Abstract: This application discloses a submarine cable fault determining method and apparatus for realizing detecting whether a fault occurs to a submarine cable, without depending on TTE. The submarine cable fault determining method includes: receiving, by a network management system, first detection information from a first device during a first preset time, and receiving second detection information from a second device during a second preset time, where the second detection information is used to indicate whether the second device receives a first heartbeat signal from the first device through a submarine cable, and the first detection information is used to indicate whether the first device receives a second heartbeat signal from the second device through the submarine cable; and determining, by the network management system based on the first detection information and the second detection information, whether a fault occurs to the submarine cable between the first device and the second device.

Abstract: There is provided mechanisms for utility communications. A method is performed by a transmitter. The method includes superimposing a control and protection signal for utility communications on top of an existing optical signal transmitted over an optical fiber to form a composite signal, wherein the control and protection signal has lower bit rate than the existing optical signal. The method includes obtaining feedback by draining a portion of the composite signal from the optical fiber. The method includes adjusting amplitude of the control and protection signal according to the portion of the composite signal.

Abstract: A failure is detected in a middle path of communication information received from one communication network. When the communication information received from the one communication network is relayed to another communication network, information is output to the other communication network by storing information about the failure detected from the communication information received from the one communication network in a header of communication information to be output to the other communication network.

Abstract: An optical transceiver module includes N light sources, N light detectors, a bidirectional fiber port, and an optical network having 2N?1 wavelength-selective elements. The number 2N represents the total number of transmit and receive channels in a bidirectional system in which transmit and receive signals corresponding to the transmit and receive channels. Each light source corresponds to one transmit channel and emits an optical transmit signal having a unique transmit wavelength. Each light detector corresponds to one receive channel and detects an optical receive signal having a unique receive wavelength. The optical network couples each light source to the bidirectional fiber port via a corresponding transmit path through the optical network. The optical network further couples each light detector to the bidirectional fiber port via a corresponding receive path through the optical network. Each transmit and receive path includes some of the wavelength-selective elements.

Abstract: An optical amplification apparatus includes an optical amplification medium configured to receive a first light signal from an end of the optical amplification medium and a second light signal from the other end of the optical amplification medium in opposite directions, the first and second light signals being branched from a light signal, an excitation light source configured to supply excitation light to the optical amplification medium through a multiplexer, a monitor configured to monitor the first and second light signals input to the optical amplification medium, respectively and to output monitoring signals respectively, and a controller configured to control the excitation light source in accordance with the monitoring signals.

Abstract: In an optical node, a transmitter produces an optical supervisory signal for supervising an optical network, a processor is operative to control a power level of the optical supervisory signal according to a per-wavelength power level of an optical communication signal when the optical node has no post amplifiers, and a multiplexer combines the controlled optical supervisory signal with the optical communication signal to be transmitted to another optical node located downstream.

Abstract: A remote enclosure houses multiple subsystems. A first subsystem is coupled to a central office over a high-speed communication channel such as an OC-3 channel. The first subsystem extracts a downstream message from a first embedded operations channel included in the high-speed communication channel. The first subsystem also, when the downstream message is targeted to a first unit included in the first subsystem, forwards the message to a unit that processes the message for the first unit. When the message is not targeted to any unit included in the first subsystem, the first subsystem forwards the downstream message to another subsystem housed within the remote enclosure via a second embedded operations channel included in a second communication channel. The second subsystem is subtended from the first subsystem and is connected thereto by the second communication channel.

Abstract: A method, an apparatus, and a system for transmitting information in a passive optical network are provided. The method mainly includes: obtaining OAM information that an RE device needs to report to an OLT device, performing modulation processing, according to the OAM information, on a downlink optical signal sent by the OLT device, and returning the downlink optical signal after the modulation processing to the OLT device; or, obtaining OAM information that an OLT device needs to deliver to an RE device, performing modulation processing, according to the OAM information, on a downlink optical signal sent by the OLT device to the RE device, and sending the downlink optical signal after the modulation processing to the RE device.

Abstract: An optical transmission system includes a first node and a second node, the first node includes a first optical amplifier which outputs a signal to the second node through a first transmission line and a first monitoring unit, the second node includes a monitor which monitors a signal from the first transmission line, a second optical amplifier which outputs a signal to the first node through a second transmission line and a second monitoring unit, upon detecting disconnection from the first transmission line, the second monitoring unit transmits a notification for making power of the first optical amplifier reduced, upon receipt of the notification, the first monitoring unit reduces power of the first optical amplifier, and transmits a completion notification to the second monitoring unit, and upon not receiving the completion notification even after expiration of an allowed time, the second monitoring unit reduces power of the second optical amplifier.

Abstract: An optical transmission device according to the present invention comprises: a Raman amplification means; a main signal light sending means which sends first main signal light; a communication interruption detection light monitoring means which sends a first signal if it cannot detect communication interruption detection light; a main signal light monitoring means which sends a second signal if it cannot detect second main signal light; a light monitoring signal analysis means which sends a result of its analysis of a light monitoring signal as a third signal in a predetermined period of time; and a control means which makes the Raman amplification means suspend the generation of the excitation light, if it cannot receive the third signal even after the elapse of the predetermined period of time in the state it has received the first signal and has not received the second signal, and stops sending of the first main signal light from the main signal light sending means when receiving the second signal further.

Abstract: A system for signaling between elements in an undersea optical communication system including a cable signal generator. The signal generator includes line current modulation circuitry configured to impart modulation in line current provided on a power conductor of the transmission cable. A method of signaling between elements in an undersea optical communication system includes modulating a line current through an element and detecting the modulated current.

Abstract: Embodiments of the present invention include systems and methods for accessing the digital diagnostic data and controller data of a remote transceiver module via the diagnostic port of a local transceiver. The invention involves modulating high-speed data and out-of-band data as a double modulated signal, wherein the out-of-band data includes the remote transceiver controller and digital diagnostic data, which is subsequently accessible by an external user device from the diagnostic port of the local transceiver.

Abstract: An optical transmission device includes a signal generator configured to generate a first signal corresponding to an amount of residual chromatic dispersion that occurs in a light signal transmitted from the optical transmission device to a downstream device, and a superimposer configured to superimpose the first signal on the light signal transmitted from the optical transmission device and transmit the light signal superimposed by the first signal to the downstream device.

Abstract: An apparatus comprising one or more optical amplifiers coupled to an optical link and configured to amplify a plurality of Wavelength Division Multiplexing (WDM) channels that are transmitted at a plurality of wavelengths on the optical link, and a processor coupled to the optical link and configured to add, delete, or both a plurality of WDM channels in the optical link based on an allowed power ratio indication for the WDM channels, wherein the allowed power ratio indication is calculated based on a plurality of gain change representations for the WDM channels at a plurality of power ratios and on a link budget requirement for the optical link.

Abstract: A data center for executing a data processing application includes processing units, sub-units or servers. Each of the processing units, sub-units or servers can execute a part or all of the data processing application. The processing units, sub-units or servers are electrical disjoint with respect to data communications, but can communicate with each other over free space optical links.

Abstract: An optical transmission apparatus includes a reception part for receiving a wavelength division multiplexed (WDM) signal reached via optical amplifiers; a measuring part for measuring an optical power level of each wavelength of the WDM signal received by the reception part; a determination part for determining whether an amount of tilt of the WDM signal calculated based on measurement results of the measuring part is suitable or not; an operation part for calculating the tilt correction amount to be applied to tilt correction processing performed by the optical amplifiers if the amount of tilt of the WDM signal is not suitable; and a notification part for notifying the optical amplifiers of the tilt correction amount.

Abstract: A method for arranging relay stations in an optical transmission system including relay stations arranged so that optical signals at a first transmission speed can be transmitted from a transmission end to a reception end, includes: judging whether a transmission of optical signals at a second transmission speed different from the first transmission speed in a section connecting arbitrary two of the relay stations where a regenerative repeater station capable of regenerating optical signals can be arranged is possible; determining a combination of sections judged to be capable of performing transmission that enables a transmission of optical signals from the transmission end to the reception end; and making both ends of respective sections of the determined combination be the relay stations where the regenerative repeater station is arranged, wherein the judging includes a judgment condition which is satisfied in a section including sections but unsatisfied in one of the sections.

Abstract: An optical transmission apparatus is provided with an optical filter on a transmission line between a reception end of a transmission line and an OSC receiver. The optical filter has transmission characteristics such as to pass main signal light and optical supervisory channel light (OSC light), and to cut off noise light contained in at least one end portion band on a short wavelength side and a long wavelength side of an OSC transmission band used for reception of OSC light. By such a configuration, even in a case where the OSC light is Raman amplified and transmitted, the influence of noise light due to Raman amplification can be reduced, and OSC light can be received reliably, enabling high dependability to be realized.

Abstract: An optical add/drop multiplexer (OADM) and system incorporating the same for maintaining loading of WDM channels with loading signals or information signals when signals are added or dropped. The OADM may include reconfigurable band pass filters having a transmittance characteristic controllable using a command signal. Selective filtering of loading signals and/or information signals received from branch and trunk paths allows an output WDM signal including information signals on utilized channels and loading signals on all unutilized channels.

Abstract: In an optical transmission apparatus, a unit includes a first connection section, a second connection section, a branching section, a first detection section, and a second detection section. The first connection section connects to a first component. The second connection section connects to a second component. The branching section is disposed at a preceding stage of the second connection section and outputs signal light to the first component through the first connection section. The first detection section determines whether the first component receives the signal light output from the branching section. The second detection section is disposed at a subsequent stage of the second connection section and detects the signal light.

Abstract: An optical communication system includes an optical-signal transmission unit transmitting an existing optical signal and a low-rate-signal superimposition unit superimposing a low-rate signal on the existing optical signal by intensity modulation. It further includes: a low-rate-signal extraction unit that extracts the low-rate signal from the existing optical signal on which the low-rate signal is superimposed and converts the extracted low-rate signal into a low-rate electric signal; an add-on optical-signal transmission unit that transmits an add-on optical signal; a low-rate-signal superimposition unit that superimposes a low-rate signal on the add-on optical signal by the intensity modulation based on the low-rate electric signal; and a repeater that repeats the add-on optical signal on which the low-rate signal is superimposed, to a transmission destination.

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

Abstract: A system for transmitting a plurality of data channels and an optical service channel through an optical fiber link of a Wavelength Division Multiplexed (WDM) optical communications system. The system comprises a first transmitter at a first end of the optical fiber link, for transmitting the data channels as a wavelength division multiplexed optical signal through the optical fiber link in a first direction. A second transmitter is connected at a second end of the optical fiber link, for transmitting the optical service channel through the optical fiber link in a second direction opposite to the first direction.

Abstract: The distributed Raman amplifier monitors an OSNR of each channel in a WDM light which has been propagated through a transmission path to be Raman amplified, and thereafter, is amplified by an optical amplifier in an optical repeating node; judges whether a monitor value of the OSNR is larger or smaller than a previously set target value thereof; and feedback controls a driving state of a pumping light source which supplies a Raman pumping light to the transmission path, based on the judgment result. The optical communication system comprises the above distributed Raman amplifier in each repeating span thereof, and performs a pumping light control of the distributed Raman amplifier corresponding to the repeating span selected based on the OSNR in each distributed Raman amplifier and the monitor result of span loss. As a result, it becomes possible to effectively improve the OSNR of each channel in the WDM light, and also, to reduce the power consumption.

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: The pulse light source according to the present invention comprises: a seed pulse generator 1 for outputting an input pulse 10 as a seed pulse; a pulse amplifier 2; and a dispersion compensator 3 for dispersion compensating a light pulse output from the pulse amplifier 2. Moreover, the pulse amplifier 2 comprises a normal dispersion medium (DCF 4) and an amplification medium (EDF 5) that are multistage-connected alternately, for changing the input pulse 10 to a light pulse having a linear chirp and outputting the light pulse. Furthermore, an absolute value of the dispersion of the DCF 4 becomes to be larger than the absolute value of the dispersion of the EDF 5.

Abstract: An ultra-long fiber-optic transmission system is configured in accordance with the current telecom standards and particularly advantageous for transmission data at a long distance which may exceed 400 km between adjacent nodes. The disclosed system has at least one intermediate amplifying node provided with a supervisory optical channel (SOC) which carries information between spaced nodes about the multi-wavelength optical signal as well as remote conditions at the optical terminal or regeneration site. The SOC comprises a transponder operative to select the direction in which an optical supervisory signal OSS, carrying information about the fiber break and malfunction of WDM channels, is transmitted along the SOC. The transponder further includes a receiver operative to measure the power of incoming OSS signal, which is indicative of the power of the transmitted and amplified WDM signal, and a Raman controller.

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: A method and apparatus for compensating for channel depletion of a multi-channel signal in an optical link or optical network comprising a chain of optical amplifiers. The method comprises determining channel depletion for each amplifier from the power of the input signal to the optical amplifier and the power of the output signal from the previous amplifier. Each amplifier is then controlled to amplify the signal to a level equal to the nominal (ideal) power plus the calculated channel depletion for that amplifier.

Abstract: In one embodiment, techniques provide a mechanism for tracking wavelengths in a DWDM network. In particular, embodiments of the present invention also provide for connection tracking using a slowly modulated pilot tone in a DWDM network without dedicated hardware for the generation and the diction of the tone.

Abstract: The present invention aims at providing a technique capable of supervising and controlling optical repeaters, without affecting transmission characteristics and wavelength bands of signal lights, by utilizing the Raman effect. To this end, the present invention provides a supervisory controlling system of an optical repeater, in an optical amplifying-and-repeating transmission system for amplifying and repeatingly transmitting signal light propagated through an optical transmission path by the optical repeater, wherein the supervisory control signal light is amplified due to the Raman effect by the signal light acting as excitation light in an optical transmission path (Raman amplifying medium), to thereby supervise and control the optical repeater in accordance with the thus Raman amplified supervisory control signal light.

Abstract: A method for laser safety protection in an optical communication system includes: a downstream station detecting whether an identification signal loaded by an upstream station on a main optical channel in a direction from the upstream station to the downstream station, exist on the main optical channel; if the identification signal is not detected, the downstream station executing a scheduled safety protection procedure. Methods for loading an identification signal on a main optical channel in an optical communication system and an optical amplifier of laser safety protection, which implement loading the identification signal by controlling the change of pump light of optical amplifier or the wave motion of signal light of main optical channel, are also provided. The solution makes it possible to reliably detect a fiber failure when RAMAN amplifiers or remotely-pumped amplifiers exist, thereby implementing laser safety protection.

Abstract: A robust and redundant status link is established by a first multi-channel optoelectronic device with a second multi-channel optoelectronic device in a multi-channel communication link. Transmitter bias currents are effectively modulated with a status link modulation signal representative of status data and subsequently modulated with primary data modulation signals. The resulting signals are transformed into optical signals and transmitted over the link as main communication links combined with a status link. At the second device, the optical signals are received and converted to electrical signals. The receipt of the optical signals creates multiple receiver bias currents, which may be monitored to detect the status link modulation signal. The second device may adjust various operating parameters in response to the information conveyed by the status link.

Abstract: In a wavelength-division multiplexing communications system including a plurality of optical transmission devices having an optical amplifier, downstream optical transmission devices transmit gain wavelength characteristic information of an optical amplifier in each of the downstream optical transmission devices to an upstream optical transmission device. The upstream optical transmission device controls gain wavelength characteristics on the basis of the received gain wavelength characteristic information.

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: 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: An optical repeater device of the present invention comprises: a preamble compensating circuit 53, for taking out a normal data signal from burst signals propagating through a communication transmission path, and for adding a preamble signal before and/or after the data signal. Furthermore, the preamble compensating circuit 53 comprises: a detector circuit 53a, for inputting the burst signal, and for outputting only the normal data signal; a buffer circuit 53b, for storing the data signal output from the detector circuit 53a, and for outputting thereof; a preamble signal generation circuit 53d, for outputting at least one type of the preamble signal; and an data output select circuit 53e, for outputting the data signal at the time of the data signal input from the buffer circuit 53b, and for outputting the preamble signal from the preamble signal generation circuit 53d at any other time thereof.

Abstract: During initial start-up of an optical communication system, an ASE reference span loss is calculated based on transmitting power and received power of ASE light generated by an optical amplifier, and an OSC reference span loss is calculated based on the transmitting power and the received power of OSC light. During normal operation of the optical communication system, a span loss is calculated using the OSC light, and an amount of change in the span loss representing a difference between the span loss and the OSC reference span loss is calculated. A current span loss between a transmitting station and a receiving station is calculated by adding the amount of change in the span loss to the ASE reference span loss.

Abstract: The present invention aims at providing a technique capable of supervising and controlling optical repeaters, without affecting transmission characteristics and wavelength bands of signal lights, by utilizing the Raman effect. To this end, the present invention provides a supervisory controlling system of an optical repeater, in an optical amplifying-and-repeating transmission system for amplifying and repeatingly transmitting signal light propagated through an optical transmission path by the optical repeater, wherein the supervisory control signal light is amplified due to the Raman effect by the signal light acting as excitation light in an optical transmission path (Raman amplifying medium), to thereby supervise and control the optical repeater in accordance with the thus Raman amplified supervisory control signal light.

Abstract: An automated optical transport system is provided which provides for automatic discovery of system components, automatic inventory of system components, automatic topology detection, automatic provisioning of channels, and automatic characterization and tuning of system components and fiber. The invention provides automation capability through inclusion of management card capabilities at each station which communicates through a reverse propagating service channel. Dynamic and propagation direction independent segments are provided in conjunction with a token-based scheme to repeatedly tune, update and monitor the transport system.

Abstract: Methods and apparatus for optical-power control in an optical network employing wavelength-division multiplexed (WDM) optical-fiber links are devised to circumvent the effect of crosstalk caused by optical-power scattering. Each carrier signal is amplitude-modulated by an identifying tone, with the power of an identifying tone having a predetermined ratio to the power of its carrier signal. A fiber span within an optical-fiber link is tapped at a preferred monitoring point, and the power spectrum of the envelope of the tapped optical signal is measured. To estimate an individual carrier power, a temporary gain is applied and the power of a corresponding tone is measured. To control optical power of each wavelength carrier in several spans in the network, a network controller selects an order of processing the spans of interest, and selects the order of processing of each channel within each span.

Abstract: The invention provides for optical circulators which redirect light from port to port sequentially in one direction used to separate traffic in a bidirectional optical fiber transmission system. The invention provides for using two optical circulators in each span of bidirectional fiber so that the OSC channel can be transmitted in one direction opposite to the WDM channels. The invention also provides for a gigabit Ethernet path between chassis which is utilized for control traffic and customer traffic. The invention is placed in a non-critical region of the optical spectrum and is independent of all other chassis equipment. The invention also provides the advantage in alternate embodiments of providing the option of a second counter propagating WDM channel being transmitted along with the OSC to provide additional system capacity. The invention also provides the advantage in an alternate embodiment of allowing the OSC to be amplified through a raman source without the need of complete system retrofit.

Abstract: An automated optical transport system is provided which provides for automatic discovery of system components, automatic inventory of system components, automatic topology detection, automatic provisioning of channels, and automatic characterization and tuning of system components and fiber. The invention provides automation capability through inclusion of management card capabilities at each station which communicates through a reverse propagating service channel. Dynamic and propagation direction independent segments are provided in conjunction with a token-based scheme to repeatedly tune, update and monitor the transport system.

Abstract: A WDM system includes a plurality of P to P WDM systems connected for wavelength-multiplexing optical signals of a plurality of wavelengths, transmitting them to a transmission path, transmitting wavelength-division multiplexed light while performing amplification by using optical AMP in the transmission path, and subjecting the wavelength-division multiplexed light to wavelength isolation at the reception side. An OSC which is a monitoring control signal such as a normal optical signal is used closely within one P to P WDM system. However, by transmitting and receiving the OSC between a plurality of P to P WDM systems, it is possible to solve a problem at the system rise. Moreover, since accumulative OSNR data is transmitted up to the P to P WDM system of the final stage, it is possible to detect an accurate OSNR value and a leak ASE light quantity at the end side.

Abstract: An optical transmission system comprises two optical fibers carrying optical signal traffic between two terminals, and a plurality of optical repeaters coupled to the two fibers each repeater having a permanently connected passive high loss loop back circuit between the two fibers. One terminal includes a transmitter, which launches a pulsed supervisory signal on a dedicated supervisory wavelength into one optical fiber, and a receiver, which detects a portion of the supervisory signal looped back from each repeater in order to identify the existence and location of faults in the transmission system. The pulsed supervisory signal is of sufficiently short duration such that portions of the signal returned from each repeater do not overlap with one another and interference with the counter-propagating traffic is avoided by utilizing a dedicated supervisory wavelength. Each return pulse is integrated sequentially by a single detector and processed by heterodyne reception and synchronous demodulation.

Abstract: The present invention aims at providing a technique capable of supervising and controlling optical repeaters, without affecting transmission characteristics and wavelength bands of signal lights, by utilizing the Raman effect. To this end, the present invention provides a supervisory controlling system of an optical repeater, in an optical amplifying-and-repeating transmission system for amplifying and repeatingly transmitting signal light propagated through an optical transmission path by the optical repeater, wherein the supervisory control signal light is amplified due to the Raman effect by the signal light acting as excitation light in an optical transmission path (Raman amplifying medium), to thereby supervise and control the optical repeater in accordance with the thus Raman amplified supervisory control signal light.

Abstract: An optical transmission apparatus for amplifying and relaying a wavelength-division-multiplexed optical signal includes (1) a variation-detecting unit which detects varying speed of input power of the wavelength-division-multiplexed optical signal and compares the varying speed with a set value, (2) an optical amplifying unit which amplifies the wavelength-division-multiplexed optical signal at a fixed amount of amplification, (3) a variable optical attenuating unit which variably attenuates the wavelength-division-multiplexed optical signal, (4) and a controlling unit which controls attenuation amount of the variable optical attenuating unit in accordance with the varying speed.

Abstract: A node for managing an optical signal includes a first system optics card for providing channels to be transported over a first optical transport link and receives channels from a second optical transport link. Channels received over the second optical transport link are provided to an optical converter card for transport to a client device, for feedback onto the first optical transport link, or pass through to a second system optics card of the node. The first system optics card is capable of dropping network channels from the second transport link to associated client devices through optical converter cards and add client channels received from optical converter cards to the first transport link. The first system optics card may include one or more express input and output ports to couple with one or more other system optics cards in order to provide multiple degrees of communication capability.