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: An optical transmission equipment in an optical communication system interconnecting two optical transmission equipment sets by a main transmission line and a backup transmission line. An optical amplifier amplifies and outputs optical signals from one transmission line in use, interconnecting the optical transmission equipment concerned with neighboring upstream optical transmission equipment, and outputs the optical signals including a signal component and a noise component. A controller controls an optical signal level so that a signal component in the optical signal reaches a predetermined level.

Abstract: An optical exchange for a wavelength division multiplexed (WDM) network performs a switching operation on a plurality of optical signals, which are input via a plurality of input ports, and outputs the resulting optical signals to a plurality of output ports, which are allocated to the input ports, by making deflection the optical signal; target amounts of the deflection to which the respective input optical signals are stored. The deflection is made using a switching controller, which reads out the target amount of deflection for such destination-of-switching output port with respect to such object-of-switching port, and controlling the deflection in such a manner that the individual input optical signals are deflected based on the respective target amounts of deflection. And during the switching, the power-level controller performs a feedback control for adjusting a power level of the individual deflected output optical signal to a target power level.

Abstract: In one of several embodiments, a method of communicating optical signals comprises communicating a plurality of optical signals over an optical communications medium, wherein each of at least some of the plurality of optical signals comprises a launch power that is a function of a noise property measured at or near a center wavelength of that signal. Launch powers of the plurality of optical signals primarily decrease with increasing center wavelengths of the plurality of optical signals.

Abstract: Disclosed herein is a system including a closed loop topology using an optical fiber applicable to WDM signal light obtained by wavelength division multiplexing a plurality of optical signals, and a plurality of nodes arranged along the closed loop topology, each node including an optical amplifier. Each node further includes a first unit for controlling the optical amplifier so that the output from the optical amplifier becomes constant, according to the number of channels of WDM signal light received from the node immediately upstream of the corresponding node, and a second unit for interrupting the optical signals other than one or more optical signals added to the corresponding node until the control by the first unit is converged. With this configuration, each node can be easily started.

Abstract: Described herein are one or more embodiments of a system and method for managing power in an optical network using a variable optical attenuator (VOA). In one embodiment, the attenuation of the VOA is controlled in a feedback loop in accordance with a plural zone method. In one example, the VOA is a mechanical VOA. In another example, the VOA is a latching VOA.

Abstract: In an optical grating device, a grating arrangement receives different wavelength output signals from a plurality of radiation sources at input ports thereof, and generates therefrom a multiplexed wavelength output signal at a zero diffraction order output port of the grating arrangement. Additionally, the gating arrangement generates at least one predetermined wavelength output signal at one of a group consisting of a separate predetermined location in an at least one of a symmetric non-zero diffraction order of the grating arrangement, within the grating arrangement itself, and a combination thereof. A separate power tap is coupled to detect the power of a separate one of the at least one predetermined wavelength output signal from the grating arrangement.

Abstract: In an optical communication network, optical communication nodes exchange information detailing power level variations to support management and administration of optical communications. This exchange of information permits nodes to determine aggregate power level variations over light paths to support operations such as selection from available light paths and configuration of optical communication characteristics.

Abstract: In an optical communication network, optical communication nodes exchange information detailing power level variations to support management and administration of optical communications. This exchange of information permits nodes to determine aggregate power level variations over light paths to support operations such as selection from available light paths and configuration of optical communication characteristics.

Abstract: In an optical communication network, optical communication nodes exchange information detailing power level variations to support management and administration of optical communications. This exchange of information permits nodes to determine aggregate power level variations over light paths to support operations such as selection from available light paths and configuration of optical communication characteristics.

Abstract: It is disclosed that a method and apparatus that automatically monitors each channel's optical signal-to-noise ration (OSNR) using optical filter and polarization extinction method in wavelength division multiplexing (WDM) scheme-based optical transmission systems. OSNR is simply measured using optical filter by comparing amplified spontaneous emission (ASE) over the signal band, of which bandwidth has changed, while leaving signal intensity intact, with that original signal and, OSNR measurement is allowable over a wider range of OSNR by minimizing the ratio of signal to ASE over the signal band using polarization extinction method.

Abstract: This invention provides a technique for realizing low-cost optical signal waveform monitoring with improved realtimeness to be applied to signal quality monitoring in an actual optical transmission system, and a technique for stably controlling an optical transmitter/receiver and various compensators by means of this waveform monitoring. Opening/closing of a optical gate is controlled by means of a clock signal synchronized with an optical signal input from a photocoupler and having a period equal to the bit interval of data or N (N: a positive integer) times longer than the bit interval to allow each pulse of the optical signal for one bit of data to pass through the optical gate for only part of the time width of the gate. A photoelectric conversion element to which the optical signal transmitted through the optical gate for only part of the time width obtains an average light intensity of the input optical signal. Information on this average light intensity is output to a monitoring output section.

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 tunable dispersion compensator whose passband center wavelength changes when the amount of dispersion compensation is changed is suitably adjusted. The relationship between temperature for keeping the center wavelength constant and the amount of dispersion compensation is stored in advance. After controlling the amount of dispersion compensation to achieve best or optimum transmission quality, the amount of dispersion compensation is converted into temperature in accordance with the stored relationship and, based on that, the temperature is controlled to keep the center wavelength constant.

Abstract: Disclosed are an optical coupler type filter, and a wavelength stabilizing apparatus of a light source using the same.

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.

Abstract: The present invention relates to an optical sender applicable to WDM (wavelength division multiplexing), and a primary object of the present invention is to prevent interchannel crosstalk in WDM. The optical sender includes a light source for outputting a light beam, an optical modulator for modulating the light beam in accordance with a main signal to output an optical signal, and a unit for shutting down the optical signal when receiving at least one of a power alarm relating to on/off of power supply and a wavelength alarm relating to the wavelength of the light beam.

Abstract: Adjusting power for a WDM optical transmission system comprising emitter means, an optical transmission line, and receiver means, the method being characterized in that for each wavelength channel, the power emitted for said channel by the emitter means is adjusted as a function of the optical powers received for said channel at a plurality of points distributed along the transmission line.

Abstract: The invention is related to a method for equalizing performance of traffic channels in a WDM system where means for controlling transmitters (12), amplifiers (38) and receivers (14) are provided. Potentially, a number of channels are defined as loading channels (100). The method follows the steps of measuring the optical power at the input (48) of the amplifier (38), setting the power levels of a predefined number of loading channels (100) to a high power level, setting the power level of the traffic channels (200) to a power level less then the power level of the loading channels (100), adjusting the power level of the traffic channels (200), adjusting the power level of the loading channels (100), stabilizing the sum of the optical power measured at the optical amplifier (38), continuing the process for each channel the receiver lock signal (75) is sent back to the transmitters.

Abstract: In the WDM systems, the OSNR and the signal loss among the optical signals are substantially minimized at the receiving terminal to combat the SRS effects. An equal amount of the signal loss is expected for every span in the transmission path so that the optical amplifier gain tilt is not affected among a number of wavelength frequencies in the optical signal. This is accomplished by controlling the amplification process according to a feedback from the monitoring units for monitoring the optical signal.

Abstract: An optical network incorporates one of wavelength based or lightpath link based pre-emphasis to reduce the power fluctuation range at optical receivers in the network. Power output from channel transmitters can be varied on a per channel basis to minimize the effects of non-constant per-channel gain as a function of wavelength. Pre-emphasis circuitry coupled to the transmitters imposes an optical power profile on transmitter output in accordance with an inverse of the gain characteristic of network amplifier elements raised to an exponent which is equal to or less than the number of spans through which an optical signal is transmitted.

Abstract: A scanning optical monitoring system and method are appropriate for high speed scanning of a WDM signal band. The system and method are able to identify dropped channels or, more generally, discrepancies between the determined or detected channel inventory and a perpetual inventory for the WDM signal, which perpetual inventory specifies the channels that should be present in the WDM signal assuming proper operation of the network. The system includes a tunable optical filter that scans a pass band across a signal band of a WDM signal to generate a filtered signal. A photodetector then generates an electrical signal in response to this filtered signal. A decision circuit compares the electrical signal to a threshold and a controller, which is responsive to the decision circuit, inventories the channels in the WDM signal.

Abstract: An optical multiplex communication system includes a transmission part and a receiving part, wherein the transmission part includes a transmission quality detecting part which measures and transmits a transmission quality information for the channels based on a request from the transmission part; the receiving part includes a variable optical attenuation part controls the optical signal level for the channels, an optical level setting part controls the variable optical attenuation part based on a setting value, a setting control part adding the setting value to the optical level setting part based on a request for setting.

Abstract: An add/drop node for an optical network comprises a passive splitter to split an ingress signal from the network into a first ingress signal and a second ingress signal. A first amplified splitter stages module is operable to passively split and amplify the first ingress signal into a plurality of drop signals. A filter module is operable to filter the second ingress signal to provide a filtered pass-through signal. A second amplified splitter stages module is operable to passively combine a plurality of add signals into a combined add signal and to combine the combined add signal with the filtered pass-through signal to create an egress signal forwardable to the network.

Abstract: The invention provides a wavelength multiplexing transmission apparatus includes a plurality of optical signal outputting sections for outputting optical signals having different wavelengths from each other, and a wavelength multiplexing section for wavelength multiplexing the optical signals outputted from the optical signal outputting sections and sending out a resulting optical signal. Each of the optical signal outputting sections includes a transmission light source driven by an electric signal for outputting an optical signal of a predetermined wavelength, and a wavelength filter capable of passing therethrough and sending out only an optical signal of the predetermined wavelength to be outputted from the transmission light source to prevent a wavelength drift of the optical signal outputted from the transmission light source.

Abstract: A system compensates for the presence of power transients. The system receives a data signal and detects the occurrence of a power transient. The system generates a threshold signal based on the detected power transient and determines a value of the data signal based on the threshold signal.

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: The WDM receiver includes a wavelength demultiplexer, a detector array and a signal extractor. The wavelength demultiplexer receives an n-channel optical input signal and transmits the n-channel optical input signal to m optical outputs. Each of the optical outputs receives a wavelength band centered at a different wavelength. The wavelength bands have a center-to-center wavelength spacing of ???. The detector array is composed of m detector elements coupled to the wavelength demultiplexer. Each of the detector elements generates a detection signal in response to light received from one of the optical outputs of the wavelength demultiplexer. The signal extractor receives the detection signals from the detector array and converts the detection signals to an n-channel receiver output signal, each channel of which corresponds to a different one of the n channels of the optical input signal.

Abstract: For exact level balancing or signal-to-noise ratio balancing of received signals in a wave-length-division multiplex transmission system, the associated transmitted signal power levels are adjusted. If the maximum permissible dynamic range is exceeded, the individual transmitted signal power levels are compressed, while the total transmitted signal power level is kept at least approximately constant.

Abstract: A self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.

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 unique sensor is used to detect a transmission impairment that may have affected incoming optical channel signals. The sensor, more specifically, selects a group of the incoming channel signals and generates a first power signal, P0, over the selected group of signals and generates a second power signals, P1, over a weighted version of the selected group of channel signals. The sensor then generates, as a function of the first and second power signals, P0 and P1, a signal indicative of whether the particular transmission impairment affected the levels of individual ones of the incoming channel signals. If so, then control apparatus offsets the impairment accordingly.

Abstract: A method of channel balance for a channel balance section in an WDM optical network with a starting node, an ending node and a plurality of intermediate OADNs (Optical Add Drop Node) first determines express wavelengths and non-express wavelengths starting from the starting node, then calculates TX (transmitter) power change which will bring the express channel performance to a target value and sets TX power using obtained TX power value. The method then moves to non-express channels by calculating TX power change for each non-express channel and sets TX power using obtained TX power value. Lastly, for each intermediate OADN, the method calculates TX power change for each added channel in each OADN and sets TX power using obtained TX power value.

Abstract: A method of controlling a network (115) through which information is transmitted in channels (?1, ?2, . . . ?n) among nodes includes: (a) providing at a node a device (108) for removing from the network (115) and replacing on the network (115) a selected one (?i) of the channels, the device (108) including a first input port from the network (115) to the node and a first output port from the node to the network (115); (b) taking a measure of the strength (P?iDROP) of the received channel (?iDROP); (c) regenerating the channel (?iIN); (d) adjusting (114) the strength (P?iADD) of the regenerated channel (?iIN) to approximate the strengths of the remaining channels ((?1, ?2, . . . ?n)-?i; and (e) combining the regenerated and strength-adjusted channel (?iADD) with the remaining channels ((?1, ?2, . . . ?n)-?i) at the output port.

Abstract: A method for maintaining amplifier saturation in a wavelength division multiplexed (WDM) optical network having a plurality of sub-bands, each sub-band including at least two signal channels which carry respective data signals, and a plurality of substitute signal transmitters, each substitute signal transmitter generating a substitute signal and corresponding to a respective one of the plurality of sub-bands, includes identifying signal channels having a predetermined characteristic within each of the plurality of sub-bands. A substitute signal transmitter is turned on if the sub-band corresponding to the substitute signal transmitter includes a predetermined number of signal channels having said predetermined characteristic. The data signals and the substitute signals are combined into a WDM signal, and the WDM signal is transmitted over an optical transmission fiber.

Abstract: In a 32-channel wavelength division multiplexing optical transmission system, for example, four optical transmitters are grouped in eight groups. Each group is provided with a control optical transmitter. The control light transmitter regulates the level of a control light so that the total level of light transmitted from the corresponding group is equal to the total level of four signal lights. An optical transmission line of the above-mentioned system is normally regulated beforehand so that the wavelength characteristic of the following signal lights is flat when light at the total level of thirty-two signal lights in a predetermined range of wavelengths is transmitted. Therefore, in the system according to the invention, independent of the number of signal lights, the receive level of a signal light is unchangeable.

Abstract: Systems and methods for controlling power of WDM channels in a WDM receiver. A preamplifier is provided prior to a demultiplexer in the WDM receiver chain. The gain of the preamplifier may be controlled based on power measurements made on individual WDM channels. A filter with controllable tilt may be employed to compensate for amplifier gain tilt and assure that all of the WDM channels remain within the dynamic range of the photodetector and receiver electronics. This provides improved bit error rate performance.

Abstract: A method for detecting power transients in a signal wavelength carried by an optical transmission medium in a band consisting of a first plurality of wavebands, such as a wavelength division multiplexed signal, comprises dividing the band into a second plurality of wavebands, equal to or less than the first plurality, and detecting power transients within each of the second plurality of wavebands. The power of each wavelength in the second plurality of wavebands is determined by detecting the power level in each second plurality of wavebands as a function of the contribution from each of the wavebands in the second plurality of wavebands to derive a plurality of simultaneous equations, equal in number to the second plurality of wavebands, and solving the plurality of simultaneous equations to determine the levels of each wave-length component of each waveband in the second plurality of wavebands. Correlation with error bursts detected in the optical receiver enable an audit of the error event to be conducted.

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

Abstract: A wavelength division multiplexed (WDM) optical network includes a plurality of optical transmitters, each optical transmitter generating a data signal sent over a respective one of a plurality of signal channels, the plurality of signal channels being divided into a number of sub-bands where each sub-band includes at least two signal channels, and a plurality of substitute signal transmitters, the number of substitute signal transmitters being equal to the number of sub-bands, each substitute signal transmitter generating a substitute signal which provides loading in a corresponding sub-band. The WDM optical network also includes a combining circuit which combines the data signals output from the plurality of optical transmitters and the substitute signals output from the plurality of substitute signal transmitters into a WDM signal, and an optical transmission fiber which receives the WDM signal from the combining circuit.

Abstract: A device is provided for detecting polarization mode dispersion of an optical data signal, wherein the device includes at least two filters, each of which is respectively followed by a power detector. A better compensation can ensue due to the combination of a large monotony range and great steepness in the employment of a number of filters.

Abstract: In the control method for the optical filter according to the present invention, WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths is supplied to an optical filter to obtain output WDM signal light including a part of the plurality of optical signals. The output WDM signal light is converted into an electrical signal per wavelength channel of the output WDM signal light. Then, the optical filter is controlled according to the electrical signal so that the characteristic of the optical filter becomes stable.

Abstract: The invention is related to a wavelength allocation scheme for a WDM (Wavelength Division Multiplex) equipment with a distribution of used optical channels that are arranged around a saturation channel in a way that the total spectrum of the optical channels is balanced independent from the number of equipped optical channels.

Abstract: The performance of a WDM system is improved by adjusting launch powers of each channel responsive to a prediction of system performance degradation. The prediction of system performance degradation could relate to the effect of Stimulated Raman Scattering (SRS) in which case, given launch power, a value representative of the effect of SRS is estimated for each channel in a WDM system using a method described herein. Using this SRS effect estimate, a value is computed for the estimated output power of each channel. These estimated output power values are then used to refine the estimate of the SRS effect on each channel. Subsequently, the refined SRS effect estimates are used to refine the estimated output power values. These steps are repeated and eventually an estimate of SRS effect on each wavelength channel is settled upon that is as accurate as that which results from other, more computationally complex, methods.

Abstract: A WDM transmission device includes a level adjustment unit adjusting levels of optical signals having different wavelengths, a multiplexer multiplexing the optical signals, an amplifier amplifying a multiplexed optical signal, and a monitor unit monitoring the multiplexed optical signal applied to the amplifier and a level of an output signal of the amplifier and controlling the level adjustment unit so that the levels of the optical signals fall within a predetermined level range in which the amplifier can operate normally.

Abstract: In one aspect of the invention, a system operable to reduce degradation of an optical signal to noise ratio where signals having multiple wavelengths are communicated over a common optical link includes an amplifier assembly operable to introduce to a lower communication band a first gain and to introduce to a higher communication band a second gain that is different from the first gain. In addition, the system is operable to introduce a variable gain tilt into at least one of the communication bands. The different gains introduced to the higher and lower bands and the variable gain tilt introduced into at least one of the bands result in a reduction of a degradation of optical signal to noise ratio that could otherwise be caused by wavelength dependent attenuation when the communication bands are combined and communicated over an optical link.

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: 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 and apparatus within an optical transmitter (300) for suppressing relative intensity noise (RIN) by generating at least two optical signals (305,310), each having differing wavelengths and combining the optical signals with a combiner (315) into a composite output signal, wherein the composite output signal has an output power value equal to the sum of the power value of the optical signals. The composite output signal is then transmitted over a communication medium, wherein information content of the optical signals are substantially equivalent, and wherein combining the optical signals before transmitting provides a reduction in RIN of the composite output signal compared to the RIN of a single optical signal transmitted over a communication medium.

Abstract: An optical channel regulator (46) is provided. The optical channel regulator (46) includes a tapped optical coupler (60) receiving an optical line carrying an optical signal. The tapped optical coupler (60) provides substantially all of the optical signal as an output. An electrically variable optical attenuator (64) receives the output of the tapped optical coupler (60) and attenuates the optical signal responsive to a feedback control signal. A second tapped optical coupler (66) receives an output of the attenuator (64). The second coupler (66) provides substantially all of the received optical signal as an output and provides a remaining portion of the optical signal as a tapped output. An optical detector (68) then receives the tapped output and provides an output signal representing the optical signal. A comparator (70) receives the output signal of the optical detector (68) and a reference signal.