Abstract: An EDFA may include an input photodiode configured to generate a control signal based on an input signal. The EDFA may include a blind stage configured to generate an amplified signal based on the control signal and the input signal. The EDFA may include a non-blind stage configured to generate an output signal based on the amplified signal within the blind stage, the control signal, and a feedback signal. The EDFA may include a filter configured to generate a filtered signal based on the output signal. The EDFA may include an output photodiode configured to generate the feedback signal based on the filtered signal. The EDFA may include an alarm device. A signal within the non-blind stage may be generated based on the feedback signal and the control signal. The alarm device may be configured to generate an alarm signal when the signal exceeds a threshold value.

Abstract: A LIDAR system includes a LIDAR chip that generates a LIDAR output signal. The LIDAR chip includes a utility waveguide configured to carry one or more light signals selected from an outgoing LIDAR signal and an incoming LIDAR signal. The system also includes an amplifier that has an amplifier waveguide with a first facet and a second facet. The amplifier being positioned such that the first facet is optically aligned with a facet of the utility waveguide but the second facet is not optically aligned with any waveguide.

Abstract: A transmission device includes a wavelength multiplexer that wavelength-multiplexes a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal, an amplifier that outputs the wavelength-multiplexed optical signal to a transmission path, and a first processor that allocates wavelength bands to the plurality of optical signals to be wavelength-multiplexed into the wavelength-multiplexed optical signal and controls power of the wavelength-multiplexed optical signal in accordance with the wavelength bands allocated to the plurality of optical signals.

Abstract: An amplifier includes a first monitor configured to measure first optical power including first signal light and ASS light of a first wavelength band propagated through the amplification medium, and a processor configured to calculate the first ASS light power corresponding to the first excitation light power, based on the determined first model formula, calculate the second ASS light power corresponding to the second excitation light power, based on the determined second model formula, calculate the first signal light power by subtracting the calculated first ASS light power and second ASS light power from the first optical power measured by the first monitor, and calculate a difference between the calculated first signal light power and first target signal light power, and controll a first excitation light source or a second excitation light source to adjust the first excitation light power or the second excitation light power based on the difference.

Abstract: The present invention discloses a method of rearrangement of optical amplifiers in a fiber-upgraded elastic optical network, including: traversing through the amplifiers on the upgraded link through a redundancy removal process to remove redundant EDFAs from the upgraded link and calculating the cost saved by the redundancy removal process; rearranging the amplifiers on the upgraded link through a full rearrangement process to rearrange all the EDFAs on the upgraded link and calculating the cost saved by the full rearrangement process; comparing the cost saved by the redundancy removal process with the cost saved by the full rearrangement process on the upgraded link and selecting a process that saved more costs as the method of rearrangement of optical amplifiers on the upgraded link; and perform rearrangement of optical amplifiers on all the upgraded links sequentially. This method can minimize the number of optical amplifiers without significantly reducing spectrum resource utilization.

Abstract: An optical receiver module which receives a first optical signal including a continuous signal or a burst signal includes: a variable optical attenuator which adjusts the first optical signal to output a second optical signal; a semiconductor optical amplifier which amplifies the second optical signal to output a third optical signal; and a controller which controls an output of at least one of the variable optical attenuator and the semiconductor optical amplifier so as to cause the semiconductor optical amplifier to operate in a region in which gain saturation of the semiconductor optical amplifier does not occur, on the basis of at least one of: a power obtained by suppressing an outside portion of the wavelength band of the first optical signal in the third optical signal; and a power obtained by extracting the outside portion of the wavelength band of the first optical signal in the third optical signal.

Abstract: An optical amplifier which can suppress, without measuring signal beam power at individual wavelengths, wavelength-dependence of gain with respect to a signal beam into which multiple signal beams having respective wavelengths different from each other are multiplexed. The optical amplifier can suppress wavelength-dependence of gain by giving loss in accordance with a linear-loss slope to an amplified signal beam. The optical amplifier includes a variable tilt equalizer for varying a loss slope value representing the slope of the loss slope and a tilt control unit for controlling a loss slope value of the variable tilt equalizer.

Abstract: An optical amplification system includes: a first amplification module configured to amplify at least a conventional band (C band) optical signal; a second amplification module configured to amplify a longer wavelength band (L band) optical signal; an attenuator configured to attenuate at least the C band optical signal to obtain a first optical signal and a second optical signal, where the attenuator is further configured to output the first optical signal to the second amplification module and output the second optical signal to a wavelength division multiplexing module, which is configured to combine and output the C band optical signal and the L band optical signal.

Abstract: Technology for a repeater is disclosed. The repeater can measure a first power level within a passband. The repeater can adjust a gain of the repeater by a selected amount. The repeater can measure a second power level within the passband. The repeater can calculate a difference between the first power level and the second power level. The repeater can determine that the repeater is approaching an oscillation when the difference is different than a selected amount by a predetermined threshold.

Abstract: A reconfigurable optical add/drop multiplexer (ROADM) includes a plurality of interconnected ROADM blocks. Each ROADM block includes an ingress switchable-gain amplifier, an output power detector coupled to an output of the ingress switchable gain amplifier, and a wavelength-selective switch coupled to the output of the ingress switchable gain amplifier. Each ROADM block includes a plurality of add/drop blocks coupled to the wavelength-selective switches of the plurality of ROADM blocks. The ROADM includes a controller configured to receive an indication of an output signal power from the output power detector and adjust gain and equalization parameters of the ingress switchable-gain amplifier based on the received indication of the output signal power.

Abstract: The present embodiment relates to a method and apparatus for measuring a tissue variation signal (e.g. a photoplethysmographic (PPG) signal) without large direct current (DC) or low frequency (LF) offset which normally limit the sensor accuracy through motion artefacts and/or dynamic range requirements. The proposed solution is based on a separation of the PPG signal from the disturbance. This can be achieved by creation of a modulated PPG signal, or by creation of a differential PPG signal and an optimized sensor configuration which is adapted to remove DC or LF components.

Abstract: Technology for a repeater is disclosed. The repeater can include a narrowband detector configured to detect one or more power levels that correspond to one or more signals communicated in one or more sub-bands of a selected band. The repeater can include a controller. The controller can select a signal from the one or more signals based on a power level of the selected signal. The controller can adjust a gain or output power of the repeater based on the power level of the selected signal communicated in the one or more sub-bands of the selected band.

Abstract: We describe a quantitative PCR (qPCR) instrument for combined qPCR and melt curve (dissociation and/or association curve) analysis. The instrument has at least one optical channel; a fluorescence excitation source; a fluorescence detector; an electronic analog signal amplifier having an input coupled to an output of the fluorescence detector; and an analog-to-digital converter (ADC) having analog input coupled to an output of the analog signal amplifier. The instrument further comprises a quantified automatic gain control (AGC) loop coupled between the signal output of the fluorescence detector and the analog input of the ADC. The AGC loop is configured to apply a determined, numerical gain value to a fluorescence signal for the analog input of the ADC. The instrument also includes a system to scale a digital output of the ADC responsive to the numerical gain value and to provide a digital fluorescence level signal from the scaled digital output.

Abstract: Systems and methods for data transport, including submarine reconfigurable optical add/drop multiplexers, branching units configured to receive signals from trunk terminals (TTs), and dummy light filters configured to pass useful signals through the filters, and to reflect dummy light. Optical interleavers are configured to separate useful signals into two or more groups of optical channels, and the optical channels are set to a frequency of either a left or a right portion of a total channel bandwidth. De-interleavers merge signal groups together from trunk terminals, and lasers at each of the transponders at the source terminals are configured to adjust a destination of a channel by fine tuning a frequency or wavelength of the one or more signals.

Abstract: An optical transceiver that includes an optical modulator of a Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified spontaneous emission in regions out of the wavelength band of the light.

Abstract: Modular kit of the spectrally flexible device for bidirectional transmissions of optical signals sensitive to timing in the Internet and other networks in the basic embodiment contains the source of the optical holding signal, which is electrically bi-directionally interconnected with the control electronics module. This source of the optical holding signal is optically interconnected is optically interconnected by its one output via the first isolator and the first wave-sensitive coupler with one optical input/output of the semiconductor optical amplifier and/or the second output of the source of the optical holding signal is interconnected via the second isolator and the second wave-sensitive coupler with the second optical input/output of the semiconductor optical amplifier. Semiconductor optical amplifier is electrically bi-directionally interconnected with the control electronics module, the input of which is connected to the output of the power supply module.

Abstract: An integrated optical modulator device. The device can include a driver module coupled to an optical modulator. The optical modulator is characterized by a raised cosine transfer function. This optical modulator can be coupled to a light source and a bias control module, which is configured to apply an off-quadrature bias to the optical modulator. This bias can be accomplished by applying an inverse of the modulator transfer function to the optical modulator in order to minimize a noise variance. This compression function can result in an optimized increased top eye opening for a signal associated with the optical modulator. Furthermore, the optical modulator can be coupled to an EDFA (Erbium Doped Fiber Amplifier) that is coupled to a filter coupled an O/E (Optical-to-Electrical) receiver.

Abstract: The adjustment of tilt in an optical signal path of a repeater. The repeater includes an optical pump that optically powers a rare-Earth doped fiber amplifier, which amplifies the optical signal. The optical signal path also includes Raman gain stage implemented in a previous optical fiber span in the optical signal path, and which contributes tilt with respect to wavelength. Adjusting the Raman gain and/or the rare-Earth doped gain also adjusts the combined tilt contributed by these gain stages. However, the rare-Earth doped gain operates at least partially in the saturated regime, thereby stabilizing the gain at the output of the rare-Earth doped amplifier. Thus tilt control may be employed by adjusting optical pump power with reduced effect on overall gain.

Abstract: An optical amplification apparatus that amplifies input wavelength-division multiplexed light includes a pump light source that outputs pump light, and an optical amplifier that amplifies the wavelength-division multiplexed light in response to a power level of the pump light. The number of wavelengths multiplexed in the wavelength-division multiplexed light is equal to or less than the maximum available number of wavelengths input to the optical amplification apparatus. The power level of the pump light is determined based on the maximum available number of wavelengths.

Abstract: An amplifier receives an optical signal including a number of labeled channels via a fiber. The amplifier determines a count of the labeled channels and a spectral distribution of the labeled channels. The amplifier adjusts a parameter of the amplifier based on the count of the labeled channels and the spectral distribution of the labeled channels. The amplifier amplifies the optical signal at an adjusted output gain resulting from adjusting the parameter of the amplifier.

Abstract: An optical transmission system includes an optical transmitting apparatus that includes a polarization controller configured to change a polarization state of a signal light at an operating frequency included in a frequency range at which polarization trackability is obtained on a receiving side, based on a notified monitoring result, the optical transmitting apparatus being configured to output the signal light having the changed polarization state, and an optical receiving apparatus that is provided on the receiving side and includes a monitoring control unit configured to receive the signal light having the changed polarization state and monitor transmission quality of the received signal light, the optical receiving apparatus being configured to notify the optical transmitting apparatus of the monitoring result.

Abstract: A receiving device includes: an amplification fiber configured to include properties to amplify signal light when pumping light is supplied to the amplification fiber and to attenuate the signal light when the pumping light is stopped supplying to the amplification fiber; a receiver configured to receive the signal light output from the amplification fiber; a pumping light source configured to supply the pumping light to the amplification fiber; and a controller configured to control supplying and stopping of the pumping light from the pumping light source to the amplification fiber, so that a level of the signal light input to the receiver is contained within a dynamic range of the receiver.

Abstract: An integrated photonic polarization-separating apparatus includes a first waveguide polarization beam splitter (PBS) having a first port, a second port, a third port, and a fourth port and a first polarization rotator optically coupled to the first port of the first waveguide PBS. The apparatus also includes a first Faraday rotator optically coupled to the first polarization rotator and a second polarization rotator optically coupled to the second port of the first waveguide PBS. The apparatus further includes a second Faraday rotator optically coupled to the second polarization rotator and a second waveguide PBS having a first port, a second port, a third port, and a fourth port. The third port is optically coupled to the first Faraday rotator and the fourth port is optically coupled to the second Faraday rotator.

Abstract: In an optical amplification apparatus an optical amplifier amplifies an optical signal at set gain. An equalizer changes loss of the amplified optical signal according to wavelengths. A processor controls the equalizer so as to make the equalizer have a loss-wavelength characteristic corresponding to a gain tilt of the optical amplifier which occurs according to the set gain.

Abstract: An optical amplifier which amplifies a wavelength division multiplexed optical signal having a variable number of channels associated with different wavelengths and outputs the amplified WDM optical signal. The optical amplifier includes a first optical amplifier which amplifies the wavelength division multiplexed optical signal and outputs the first optical amplifier amplified wavelength division multiplexed optical signal; a variable optical attenuator which controls a level of the first optical amplifier amplified wavelength division multiplexed optical signal and outputs the controlled wavelength division multiplexed optical signal; a second optical amplifier which amplifies the controlled wavelength division multiplexed optical signal and outputs the amplified, controlled wavelength division multiplexed optical signal; and a controller which controls the wavelength division multiplexed optical signal to be amplified with a constant gain.

Abstract: The present invention includes an optical amplifier and method for reducing the impact of transient events within an optical transmission system. Specifically, a positive transient power or amplifier setting adjustment limit is applied based upon a number of active channels or a current “steady state” operating condition. This adjustment limit is described in terms of a number of channels to be amplified. By controlling the adjustment limit in this manner, automatic control of the amplifier is provided for a loss of channel condition as well as for the addition of a single or few channel condition. If a larger positive transient occurs, the control will not adjust the power limit, and the positive transient power will therefore be suppressed.

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: 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: An optical amplifier includes: a first amplifier amplifying a signal light by a first excitation light; a variable optical attenuator attenuating the signal light; a second amplifier amplifying the signal light by a second excitation light; a mode selector selecting one of first and second modes; a gain controller, in first mode, controlling first and second excitation lights so that a gain of power of the signal light becomes constant; a first output controller, in second mode, controlling the first excitation light; a second output controller that, in second mode, controlling the second excitation light so that a spontaneous emission light having fixed level is outputted; and an attenuation controller controlling an attenuation of the variable optical attenuator according to an input level of the signal light in first mode, and controlling the attenuation to become a given value larger than a value of first mode in second mode.

Abstract: The automatic gain control unit for a radiofrequency receiver includes a first current source for charging a storage capacitor by a first current, four comparators for comparing on the lower side an in-phase positive intermediate signal, an in-phase negative intermediate signal, a quarter-phase positive intermediate signal, a quarter-phase intermediate signal with a first reference threshold to a high amplitude level of the intermediate signals. Each comparator controls a MOS transistor connected in series between a second current source and the storage capacitor in order to discharge the storage capacitor when each transistor is in a conductive state. A bi-stable trigger element is connected to the storage capacitor and to provide an AGC signal depending on the voltage level on the storage capacitor for attenuating or not the gain of the low noise amplifier or of a mixer unit amplifier of the receiver.

Abstract: It is described an optical amplification device for receiving an optical input signal and transmitting an amplified optical output signal on the basis of the optical input signal comprising an optical amplifier that comprises an input and an output. An optical gain control unit is connected to the output path of the optical amplifier and the optical gain control unit is connected to the input path of the optical amplifier. The optical gain control unit is configured to control the gain of the optical output signal. Additionally, an electrical gain control unit is connected to the output path of the optical amplifier. The electrical gain control unit is also connected to the input path of the optical amplifier. The electrical gain control unit is configured to control the gain of the optical output signal. By providing both an electrical gain control unit and an optical gain control unit, a control characteristic can be improved.

Abstract: An optical amplifier comprising: a pumping light source supplying a pumping light to an optical fiber as an amplification medium; an ASE light power detector detecting an ASE light power including an external ASE power flowing from an upstream side outside an amplification signal band; and a control unit setting a gain within the amplification signal band by using the ASE light power detected by the ASE light power detector outside the amplification signal band. The control unit controls the pumping light source by compensating for an influence of the external ASE power, obtained by measuring a relationship between the gain within the amplification signal band and the ASE light power outside the amplification signal band, to set initially the gain within the amplification signal band.

Abstract: Methods for optimizing a noise figure of a variable gain hybrid amplifier (HA) which includes a variable gain Raman amplifier with adjustable average gain GR and gain tilt TR and a variable gain lumped amplifier with adjustable average gain GL and gain tilt TL. In various embodiments, the methods include receiving as input a required hybrid amplifier average gain GH value and a required gain tilt TH value and deriving a set of GR, TR, GL and TL values which yield an optimal optimized hybrid amplifier NF and satisfy the conditions GR+GL=GH and that TR+TL is within a specified hybrid amplifier operating tilt range. In some embodiments, the derived TR and TL values satisfy the condition TR+TL=TH.

Abstract: An optical amplifier with improved transient performance has two amplifier stages and a dispersion compensating fiber inserted between the amplifier stages. A control unit generates a pump control signal for a common pump source pumping both amplifier stages via a power splitter. The pump control signal has a feedforward component with a delayed reaction. A feedforward delay time is adjusted to minimize gain variations resulting from input power drops. In a preferred embodiment, the splitting ratio of the power splitter is adjustable to achieve, for instance, either optimum steady-state performance or optimum transient performance.

Abstract: An embodiment of the present invention discloses a method of performing target Raman gain locking and a Raman fiber amplifier. The Raman fiber amplifier comprises a coupler (1) and a control unit (15), wherein the control unit comprises a target gain locking module. A detection circuit formed by filters and optical power detectors is connected between an output side of the coupler (1) and an input side of the control unit (15). Said method uses the control unit (15) to adjust power of the pump laser, making the detected out-of-band ASE power value reach target out-of-band ASE optical signal power value. Thus, the target amplification gain locking can be realized. Optical path according to embodiments of the present invention has a simple structure. The Raman gain can be configured flexibly according to line condition, and automatic control and locking of gain of the Raman fiber amplifier can be realized.

Abstract: A light power control system is used in a network in which a control signal is transmitted to instruct setting of a wavelength path. The light power control system is provided with a light amplifier control section configured to carry out a constant output control to a light amplifier which amplifies a light signal transmitted from a node to another node, when said node in said network receives the control signal; and a variable optical attenuator control section configured to adjust an attenuation quantity of a variable optical attenuator to attenuate a light power of the light signal on any of wavelength paths, when said node receives the control signal and moreover the light signal is transmitted on said any of wavelength paths of said node. It becomes possible to receive the data right in a receiving end by a simple unit when there is a change of the number of wavelength paths.

Abstract: An amplifier receives an optical signal including a number of labeled channels via a fiber. The amplifier determines a count of the labeled channels and a spectral distribution of the labeled channels. The amplifier adjusts a parameter of the amplifier based on the count of the labeled channels and the spectral distribution of the labeled channels. The amplifier amplifies the optical signal at an adjusted output gain resulting from adjusting the parameter of the amplifier.

Abstract: An optical amplifier which amplifies a wavelength division multiplexed optical signal having a variable number of channels associated with different wavelengths and outputs the amplified WDM optical signal. The optical amplifier includes a first optical amplifier which amplifies the wavelength division multiplexed optical signal and outputs the first optical amplifier amplified wavelength division multiplexed optical signal; a variable optical attenuator which controls a level of the first optical amplifier amplified wavelength division multiplexed optical signal and outputs the controlled wavelength division multiplexed optical signal; a second optical amplifier which amplifies the controlled wavelength division multiplexed optical signal and outputs the amplified, controlled wavelength division multiplexed optical signal; and a controller which controls the wavelength division multiplexed optical signal to be amplified with a constant gain.

Abstract: System for converting relatively long pulses from rep-rate variable ultrafast optical sources to shorter, high-energy pulses suitable for sources in high-energy ultrafast lasers. Fibers with positive group velocity dispersion (GVD) and self phase modulation are advantageously employed with the optical sources. These systems take advantage of the need for higher pulse energies at lower repetition rates so that such sources can be cost effective.

Abstract: An apparatus includes: an optical amplifier configured to perform optical amplification for gain by controlling so as to be a target gain; a correction power calculator configured to calculate, in response to amplified spontaneous emission light input to the optical amplifier, correction power corresponding to an amount of gain depression in a bandwidth in which spectral hole-burning occurs in the optical amplifier; and a gain controller configured to calculate, using the correction power calculated in the correction power calculator, a gain for controlling the optical amplification performed in the optical amplifier and perform, using the calculated gain, a control operation so that the gain of the optical amplification becomes the target gain.

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: The invention refers to a method for operating an amplifier with a first amplifier stage (A1) and a second amplifier stage (A2), pumped by a single pump light source (11) generating a primary pump signal (SPUMP), which is split into first pump signal (S1) and a second pump signal (S2) according to a variable splitting factor (?) for pumping the first amplifier stage (A1) and the second amplifier stage (A2) respectively. The splitting factor (?) is varied to achieve an optimized noise figure.

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: An optical amplifier includes an input port, an output port, an amplification medium, a light source, a monitor, and a controller. The amplification medium with which doped an rare-earth element for optical amplification is allocated on an optical path between the input port and the output port. The light source supplies the amplification medium with an excitation light. The monitor monitors a total power of an optical signal of each wavelength according to a monitor period which is longer than a transient response time of the amplification medium. The controller controls the light source so that a power of the excitation light is constant when a monitor value of the monitor is equal to or smaller than a predetermined threshold value and controls the light source so that an optical gain in the amplification medium is constant when the monitor value is larger than the predetermined threshold value.

Abstract: There is provided an optical amplifier including a pump light source to generate a pump light being capable of changing a wavelength thereof, a first rare earth doped medium to amplify an input signal light by using the pump light generated by the pump light source, a second rare earth doped medium to amplify the input signal light output from the first rare earth doped medium by using a residual pump light that is a portion of the pump light generated by the pump light source, and a wavelength controller to control a wavelength of the pump light generated by the pump light source, based on an input level of the input signal light.

Abstract: Included are a semiconductor device unit in which a semiconductor optical amplifier and a first semiconductor photo detector being configured to monitor a part of an input light input to the semiconductor optical amplifier or a part of an output light output from the semiconductor optical amplifier are integrated on a mutually same substrate, and a passive waveguide unit connected to the semiconductor device unit and in which a first passive waveguide being configured to cause the input light to be input to the semiconductor optical amplifier or to cause the output light to be output from the semiconductor optical amplifier and a second passive waveguide branching from the first passive waveguide and being configured to cause a part of the input light or a part of the output light to be input to the first semiconductor photo detector are provided on a mutually same substrate.

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: An optical amplifier has a pump and an “anti-pump” for reducing a variation of the amplifier gain with the input optical power. The wavelength of “anti-pump” light is longer than the wavelength of the optical signal being amplified, so that the optical signal serves as a pump for the “anti-pump” light, whereby an optical loss variation with the signal power at the signal wavelength is created, which reduces optical gain variation with the signal power. To compensate for gain loss due to the anti-pump light, two and three stages of amplification can be used.

Abstract: In some embodiments, the present invention provides an apparatus and process wherein excess stored optical energy is removed from one or more stages in a fiber-amplifier, in order to stabilize the gain and obtain a constant level of energy per pulse. In some embodiments, a method of the invention includes providing a gain fiber, optically pumping the gain fiber using pump light, amplifying seed-signal pulses having a signal wavelength using the gain fiber to obtain amplified output pulses, and automatically limiting a gain of the gain fiber. In some embodiments, an apparatus of the invention includes a gain fiber, a source of pump light coupled to the gain fiber, a source of seed-signal pulses having a signal wavelength coupled to the gain fiber, wherein the gain fiber outputs amplified signal pulses, and an automatic-gain-control mechanism configured to limit gain of the gain fiber.