Abstract: An optical amplifier includes a light source that outputs light having an intensity corresponding to a supplied driving power; a modulator that modulates the light output from the light source in response to an input modulation signal; a Raman amplifier that performs Raman amplification on the light modulated by the modulator using a highly-nonlinear medium; and a driver that supplies the driving power to drive the light source and inputs the modulation signal to the modulator. The driver starts inputting the modulation signal to the modulation unit before the intensity of the light propagating through the Raman amplifier exceeds an intensity value at which stimulated Brillouin scattering occurs in the Raman amplifier.

Abstract: Cross-distribution of the output pump power from optical pump units amongst multiple amplifier gain stages even in a single direction of an optical link in an optical communications system. For example, an optical pump unit may output optical pump power that is shared amongst a discrete optical amplification unit and a distributed optical amplification unit (such as a forward and/or backward Raman amplifier). Such sharing has the potential to increase reliability and/or efficiency of the optical communications system.

Abstract: A submarine optical repeater that shares optical pump power in multiple gain stages such that approximately the same wavelengths of optical pump is provided to each of the gain stages. Also, tilt control mechanism may adjust gain dependency on wavelength by adjusting the amount of optical pump power delivered to the optical gain stages. Residual optical pump power from both forward and backward Raman amplification may be used to power corresponding optically pumped amplifiers.

Abstract: A light output control apparatus, includes: an excitation light source that outputs excitation light; an excitation light guiding unit that guides the excitation light to an optical amplifying medium for transmitting a signal light; and a loss causing unit that includes an optical transmission medium located between the excitation light source and the excitation light guiding unit, and changes a radius of curvature of the optical transmission medium.

Abstract: An optical signal processing system is provided that includes a first light modulator for receiving, placing information on a first optical signal, and for producing a second optical signal. The second optical signal includes a desired signal portion and an undesired signal portion. The optical signal processing system includes a second light modulator that tunes a first optical pump signal to a Brillouin frequency that is less than, but corresponding to, a frequency of the undesired signal portion. The optical signal processing system includes a light conductor configured to receive as a first input the second optical signal and as a second input the first optical pump signal tuned to the Brillouin frequency. The optical signal processing system causes the first optical pump signal tuned to the Brillouin frequency to induce a Stimulated Brillouin Scattering effect at the light conductor to attenuate the undesired signal portion.

Abstract: An optical amplifier that amplifies signal light with Raman amplification in the Raman amplification medium. The optical amplifier includes a light source that supplies pump light into the Raman amplification medium, a first detector that detects input power of the pump light to be input to the Raman amplification medium, a second detector that detects output power of the pump light output from the Raman amplification medium, and a processor operable to calculate transmission loss of the pump light in the Raman amplification medium by comparing the input power with the output power, and calculate transmission loss of the signal light in the Raman amplification medium based on the transmission loss of pump light corrected based on a wavelength of the signal light and a wavelength of the pump light.

Abstract: A double clad fiber includes a core, a first cladding provided so as to cover the core, and a second cladding provided so as to cover the first cladding. The second cladding has a plurality of pores extending in a length direction and arranged so as to surround the first cladding. In at least one fiber end, the second cladding has been removed by mechanical processing so that the at least one fiber end is formed by the core and the first cladding.

Abstract: An analog multi-gigabit receiver and/or transceiver can be implemented for the reception and demodulation of multi-gigabits quadrature phase shift keying (QPSK) modulated using a CMOS (complementary metal-oxide semiconductor) process. Further, an analog multi-gigabit receiver and/or transceiver can be implemented for the reception and demodulation of multi-gigabits binary phase shift keying (BPSK), minimum shift keying (MSK), and/or amplitude shift keying (ASK) signal modulated in CMOS processes.

Abstract: An optical amplifier provided in a repeater station of an optical transmission system is proposed. The optical amplifier amplifies an signal light and performs ALC of output power by means of a variable optical attenuator (VOA). The optical amplifier receives a difference between a target output value and measured output value of an upstream optical amplifier as an expected control volume, and updates a target attenuation value for the VOA in accordance with a current target attenuation value set to the VOA for ALC, a difference between its own target output value and measured output value, and the expected control volume. The target attenuation value is updated at intervals of time exceeding output convergence time by ALC. The difference between the target output value and measured output value of the optical amplifier is adopted as the expected control volume for a downstream optical amplifier.

Abstract: Provided is a gain-clamped (GC) optical amplifier using a fiber Raman amplifier (FRA) having a Raman cavity. The FRA having a Raman cavity comprises a Raman fiber module (RFM) amplifying and outputting an input optical signal and a resonant cavity generating a Raman laser and a gain clamping laser (GC laser), wherein the resonant cavity is formed as a feedback loop between an input terminal and an output terminal of the RFM. Accordingly, a gain of an optical signal propagating along a core of RFM keeps a constant value regardless of input signal intensity by generating the GC laser for gain clamping between a wavelength band of the Raman laser and a gain band of input signals.

Abstract: A laser device having a semiconductor gain element optically coupled to an optical fiber by using an angled anamorphic fiber lens and including a wavelength-selective front reflector. The laser device possesses improved output characteristics such as a highly linear laser emission output, even when the amplification section produces a high amount of gain. Such a laser source can also be used in various applications such as pump lasers for fiber amplifiers or frequency doubling systems.

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 an optical amplifier, an input light is supplied to one end of an optical fiber connected to an output port, and the power of a light in an opposite direction which is input to the output port from the one end of the optical fiber, is measured, thereby obtaining a stimulated Brillouin scattering (SBS) occurrence threshold in the optical fiber based on the measurement result. Then, using the SBS occurrence threshold, a relation between the input light power and an occurrence amount of the self phase modulation (SPM) or the like in the optical fiber is obtained to be reflected on a control of the optical amplifier, so that an occurrence of the SPM or the like in the optical fiber is suppressed. As a result, it becomes possible to accurately measure, with a simple configuration, the nonlinear optical properties of the optical fiber actually connected to the output port of the optical amplifier, so that the optical S/N ratio degradation due to a nonlinear optical effect can be effectively suppressed.

Abstract: An optically amplified wavelength division multiplexing network has the functionality to add/drop channels at the optical add/drop multiplexing (OADM) nodes. The OADM node includes a receiver amplifier, an OADM module, and a transmitter amplifier. Once the OADM node detects a loss of signal (LOS) due to a fiber cut or network element failure upstream, the receiver amplifier is kept in operation as a noise source. The output of the receiver amplifier is immediately raised by increasing pump power to compensate for the LOS. The noise power received at the transmitter amplifier from the receiver amplifier is substantially equal to the signal power expected before LOS. The transient effect of downstream optical amplifiers is therefore completely suppressed and the inter-channel stimulated Raman scattering (SRS) induced spectrum tilt does not change. After the noise power is raised, the receiver amplifier may be shut down at a speed much slower than the speed of downstream amplifier control circuitry.

Abstract: A Raman amplifier includes a semiconductor laser and an optical amplification fiber connected to an optical transmission fiber used for transmitting optical signals. In the Raman amplifier, excitation light emitted from the semiconductor laser is introduced into the optical amplification fiber while excitation light is incident on the optical transmission fiber, thus amplifying optical signals owing to stimulated emission of Raman scattering in both the optical amplification fiber and the optical transmission fiber. The optical amplification fiber is connected to the upstream/downstream side of the optical transmission fiber along the transmitting direction of optical signals, so that excitation light is introduced into the optical amplification fiber inversely toward the downstream/upstream side of the optical transmission fiber along the transmitting direction. The Raman amplifier including a single semiconductor laser can be reduced in manufacturing cost.

Abstract: Devices for generating a laser beam are disclosed. The devices include a silicon micro ring having at least one silicon optical waveguide disposed at a distance from the micro ring. The radius and the cross-sectional dimension of the micro ring, the cross-sectional dimension of the waveguide, and the distance between the micro ring and the waveguide are determined such that one or more pairs of whispering gallery mode resonant frequencies of the micro ring are separated by an optical phonon frequency of silicon. Methods of manufacturing a lasing device including a silicon micro ring coupled with a silicon waveguide are also disclosed.

Abstract: An optical transmission and amplification system includes a multichannel transmission span with a length of a multicore transmission fiber having a plurality of individual transmission cores. A first tapered multicore coupler provides connectivity between the plurality of transmission cores of the multicore fiber and a respective plurality of individual transmission leads. A fiber amplifier is provided having a plurality of individual cores including at least one pump core and a plurality of amplifier core. A second tapered multicore coupler provides connectivity between the amplifier cores of the fiber amplifier and a respective plurality of amplifier leads, and between the at least one pump core and a respective pump lead.

Abstract: A Raman amplification apparatus includes a pumping light supplying section, a main signal wavelength light level acquisition section, a monitoring signal wavelength light level acquisition section, a function information storage section for storing, as function information, information regarding functions for deriving a noise amount and a gain by Raman amplification with regard to a monitoring signal wavelength light with respect to pumping light power supplied from the pumping light supplying section, and a transmission characteristic derivation section for deriving a transmission characteristic on an optical transmission line based on information acquired by the main signal wavelength light level acquisition section and the monitoring signal wavelength light level acquisition section and the function information stored in the function information storage section, and Raman gain is derived with high accuracy in comparison with the conventional technique.

Abstract: A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Abstract: A method for selecting a relation between a gain Gf of a Forward Raman Amplifier (FRA) at a transmitting end of a fiber optic transmission line and an optical signal to noise ratio (OSNR) at a receiving end of the fiber optic transmission line satisfying limitations for real long transmission lines. The method comprises selecting the relation using a regulation function ROSNR obtained either in the form of a simplified equation, or in the form of one or more linear approximations of the function for practical ranges of the FRA gain.

Abstract: A method of compensating for channel power depletion induced by Raman amplification noise in a hybrid distributed Raman amplifier-Erbium doped fibre amplifier. In the method, an equivalent noise figure is determined for a virtual amplifier equivalent to the hybrid distributed Raman amplifier-Erbium doped fibre amplifier, and having an input power equal to the input power of the Erbium doped fibre amplifier when the distributed Raman amplifier is off and an output power equal to the Erbium doped fibre amplifier output power. A compensation power, dependent at least in part upon the equivalent noise figure, is determined. A control signal is provided for controlling the hybrid amplifier such that an optical signal amplified by the hybrid amplifier has a total output power equal to a predetermined nominal output power plus the compensation power.

Abstract: A method of optical communication includes generating an amplified optical signal from at least a portion of a first optical signal having a first carrier wavelength, ?1. The amplified optical signal is applied to Brillouin media to stimulate generation of a Brillouin effect signal at a wavelength ?2. The Brillouin effect signal is modulated to produce a second optical signal having a second carrier wavelength, ?2. In one embodiment, the first optical signal is a downstream optical signal and the second optical signal is an upstream optical signal of a passive optical network.

Abstract: A laser amplifier system is presented including a pump regenerative amplifier. The amplifier generally has a cavity defined by a pair of end cavity mirrors between which an amplified pump pulse oscillates. The amplifier also includes an interaction cell with a tunable gain medium amplifies laser pulses (e.g., Raman gain). The interaction cell may be positioned within the pump amplifier cavity and an input pulse may be injected into the cavity of the amplifier to transit through the tunable gain medium of the interaction cell. A pump pulse transfers energy via interaction with the input pulse (e.g., Raman interaction) as the pulses counter-propagate through the gain medium of the interaction cell. Amplification of output laser pulses, however, is generally achieved according to the wavelength of the pump laser pulses thereby providing a wavelength dependent, or “tunable”, means for amplifying laser pulses.

Abstract: The object of this invention is to provide a phase stabilization device for stimulated brillouin scattering-phase conjugate mirrors and a light amplification apparatus using the phase stabilization device. A light amplification apparatus of the present invention includes a polarizer (70) for polarizing light beams reflected from a plurality of stimulated brillouin scattering-phase conjugate mirrors and causing the light beams to interfere with each other. A detector (80) acquires an interfering beam resulting from interference of the polarizer (70), and outputs the interfering beam. A phase controller (90) controls phase using the interfering beam acquired by the detector. Therefore, the apparatus of the present invention can stably lock the phase for a long period of time, and can be used in various industries and for scientific research in cases where a high repetition rate and high power are required.

Abstract: The optical transmission system modulates backward Raman pump light provided to an optical transmission line on one link side of an uplink and downlink, to thereby transmit a pilot signal for confirming a connection state of the optical transmission line to a node on an upstream side. When the pilot signal is received by the node on the upstream side, the backward Raman pump light provided to the optical transmission link on the opposite link side is modulated to thereby send back a response signal to an own node. Then by confirming receipt of the response signal at the own node, the backward Raman pump light provided to the optical transmission line on the one link side is changed over from a low output state to a high output state.

Abstract: A system is provided that includes optical amplifiers provided upstream from an optical add-drop multiplexer (OADM). One of the optical amplifiers may be a Raman amplifier that supplies amplified light to another optical amplifier, such as an erbium doped fiber amplifier (EDFA), which, in turn, further amplifies and feeds the light to an input of the OADM. During turn-up, for example, the EDFA may initially be disabled, the power of the pump lasers of the Raman amplifier may be gradually increased until light input to the EDFA exceeds a power threshold at which the EDFA can amplify the input light. Light supplied to the EDFA does not have an excessive amount of power. Accordingly, at this point, the gain of the EDFA may be appropriately adjusted and then activated to supply optical signals to the OADM. Such optical signals may have a low power but not too low so as to prevent proper operation of downstream EDFA. Moreover, these optical signal do not have power that is so high as to cause “spiking.

Abstract: A Raman amplifier provided with a pump source outputting a pumping light; a rare-earth doped fiber inputting the pumping light and outputting an excitation light; and a guiding unit guiding the excitation light to an optical fiber to a direction opposite to which a signal light propagates in the optical fiber. Also a Raman amplifier provided with a plurality of pump sources outputting a plurality of pumping lights; a plurality of rare-earth doped fibers inputting the each of the plurality of pumping lights and outputting a plurality of excitation lights; a guiding unit guiding the plurality of excitation lights to an optical fiber to a direction opposite to which a signal light propagates in the optical fiber.

Abstract: Imaging systems and methods are provided. In one embodiment, an image system is disclosed that comprises a Raman gain medium configured to receive an image from a target area and a tunable laser configured to pump light into the Raman gain medium over a plurality of first wavelengths to induce amplification of the image over a plurality of second wavelengths strokes shifted from the plurality of first wavelengths. The image system further comprises an image detector system that receives and processes the amplified image over the plurality of second wavelengths.

Abstract: The WDM optical transmission system using distributed Raman amplification, before starting operation of main signal light, transfers a plurality of lights having different wavelengths to that of the main signal light (for example Raman amplification pump lights or the like) between first and second optical transmission devices connected to opposite ends of a transmission line, monitors transmission line input and output power for each light, calculates a transmission line loss in each wavelength using the monitor results, and specifies a type of the transmission line based on a loss wavelength characteristic that can be estimated from the calculation result. Then the power of pump light provided to the transmission light is optimized in accordance with the type of transmission line.

Abstract: A method for cost-effective optical transmission with fast Raman tilt or other transient event control uses a combination of Erbium-doped fiber amplifiers (EDFAs) and Raman fiber amplifiers (RFAs), where EDFAs are used as the primary optical amplifiers to compensate the span loss while the RFA (advantageously a forward-pumped RFA) is used only in some specific spans with a feed-forward control circuit serving as a fast Raman tilt transient compensator, the RFA also serving as an optical amplifier. A long haul optical transmission system using feed-forward controlled RFA's periodically spaced along its length, for example, when add-drop multiplexing is used, makes full use of the economics of EDFAs and the fast tilt transient control capability of a RFA enabled by an adjustable speed feed-forward or feed-back control technique.

Abstract: Embodiments of the present invention provide an array of semiconductor optical amplifiers, within a photonic integrated circuit (hereinafter, “PIC”), that apply a gain to one or more optical bands within a WDM signal. According to various embodiments of the invention this array of SOAs can function as both an amplifier and a ROADM by adjusting the gain characteristics of one or more of the SOAs within the array. A band within the WDM signal may be blocked by adjusting the SOA, corresponding to the particular band, to attenuate the band below a threshold.

Abstract: A Raman amplifier that amplifies a signal light intensity by using a Raman amplification effect of an optical fiber transmission channel has an excitation unit that supplies excitation lights of a plurality of wavelengths to the optical fiber transmission channel and performs Raman amplification, a signal light monitor that monitors the signal light intensity of each wavelength contained in the signal light that is Raman amplified, an output light intensity deviation monitoring circuit that finds a deviation in the intensity of each signal light detected by the signal light monitor, and an excitation light control circuit that controls an excitation light intensity from excitation light sources of each wavelength constituting the excitation unit so as to correspond to a predetermined characteristic based on a deviation of the intensity of signal light found by the output light intensity deviation monitoring circuit.

Abstract: Modular set is formed by optical module interconnected with control module of electronic system. Optical module is formed by at least two pairs of laser diodes connected in series and including Peltier cooler and thermistor, which are connected to inputs of polarizing fiber combiners, and depolarized outputs of these polarizing fiber combiners are connected to inputs of a wavelengths combiner. Module of the electronic system is formed by a control microprocessor interconnected with direct current power supply source, with PID regulators of laser diodes temperature, a display indicating temperature of individual laser diodes and current flowing through them, and a control panel.

Abstract: A laser amplifier system is presented including a pump regenerative amplifier. The amplifier generally has a cavity defined by a pair of end cavity mirrors between which an amplified pump pulse oscillates. The amplifier also includes an interaction cell with a tunable gain medium amplifies laser pulses (e.g., Raman gain). The interaction cell may be positioned within the pump amplifier cavity and an input pulse may be injected into the cavity of the amplifier to transit through the tunable gain medium of the interaction cell. A pump pulse transfers energy via interaction with the input pulse (e.g., Raman interaction) as the pulses counter-propagate through the gain medium of the interaction cell. Amplification of output laser pulses, however, is generally achieved according to the wavelength of the pump laser pulses thereby providing a wavelength dependent, or “tunable”, means for amplifying laser pulses.

Abstract: An optical communication system is operable to communicate a plurality of wavelength signals at a bit rate of at least 9.5 gigabits per second over a multiple span communication link spanning at least 400 kilometers without optical regenerators. The plurality of wavelength signals include a bandwidth of more than 32 nanometers separated into at least 160 optical channels. The system includes a plurality of optical transmitters implementing a forward error correction (FEC) coding technique. The FEC encoded wavelength signals comprise a bit error rate of 10?09 or better after FEC decoding. The system also includes at least five (5) optical add/drop multiplexers (OADMs), each coupled to one or more spans of the multiple span communication link. The system further includes a plurality of amplifiers each coupled to one or more spans of the communication link, at least a majority of the amplifiers comprise a distributed Raman amplification stage.

Abstract: An example method includes receiving power measurements for a plurality of optical channels. Deviation measurements representing a difference between respective power measurements and corresponding power targets for the plurality of optical channels are created. Correctable deviations for the plurality of optical channels are determined based on the deviation measurements. The correctable deviations may be determined by projecting the measured deviations into a space that defines Raman gain profiles achievable with a set of channels and pumps. Pump settings for a plurality of pumps are determining based upon the correctable deviations for each channel by solving an optimization problem. The pump setting so determined may be applied to the plurality of pumps.

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 Raman amplifier according to the present invention comprises a plurality of pumping means using semiconductor lasers of Fabry-Perot, DFB, or DBR type or MOPAs, and pumping lights outputted from the pumping means have different central wavelengths, and interval between the adjacent central wavelength is greater than 6 nm and smaller than 35 nm. An optical repeater according to the present invention comprises the above-mentioned Raman amplifier and adapted to compensate loss in an optical fiber transmission line by the Raman amplifier. In a Raman amplification method according to the present invention, the shorter the central wavelength of the pumping light the higher light power of said pumping light.

Abstract: Apparatus and method for gain measurement and control of a Distributed Raman Amplifier (DRA). Various embodiments of the apparatus include a detection unit operative to measure, during operation of the DRA, the optical power of a filtered component of the light entering the DRA from the transmission fiber and a gain calculation and control unit coupled to the detection unit and operative to calculate a signal Raman gain property from the measured optical power. The filtered component may exemplarily be a result of passing the light through a band pass filter, a spectral filter with a given spectral shape or a notch filter. The signal Raman gain property may be an average on-off signal Raman gain, an average net signal Raman gain or a signal Raman gain tilt within a communication band. The apparatus and method may be used to operate the DRA in Automatic Gain Control, i.e. to maintain a required constant signal Raman gain and/or signal Raman gain tilt.

Abstract: An optical waveguide device comprises a plurality of mirrors, wherein at least one mirror comprises a first and second reflective end that reflect and transmit light. The plurality of mirrors comprises at least one first material having at least one first refractive index; an axis line; a first cladding comprising a second material having a second refractive index; a second cladding, formed above the first, comprising a third material having a third refractive index; a core comprising a fourth material; and a plurality of core parts formed within at least one of the first or second claddings. The fourth material has a fourth refractive index that is greater than the second and third refractive indices and the core parts have a plurality of core part ends coupled to one of the reflective ends where at least one core part end is approximately parallel to one of the reflective ends.

Abstract: The invention includes a master lens, which initially focuses a laser pulse, and then the pulse passes through a zonal lenslet array, which uses different lenslet elements that provide for predetermined focal lengths so as to establish a three or two dimensional, predetermined dispersion of foci of the laser pulse. The zonal lenslet array of the present invention may be thought of as a variant of a Shack-Hartman wave front sensor, but used for an entirely different application.

Abstract: Fiber-laser light is Raman shifted to eye-safer wavelengths prior to spectral beam combination, enabling a high-power, eye-safer wavelength directed-energy (DE) system. The output of Ytterbium fiber lasers is not used directly for spectral beam combining. Rather, the power from the Yb fiber lasers is Raman-shifted to longer wavelengths, and these wavelengths are then spectrally beam combined. Raman shifting is most readily accomplished with a “cascaded Raman converter,” in which a series of nested fiber cavities is formed using fiber Bragg gratings.

Abstract: In an optical parametric amplifier of the invention, pumping light which is amplified using a practical optical amplifier such as an EDFA is supplied together with signal light having a wavelength outside the amplification band of the optical amplifier, to a nonlinear optical medium via a multiplexer, to thereby amplify the signal light by an optical parametric amplification effect due to the pumping light in the nonlinear optical medium. As a result, the amplification band of a practical optical amplifier such as an EDFA, can be extended, and the noise characteristics can be improved.

Abstract: A monitoring apparatus, based on an optical power monitored in photodetectors arranged at input and output ends of a transmission line, in a condition where pump light is supplied to the transmission line at a time of initial startup of an optical communication system, obtains a relationship for the noise light generated due to Raman amplification, between forward direction noise light power and backward direction noise light power, and while in service, converts the backward direction noise light power monitored by the photodetectors at the input ends of the transmission line into the forward direction noise light power in an arithmetic processing section, in accordance with the relationship obtained at the time of the initial startup. As a result the power of noise light generated due to Raman amplification, can be monitored in real time at high speed.

Abstract: An optical circuit is described which may include an SOA-MZI circuit providing an output signal; and a polarization filtering device (PFD) configured to receive the output signal of the SOA-MZI and to provide at least one signal at the output of the PFD.

Abstract: An optical amplifier including gain equalization and system incorporating the same. The amplifier includes a Raman portion and an EDFA portion with a gain flattening filter coupled between the Raman portion and the EDFA.

Abstract: Systems and methods for controlling a Raman amplifier by measuring power at one end of an optical fiber span. The Raman amplifier may include a laser that pumps an optical signal into the optical fiber span. The Raman amplifier may be connected to a controller that receives backscatter measurements. The controller may then adjust the Raman amplifier to maintain the backscatter substantially constant.

Abstract: A Raman amplifier includes at least a first and a second optical Raman-active fiber disposed in series with each other. A first pump source is connected to the first Raman-active fiber, and is adapted for emitting and coupling into the first Raman-active fiber a first pump radiation including a first group of frequencies. A second pump source is connected to the second Raman-active fiber, and is adapted for emitting and coupling into the second Raman-active fiber a second pump radiation including a second group of frequencies. The whole of said first and second group of frequencies extends over a pump frequency range having a width of at least the 40% of the Raman shift. The minimum and the maximum frequency in each of said first and second group of frequencies differ with each other of at most the 70% of said Raman shift.

Abstract: A method and apparatus is provided for transmitting a WDM optical signal. The method begins by modulating an odd number of optical channels that are each located at a different wavelength from one another with (1) a respective one of a plurality of information-bearing electrical signals that all embody the same broadcast information and (2) a respective one of a plurality of RF signals having a common functional broadcast waveform, at least one of the RF signals being out of phase with respect to remaining ones of the plurality of RF signals. Each of the modulated optical channels are multiplexed to form a WDM optical signal. The WDM optical signal is forwarded onto an optical transmission path.

Abstract: Optical apparatus includes a multimode, gain-producing fiber for providing gain to signal light propagating in the core of the fiber, and a pump source for providing pump light that is absorbed in the core, characterized in that (i) the pump source illustratively comprises a low brightness array of laser diodes and a converter for increasing the brightness of the pump light, (ii) the pump light is coupled directly into the core, and (iii) the area of the core exceeds approximately 350 ?m2. In one embodiment, the signal light propagates in a single mode, and the pump light co-propagates in at least the same, single mode, both in a standard input fiber before entering the gain-producing fiber, and a mode expander is disposed between the input fiber and the gain-producing fiber. In another embodiment, multiple pumps are coupled into the core of the gain-producing fiber. The pumps may generate light of the same wavelength or of different wavelengths.