Abstract: An optical communication system includes a plurality of optical channels, each of which passes a single optical wavelength signal. Each of the plurality of optical channels includes an optical amplifier which is controlled to operate at a predetermined output power level independent of channel wavelength and input power level by operating each optical amplifier in a saturation mode. Pumping power for operating each optical amplifier in the saturation mode is supplied from shared optical pumps or a plurality of one per channel optical pumps.

Abstract: A method includes taking backscattering light of a first wavelength in a first direction of a first transmission line and coupling the same so that the light may travel in a second direction of a second transmission line; taking a second wavelength in the first direction of the first transmission line and coupling the same so that the second wavelength may travel in the first direction of the second transmission line; taking backscattering light of the first wavelength in the second direction of the second transmission line and coupling the same so that the backscattering light may travel in the first direction of the first transmission line; taking the second wavelength in the second direction of the second transmission line and coupling the same so that the second wavelength may travel in the second direction of the first transmission line.

Abstract: In Raman gain slope measurement method and device measures Raman gain slope which is a value obtained by normalizing a gain generated by Raman amplification caused by pump light incident on an optical fiber by optical power of the pump light in question. The method and device measures the power of noise light and operates based on a relationship between the optical power of pump light incident on an optical fiber and the optical power of the measured noise light generated by the application of the pump light, Raman gain slope of the optical fiber in question is thus calculated.

Abstract: A request method for performing optical power management to accomplish planned addition and removal of wavelengths in an optical communications system is disclosed, wherein each wavelength has a path of transmission through the system. The method comprises communicating a request for a power ramp to at least one path network component in the path, determining that the path network component has made preparations for the power ramp, and performing a power ramp in response to the determination. Further, a response method for performing power management to accomplish planned addition and removal of wavelengths in an optical communications system is disclosed, wherein each wavelength has a path of transmission through the system. The method comprises receiving a request for a power ramp, making preparations for the power ramp, determining that the power ramp has been completed, and resuming normal operation in response to the determination.

Abstract: In an optical transmission system, an optical terminal transmits a plurality of tone signals corresponding to a plurality of gain bands, where the frequencies of the plurality of tone signals are different from each other, and each of the plurality of tone signals has a characteristic which is varied according to detected power of optical signals in the corresponding gain band. Each optical repeater receives the plurality of tone signals, extracts the characteristics of the plurality of tone signals, and compares a signal representing each characteristic with a reference signal. The optical repeater controls the gains of optical amplification in the plurality of gain bands based on the comparison result so as to equalize the gains in the plurality of gain bands.

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

Abstract: The invention provides a method for measuring transmission loss in an optical transmission line between a master station and a slave station, and also a slave station, a master station and a star network communication system using this method. Power of an optical signal is measured at a second end of an optical transmission line connected with an added slave station and at a first end other than the second end. The result at the first end is stored in a storing unit or transmitted to an incorporating unit by a transferring unit. The incorporating unit incorporates the result into a downstream optical signal, which is transmitted to the slave station. In the slave station an information extracting unit extracts the result from the downstream optical signal, and a processing unit calculates a difference between the measurement results of the first and second ends to obtain transmission loss therebetween.

Abstract: An optoelectronic receiver having a variable transfer function to compensate for operational condition change. The receiver comprises a linear circuit having a tunable filter. A control circuit provides a signal to the tunable filter. The control circuit is connected to one or more sensors which sense one or more operational conditions. The control circuit signal is a function of the one or more sensed operational conditions. The control signal is input to the tunable filter which adjusts the linear circuit's transfer function based on the control signal. Further disclosed are an integrated circuit and optical communication system having the inventive optoelectronic receiver. A method for adjusting an optoelectronic signal in a receiver is also disclosed.

Abstract: An optical monitoring apparatus based on the scanning of the gain profile of erbium-doped fiber amplifiers (EDFA) and applied in a wavelength division multiplexing network has been proposed and experimentally demonstrated. The EDFA with an injected saturated tone can provide variable gain or loss profile by controlling the pump power. The components used in the present optical monitoring apparatus for use in a wavelength division multiplexing network are easily available and cost-effective, valuable for monitoring frequency and power of a WDM optical communication system, and capable of greatly enhancing resolution of monitoring frequency spectrum for the optical fiber network system.

Abstract: A system for managing signals in an optical network is provided. When a signal is originated by a source node for transmission to a destination node, the source node generates a message. Upon receiving this message, the destination node responds by sending an acknowledgment. Intermediate nodes examine these messages, allowing the nodes to obtain information which is used to take appropriate actions. A node is able to detect a switching event and the output power levels of signals leaving the node are maintained at a predetermined level. When transmission components transmitting a signal are powered up, a sequence of messages is exchanged, allowing the nodes to activate their transmission components in a sequential manner, avoiding signal level interference. Another sequence of messages is exchanged during protection line switching, allowing the nodes to adjust their respective transmission components in a sequential manner so as to avoid a “ringing” effect.

Abstract: A repeater, useable for connecting switches in a data communication network, is provided in a distributed and/or modular fashion. The repeater includes a plurality of separate and distinct components or modules connected to or at least partially housed in, the various switches which the repeater modules couple. Preferably, the repeater autodetects and/or autoconfigures some or all aspects of repeater operations, such as detecting and/or configuring appropriate full/half-duplex mode operation or detecting and/or configuring in response to appropriate or approved cable-type connections. The distributed and/or modular repeater facilitates accommodating various switching or repeater needs as a network grows or contracts.

Abstract: A method for measuring in-band crosstalk in an optical amplifier, such as a Raman amplifier, in which a modulated optical signal is generated using an input modulator. The modulated optical signal is passed through the optical amplifier to obtain a first output optical signal, the power level of which is measured when the input modulator is in its off-state. The modulated optical signal is then attenuated by a factor equal to the extinction ratio of the input modulator to obtain an attenuated modulated optical signal which is passed through the optical amplifier to obtain a second output optical signal. The power level of the second output optical signal is measured when the input modulator is in its on-state. The in-band crosstalk is calculated by subtracting the power level of the second output optical signal from the power level of the first output optical signal.

Abstract: An optical cross-connect includes multiple input ports that each receive an optical input signal and multiple output ports that each output an optical output signal. The optical cross-connect also includes a distributing amplifier associated with each input port that generates multiple copies of the input signal received at the associated input port. Furthermore, the optical cross-connect includes multiple filter units that receive a copy of one or more of the input signals from one or more of the distributing amplifiers and forward traffic in selected channels of one or more of the received copies. In addition, the optical cross-connect includes a combining amplifier associated with each output port. Each combining amplifier receives the traffic in one or more of the channels forwarded by one or more of the filter units and combines the received traffic into an output signal to be output from the associated output port.

Abstract: Different bands (C-band and L-band) are allotted respectively to an upstream optical signal and a downstream optical signal. In a transmission-path optical fiber for Raman amplification, the C-band optical signal is amplified by pumping light from a C-band pumping light source, and the L-band optical signal is amplified by pumping light from an L-band pumping light source. As a result of this configuration, the optical signals are Raman-amplified through backward pumping in both upstream and downstream directions, whereby negative effects, which could be exerted on the optical signals by forward pumping, can be avoided.

Abstract: A performance monitoring method for an optically amplified transmission system. The method provides the optical power at each amplifier site, taking into account the inaccuracies introduced by the SRS in the power estimation obtained with the current methods. An optical spectrum analyzer is used at the output of the transmission link of interest to accurately measure the output power of each wavelength. This value is sent upstream to the last amplifier in the link, to compute an error term as the difference between the actual measurement and the estimation. The error term is used to infer the SRS-induced error by system elements not accounted for in the model. The error term is then fed-back to each amplifier in the link, so that the estimated power is adjusted to account for the SRS-induced inaccuracy.

Abstract: An apparatus and method for detecting a signal in an optical data network is disclosed. A peak power level and an average power level are measured for an optical input to an optical detector. A threshold power level is associated with each average power level that is sufficient to distinguish a data signal form optical noise at the average power level. A signal is detected if the measured peak power level exceeds the threshold power level appropriate for the average power level. In one embodiment, a threshold value of a ratio of the peak power level to the average power level is calculated and a signal is detected if the ratio of the measured peak power level to the average power exceeds the threshold value.

Abstract: An arrangement and a method for testing a telecommunications circuit over Dense Wavelength Division Multiplexing (DWDM). A transmitter, which is optically coupled to the circuit, transmits a test-drive signal on the circuit. Through a network, a performance of the circuit is monitored at points along the circuit based on the transmitted test-drive signal.

Abstract: Optical systems and devices are provided that include or facilitate the ability to provide early detection of the failure of an optical transmitter such as a laser. Such detection may be made with reference to various aspects of the operation and performance of the optical transmitter. For example, some of the optical systems and devices employ wavelength shift information to make determinations concerning potential failure of an optical transmitter. Other optical systems and devices use information concerning the efficiency with which an incoming pump current is converted into the ballast laser signal changes to make determinations concerning potential failure of an optical transmitter.

Abstract: A system and method that effectively measures the polarization dependent gain of an optical amplifier without significantly introducing error into that measurement is provided. A saturating optical signal source generates an optical signal capable of saturating the optical amplifier. A slow polarization scrambler then randomly polarizes the optical signal to yield a polarized optical signal, which is used as an input signal of the optical amplifier. The output signal of the optical amplifier is then transferred to a fast polarization scrambler, resulting in a PDG measurement signal, which is then presented to an optical signal analyzer that measures the intensity level of each channel of the PDG measurement signal. Alternately, a wavelength division multiplexing (WDM) polarization mixer is employed to mix the polarization states of WDM channels of the polarized optical signal from the slow polarization scrambler with respect to each other, yielding the input signal for the optical amplifier under test.

Abstract: In a method and system for evaluating distributed gain in an optical transmission system, a data signal and a residual pump laser signal propagating in opposite directions within a waveguide are monitored. Modulation of the residual pump laser signal is correlated with low frequency components of the data signal. This correlation is used to determine cross-talk between the data signal pump laser signals, as a function of location within the waveguide. The distributed gain is then evaluated from the cross-talk, using a known relationship, or proportionality, between gain and cross-talk.

Abstract: The present invention provides an optical wavelength multiplexing transmission apparatus and an optical output control method for an optical wavelength multiplexing transmission apparatus in an optical wavelength multiplexing transmission system using a main signal light and an OSC light. The optical wavelength multiplexing transmission apparatus (10a) is made up of a first transmitting/receiving section (52a) a second transmitting/receiving section (52b) and an apparatus supervisory control unit (54). This can not only achieve quick restoration from troubles, but also stably calculate an optical output level even if a change of the number of wavelengths to be multiplexed takes place in a main signal light, and even save troublesome adjustments for the improvement of reliability of a transmission line while eliminating the need for a signal source for the adjustment of a receive optical level at the initial installation.

Abstract: The present invention provides an optical wavelength multiplexing transmission apparatus and an optical output control method for an optical wavelength multiplexing transmission apparatus in an optical wavelength multiplexing transmission system using a main signal light and an OSC light. The optical wavelength multiplexing transmission apparatus (10a) is made up of a first transmitting/receiving section (52a), a second transmitting/receiving section (52b) and an apparatus supervisory control unit (54). This can not only achieve quick restoration from troubles, but also stably calculate an optical output level even if a change of the number of wavelengths to be multiplexed takes place in a main signal light, and even save troublesome adjustments for the improvement of reliability of a transmission line while eliminating the need for a signal source for the adjustment of a receive optical level at the initial installation.

Abstract: A method and devices for individually controlling the signal strength of single or multiple optical channels. A controller module monitors the signal strength of channels and amplifies those that need amplifying while attenuating those that are too strong using the same Erbium doped fiber amplifier. A controllable compensation module receives at least one channel and, when required, can either amplify or attenuate the signal strength of the channel(s). The module can be constructed out of a single fiber with an associated pump laser. If the laser provides insufficient pumping power, the fiber acts as an attenuator. If the laser provides a higher level of pump power, the fiber acts as an amplifier.

Abstract: A supervisory system and supervisory method of an optical amplifier repeater are proposed that can implement operation supervision taking account of the characteristics of individual supervisory targets of the optical amplifier repeater, thereby achieving higher reliability.

Abstract: An optical signal performance monitoring apparatus in a multi-channel optical transmission system and a method for monitoring the optical signal performance.

Abstract: An optical communication system includes a plurality of optical channels, each of which passes a single optical wavelength signal. Each of the plurality of optical channels includes an optical amplifier which is controlled to operate at a predetermined output power level independent of channel wavelength and input power level by operating each optical amplifier in a saturation mode. Pumping power for operating each optical amplifier in the saturation mode is supplied from shared optical pumps or a plurality of one per channel optical pumps.

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

Abstract: An optical regenerator enabling matching of self-phase modulation induced spectral broadening and optical regenerator filter center wavelengths and bandwidths for different fiber dispersion values. The regenerator monitors the central part of an input signal spectrum at the output of a non-linear medium and suppresses the power at the center wavelength to allow for a constant spectral broadening for different fiber dispersion values. The regenerator utilizes a control filter to control a variable amplifier via a feedback loop, and the variable amplifier adjusts the power of the signal launched into the non-linear medium to ensure a sufficient self-phase modulation broadened spectrum.

Abstract: A method is provided for using optical time-domain reflectometry (OTDR) with a bi-directional optical transmission system that includes a plurality of terminals interconnected by first and second unidirectional optical transmission paths having at least one repeater therein. The method begins by transmitting a probe signal from a first terminal through the repeater over the first optical transmission path. A returned OTDR signal is received over the first optical transmission path in which status information concerning the first optical transmission path is embodied. The returned OTDR signal is transformed to a digitized electrical signal and the digitized electrical signal is transformed to an optical data signal. Finally, the optical data signal is transmitted over the second optical transmission path to the first terminal for extracting the status information embodied therein.

Abstract: The present invention relates to an optical fiber transmission line and the like comprising a structure for enabling repeating sections to become further longer. The optical fiber transmission line comprises first and second optical fibers successively disposed along the advancing direction of signal light, and an optical multiplexer for supplying Raman amplification pumping light to one of the first and second optical fibers. The first and second optical fibers are fusion-spliced to each other, whereas at least one of them has a core region substantially made of pure silica glass. The second optical fiber has an effective area smaller than that of the first optical fiber, and a chromatic dispersion and a length which are different from those of the first optical fiber. In particular, the respective lengths of the first and second optical fibers are appropriately regulated so as to effectively suppress nonlinear phenomena other than Raman amplification.

Abstract: An approach for providing transmission level control in an optical network having an amplifier chain is disclosed. An optical communications system includes a gateway network element configured to receive an amplifier requirement from a host. The system also includes a network element communicating with the gateway network element over an optical amplifier chain, the network element being configured to receive the amplifier requirement from the gateway network element, and to adjust transmission power level in response to the amplifier requirement (e.g., error rate information including Signal-to-Noise (S/N) ratio, bit error rate (BER), and/or Quality (Q) value).

Abstract: A compensator for optical transmission systems exploits gain tilt inherent in optical amplifiers. The amount of SRS induced spectral power gradient is determined, and the amplifier gain is changed to cause a compensating gain gradient in the optical amplifier to compensate for the SRS induced spectral power gradient. Fewer components are needed, and so it can be less expensive. It can be implemented as a simple software upgrade to existing systems. Many such compensators can be distributed through the system, without requiring a large inventory of individually specified filters. More accurate compensation can be achieved by making it dependent on the distribution of wavelengths within a band.

Abstract: A supervisory apparatus able to prevent recirculation of a supervisory frame when sending a supervisor frame for supervision, which supervises an optical communications apparatuses connected to transmission lines in cooperation with the same by adding a sequence number to a supervisory frame when sending the supervisory frame.

Abstract: An optical communication system (20) is provided for transmitting a multi-rate data signal between a transmitter (22) and a receiver (24) in a power efficient manner. The optical communication system (20) includes an optical source (32) that supplies an optical carrier signal; an encoder (44) that receives and encodes a data signal; an external phase modulator (42) that modulates the optical carrier signal with the encoded data signal, such that the modulator (42) varies the duty factor of the modulated optical signal based on the encoded data signal; and an optically saturated erbium doped fiber amplifier (36) that amplifies the modulated optical signal prior to transmission by the transmitter (22). In accordance with the present invention, the modulation scheme of the optical communication system (20) varies the duty cycle of the modulation to attain power efficiency during periods of low data demand.

Abstract: An optical termination element for terminating an optical fiber carrying a signal of first maximum power level comprises a termination fiber which is unable to propagate a fiber fuse when the signal power is below a threshold power level which is greater than the first maximum power level. The termination fiber is designed by selecting values of the core diameter and the higher mode cutoff wavelength. The intention provides a termination component in which a fiber fuse can not be initiated at the maximum power to be provided to the termination.

Abstract: Data is transferred in a normal mode or a compressed mode. In the normal mode, a nominal ratio(Aj) is calculated on the basis of signalled reference amplification factors (&bgr;c,ref &bgr;d,ref) whereupon amplification factors (&bgr;c,j, &bgr;d,j) are determined by approximation with respect to said ratio. In the compressed mode, a corrected nominal ratio(AC,j) is calculated on the basis of the nominal ratio (Aj) and amplification factors (&bgr;c,C,j, &bgr;d,C,j) are determined by approximaion with respect to said nominal ratio.

Abstract: This invention relates to an optical transmission monitoring apparatus or the like which has a simple structure for identifying causes of variations in the power of WDM signals. The optical transmission monitoring apparatus includes a monitoring section for setting first and second wavelength bands in a monitor wavelength band, comparing variations in the optical powers of a plurality of types of light containing different light signals which are detected from the respective wavelength bands, and identifying causes of the variations in optical power in the optical transmission path.

Abstract: A method, and optical network management system, including detecting, in an electrical domain, a change in performance of an optical transmission system, and determining a cause of the change based on data associated with an optical performance parameter. The data is collected from optical network elements that have a value for the optical performance parameter exceeding a threshold. Another embodiment includes an electrical monitoring device, including outputting an electrical signal that indicates a degradation in the performance, and transmitting a command to the optical network elements to collect the data. A further embodiment includes an optical network element, including transmitting an optical signal to the electronic monitoring point that converts the optical signal to the electrical signal, which is examined to detect the degradation, and transmitting the data to the network management system, if the value exceeds the threshold value.

Abstract: A method and system for multi-level power management in an optical network is provided. They include three levels of control of an amplifier. The first level of control maintains the gain of the amplifier operating in automatic gain control (AGC) mode at a target amplifier gain. The second level of control eliminates channel gain excursion by dynamically changing the amplifier target gain so as to provide that the gain for each channel is within a gain ripple of the amplifier. The third level of control sets the target gains of amplifiers according to fiber span losses. The third level of control also performs pre-emphasis of channel powers by changing the power of one or more channels passing through the amplifier so as to compensate for gain ripple of the amplifier. As a result, this multi-level control of the amplifiers in the network provides an increased level of optical signal to noise ratio (OSNR), protection of network components, and stabilization of channel power in the network.