ring network is disclosed. The ring network includes two optical carriers that are arranged for bidirectional transmission. Multiple optically reconfigurable nodes are connected along the optical carriers. The nodes communicate in pairs, defining non-overlapping working links. Under normal conditions, the nodes of each pair are optically configured to exchange optical signals over the working link at a first wavelength on the first carrier and at a second wavelength that is different from the first wavelength on the second carrier. During a failure condition, the first wavelength on the second carrier and the second wavelength on the first carrier are reserved for effecting a protection scheme, while the first wavelength on the first carrier and the second wavelength on the second carrier can still be used for unaffected working links.

Abstract: A system and method for facilitating full utilization of an ultra-wide optical communication band spanning the useable band of the optical transmission spectrum, and providing appropriate protection strategies on the same mesh/ring network for all channels within the ultra-wide optical communication band. A network node architecture includes a band splitter to receive all of the optical signals sent on various wavelengths within the wide optical communication band. The band splitter separates a first group of the optical signals from a second group of the optical signals based on their range of wavelength. The first group of optical signals are those within a first wavelength range of the optical communication band, and the second group is from the second wavelength range of the optical communication band. A cross-connect circuit receives the first and second groups of optical signals, and routes them to targeted output ports at the output section of the node.

Abstract: A method for monitoring the transmission quality of an optical transmission system, such as, for example, an optical wavelength division-multiplex network. An amplitude histogram of an optical signal (transmission signal) transmitted over the transmission system may be plotted and classified, with the assistance of a neural network, according to bit error rates and/or causes of faults. The need for setting requirements for transmission mode, transmission format and/or transmission timing cycle of the transmission system may be eliminated. The amplitude histogram may be implemented for any signal, and causes of faults, which are not able to be determined by a conventional bit rate classification, may be allocated.

Abstract: A method and system for I/O adapters that must rely on a central processor to handle all inbound link events to reduce the number of events signaled to the central processor with hardware state machines that sort out the significant link events and automatically generate the appropriate response on the outbound link thereby greatly reducing the central processor utilization. As optical links fail (unplugging the link is a failure) or when receiving multiple continuous sequences, numerous events must be filtered by the hardware state machines to limit the number of interrupts presented to the central processor.

Abstract: The control of the transmission of useful optical signals on different line paths of an optical transmission device is accomplished via at least one of the following features: using signal sources and signal sinks, the useful optical signals are coupled into the line paths, or are coupled out of them; at least one portion of the optical line paths is configured as normal line paths having coupling nodes via which a switchover to an alternative line path can be undertaken if a normal line path is disturbed; in addition to the useful optical signals, test signals, whose evaluation is used for the switchover between the line paths, are transmitted bidirectionally section-by-section; at least two types of test signals can be transmitted, of which a first type is used as an indicator for an intact line path and a second type as an indicator for a disturbed line path; and any switchover to an alternative line path is only undertaken if, before the detection of the disturbance, a test signal of the first type has be

Abstract: Devices, such as node and network elements for use in communications systems, which include a plurality of ports, each having an input and an output, a plurality of splitters corresponding to the port inputs, a plurality of combiners corresponding to the port outputs, a plurality of signal paths between the splitters and the combiners, wherein each of the signal paths includes a signal varying device, and a plurality of protection devices connected between the splitters and the combiners, wherein each of the plurality of protection devices includes a signal varying device and provides a protection path corresponding to a plurality of the signal paths, and wherein at least one splitter has at least one unused output after the signal paths and the protection paths are connected, and wherein at least one combiner has at least one unused input after the signal paths and the protection paths are connected.

Abstract: To automate fiber connectivity management in optical systems, a dedicated low bit-rate communications channel unique to each fiber connection in an optical system is provided. The dedicated communications channel simplifies fiber connectivity management by supporting the exchange of port identification information from one optical component to another after which processing determines if the specific connection is a desired association. The dedicated communications channel supports optical interconnection surveillance for all card-to-card optical connections within a group of related cards or within an optical network link. Automating fiber connectivity management in this manner will enhance future products by simplifying the fiber connection validation process and ensuring that any specific connection between optical components is the required association.

Abstract: A system and method for optical power transient control and prevention in communication networks. An optical signal propagating on a network is demultiplexed into individual spectral bands, e.g. at an OADM, and an optical power monitor point is included into each band. A separate idler laser is provided for each OADM band. The power output of each laser is adjusted such that it compensates for the signal power lost from each band. The wavelength of each laser is chosen to fall within the associated OADM spectral band, but outside of the window of individual signal wavelengths, so that it may propagate through the network without causing deleterious interference at the receiver.

Abstract: A method of managing a free-space optical network includes monitoring environmental and weather conditions in the vicinity of one or more free-space optical links in the network. Data is gathered by environmental condition instruments, such as visibility meters, and is used to assess whether atmospheric conditions have deteriorated to the point where operation of one or more free-space links might be in jeopardy. If data from an environmental condition instrument falls below a predetermined level, network data traffic is routed over an alternate communication path, which may include radio frequency (RF) paths, fiber optic cables, wire cables, or other free-space links.

Abstract: The present invention provides methods, apparatus and systems for protecting connections between optical cross-connect switches and client equipment. A connection failure is detected, signaled, and a switch made by the client equipment and the optical cross-connect switch to a protection connection between them so as to minimize service interruption. An out-of-band channel or an in-band channel can be used to signal the connection failure.

Abstract: The present invention provides a system and method for communicating data between network subsystems over optical fibers using a backchannel probe signal. In one embodiment, the present invention includes an optical network having an optical fiber coupled between first and second optical couplers residing in two different subsystems. A first processing unit is coupled to a first tap of the first optical coupler for providing an optical payload signal, and a second processing unit is coupled to a first tap of the second optical coupler for receiving the optical payload signal. A probe signal transmitter is coupled to a second tap of the second optical coupler for providing a probe signal, and a probe signal receiver coupled to a second tap of the first optical coupler for receiving the probe signal. The probe signal may be used to detect erroneous fiber connections or lossy inter-subsystem fibers.

Abstract: A communication path impairment detection module for connection to a duplex optic communication link is provided. The duplex optic communication link includes an outgoing communication path and an incoming communication path, each being characterized by a data channel and an optical service channel. The communication path impairment detection module includes a first port and a second port suitable for coupling to the outgoing and incoming communication paths respectively. The communication path impairment detection module is responsive to impairment of the data channel and of the optical service channel in the incoming communication path to impair the data channel and the optical service channel in the outgoing communication path.

Abstract: An optical transmission system with a mechanism to locate a fault on a transmission line effectively and efficiently to ensure the quality of communication between end stations and repeaters. Repeaters respond to a monitoring control command sent from an end station, returning a monitoring report signal that indicates their current operating status and input/output signal conditions. In the end station, a monitoring report processor identifies a faulty link section of the optical transmission line, if the monitoring report signal indicates a fiber fault. The end station sends a troubleshooting control command to cause a relevant repeater to transmit a probing light pulse signal and a complementary light pulse signal simultaneously in opposite directions. Some of the probing light pulse is reflected back as a result of Rayleigh scattering. The end station locates the fiber fault by analyzing the backscatter, using the complementary light pulse signal for synchronization.

Abstract: A data transfer method includes a connection establishment step of detecting connection with a remote device and setting parameters for data transfer, and a transfer execution step of starting data transfer after completion of the connection establishment step and continuing data transfer until a transfer error is recognized to have occurred. In the transfer execution step, the frequency of errors in received data is monitored and, when the frequency reaches a predetermined value, a transfer error is recognized to have occurred.

Abstract: Disclosed is a WDM network which has: a lightwave path which connects between clients and each of which is provided with an overhead, and a sub-network which is defined by dividing the WDM network. In this WDM network, the sub-network has a partial lightwave path to go through the sub-network, the overhead has a partial lightwave path supervisory control information region which is terminated at both nodes of the partial lightwave path, and when a fault occurs on a lightwave path, the fault information of partial lightwave path including the position information of fault occurred is added to the partial lightwave path supervisory control information region of the overhead.

Abstract: An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit via a working optical fiber, (2) a protection OSU of a protection circuit via a protection optical fiber, and (3) one or more optical network terminals (ONTs), where the protection OSU has a protection burst mode receiver (BMR) configured to receive an upstream optical signal from the optical splitter. The algorithm determines whether the protection OSU is functioning improperly. A reset pulse is applied at the protection BMR at a particular timing position and an attempt is made to interpret the current upstream cell received at the protection BMR. This process is repeated using different timing positions for the BMR reset pulse until the current upstream cell is correctly interpreted, e.g., based on the correct identification of an ATM header error correction (HEC) byte in the upstream cell.

Abstract: The present invention relates to a branch line monitoring system and branch line monitoring method comprising a configuration which improves the S/N ratio of measurement information and can be realized inexpensively. This system is provided with optical filters which correspond to optical fiber lines to be monitored as branch lines. These optical filters each have such a cutoff characteristic as to cut of f respective one channel of monitor light but transmit therethrough the remaining monitor light and signal light. When the optical filters having such a cutoff characteristic are provided, each of the optical fiber lines is monitored by use of a plurality of channels of monitor light other than the one cut off by the optical filter provided so as to correspond thereto. Consequently, as compared with the case where one optical fiber line is monitored by its corresponding one channel of monitor light, the S/N ratio of measurement information is improved, whereby highly accurate monitoring is possible.

Abstract: An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit, (2) a protection OSU of a protection circuit, and (3) one or more optical network terminals (ONTs), where an ONT has (i) a working line termination (LT) unit of the working circuit and connected to the optical splitter via a working optical fiber and (ii) a protection LT unit of the protection circuit and connected to the optical splitter via a protection optical fiber. The present invention enables fast protection switching from the working circuit to the protection circuit. The arrival times of corresponding downstream cells are measured at both the working and protection LT units of the ONT, and information related to the arrival times is transmitted from the ONT to the protection OSU.

Abstract: The present invention relates to an automatic retrieval method of a wavelength-division multiplexed (WDM) ring network to the normal state after recovery of a failure. More specifically, the present invention relates to an automatic retrieval method of a WDM ring network to the normal state after recovery of a failure by inducing a lasing by making the gain of the closed loop larger than 1 using the fact that the recovered section in the ring network forms a closed loop immediately after the recovery of the failure.

Abstract: A system and method for transmitting and restoring an optical signal in an optical ring is presented. The optical ring comprises a plurality of nodes, each node containing an optical cross connect switching fabric coupled to a data switch. The optical cross connect switching fabric and the data switch are coupled to a short reach side of a wavelength translation device. A long reach side of the wavelength translation device is coupled to a dense wave division multiplex (DWDM) coupler. The optical cross connect switching fabric and the data switch include a protect channel and a working channel for transporting the optical signal. The wavelength translation device receives the optical signal at a high speed rate, where the optical signal is a short reach optical signal and originates from a high speed interface on the data switch.

Abstract: An optical transmitter-receiver that does not have a harmful effect on the human eye when an optical fiber is disconnected from the apparatus and is able to determine easily when the fiber has been reconnected. A normal signal detector and a dummy signal detector determine when a signal from another optical transmitter-receiver is no longer received due to disconnection of an optical fiber. This result switches an output switch and causes a second reference voltage to be transmitted to an optical output automatic controller, thereby reducing the power of a laser diode. At the same time, a signal switch provides a dummy signal having a low frequency to the laser diode in place of the normal signal, resulting in output of a dummy optical signal. At this time, the other optical transmitter-receiver also outputs a dummy optical signal. When the optical fiber is reconnected, the dummy signal transmitted from the other optical transmitter-receiver is detected.

Abstract: An automatic optical power management system for use with an optical communications system includes a light source residing in a first circuit pack and adapted to emit light at a nominal power level only absent receipt of an indicator signifying a loss of signal resulting from a fiber discontinuity relating to the first optical fiber, wherein the nominal power level is of sufficient magnitude to violate laser safety guidelines in the event of the fiber discontinuity. A redundant detection system includes a first optical detector residing in the first circuit pack, and a second optical detector residing in a second circuit pack that is optically adjacent to the first circuit. A redundant response system communicates an indicator signifying loss of signal from the first and second optical detectors to the light source upon detection of loss of signal by either detector.

Abstract: The present invention provides a method of monitoring a transmission fiber including the steps of transmitting a monitor signal on the transmission fiber in a direction opposite to the propagation of traffic signals on the transmission fiber, at an optical amplifier connected to the transmission fiber detecting the monitor signal and automatically shutting down the optical amplifier in response to a predetermined change in the detected monitor signal. The invention facilitates a faster shut down of amplifiers when a fault occurs than is currently available because it shuts down the amplifier feeding directly into the area of broken fiber first rather than last as in conventional communication systems.

Abstract: A method of routing of signals through an optical network involves determining a route through the network for which the power level within each branch of the network along the route is below a threshold power level which is a function of the fiber characteristics of the branch. This threshold power is the power below which a fiber fuse can not be initiated. This method enables power levels within a network to be controlled such that the threshold power is not exceeded, and a fiber fuse will not be initiated. The invention provides a network controller for carrying out this method.