Abstract: An example system includes a hub transceiver and a plurality of edge transceivers. Each of the edge transceivers has one of several types of configurations for communicating with an optical communications network. Each type of configuration is associated with a different responsive optical subcarrier assignment protocol. The hub transceiver is operable to determine a plurality of optical subcarriers available for assignment by the hub transceiver to the plurality of the edge transceivers for use in communicating over the optical communications network, and assign, to each of the edge transceivers, a respective subset of the optical subcarriers. Assignment includes, determining that each of the edge transceivers has a particular type of configuration, and assigning a respective subset of the optical subcarriers to the edge transceiver according to the optical subcarrier assignment protocol associated with the that type of configuration.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, an optical communication system includes a primary transceiver, a component, and secondary transceivers. The primary transceiver is operable to supply first optical subcarriers to an optical communication path, the first optical subcarriers being amplitude modulated at a first frequency to carry first control information and amplitude modulated at a second frequency to carry second control information. The component is operable to be coupled to the optical communication path and includes circuitry operable to detect the first control information. The secondary transceivers are coupled to a terminal end of the optical communication path. At least one of the secondary transceivers is operable to detect the second control information and block the first control information.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, an apparatus includes an optical tap coupled to an optical communication path carrying a modulated optical signal carrying a plurality of optical subcarriers. The optical tap has a first output configured to supply a first portion of the modulated optical signal and a second output configured to supply a second portion of the modulated optical signal. The plurality of optical subcarriers are amplitude modulated based on control data at a first frequency, and each of the plurality of optical subcarriers is modulated to carry user data at a second frequency greater than the first frequency. The apparatus is configured to supply the control based on the first portion of the modulated optical signal.

Abstract: Pre-programming Layer-0 optical protection path restoration speeds is provided based on available path margin. Higher layer routers and switches can be made aware of the expected Layer-0 restoration time, and their switch time can be programmed accordingly. The proposed method can provide users an option to program a restoration speed for a specific photonic service on a per restoration path basis. The method can highlight which services will potentially be impacted by the selected restoration speed on that path. The user can proceed with the selected speed for restoring high priority layer-0 services even if that means the fast restoring event can potentially impact other low priority services already in-service on the restoration path.

Abstract: Pre-programming Layer-0 optical protection path restoration speeds is provided based on available path margin. Higher layer routers and switches can be made aware of the expected Layer-0 restoration time, and their switch time can be programmed accordingly. The proposed method can provide users an option to program a restoration speed for a specific photonic service on a per restoration path basis. The method can highlight which services will potentially be impacted by the selected restoration speed on that path. The user can proceed with the selected speed for restoring high priority layer-0 services even if that means the fast restoring event can potentially impact other low priority services already in-service on the restoration path.

Abstract: An apparatus and method for deriving fiber characteristics between two nodes in an optical communication network are disclosed. A roundtrip time for a signal to travel between two nodes is measured by sending the signal via the optical supervisory channel from a first node to a second node, which is configured for loopback operation. Fiber characteristics can be calculated based on the measured roundtrip time.

Abstract: A system and method is disclosed that allows for the monitoring, analyzing and reporting on performance, availability and quality of optical network paths. The correlation of PM parameter metrics to client connections, coupled with threshold-based alarm generation provides a proactive and predictive management, reporting and analyzing of the health and effectiveness of individual path connections to alert Operational Support (OS) staff and/or customers to signal degradation and impending Network Element (NE) failures. The system and method performs in real-time processing intervals required for alarm surveillance in a telecommunications network.

Abstract: The present invention includes method and apparatus for storing provisioned information within the optical switches and retrievable by every controller. The optical switches perform failure isolation according to their provisioning information. The optical switches monitor each channel for loss of signal. The provisioning information is shared autonomously between the optical switches allowing the switches to retrieve the provisioning information of the network topology from any other optical switch in the network. Fault isolation is done by the optical switch on the level of optical switch provisioning following the paradigm of “single alarm for single fault,” thus avoiding alarm floods and ambiguous alarms, thereby saving the operator time and money.

Abstract: A method includes generating a test signal and modulating the test signal. The method may also include transmitting the test signal on an optical path, where the optical path may include a number of add-drop multiplexer devices and amplifiers. The method may also include receiving the test signal at a destination device and converting the received test signal into an electrical signal. The method may further include identifying a portion of the electrical signal that is associated with the modulated test signal.

Abstract: The present invention relates to communications technologies, and discloses a method for monitoring the state of a fiber line, a repeater, and a submarine cable system. The repeater includes a first optical amplifier (OA), a second optical amplifier, a first gating unit, a second gating unit, a first coupler, a second coupler, a third coupler, and a fourth coupler. The first coupler, the fourth coupler, and the first gating unit form an in-to-in loopback path between the input end of the first OA and the input end of the second OA; and the second coupler, the third coupler, and the second gating unit form an out-to-out loopback path between the output end of the first OA and the output end of the second OA.

Abstract: Extender apparatus for an optical network includes first and second extender units having an network-facing port for connection to a backhaul fiber and a subscriber-facing port for connection to a feeder fiber. Each extender unit includes a gain assembly and is operable selectively either in an enabled state, in which the gain assembly amplifies a signal received at either port of the extender unit and couples it to the other port of the extender unit, or in a disabled state, in which the gain assembly blocks coupling of a signal from either port of the extender unit to the other port of the extender unit. A failover unit is operable when the first extender unit is in the enabled state and the second extender unit is in the disabled state to detect occurrence of at least one fault condition in the first extender unit. The failover unit is responsive to the fault condition in the first extender unit to switch the first extender unit to the disabled state and the second extender unit to the enabled state.

Abstract: An optical transmission apparatus includes an amplifier, a first output port to select a wavelength from the wavelength-division-multiplexed signal light amplified and output signal light with the selected wavelength to an operation line, a second output port to output multiplexed light obtained by multiplexing any one of first spontaneous emission light and second spontaneous emission light to a preliminary line, the first and the second spontaneous emission light being parts of spontaneous emission light generated by the amplifier, the first spontaneous emission light being in a wavelength range that is not selected, and the second spontaneous emission light being in a wavelength range other than a range of the wavelength-division-multiplexed signal light, and a judger to judge a continuity state of the operation line by using the signal light output to the operation line and a continuity state of the preliminary line.

Abstract: A repeater (1) includes a master unit (2) for communicating with a base station of a mobile network, a plurality of remote units (3) for communicating with mobile communications terminals, and a common optical waveguide (4) connecting the remote units (3) with the master unit (2) for transmitting the optical signals from each of the remote units (3) to the master unit (2). The remote units (3) include, as a transmitter for the optical signals, a laser (7) of a construction similar or somewhat identical to that of the other lasers (7). The lasers (7) have similar or somewhat identical nominal wavelengths (?N), and the individual lasers (7) are selected by adjusting their operating temperatures (TD1-TD4) in such a way that each laser transmits on a different transmission wavelength (?ü1-?ü4).

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: There are provided surge protection devices for undersea optical repeaters. An optical repeater drive circuit incorporating a diode chain design includes a diode array formed of a plurality of banks of two or more parallel forward-biased diodes, each diode in a given bank being in electrical contact with all the diodes in adjacent banks; and, optical repeater control circuitry connected in parallel with the diode array. A component for providing surge protection to an optical repeater incorporates a substrate formed of an insulating material and a first substantially planar conducting coil embedded within the substrate.

Abstract: A method, system and device for protecting a Long Reach Passive Optical Network (LR-PON) system are provided. The Electrical Relay (E-R) device receives the optical signal transmitted on two fiber transmission paths by the Optical Line Terminal (OLT) or Optical Network Unit (ONU) on one side, performs optical-to-electrical (O/E) conversion, signal regeneration, and electrical-to-optical (E/O) conversion for the optical signal, and sends the signal to the ONU or the OLT on the other side through the two fiber transmission paths. Through backup of the fiber transmission path, an LR-PON system protection method is provided to improve the reliability of the LR-PON system. The method, system, and device for protecting the LR-PON system under the present invention all support and are compatible with the existing functions of all devices in the existing LR-PON system.

Abstract: A repeater is disclosed that transmits an optical signal using wave division multiplexing. The repeater includes a demultiplexing unit that separates plural channels contained in the optical signal, an adjusting unit that adjusts at least optical power of each of the channels according to a control signal, a multiplexing unit that outputs a multiple wavelength signal in which the channels are multiplexed, and a monitoring unit that determines a modulation scheme and a bit rate of the optical signal for each of the channels so as to generate the control signal.

Abstract: An optical network is disclosed comprising one or more photonic switching nodes is disclosed. Each of the switching nodes comprises a plurality of input ports; at least one output port; and a switch configured to route messages between the plurality of input ports and the at least one output port and provide bufferless resolution of contention between messages for a common output port.

Abstract: A system and method is disclosed that allows for the monitoring, analyzing and reporting on performance, availability and quality of optical network paths. The correlation of PM parameter metrics to client connections, coupled with threshold-based alarm generation provides a proactive and predictive management, reporting and analyzing of the health and effectiveness of individual path connections to alert Operational Support (OS) staff and/or customers to signal degradation and impending Network Element (NE) failures. The system and method performs in real-time processing intervals required for alarm surveillance in a telecommunications network.

Abstract: An optical repeater connected to an optical transmission line between an optical network unit having an optical network unit (ONU) function on the side of a subscriber and an optical line termination (OLT) on the side of a center includes first electrical/optical conversion means connected to a first optical transmission line on the side of the center, a second electrical/optical conversion means connected to a second optical transmission line on the side of the subscriber, and transmission means connected between the first electrical/optical conversion means and the second electrical/optical conversion means to transmit an optical repeater supervisory signal between the optical transmission lines.

Abstract: A system and method for fault identification in optical communication networks. One or more repeaters in the system includes a loop back path that couples an output a first amplifier for amplifying signals carried in a first direction through a repeater to an input of a second amplifier for amplifying signals carried in a second direction through said repeater. Fault analysis is conducted using loop gain data associated with test signals transmitted on the first or second paths and returned on the opposite path through the loop back paths.

Abstract: Embodiments of the present invention disclose a service transmission processing method, a node device and a network system are provided. One method includes: receiving service data after relay processing by a 3R relay node, where the relay processing includes terminating and regenerating an Optical Channel (OCh) of the service data, and when the OCh is terminated, transparent transmission is performed on an Optical channel Transport Unit (OTU); and performing defect detection on a path of the OTU to obtain a detection result of the path of the OTU. Another method includes: obtaining an overhead in an Optical Transport Network (OTN) frame; and judging whether the overhead includes a Client Signal Fail (CSF) inserted after a signal fails, and if the overhead includes the CSF, determining a path where a defect occurs according to the CSF.

Abstract: An optical repeater connected to an optical transmission line between an optical network unit having an ONU function on the side of a subscriber and an optical line termination (OLT) on the side of a center includes first electrical/optical conversion means connected to a first optical transmission line on the side of the center, a second electrical/optical conversion means connected to a second optical transmission line on the side of the subscriber, and transmission means connected between the first electrical/optical conversion means and the second electrical/optical conversion means to transmit an optical repeater supervisory signal between the optical transmission lines.

Abstract: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: A wavelength division multiplex optical ring network comprises optical fibre (1-4) arranged in a ring configuration and a plurality of doped fibre optical amplifiers (17-20) arranged in the ring. The spectral response in the ring is configured such in use amplified spontaneous emission (ASE) noise circulates around the ring in a lasing mode to clamp the gain of each doped fibre optical amplifier. Each optical amplifier (17-20) includes respective control means (28) which in use control the optical amplifier to produce a substantially constant output power or to maintain a substantially constant pump power. In the event of loss of the lasing peak, detection means switches the doped fibre optical amplifiers to a different mode of gain control, for example, a mode to produce constant gain at the value before the loss of the lasing peak. Optionally, after a predetermined delay, the optical amplifiers may revert to constant output power or pump power mode.

Abstract: A heating system and a method of controlling the heating system are provided. When a heating unit and a switch are turned on and off repeatedly by the predetermined number of times or more, only some of heaters of the heating unit are turned on, thereby increasing service life of the heating unit and the switch.

Abstract: A method and apparatus for restoration of operating conditions of a WDM optical ring network comprising a plurality of amplifiers linked together in a ring after a break or fault has occurred in the network. The method comprises in response to repair of the break or other fault, increasing output power or/and pump power of an amplifier in the network such that the output power or/and pump power increases substantially in accordance with a ramp function.

Abstract: A relay station has an optical switch that switches a reception path of an optical signal. The relay station generates a subsignal that has a wavelength different from the wavelength of a data signal corresponding to a signal to be transmitted and transmits an optical signal obtained by multiplexing the generated subsignal and the data signal. In this state, when the data signal is not included in the received optical signal, the relay station determines whether the subsignal is included in the optical signal. When it is determined that the subsignal is included, the relay station maintains a connection path of the optical switch without switching the connection path.

Abstract: Various high loss loop back (HLLB) repeater architectures are disclosed that enable selectively monitoring (e.g., measuring, analyzing, etc) of Rayleigh signals from both inbound and outbound directions of an optical communication system. In one such embodiment, first and second optical test signal frequencies (or ranges) are used, in conjunction with selective filtering, for monitoring the outbound and inbound paths, respectively. The repeater architectures allow optical time domain reflectometry (OTDR) monitoring techniques to be employed, for example, in particularly long repeater spans, such as those in excess of 90 km in length.

Abstract: The WDM optical transmission system using distributed Raman amplification, before starting operation of main signal light, transfers a plurality of lights having different wavelengths to that of the main signal light (for example Raman amplification pump lights or the like) between first and second optical transmission devices connected to opposite ends of a transmission line, monitors transmission line input and output power for each light, calculates a transmission line loss in each wavelength using the monitor results, and specifies a type of the transmission line based on a loss wavelength characteristic that can be estimated from the calculation result. Then the power of pump light provided to the transmission light is optimized in accordance with the type of transmission line.

Abstract: An output light intensity monitor unit of an optical repeater monitors an output light of an output point of the optical repeater. A reflected light intensity monitor unit monitors a reflected light returning from an optical fiber to the output point, An optical fiber transmission line loss from the apparatus output point to an optical fiber open end and a light intensity emitted from the open end are estimated from a monitored reflected light intensity, and a reflection abnormality detection threshold for detecting the reflection abnormality if the light intensity emitted from the open end exceeds a reference light intensity is prescribed. An output light intensity lowering amount and a reflection abnormality recovery threshold are prescribed from an output light intensity monitored at the apparatus output point and the reflected light intensity so that an open end output light intensity may be lowered to the reference light intensity.

Abstract: An apparatus and a method for accurately detecting Loss of Optical Power (LOS) by noise power cancellation effect and optical power is measured at two output ports of an athermal periodic filter, wherein one output port in the optical frequency domain, is aligned with the signal channels of an input WDM signal (on-grid port), whereas the second output port is aligned complementary to the first output port (off-grid port). In a preferred embodiment, the apparatus computes the ratio of the measured optical powers at the two output ports of the periodic filter, and comparing them to a threshold value that is determined from the overall common-mode rejection ratio (CMRR) of the detection apparatus. In an alternative embodiment, the apparatus additionally compares the optical power measured at the on-grid port to a threshold power that is determined from system design parameters.

Abstract: The present invention provides methods and systems to stabilize an optical network against nodal gain changes through two nested control loops for controlling node gain and node output power. The present invention includes two nested control-loops running at different update speeds including: an inner, faster, control-loop which sets the gains and losses within a node to achieve a node-gain target, and a node-gain target for the inner loop is set by an outer, slower, control loop that whose target is the node output power. Advantageously, the present invention reduces the problem of concatenated overshoot by minimizing the control-loop response to events that occur at other nodes.

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: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: A system and method using differential loop gain for fault analysis in line monitoring equipment. Differential loop gain data is calculated from loop gain data, and fault analysis is conducted using differential loop gain data, e.g. by comparing the differential loop gain data to predefined fault signatures.

Abstract: A method and apparatus for initializing an end-to-end link in a fiber optic communications system in which a pair of nodes interconnect a pair of end devices. A first node, upon initializing a device link segment with an end device to which the node is coupled, sends a signal to the other node over a network link segment indicating that the sending node has initialized its device link segment. The first node completes initialization of the end-to-end link upon receiving a signal from the other node over the network link segment indicating that the other node has initialized its device link segment. In an alternative initialization scheme, a node momentarily operates its data channel in a loopback mode to allow its end device to initialize the device link segment in accordance with a predetermined protocol before returning to a transparent mode.

Abstract: In order to compensate for chromatic dispersion ad dispersion slope over an entire wavelength band of the optical signal, the wavelength band is split into a plurality of bands, and chromatic dispersion compensation is made to make chromatic dispersion in a central wavelength of each of the bands zero.

Abstract: Error detection and recovery of an optical network element are described herein. In one embodiment, an exemplary process includes, but is not limited to, transmitting from a transmitting module of the optical network element a first packet of data to a receiving module of the optical network element, and the transmitting module transmitting a first value representing a number of bits of the first packet having a predetermined logical value to the receiving module, wherein the first value is used by the receiving module to verify an integrity of the first packet in order to determine whether the packet has been transmitted successfully. Other methods and apparatuses are also described.

Abstract: A repeater is disclosed that transmits an optical signal using wave division multiplexing. The repeater includes a demultiplexing unit that separates plural channels contained in the optical signal, an adjusting unit that adjusts at least optical power of each of the channels according to a control signal, a multiplexing unit that outputs a multiple wavelength signal in which the channels are multiplexed, and a monitoring unit that determines a modulation scheme and a bit rate of the optical signal for each of the channels so as to generate the control signal.

Abstract: An optical transmission apparatus comprises a preamplifier controlling unit for controlling a preamplifier so that amplified spontaneous emission including all wavelength bands of a wavelength-multiplexed signal beam is outputted toward a wavelength demultiplexing unit, with the wavelength-multiplexed signal beam not inputted, power monitors for monitoring optical powers of the amplified spontaneous emission fed from the preamplifier and wavelength-demultiplexed by the wavelength demultiplexing unit, and a determining unit for determining the continuity state of an optical propagation path of each wavelength component on the basis of a result of monitoring by the power monitors. The optical transmission apparatus allows the continuity test on optical propagation paths of channels including a channel not used at the time of a start of the operation to be made easier than the known techniques.

Abstract: In order to easily and efficiently carry out various characteristic evaluations of optical fibers which have been laid down, a table file which is for carrying out association of optical fibers serving as measuring objects with measured data when the optical fibers have been measured, based on optical fiber management information provided in advance of undertaking a cable laying/maintenance construction, such as various types of information on the optical fibers serving as measuring objects, and information on a construction site, and the like, is created at an external terminal. An OTDR measures the optical fibers serving as measuring objects based on the table file created at the external terminal, and stores measured result data in which the measured optical fibers and measured data of the optical fibers have been associated with one another, and edited result data expressing edited contents when the table file and the measured result data have been edited.

Abstract: In a wavelength-division-multiplexing optical transmission system in which optical-node apparatuses that perform relay transmission of wavelength-division-multiplexed light are located at specified nodes in a main optical transmission path, an optical amplifier switches level control to constant-gain control when there is a notification of a change in the number of multiplexed wavelengths, and then after a specified amount of time restarts level control so that the level becomes a target level that corresponds to the actual number of wavelengths.

Abstract: A modulation device comprises for each carrier frequency: means of discrimination between a signal coming from a first channel of a communications link and a signal coming from a second channel of said link, so as to obtain differentiated first and second signals; first assigning means, enabling the assigning of the first differentiated signal to one of the two modulation arms, and the second differentiated signal to the other of the two modulation arms.

Abstract: A loss of signal beat detector makes use of multiplication of a local clock signal and a recovered clock signal to obtain frequency deltas used to indicate loss signal. Through a hardware implementation, a high speed detection is offered, allowing changeover from the recovered clocking signal to the local clock signal when loss of signal is detected to prevent the transmission of a timing transient to downstream nodes.

Abstract: There is provided in a telecommunications network comprising an optical fiber cable, and an optical component connected to a first point of the optical fiber cable, with an optical time domain reflectometer (OTDR) connected to a second point of the optical fiber cable so that it can emit OTDR signals along the optical fiber cable towards the optical component, a method of preventing OTDR signals from being applied to the optical component, comprising introducing one or more optical signals into the optical fiber cable at the first point thereof using the optical fiber cable to carry the optical signals to the second point thereof, and configuring the OTDR to detect the or each optical signal from the optical fiber cable and to prevent emission of OTDR signals at any time during which detection of an optical signal occurs. The optical component may comprise, for example, an optical receiver which may introduce the optical signals into the optical fiber cable.

Abstract: An optical amplifier may be quickly returned from a shutdown state to a regular state after getting recovery information of a fault. Gain setting by ASE is conducted to the repeaters on the up-stream side during the shutdown state, by outputting ASE light with the same intensity as the WDM signal. Accordingly, before realizing the recovery of shutdown, the gain setting is completed with the light whose intensity is within the safe criterion. After realizing the recovery of shutdown, the optical transmission system can be returned quickly to the regular operating state after recovery of shutdown state.

Abstract: In a wavelength division multiplexed (WDM) optical communication system having optical transmitters and receivers communicating via a optical channels, the bit error rate (BER) for the optical channels is tested simultaneously by performing a BER measurement for the cascaded chain. A BER test signal is supplied from a BER tester to a first optical transmitter. The BER test signal passes through the optical channels. The last optical receiver in the cascaded chain supplies the test signal to the BER tester measure the BER. The measured BER is compared to a predetermined system BER threshold to determine if the optical channels meet their specified BER values. Each optical transmitter and receiver includes a performance monitoring circuit that monitors the quality of the BER signal supplied to the optical transmitter/receiver for identifying one or more optical channels that the measured BER exceeds a predetermined system BER threshold.

Abstract: In an optical transmission node network in which a first optical transmission node is connected with a second optical transmission nodes through an optical fiber cable and automatic optical output (APSD: Automatic Power Shut-Down) control is activated, after the APSD control is brought into an inhibited status, if an optical conduction to the second optical transmission node is detected, the APSD control inhibited status is canceled. In this way, if an optical transmission fiber is resorted (reconnected) after optical output power measurement or the like is carried out, the APSD control inhibition status (invalid status) is canceled for automatically restoring the APSD control activated status. Thus, optical output can be prevented from being inadvertently emitted at a high energy level from the optical fiber cable.

Abstract: A method is provided for locating a fault in one or more optical amplifiers operating in saturation and located along an optical transmission path. The method begins by generating a coherent optical time domain reflectometry (COTDR) trace representing a backscattered and/or reflected optical power level along the transmission path and comparing the trace to a reference trace to generate a difference trace that represents a change in gain. The change in gain is assigned to at least one of the optical amplifiers based on the difference trace. The method comprises assigning the difference trace to faults in the optical amplifiers, equating the difference trace with a linear combination of difference trace vectors each arising from a fault in a different one of the optical amplifiers, and iterating to determine a coefficient value associated with each difference trace vector. Each nonzero coefficient value denotes a fault in an optical amplifier.