Abstract: There is provided a method of, and apparatus for, regulating radiation component (wavelength channel) power in a wavelength division multiplexed (WDM) optical communications system (10). The system (10) comprises a plurality of nodes (20) interconnected through optical waveguides (30, 40) (optical fibers). The method is characterised by: passing one or more tokens (300) around the system from node to node; adjusting nodal settings (150, 170), such as optical attenuation, applied at each node to regulate the power of WDM radiation components at the node in response to receiving one or more tokens; and repeating the method until WDM radiation component power within the system is substantially regulated.

Abstract: Provided is an apparatus for testing the performance of an optical transceiver by referencing various performance clocks provided by an OTU2 signal connection transceiver and an STM-64/OC-192 signal. The apparatus for testing performance of an optical transceiver includes: a transmitter/receiver reference clock selector for selecting one of various transmitter/receiver reference clocks provided by an STM-64/OC-192 connection optical transceiver or an OTN connection optical transceiver; a transmitter test reference clock selection switch for selecting a receiver data synchronous clock provided by the transceivers or the selected transmitter/receiver reference clock as a transmitter test reference clock; and a receiver test reference clock selection switch for selecting a transmitter supervisory clock provided by the transceivers or the selected transmitter/receiver reference clock as a receiver test reference clock.

Abstract: In each of a plurality of submarine observation apparatus (1 to n), a branching unit (63) branches fixed-wavelength light (?1) from an incoming wavelength-multiplexed light signal. An observation signal modulating unit (64) modulates the intensity of the branched fixed-wavelength light (?1) with observation information multiplexed by an observation signal multiplex unit (61). A combining unit (65) combines light signals (?2) to (?n) passing through the branching unit (63) and the fixed-wavelength light (?1a) modulated by the observation signal modulating unit (64) into a composite light signal, and outputs it to an optical fiber (12a). Therefore, in each of the plurality of submarine observation apparatus (1 to n), there is no necessity for providing a wavelength-division-multiplexing-transmission optical transmitter which requires high wavelength stability.

Abstract: An optical signal connection apparatus includes first and second routers configured to handle optical signals and electrical signals. A first node includes a first port coupled to the first router and is configured to handle a first type of optical signals associated with the first route; a first line-setting unit configured to couple the first and second nodes for data communication between the first and second nodes; a first control unit to control setting an optical communication link between the first and second nodes; and a first signal-type storage unit. A second node includes a second port coupled to the second router and configured to handle a second type of optical signals, wherein the first information is compared with second information on the second type of optical signal to determine whether the first and second communication links are compatible to each other.

Abstract: The invention concerns shutting down and restarting optical amplifiers, such as Raman amplifiers, in an optical link, depending whether the optical amplifier is a transmitting side amplifier or a receiving side amplifier. For controlling the amplifiers, at least one diagnostic signal is to be transmitted via an auxiliary optical channel in the optical link, and a number of physical events simultaneously taking place are to be taken into account to conclude whether to shut down or to restart one of the optical amplifiers.

Abstract: An apparatus for shared optical performance monitoring (OPM) is provided. A wavelength sensitive device receives light at an input port and routes it wavelength selectively to a set of output ports. To perform optical performance monitoring on the output ports, a monitoring component of each output signal is extracted, and these monitoring components are then combined. A single OPM function is then performed on the combined signal. However, with knowledge of the wavelengths that were included in each output signal, a virtual OPM function can be realized for each output port. The per port functionality can include total power per port, power per wavelength per port, variable optical attentuation, dynamic gain equalization, the latter two examples requiring feedback.

Abstract: An apparatus and method for processing a supervisory signal for optical network applications. The apparatus includes a subcarrier transmission system configured to receive a first supervisory signal and output a second supervisory signal, and an electrical-to-optical conversion system configured to receive the second supervisory signal and a first data signal and output a first optical signal. Additionally, the apparatus includes an optical-to-electrical conversion system configured to receive the first optical signal and output a first electrical signal and a second data signal, and a subcarrier reception system configured to receive the first electrical signal and output a third supervisory signal. The second supervisory signal is associated with a first subcarrier frequency. The first data signal is associated with a first data bandwidth, and the first data bandwidth includes a first data frequency. A ratio of the first subcarrier frequency to the first data frequency ranges from 0.8 to 1.

Abstract: A system and method for detecting digital symbols carried in a received optical signal. The system comprises a functional element operative to receive a stream of samples of an electrical signal derived from the received optical signal and to evaluate a non-linear function of each received sample, thereby to produce a stream of processed samples. The system also comprises a detector operative to render decisions about individual symbols present in the received optical signal on the basis of the stream of processed samples. In an embodiment, the non-linear function computes substantially the square root of each received sample.

Abstract: A method of optical communication includes providing a plurality of optical signals each associated with a distinct channel of a composite optical signal. A unique pilot tone signature is superimposed on each channel. The spectral composition of each signature includes a plurality of frequencies. In one embodiment, binary frequency shift keying at a frequency fm is used to shift between instantaneous frequencies f1 and f2 wherein f2+?f=f1??f=fc. Choosing ? ? ? f f m ? 1.1602 produces a spectrum having a plurality of dominant components at least some of which have substantially the same amplitude. A method of detecting the presence of a selected pilot tone signature having a plurality n of dominant spectral components F1 . . . Fn includes generating a power spectrum P0(f). Sk(f) is calculated as a product of a plurality of frequency shifted versions of P0(f), where k?{1 . . . n}. The existence of a dominant spectral component at Fk indicates the presence of the selected pilot tone signature.

Abstract: In an optical transmission system: a first unit generates a first optical supervisory signal being arranged on the shorter-wavelength side of main signals and containing information for determining continuity of an optical transmission line and a second optical supervisory signal arranged on the longer-wavelength side of the main signals and used for supervisory control of optical communication; a second unit generates a wavelength-multiplexed signal by optically multiplexing the main signals and the first and second optical supervisory signals, and transmits the wavelength-multiplexed signal onto the optical transmission line; a third unit receives the wavelength-multiplexed signal, and optically demultiplexes the wavelength-multiplexed signal into the main signals and the first and second optical supervisory signals; and a fourth unit determines whether or not the optical transmission line is optically continuous, based on the first optical supervisory signal, and performs supervisory control of optical com

Abstract: System and method for supervisory signal modulation on Wavelength Division Multiplex (WDM) channels wherein variable optical attenuators (VOAs) are used for amplitude modulation of the supervisory signal. Alternatively, at least two spectral bands of the supervisory signal are amplitude modulated by means of VOAs at a same frequency but in phase difference, preferably in anti-phase such that the signal resulting from the combination of the two spectral bands is maintained at a predetermined value, preferably at a minimum value and more preferably at zero value.

Abstract: Embodiments of present system encompass: a plurality of laser sources that produce a plurality of respectively different optical wavelengths; a matrix switch having a plurality of inputs operatively coupled to the plurality of laser sources, each of the plurality of inputs receiving a respective optical wavelength; and the matrix switch having an output that produces a series of interleaved pulses of the different optical wavelengths.

Abstract: A transmission apparatus that receives an optical signal by selecting any one of a plurality of provided optical signal transmission paths through protection control is configured to include a plurality of optical signal outputting sections that output the optical signals transmitted through said optical signal transmission paths respectively as optical signals having wavelengths that are different from each other, a wavelength selective optical switch capable of selectively outputting light of a wavelength corresponding to any one of the optical signals coming from the optical signal outputting sections on the basis of the frequency of a controlling frequency signal, and an optical switch controlling section that supplies said controlling frequency signal to the wavelength selective optical switch so as to output the optical signal coming from the optical signal transmission path side that is selected by said protection control among the optical signals coming from the optical signal outputting sections.

Abstract: A method for determining gain for an optical signal includes measuring a first power level that is an output power level of an optical signal at a first optical node, communicating the optical signal to a second optical node, and communicating the first power level to the second optical node in an optical supervisory channel of the optical signal. The method further includes receiving the optical signal at the second optical node, measuring a second power level of the optical signal at the second optical node, and determining a gain for the optical signal based on the first and second power levels.

Abstract: Optical communication apparatuses and optical communication methods are provided. According to one aspect, an optical communication apparatus includes a communication path configured to communicate a first signal; a signal generator configured to provide a second signal; a combiner configured to combine the first signal with the second signal to provide a composite signal; and a light source coupled with the combiner and configured to receive the composite signal and to output an optical signal corresponding to the composite signal to an optical conduit, wherein the signal generator is configured to monitor the application of the optical signal to the optical conduit and to alter the second signal responsive to the monitoring.

Abstract: An optical spike is generated at an arbitrarily selected location within an arbitrary optical link. The optical spike is generated by deriving a spike signal having a plurality of components, and launching the spike signal into the a transmitter end of the optical link. An initial phase relationship between the components is selected such that the involved signal components will be phase aligned at the selected location. In order to achieve this operation, the initial phase relationship between the components may be selected to offset dispersion induced phase changes between the transmitter end of the link and the selected location. One or more optical spikes can be generated at respective arbitrarily selected locations within the link, and may be used for performance monitoring, system control, or other purposes.

Abstract: An optical transmitter for sending supervisory data signals and line data signals as a composite optical signal through an optical fiber link is disclosed. The transmitter may take the form of a transmitter, transceiver or transponder and includes circuitry for receiving incoming line data bit rate information for varying and or controlling the modulation index by varying the supervisory carrier frequency amplitude in dependence upon the line data bit rate.

Abstract: In one embodiment, a control method, according to which a cascade of control messages is propagated between nodes of an optically transparent network, with each message being sent from a node to an adjacent downstream node to inform the latter about a control operation scheduled to be performed at the message-sending node and/or an upstream node that impacts an optical communication signal received at that downstream node. The cascade of control messages effectively creates an ad hoc control domain, in which control operations performed at various nodes of that domain can be coordinated to reduce unfavorable interactions between those control operations. By repeatedly propagating appropriate cascades of control messages through the network, control domains can be changed dynamically and adaptively to reflect any changes to the network topology, equipment, and/or traffic distribution.

Abstract: An optical wavelength division multiplex transmission system (1) for transmitting optical signals (S) on a plurality of wavelength channels has a transmitting terminal (2) and a receiving terminal (3) interconnected by a transmission line (5) with at least one, preferably a plurality of optical amplifiers (4). Each of the optical amplifiers (4) comprises a Raman amplifier (6) with at least one pump light source (8.1-8.3) for pumping the transmission line (5) upstream the optical amplifier (4). It is proposed that each optical amplifier (4) comprises a single tap coupler (11) arranged downstream of the Raman amplifier (6). Optical receiving and transmitting means (14, 15) may be connected to the transmission line (5) via the tap coupler (11) for communication of data (TX, Di) between at least the transmitting terminal (2) and the optical amplifiers (4) on an optical supervisory channel (OSC) with a given wavelength.

Abstract: A reconfigurable optical add-drop multiplexer is disclosed that enables Optical Multiplex Section (OMS) shared protection rings. The ROADM comprises a first optical supervisory module, coupled to a first amplifier module, which in turn is coupled to a first broadcast and select module, where the first broadcast and select module is coupled to both a first multiplexer/demultiplexer module and the first optical supervisory module. Each optical supervisory module has an optical tap for tapping a fraction of an outgoing OMS signal that is fed back or looped back to a 2×1 optical switch in the optical supervisory module.

Abstract: A method for optical supervisory signaling includes determining a wavelength channel status (WCS) value, a wavelength channel failure (WCF) value, and a wavelength channel lit (WCL) value for each one of multiple data channels services by an optical communication node. The method further includes communicating the values to a second optical communication node.

Abstract: A node is provided in an optical communications network that utilizes a first set of add/drop filter elements for extracting and combining optical signals that are carried on wavelength division multiplexed channels in a first wavelength band. Additionally, an extraction element and a combining element for dropping and adding a service channel associated with the wavelength division multiplexed channels. The extraction element is arranged downstream of the add/drop filter elements. The extraction and combining elements are additionally adapted to drop and add, respectively, at least one further wavelength band carrying at least one optical traffic data channel.

Abstract: The present invention relates to a method of monitoring the transmission of optical signals including a step of inserting a monitoring signal (S) more particularly suited to monitoring the quality of service. During the transmission of optical signals each carried by a predefined wavelength defining a transmission channel (Ci), said signals are grouped onto the same fiber in a band (B) of channels. The method then includes a step of simultaneously modulating said signals grouped in the band of channels using the monitoring signal to be transmitted, so that each of the signals constitutes a carrier of the monitoring signal.

Abstract: An ring type optical LAN device includes a master node and a plurality of slave nodes that are interconnected by an optical fiber cable. A plurality of optical bypass transmission lines are provided in correspondence with each one of the slave nodes. Each of the optical bypass transmission lines bypasses the corresponding one of the slave nodes. Each slave node includes an E/O converter and an optical cutoff circuit. Each of the E/O converters is controlled to flash for generating an optical signal, which is transmitted to a network. When any one of the slave nodes fails such that the corresponding E/O converter is maintained in a turned on state, the associated optical cutoff circuit forcibly switches the E/O converter to a turned off state. This suppresses a network crash caused by the failure maintaining the E/O converter in the turned on state.

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: 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: A main optical signal is wavelength-multiplexed with an optical identifier which is different in wavelength from this main optical signal, before a wavelength-demultiplexing is take place at a desired point so as to isolate the optical identifier from the main optical signal for the purpose of monitoring establishment of correct or incorrect transmission route between transmission and receiving sides based on the detected optical identifier with reference to the stored corresponding data to the relationship between the main optical signal and the optical identifier which belongs to the main optical signal, wherein the monitoring is made without any photoelectric conversion of the main optical signal and any deterioration in quality of the main optical signal.

Abstract: An optical transmission system having a supervisory system of devices disposed along an optical link. Counter-propagating Raman amplifiers are disposed along the optical link. Low-frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line. Counter-propagating Raman amplifiers amplify optical signals and do not introduce a substantial amount of attenuation on the low-frequency supervisory signals.

Abstract: An apparatus and method for processing a supervisory signal for optical network applications. The apparatus includes a subcarrier transmission system configured to receive a first supervisory signal and output a second supervisory signal, and an electrical-to-optical conversion system configured to receive the second supervisory signal and a first data signal and output a first optical signal. Additionally, the apparatus includes an optical-to-electrical conversion system configured to receive the first optical signal and output a first electrical signal and a second data signal, and a subcarrier reception system configured to receive the first electrical signal and output a third supervisory signal. The second supervisory signal is associated with a first subcarrier frequency. The first data signal is associated with a first data bandwidth, and the first data bandwidth includes a first data frequency. A ratio of the first subcarrier frequency to the first data frequency ranges from 0.8 to 1.

Abstract: An apparatus for accelerating assessment of an optical transmission system using Bit Error Rate (BER) tests calculates Q-factors for at least two different extinction ratios from measured test BER values, and extrapolates to determine a Q-factor for an operational extinction ratio, whereby the operational BER value for the operational extinction ratio can be calculated.

Abstract: A method for the automatic provisioning of a network element (NE) includes receiving a client signal at a tunable optical translator (OT) in the NE, determining the set of channels supported by the OT that are able to correspond to the client signal, eliminating the channels that have connections, that may be present on a line side of the NE in a laser off scan process, or that have not been equipped or otherwise provisioned for transmission, tuning the OT to each of the remaining channels and determining the optical power level of each channel on a line side of the NE in a laser on scan process. Subsequently, the channel with the highest power level is selected to transmit the client signal and associations for a point to point connection for that channel are added for that OT to a database of associations for the NE.

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: An optical transmission system having a supervisory system of devices disposed along an optical link. Co-propagating Raman amplifiers are disposed along the optical link. Low frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line or by the same co-propagating Raman amplifiers. Regeneration of the supervisory signal is provided in at least one device disposed along the optical link in order to counteract attenuation introduced on the supervisory signal by the co-propagating Raman amplifiers.

Abstract: The invention concerns a transmitter-receiver device (A, B) which comprises a receiver unit (RXA) arranged to receive light and optical signals from a transmitter unit (TXA) arranged to transmit light and optical signals. The device also comprises a supervising unit (CUA) which prevents the transmitter unit (TXA) from continuously transmitting light when the supervising unit (CUA) detects that the receiver unit (RXA) does not receive light. The supervising unit (CUA) is arranged to, when it detects that the receiver unit (RXA) does not receive light, change to a test mode where the transmitter unit (TXA) is controlled to intermittently transmit short light pulses the supervising unit has an output (109) where a status signal indicates whether the transmitter-receiver device is in said test mode. The invention also concerns a communication system which comprising at least two such transmitter-receiver devices.

Abstract: A method of coordinating channel power information in a wavelength division multiplexed (WDM) optical communication system is disclosed. The method determines weighting values for each channel of the WDM signal based on channel launch powers. A source data object may used to transmit the channel weights and channel information from network elements having channel sources such as transmitters to downstream network elements. Block data objects may be used to identify channel blocks in the system and are also transmitted downstream. The source and block objects may be correlated to determine which channels are in-view at a particular point in the network and thereby determine which of the channel weights should be used as a basis for managing the network at that point. A WDM system is also disclosed which may actively control channel launch powers and feed the adjusted launch powers into the method of coordinating channel power information.

Abstract: A network diagnostic system is provided for an optical transport network having a plurality of network elements. The network diagnostic system includes at least one network element having a network diagnostic operation integrated therein and operable to perform the network diagnostic operation, thereby determining a network performance characteristic associated with the optical transport network; a wayside communication subsystem interconnecting the network elements residing in the optical transport network; and a network diagnostic device in data communication with the at least one network element and operable to initiate the network diagnostic operation at the network element.

Abstract: Communicating a signal includes receiving the signal at a primary device of a switching system, where the primary device is associated with a primary path along which the signal is propagating. A primary overmodulation signal associated with the primary path is generated. The absence of the primary overmodulation signal is detected, and an operating signal is sent from the primary device to a secondary device of the switching system, where the secondary device is associated with a secondary path. The operating signal operates to initiate propagation of the signal along the secondary path.

Abstract: Techniques for providing normal operation and service restoration capability in the event of failure of terminal equipment or transmission media in a heterogeneous network, such as a hybrid network containing single- and multi-wavelength lightwave communications systems. An optical switching node (OSN) is placed at each node in the ring network to provide the required connections between various fibers and terminal equipment, but having switch states that allow signals on the protection fibers to bypass the terminal equipment at that node. Ring-switched signals propagate around the ring on protection fibers without encountering the terminal equipment at the intervening nodes. To the extent that the protection fiber links between any given pair of nodes are incapable of supporting all the relevant communication regimes, such links are modified to provide such support.

Abstract: An optical transmission apparatus, an optical repeater using the optical transmission apparatus, and an optical cross-connect equipment for controlling switches depending on supervisory information, comprising: a doped fiber for amplifying an optical signal of wavelength ?d; a wavelength multiplexer for outputting a pumping light to the doped fiber; a wavelength multiplexer for multiplexing an amplified optical signal and a supervisory optical signal to as to output it to an optical fiber at downstream side; a pumping and supervisory light source; an optical coupler for distributing the light from the light source at a ratio of N:1 to the wavelength multiplexers; and a driver for controlling the light source by adding the supervisory information and a direct current signal.

Abstract: In a communication system, channel operating parameter carrier frequencies are located in the vicinity of data nulls in a data spectrum. The operating parameter carriers are summed with the data signal. At the receiver, the operating parameter carrier frequencies are recovered by demodulation techniques, and the operating parameters are recovered and processed.

Abstract: A dedicated IP-based wavelength routing/signaling control plane for optically switched network, is provided. The IP-based control plane is an out-band routing/signaling mechanism and does not require optical-electrical-optical (OEO) conversion. The control plane can accommodate the various network topologies of the data plane and if one of the supervisory, or control channel fails, the IP-based control plane can re-route the traffic to destination. Using non-broadcasting addressable protocols the control plane selects a different path to re-direct the control information without declaring the whole communications trail down and without affecting the client traffic over the data path.

Abstract: An optical network includes an optical ring and a plurality of add/drop nodes coupled to the optical ring. Each of the add/drop nodes is operable to passively add and drop one or more traffic streams to and from the optical ring, and each traffic stream comprises a channel. A hub node also coupled to the optical ring is operable to selectively pass and terminate individual traffic streams.

Abstract: An optical transmission system accomplishes optical transmission over a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission over a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-toelectric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, and with no use of any optical booster amplifier and optical preamplifier in multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.

Abstract: A system and method for a transparent WDM metro ring architecture in which optics enables simultaneous provisioning of dedicated wavelengths for high-end user terminals, while low-end user terminals share wavelengths on “virtual rings”. All wavelengths are sourced by the network and remotely modulated at customer “End Stations” by low cost semiconductor optical amplifiers, which also serve as transmission amplifiers. The transparent WDM metro ring architecture permits the communication of information and comprises a fiber optical feeder ring, at least one fiber optical distribution ring, a network node (NN), at least one access node (AN) said network node and said at least one access node connected via said fiber optical feeder ring and at least one end station (ES) connected via said fiber optical distribution ring to said at least one access node, wherein said user is attached to said at least one end station.

Abstract: An optical repeating system includes an optical transmitter and a plurality of optical amplifying repeaters. The optical transmitter specifies a part or all of the optical amplifying repeaters, and transmits a supervisory command to the specified optical amplifying repeaters as a first sub-signal via an uplink or downlink optical transmission line. The supervisory command is a command to supervise internal circuits of the optical amplifying repeaters. Receiving the supervisory command addressed thereto via the uplink or downlink optical transmission line, the optical amplifying repeaters each transmit a supervisory signal indicating a supervisory result corresponding to the supervisory command to optical receivers via the uplink and downlink optical transmission lines as a second sub-signal. The optical system can reduce the time take to acquire the supervisory information about the plurality of the optical amplifying repeaters.

Abstract: A method is disclosed for optimizing optical channel signal demultiplexing in a monolithic receiver photonic integrated circuit (RxPIC) chip by providing an integrated channel signal demultiplexing with multiple waveguide input verniers provided to an WDM signal demultiplexer. The RxPIC chip may optionally include an integrated amplifier in at least some of the waveguide input verniers. The RxPIC chip may be comprised of, in monolithic form, a plurality of optional semiconductor optical amplifiers (SOAs) at the input of the chip to receive a WDM signal from an optical link which is provided along a plurality of waveguide input verniers to an integrated optical demultiplexer, such as, but not limited to, an arrayed waveguide grating (AWG), as a WDM signal demultiplexer. Thus, optical outputs from the respective semiconductor laser amplifiers are provided as vernier inputs to the optical demultiplexer forming a plurality of input verniers at the input to the optical demultiplexer.

Abstract: A system and method for improving the transmission quality of a WDM optical communications system begins by determining the bit-error rate for an optical channel before forward error correction is performed at a receiver. The pre-corrective bit-error rate is fed back through a feed back circuit that includes a parameter adjustment module which adjusts an optical signal parameter based on the bit-error rate. As examples, the signal parameter may be a channel power, dispersion, signal wavelength, the chirp or eye shape of an optical signal. The feedback circuit may also adjust various parameters within the WDM system, including amplifier gain, attenuation, and power for one or more channels in the system. By adjusting these parameters based on a pre-corrective bit-error rate, transmission quality is improved and costs are lowered through a reduction in hardware.

Abstract: A Raman amplifier repeater comprising a Raman excitation light production/answer signal superimposition unit for producing a first reply signal for a down-direction line with respect to a monitor control command, an answer signal production unit for producing a second reply signal with respect to the monitor control command, and a command reply switch for selectively using the first reply signal when an optical signal passing through a down-direction line on a second terminal station side is inputted as an answer signal with respect to the monitor control command and the second reply signal when the optical signal is not inputted through the second terminal station side down-direction line. With this configuration, high-quality monitor control is feasible even if a disconnection/break trouble occurs in an optical fiber in conducting the optical amplification repeating by the Raman amplification.

Abstract: Disclosed herein is a signal transmission method in a wavelength-division-multiplex (WDM) transmission system. The WDM transmission system comprises a first WDM terminal for transmitting a WDM signal, a second WDM terminal for receiving the WDM signal, and an optical add-drop multiplexer (OADM) node for transmitting to a network element an optical signal of a specific wavelength of the WDM signal which is transmitted between the first and second WDM terminals. The WDM signal is transmitted from the first WDM terminal to the second WDM terminal regardless of whether an optical signal is added or dropped at the OADM node. The network element employs an optical signal of an idle wavelength of the WDM signal that has no transmission data, to transmit another transmission data that is transmitted by the network element.

Abstract: A method and system for multi-level power management in an optical network is provided. They include three levels of power management. The first level of power management dynamically changes equipment settings in each module of equipment so that required module setpoint values in each module are achieved. The second level of power management determines module setpoint values for each module of equipment within each node in the optical link so that required node setpoint values are achieved. The third level of power management determines node setpoint values at each node in the optical link so that the optical link meets predetermined power specifications. If any of the three levels cannot achieve the required setpoint values, an error signal is generated by that level of power management and sent to the level of power management above it, thus initiating a higher level of power management.