Abstract: Methods of operating an optical communication system in coherent optical transmissions for metro applications. Relative to conventional solutions, the optical communication system can be implemented with reduced cost and can operate with reduced power consumption, while maintaining high data rate performance (e.g., 100G). Furthermore, a programmable transceiver enables compatibility with a range of different types of optical networks having varying performance and power tradeoffs. In one embodiment, the optical communication system uses 100 Gb/s dual-polarization 16-point quadrature amplitude modulation (DP-16QAM) with non-linear pre-compensation of Indium Phosphide (InP) optics for low power consumption.

Abstract: A monolithic laser device assembly 10A in the present disclosure includes a first gain portion 20 having a first end portion 20A and a second end portion 20B, a second gain portion 30 having a third end portion 30A and a fourth end portion 30B, one or multiple ring resonators 40, a semiconductor optical amplifier 50 for amplifying a laser light emitted from the first gain portion 20, and a pulse selector 60 disposed between the first gain portion 20 and the semiconductor optical amplifier 50, in which the ring resonator 40 is optically coupled with the first gain portion 20 and with the second gain portion 30, and laser oscillation is performed on either the first gain portion 20 or the second gain portion 30.

Abstract: Systems and methods are provided for compensating errors. A system includes a microelectromechanical systems (MEMS) oscillating structure configured to oscillate about a rotation axis; a phase error detector configured to generate a phase error signal based on measured event times and expected event times of the MEMS oscillating structure oscillating about the rotation axis; and a compensation circuit configured to receive the phase error signal, remove periodic jitter components in the phase error signal to generate a compensated phase error signal, and output the compensated phase error signal.

Abstract: Disclosed are fiber amplifiers with multiple pumping sources including multiple optical sources or an optical comb source with multiple spectral lines. A comb source may include generating a plurality of evenly spaced or nearly evenly spaced spectral lines. The optical comb source may pump a fiber by propagating optical energy at the multiple spectral lines through the fiber. The comb source may cause gain in the fiber at in a band of wavelengths different from the spectral lines of the comb source. A weak signal injected into the fiber that propagates in the fiber will experience optical gain in the fiber producing an amplified signal at the wavelength within a band of wavelengths different from the comb source wavelengths. When the bandwidth of the multiple bands of gain is wide, the amplifier may be referred to as an ultra-wideband amplifier.

Abstract: A mode-locked semiconductor laser capable of changing the spacing between the carrier frequencies of its output comb. In an example embodiment, the mode-locked semiconductor laser is implemented as a hybrid solid-state device comprising a III-V semiconductor chip and a silicon chip attached to one another to form a laser cavity. The III-V semiconductor chip includes a gain medium configured to generate light in response to being electrically and/or optically pumped. The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity. Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity and, as a result, the output-comb frequency spacing. In some embodiments, the output-comb frequency spacing can be changeable at least by a factor of 1.5.

Abstract: A densely-spaced wavelength division multiplexing (DWDM) transceiver utilizes a comb laser source to provide a multi-channel system capable of supporting at least twenty separate channels. The optical transmitter portion of the transceiver utilizes a double-pass (e.g., reflective) modulator configuration. The double-pass arrangement allows for a single grating (or other suitable dispersive element) to be used as a demultiplexer in combination with the comb laser source to separate the input optical beams into individual wavelength components, as well as a multiplexer for combining the plurality of separate modulated optical signals into a single, multi-channel DWDM optical output signal. The optical receiver portion of the transceiver includes a grating element to direct the multi-channel received optical signal into separate, wavelength-based channels, with the signal propagating along each channel directed into a separate photodiode.

Abstract: An optical network unit (ONU) of a gigabit-capable passive optical network (GPON) adapts to an optical line termination (OLT) to which it is coupled. The ONU determines a type of the OLT to which it is coupled, and based on the type, configures an optical transmitter of the ONU to be compatible with the OLT. The ONU can also determine which OMCI software stack to load based on the type of the OLT.

Abstract: A system for monitoring optical signal-to-noise ratio (OSNR) is provided. In some specific examples, the system may use a pilot tone power of a signal modulated with pilot tone to derive the pure signal power and the variance of the whole electric field to derive the total power (pure signal power plus amplified spontaneous emission (ASE) power of the signal). The ASE power can be obtained by subtracting the pure signal power from the total power (ASE+pure signal). Once the ASE power and the pure signal power are known, the OSNR can be calculated.

Abstract: An optical fiber temperature distribution measuring device includes: an optical fiber as a sensor; a light source for outputting, to the optical fiber, signal light which has been amplified by excitation light; a temperature distribution calculation unit for measuring a temperature distribution along the optical fiber by using backward Raman scattered light from the optical fiber; an ASE light intensity variation measurement unit for measuring an intensity variation of an ASE light generated at the light source; and a temperature distribution correction unit for correcting the temperature distribution based on a measurement result of the ASE light intensity variation measurement unit.

Abstract: A method for monitoring optical performance in an optical data transmission network, the optical data transmission network including a first router node, a second router node, and an optical data transmission line connecting the first router node with the second router node providing optical data transmission from the first router node to the second router node using at least two channels, includes: in a measurement step, determining, at the spare IP router interface, optical performance parameters of the at least two channels; in a transmission step subsequent to the measurement step, transmitting the determined optical performance parameters to a remote control unit; and in an analysis step subsequent to the transmission step, analyzing the transmitted optical performance parameters and determining whether to take a corrective action to improve optical performance of the at least two channels.

Abstract: A system and method for passive real-time order state replication and recovery. Upstream data is received from an upstream system via a reliable transport, the upstream data also received by a supported system. Downstream data is received from the supported system via the reliable transport. Data acknowledgements are received from the supported system acknowledging receipt of the upstream and downstream data. A replicated current order state of the supported system is continuously updated in real-time based on the received upstream data, downstream data and the data acknowledgements. A recovery request is received after the supported system has experienced an outage. The current order state is restored to the supported system by transmitting a recovery message to the supported system containing the replicated current order state.

Abstract: A signal representing physiological information may include information related to respiration. A patient monitoring system may utilize a wavelet transform to generate a scalogram from the signal. A threshold for the scalogram may be calculated, and scalogram values may be compared to the threshold. One of the scales meeting the threshold may be selected as representing respiration information such as respiration rate. The respiration information may be determined based on the selected scale.

Abstract: A system includes a first low noise amplifier (LNA) having a first gain to amplify an optical input signal and to generate an amplified optical output signal. The first gain is set to compensate for signal losses in the optical input signal due to atmospheric fading. A second LNA having a second gain amplifies the amplified optical output signal from the first LNA and generates a saturated output signal when the combined first and second gain of the first LNA and the second LNA exceeds a predetermined output saturation level of a photo detector.

Abstract: Exemplary embodiments of the invention are drawn to a method and apparatus for the differentiation of power and channel count changes in optically amplified links. Additionally, configuration of a corresponding optical amplifier can be based on the determination of the power and channel count changes.

Abstract: A single frequency laser system is configured with an elongated housing extending along a longitudinal axis and having opposite axially spaced upstream and downstream ends. The housing encloses a laser chip configured to emit a radiation which propagates along a light path and emitted through the downstream faucet thereof. One or more spaced frequency discriminators are mounted in the housing downstream from the chip so as to define an external resonant cavity with the upstream faucet of the of the laser chip. At least two or more separate thermoelectric coolers (“TEC”) are mounted in the housing to control the chip arid discriminators so that the system emits radiation at the desired frequency.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a pre-determined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: A tilt correction pump laser is injected into an optical fiber in an opposite direction of the transmission direction of a wavelength multiplex signal and an optical isolator or filter is provided to block the tilt correction signal in order to restrict the effective fiber length for the tilt correction pump signal to enable a faster adjustment of the tilt.

Abstract: An optical amplifier includes: a rare-earth doped fiber configured to amplify signal light to thereby produce a amplified signal light; a gain control circuit configured to control an optical gain of the rare-earth doped fiber; a photodetector configured to detect intensities of different wavelength of light obtained from the amplified signal light; and an abnormality detection circuit configured to detect an abnormality of the signal light in accordance with a ratio or a difference between the intensities of the different wavelength.

Abstract: A device may include one or more components and a processor. The one or more components may obtain bit-error-rates of a signal and signal-to-noise ratios of the signal. The processor may select a target signal-to-noise ratio for the signal, determine a target noise level based on the target signal-to-noise ratio, set a noise level of the signal to the target noise level, determine a signal-to-noise ratio of the signal via the one or more components, adjust the noise level of the signal based on the determined signal-to-noise ratio, to stabilize the signal-to-noise ratio, determine a bit-error-rate of the signal via the one or more components, and record the bit-error-rate.

Abstract: An optical amplifier includes: a temperature-adjustment-unit that is provided in a wavelength-fixing-unit that fixes a center-wavelength of an excitation-light-source, and adjusts a temperature of the wavelength-fixing-unit, which causes the center-wavelength of the excitation-light-source to vary; a temperature-measurement-unit that measures the temperature of the wavelength-fixing-unit and a temperature of a gain-equalization-unit that equalizes gains of the signal-light on which the Raman amplification is performed using the excitation-light-source; a shift-amount-obtaining-unit that obtains a shift amount data of the center-wavelength of the excitation-light-source from a first-storage-unit and obtains a shift amount of the center-wavelength of the wavelength-band from a second-storage-unit; and a control unit that obtains a temperature-data of the-wavelength-fixing-unit, which corresponds to a difference between two shift amounts that are obtained by the shift amount obtaining unit, from the first-storag

Abstract: Chip identification pads for identification of integrated circuits in an assembly. In one example embodiment, an integrated circuit (IC) assembly includes a controller, a plurality of ICs, a shared communication bus connecting the controller to the plurality of ICs and configured to enable communication between the controller and each of the plurality of ICs, and a set of one or more chip identification pads formed on each IC. Each set of chip identification pads has an electrical connection pattern. The electrical connection pattern of each set is distinct from the electrical connection pattern on every other set. Each distinct electrical connection pattern represents a unique identifier of the corresponding IC thereby enabling the controller to distinguish between the ICs.

Abstract: Raman amplifier gain compression systems and methods based on signal power monitoring are described which estimate distributed Raman amplifier saturation based on a total power measurement at an output of a distributed Raman amplifier and correct for any changes by adjusting the pump power. Since the power measurement, gain estimation, and the pump control and done locally at the Raman amplifier, the duration of any transients is minimized. The systems and methods quickly detect transients on a fiber link using a power monitor in the Raman amplifier, estimate the change in gain due to change in input power from distributed Raman gain, and perform a feedback loop that corrects pump power to eliminate the change in Raman gain locally.

Abstract: Embodiments of the present invention relate to a relay station and a method for adjusting output optical signals of the relay station. The relay station includes: a detection control unit, an output light stabilization unit, a reply stabilization unit, an adjustable gain amplification unit, and a pump light output unit. The method for adjusting output the optical signals of the relay station includes: adjusting a drive current which drives generation of pump light; adjusting a pilot tone modulation depth of an Alternating Current (AC) signal on which a replay signal is modulated; and finally, outputting a stable output optical signal through disturbed pump light. Adjusting the output optical signals and the pilot tone modulation depth of the AC signal on which the replay signal is modulated, the reply signals are stably output, thereby achieving the purpose of fixing the pilot tone modulation depth.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: An embodiment of the invention comprises determining a gain tilt based on power measurements from a power measurement block, determining a noise figure penalty based on the gain tilt, determining a gain tilt compensation to compensate for the gain tilt taking into account the noise figure penalty, and communicating the gain tilt compensation to an amplifier block to apply the gain tilt compensation to subsequently received wavelengths.

Abstract: For the purpose of reducing the cost and power consumption of an optical amplification system provided with an optical amplifier, an excitation light distribution device of the present invention comprises an excitation light source output unit which outputs excitation light, an optical branching unit with variable branching ratio which branches and outputs the excitation light, and a control unit which, on the basis of information on an optical signal to be amplified by the excitation light outputted by the optical branching unit, controls at least either the branching ratio of the optical branching unit or the optical output power of the excitation light source output unit.

Abstract: A control method of a semiconductor optical amplifier includes: controlling a driving current of the semiconductor optical amplifier in a region where a light output intensity decreases in accordance with increasing of the driving current, a drive current in the region being higher than a drive current in a region where a light output intensity increases in accordance with increasing of the driving current.

Abstract: An optical amplifier module includes a first optical amplifier to amplify main signal light to be supplied to a dispersion compensation fiber (DCF), a second optical amplifier to amplify the main signal light supplied from the DCF, a generating part to generate monitoring light having a wavelength longer than a wavelength of the main signal light, a multiplexing part to multiplex the monitoring light generated by the generating part and the main signal light to be supplied to the DCF, a demultiplexing part to demultiplex the monitoring light from the main signal light supplied from the DCF, and a detection part to detect a light intensity of the monitoring light demultiplexed by the demultiplexing part.

Abstract: A control apparatus of an optical amplifier includes a monitoring section that measures power of light inputted to the optical amplifier, a power-wavelength characteristics variable section that is operable to change a wavelength characteristic of power of the light inputted, a wavelength number decrease recognition section that compares the value of the power of light measured by the monitoring section with a predetermined threshold, and a control section that controls the power-wavelength characteristics variable section when the wavelength number decrease recognition section judges that the value of the power of light falls below the threshold.

Abstract: An optical amplifying device includes an optical amplification medium configured to be excited by excitation light and amplify signal light, a light loss detector configured to detect a light loss of an optical component optically connected to the optical amplification medium in the amplifying device, and a noise figure deterioration detector configured to detect, based on the light loss detected by the light loss detector, deterioration of a noise figure of the optical amplification medium.

Abstract: A laser processing device includes a light amplifying fiber, a seed semiconductor laser (LD) for pulsing seed light multiple times during an emission period, an excitation LD for generating the exciting light of power at a first level during a non-emission period immediately before the emission period and generating the exciting light of power at a second level higher than the first level during the emission period, a light receiving element and a peak value detector for detecting power of an output light pulse which is output from the light amplifying fiber, and a control device. The control device controls the power of the exciting light of the non-emission period based on the detected value from the peak value detector to cause the power of first output light pulses which are generated during the emission period to be the same as the power of final output light pulses.

Abstract: A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Abstract: Systems and methods for amplification are shown that include a pump preparation module configured to provide a pump output that includes a plurality of pump modes; an amplification module configured to accept a multimode signal input and the pump output, such that the pump output causes an amplification of a plurality of modes in the signal input to produce an amplified signal output; and a gain control module configured to adjust a balance of the plurality of pump modes in the pump output to produce a predetermined amplified signal output.

Abstract: A method for controlling a variation in gain in an optical amplifier stage and an optical amplifier. The optical amplifier stage includes a pumping device for providing pumping power and a control unit for determining a change in an input power of the optical amplifier. The method includes the steps of determining a change in an input power of the optical amplifier, adjusting a pumping power of the pumping device to a first power level for a predetermined period of time and adjusting the pumping power of the pumping device to a second power level. The second power level is able to drive the amplifier gain to a predetermined gain value after the change in the input power occurred.

Abstract: An optical amplifier control apparatus according to the present invention includes control circuit 300; optical amplifiers 4, 5 respectively located on paths; a plurality of light sources 200, 201 that output excitation lights that differ in light intensity; and optical switch 32 that changes optical routes of excitation lights that are output from light sources 200, 201 and inputs the excitation lights to optical amplifiers 4, 5 as determined by control circuit 300. Control circuit 300 is provided with determination section 301 that determines which paths to allocate which excitation lights that differ in light intensity based on a parameter that relates to wavelength lights on a plurality of paths when wavelength lights of WDM signal light that propagate to one of the plurality of paths are optically amplified.

Abstract: An optical receiving apparatus includes an optical amplification medium that receives an excitation light and an input light, an optical loss medium that receives an output light from the optical amplification medium, a monitor that detects a power level of an output light from the optical loss medium, a controller that controls a power of the excitation light such that the power level of the output light detected by the monitor is at a target value, and a receiver that receives the output light from the optical loss medium, the output light not being optically amplified.

Abstract: A method and apparatus for suppression of four-wave mixing using polarization control with a high power polarization maintaining fiber amplifier system. The apparatus includes a master oscillator (MO) that generates a beam; a polarization controller that receives the beam from the MO and transmits the beam with a desired polarization; a pre-amplifier that receives the beam from the polarization controller, pre-amplifies the beam, and transmits the beam; a high power fiber amplifier that receives the beam from the pre-amplifier, amplifies the beam, and transmits an output beam; and a polarization detector that detects the polarization of the output beam. The polarization detector transmits feedback to the polarization controller to ensure that the output beam components aligned with the principal birefringent axes of the high power fiber amplifier have approximately equal power.

Abstract: Consistent with the present disclosure a compact, integrated tunable filter is provided that can adjust the power levels of optical signals output from an optical amplifier, for example, so that the amplifier has a uniform spectral gain. The tunable optical filter includes a planar lightwave circuit (PLC) having cascaded Mach-Zehnder interferometers, each of which having corresponding differential optical delays. At least one of the differential optical delays is different than the rest. Alternatively, the differential optical delays are different from one another. Each of the Mach-Zehnder interferometers is connected to one another by a tunable optical coupler. Such a filter has an improved frequency response in that the number of shapes that the transmission spectrum may have is increased. Accordingly, the optical filter may be more finely tuned to more effectively flatten, for example, the output of the optical amplifier.

Abstract: A gain equalizer for compensation a variation of intensity among a plurality of optical signals each including a different wavelength in a wavelength multiplexed optical signal includes an input part for receiving the wavelength multiplexed optical signal, an outputting part and a gain equalizing unit for repeatedly giving a loss to the wavelength multiplexed optical signal received by the input part, and for outputting the wavelength multiplexed optical signal to the outputting part. Here, the loss is set for each wavelength and is smaller than a loss characteristic required for compensation the variation of intensity.

Abstract: A tunable laser includes an optical gain medium, a first resonator, a periodically tunable optical filter, and a second resonator in which light of a laser wavelength exhibits a round trip time T. The optical filter is arranged between the first resonator and the second resonator and is tuned with a period t. The period t is governed by t=(n/m) T, where n and m are integers and m/n is not an integer.

Abstract: According to an aspect of the invention, an amplification device includes an amplifier configured to amplify a signal light by inputting the signal light and an excitation light to a rare-earth doped amplification medium, a wavelength arrangement monitor configured to acquire wavelength arrangement information indicating a wavelength of the signal light, and a light power controller configured to control power of the input excitation light based on the acquired wavelength arrangement information.

Abstract: An optical amplifier reducing gain deviation caused by wavelength arrangement has a first-stage optical amplifying unit, an attenuator, a second-stage optical amplifying unit, an automatic gain controller controlling the first- and second-stage optical amplifying units so that a gain of signal light outputted from the second-stage optical amplifying unit to signal light inputted to the first-stage optical amplifying unit is constant, and an attenuation amount controller controlling an attenuation amount at the attenuator to adjust gain-versus-wavelength characteristic at the automatic-gain-controlled first- and second-stage optical amplifying units on the basis of information on wavelength arrangement and an input level of the signal light inputted to the first-stage optical amplifying unit so that gain slope characteristic at the first- and second-stage optical amplifying units due to the wavelength arrangement and the input level is flattened.

Abstract: An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a pre-determined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: In a Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) utilizing a conventional downstream optical signal reusing method, there is an inventory problem that different optical transmitter types need to be provided for the operation, management, replacement, etc. of a system. A WDM-PON system according to the present invention, includes: a seed light (SL) unit generating a seed light whose wavelength intervals and center wavelengths are adjusted using at least one seed light source; an optical line terminal (OLT) receiving the wavelength-multiplexed seed light from the seed light unit, transmitting a downstream optical signal to a subscriber of the WDM-PON, and receiving a upstream optical signal from the subscriber; and an optical network unit (ONU) receiving the downstream optical signal from the OLT, flattening and modulating the downstream optical signal with upstream data so that the downstream optical signal is reused for carrying upstream data.

Abstract: An optical amplifier module includes a first optical amplifier to amplify main signal light to be supplied to a dispersion compensation fiber (DCF), a second optical amplifier to amplify the main signal light supplied from the DCF, a generating part to generate monitoring light having a wavelength longer than a wavelength of the main signal light, a multiplexing part to multiplex the monitoring light generated by the generating part and the main signal light to be supplied to the DCF, a demultiplexing part to demultiplex the monitoring light from the main signal light supplied from the DCF, and a detection part to detect a light intensity of the monitoring light demultiplexed by the demultiplexing part.

Abstract: A telecommunications system and constituent two-wire interface module. The two wire interface module includes a logic component configured to communicate over the same pair of wires using different two-wire interface protocols depending on an input signal presented on a configuration input. This configurability allows the two-wire interface module to use the same two wires to communicate with a variety of other two-wire interface modules, even if those two-wire interface modules communicate using different two-wire interface protocols.

Abstract: An optical amplifying device includes a first optical amplifier for amplifying signal light; a second optical amplifier serially connected with the first optical amplifier; an optical device for compensating deterioration of the signal light, the optical device arranged between the first optical amplifier and the second optical amplifier; a variable optical attenuator for attenuating the signal light, the variable optical attenuator arranged between the first optical amplifier and the second optical amplifier; a first automatic level controller for detecting a second amplifier output power and for controlling driving status of the second amplifier in a predetermined output power level; and a first automatic gain controller for detecting an input power of the second optical amplifier and an output power of the second optical amplifier, and for controlling an optical attenuation value of the variable optical attenuator.

Abstract: An optical amplifier apparatus for amplifying a wavelength division signal light includes a detector for detecting an inputted wavelength division signal light, a dispersion compensator for compensating for a dispersion of the inputted wavelength division signal light, an optical amplifier for amplifying the inputted wavelength division signal light after compensation by stimulated emission of an optical gain medium including a rare-earth element, a propagation delay detector for detecting a propagation delay time of the wavelength division signal light between the detector and the optical amplifier, and a controller for controlling the gain of the optical amplifier on the basis of the propagation delay time such that the change of the gain of the optical amplifier is adjusted by the propagation delay time.

Abstract: Raman tilt is induced by the propagation of optical signals in optical communication fibers during and after transient events. Certain characteristics of the light are monitored at each amplification node and Raman tilt correction is achieved by spectral tilt control optics. The light is monitored either as total power, and/or the power of light after passing through one or more optical filters. In the case of EDFA (Erbium Doped Fiber Amplifier) the correction is performed by adjusting stage gains and VOA loss distribution within the amplifier. The light detection is relatively fast, whereby the tilt is compensated by fast controlled VOA and pump power adjustment during a transient event.