Abstract: In some implementations, an amplifier device may include a first amplifier configured to amplify signals in a first range of optical wavelengths. The first amplifier may include a first portion that includes one or more first optical gain components, and a second portion that includes one or more second optical gain components and a variable optical attenuator. The amplifier device may include a second amplifier configured to amplify signals in a second range of optical wavelengths. The amplifier device may include a filter for the first range of optical wavelengths and the second range of optical wavelengths. The filter may be located between the first portion and the second portion of the first amplifier.

Abstract: A fiber laser system, includes: N fiber laser units that generates respective laser beams, where N?2; an output combiner that: combines the respective laser beams, and generates output light including, as the respective laser beams, laser beams different from each other in terms of NA power cumulative distribution; and a control unit that sets a power of each of the respective laser beams such that an upper limit NA corresponding to each of not more than (N?1) predetermined power cumulative rate(s) is equal to a specified value for the output light.

Abstract: The present embodiment relates to an optical amplifier and the like having a structure for enabling efficient use of pumping light while avoiding complication of a device structure. In such an optical amplifier, since pumping light from a pumping light source is supplied to each core of an amplification MCF, a coupling MCF in which adjacent cores form a coupled core is arranged between the amplification MCF and the pumping light source. The pumping light source is optically connected to a specific core of the coupling MCF, and pumping light is coupled from the specific core to remaining cores except the specific core in the coupling MCF before pumping light is supplied to each core of the amplification MCF. This enables coupling of pumping light between optically connected cores between the amplification MCF and the coupling MCF.

Abstract: In order to solve the problem that the power consumption of optical amplifiers is not optimized over the life time of a network whose capacity in use varies, an optical amplifier according to an exemplary aspect of the invention includes a gain medium for amplifying a plurality of optical channels, the gain medium including a plurality of cores through which the plurality of optical channels to propagate respectively and a cladding area surrounding the plurality of cores; monitoring means for monitoring the plurality of optical channels inputted into the gain medium and producing a monitoring result; a first light source configured to emit a first light beam to excite the cladding area; a second light source configured to emit a plurality of second light beams to excite each of the plurality of cores individually; and controlling means for making a decision as to whether each of the plurality of cores to transmit one of the plurality of optical channels based on the monitoring result, and controlling the firs

Abstract: A phase control system for controlling the relative phase (?) of two laser beams of a laser system, which are to be coherently combined, is disclosed that enables providing a phase-controlled sum laser beam. An optical system of the phase control system includes a beam input for receiving a measuring portion of two collinear coherent laser beams, which are superimposed to form a sum laser beam, and provides measuring beams or measuring beam regions, which are used with associated photodetectors for outputting photodetector signals. For determining the relative phase from the photodetector signals, the phase control system has an evaluation device and a delay device for being inserted into the beam path of at least one of the two laser beams. The optical system is configured such that the measuring beams or measuring beam regions are related to different phase offsets.

Abstract: An optical fiber amplifier comprising first, second and third optical fibers, and first, second and third lenses, is disclosed. First cores of the first optical fiber and second cores of the second optical fiber have homothetic arrangement each other in the arrangement of outer cores. The first core has a mode field diameter MFD1S when transmitting an optical signal and a core pitch P1, and the first lens has a focal distance f1S at the wavelength of the optical signal. The second core has a mode field diameter MFD2S when transmitting the optical signal and a core pitch P2, and the second lens has a focal distance f2S at the wavelength. The MFD1S of each first core is within ±25% of MFD2S×(P1/P2) of the corresponding second core, and the MFD1S of each first core is within ±25% of MFD2S×(f1S/f2S) of the corresponding second core.

Abstract: An unrepeatered transmission system includes a receiver coupled to a receive span; a transmitter coupled to the receive span; and a plurality of cascaded amplifiers in the receive span with dedicated fiber cores to supply one or more optical pumps from the receiver to each amplifier, wherein the plurality of cascaded amplifiers increase system reach by increasing the length of a back span in an unrepeatered link.

Abstract: A fiber sensor that includes: an optical fiber configured for one of single or few mode operation at a wavelength from about 300 nm to about 2000 nm, and further defined by a transmission end, a scattering end, a fiber outer diameter and a fiber length from about 10 m to about 100 km. The fiber includes: a plurality of cores having equivalent core diameters and compositions; and a cladding defined by the fiber outer diameter and surrounding the cores. The fiber is tapered at the transmission end to define a tapered portion characterized by a tapered fiber out diameter and tapered core diameters smaller than the respective fiber outer diameter and core diameters. Further, the transmission end of the fiber exhibits a total backscattered signal that emanates from the cores after light from a single source has been injected into the cores at the transmission end of the fiber.

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: Methods, systems, and apparatus for optical communications. In one aspect, an optical amplifier includes a feed-forward first amplification stage including a rare-earth doped fiber receiving an optical signal and an injected pump light; and a plurality of subsequent amplification stages each including a corresponding rare-earth doped fiber, wherein each of the subsequent amplification stages receives a separately injected portion of the remnant pump light from the first amplification stage, the remnant pump light being split into portions directed to each respective subsequent amplification stage.

Abstract: Doped fiber amplifiers (DFA) using rare-earth doping materials with linear and non-linear interactions between the optical signal to be amplified and the pump laser have become a standard element of optical telecommunications systems for multiple applications including for example extending the reach of optical links before opto-electronic conversion is required or support increased fanout. However, in many applications wherein multiple DFAs are employed the electrical power budget wherein the pump laser diode (LD) represents approximately 25% of the module power consumption directly, and closer to approximately 40-50% once the control and drive electronics for the thermoelectric cooler and LD are included. Accordingly, it would be beneficial to reduce the overall power consumption of a DFA by exploiting unused optical pump power such that multiple gain stages, within the same or different DFAs, may be driven from a single pump LD.

Abstract: The present invention relates to a man-made composite material and a man-made composite material antenna. The man-made composite material is divided into a plurality of regions. An electromagnetic wave is incident on a first surface exits from a second surface of the man-made composite material opposite to the first surface. A line connecting a radiation source to a point on the bottom surface of the ith region and a line perpendicular to the man-made composite material form an angle ? therebetween, which uniquely corresponds to a curved surface in the ith region. A set formed by points on the bottom surface of the ith region that have the same angle ? forms a boundary of the curved surface to which the angle ? uniquely corresponds. The refraction, diffraction and reflection of the present invention at the abrupt transition points can be reduced.

Abstract: An optical fiber coupler connects transmission multicore optical fiber (TMCF) with an amplifier multicore optical fiber (AMCF) and a plurality of optical pump fibers. The coupler includes a plurality of signal cores extending between a multicore input endface and a coupler output endface, and a plurality of pump cores extending between a pump input and the coupler output endface. The multicore input endface is connectable to the TMCF, and the pump input is connectable to the optical pump fibers. Each pump core is paired with a corresponding signal core to form a core pair that is adiabatically tapered such that signal light carried by the signal core is combined with pump light carried by the pump core. The coupler output endface is connectable to the AMCF such that the combined light output of each core pair is provided as an input to a respective AMCF core.

Abstract: An optical source configured for providing output light for providing input signal light or pump light can comprise pump source for pumping a four wave mixing (FWM) process with light pulses (“FWM pump light”); a FWM element in optical communication with the pump source, the FWM element configured for hosting the FWM process to generate, responsive to the FWM pump light, pulses of FWM signal light and FWM idler light having different wavelengths. The optical source can be configured such that the output light comprises pump light having a pumping wavelength or as input signal light having a gain wavelength for pumping or seeding an amplifying optical device comprising a gain material for providing optical gain. The gain material can have absorption and emission spectra defining gain and pumping wavelengths at which, respectively, the gain material is arranged in the device to provide optical gain via a process of stimulated emission responsive to being pumped.

Abstract: An amplification optical fiber with an optical component capable of efficiently absorbing pumping light and a fiber laser device including the same are provided. An amplification optical fiber with an optical component in a fiber laser device 1 includes: an amplification optical fiber 30 having a core 31 doped with an active element and a clad 32 through which pumping light for amplifying light to be amplified propagating through the core 31 propagates; and an optical component 50 including at least one optical fiber 53a to 53f having a first end coupled to a portion of the clad 32 and a second end coupled to at least another portion of the clad 32 at one end 35 of the amplification optical fiber 30.

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 fiber coupler connects transmission multicore optical fiber (TMCF) with an amplifier multicore optical fiber (AMCF) and a plurality of optical pump fibers. The coupler includes a plurality of signal cores extending between a multicore input endface and a coupler output endface, and a plurality of pump cores extending between a pump input and the coupler output endface. The multicore input endface is connectable to the TMCF, and the pump input is connectable to the optical pump fibers. Each pump core is paired with a corresponding signal core to form a core pair that is adiabatically tapered such that signal light carried by the signal core is combined with pump light carried by the pump core. The coupler output endface is connectable to the AMCF such that the combined light output of each core pair is provided as an input to a respective AMCF core.

Abstract: Method and apparatus for detecting an opening in a transmission fiber connecting a discrete gain unit to a pump unit of a Remote Optically Pumped Amplifier (ROPA) system. The method comprises measuring an optical power entering the pump unit from the transmission fiber, the optical power being in a selected wavelength range, and establishing that the optical power lacks an ASE noise power component generated by the gain unit. The lack of this component indicates the presence of a break or opening in the transmission fiber, and triggers corrective action whereby pump lasers within the pump unit are shut down or have their power reduced to a safe level.

Abstract: An optical amplifier includes a rare-earth doped optical fiber for receiving input light through one end and outputting output light through another end, the input light being input from an input port; an excitation light source for generating excitation light; an optical coupler for supplying the generated excitation light to the one end and/or the another end of the rare-earth doped optical fiber; and a reflector for reflecting an amplified spontaneous emission light out of a signal band traveling in opposite direction to the input light, the amplified spontaneous emission light being generated in the rare-earth doped optical fiber.

Abstract: An optical amplifier having two erbium doped fiber coils and a pump laser diode is described. A tunable optical power splitter is used for variably splitting the optical pump power for the laser diode between the two erbium doped fiber coils, and variable tilters can be used for correcting the gain tilt of the amplifier. The variable splitter and the tilters can include thermally tunable Mach-Zehnder interferometers.

Abstract: Devices and techniques are disclosed for amplifying a plurality of optical signals using a single pump laser coupled to a set of optical splitters arranged in a binary tree configuration for powering a plurality of fiber optical amplifying path circuits (FOAP circuits) each configured to amplify one of the plurality of optical signals, where each of the optical splitters at the leaves of the binary tree is coupled to one of the plurality of FOAP circuits to provide the power required to amplify the optical signal.

Abstract: A high power short optical pulse source 10 can include a master oscillator 12, preamplifier 14, and pump laser 16 provided within a first enclosure 28 at a first location. The high power short optical pulse source can further include a high power fiber amplifier 20 provided within an optical head 18, which is located at a second location, remote from the first location. The optical head 18 can have a small footprint and can be positioned at the intended target of optical pulses output from the high power short optical pulse source. The large, noisy elements of the high power short optical pulse source 10 are thereby provided away from the application site of the pulses.

Abstract: An optical amplifier includes a first excitation light source that outputs a first excitation light; a second excitation light source that outputs a second excitation light; a first amplifying optical fiber doped with a rare-earth element and excited by the first excitation light to amplify light input to the first amplifying optical fiber; and a second amplifying optical fiber doped with a rare-earth element and excited by the second excitation light to amplify the light from the first amplifying optical fiber. A ratio between the intensity of the first excitation light and the intensity of the second excitation light is controlled according to the number of signal lights wavelength-multiplexed in the light input.

Abstract: A device for amplifying optical signals propagating in optical fibers comprising a double cladding fiber amplifier having multiple gain stages, a port for coupling pump light into the double cladding fiber amplifier, and a double cladding fiber coupler for splitting the coupled pump light between the gain stages of the double cladding fiber amplifier. Also, a method for amplifying optical signals propagating in optical fibers comprising the steps of providing a double cladding fiber amplifier having multiple gain stages, coupling pump light into the double cladding fiber amplifier, and splitting the coupled pump light between the gain stages of the double cladding fiber amplifier.

Abstract: An optical amplifier includes a first amplification medium to receive light obtained by combining signal light input into an input port and the excitation light generated by a light source; a second amplification medium disposed between the first amplification medium and an output port; a loss medium to receive the signal light separated from light output from the first amplification medium; a variable optical attenuator that is disposed on a path that bypasses the loss medium, and to receive the excitation light separated from the light output from the first amplification medium; a first photodetector to detect power of light separated from the signal light transmitted from the second amplification medium; and a controller to control the amount of attenuation for the variable optical attenuator or output power of the light source so that signal light power per wavelength of the signal light becomes closer to a target value.

Abstract: An optical source can include a remote optical head for outputting high power short optical pulses. The optical source can include signal source operable to output short optical pulses; an optical pump light source; an optical head provided at a location remote from the location of the optical signal source; and an optical fibre amplifier having at least its optical output located within the optical head. The source can also include an optical signal delivery fibre arranged to deliver optical pulses from the optical signal source to the optical fibre amplifier and a pump light delivery fibre arranged to deliver optical pump light to the high power optical fibre amplifier.

Abstract: The alteration of the bandwidth of an optical amplifier. Before alteration, optical signals having a first set of wavelengths are provided through a gain medium of the optical amplifier. In addition, a first pump having a set of pump wavelengths is propagated through the gain medium to thereby amplify the optical signals. After alteration, optical signals having at least a partially different set of wavelengths are able to be optically amplified by coupling a second pump into the optical medium. The second pump is at least partially distinct from the first pump in that the second pump includes at least one pump wavelength that was not included in the first pump.

Abstract: An optical amplification mechanism that introduces optical pump(s) into one port of an optical circulator. The optical circulator directs the optical pumps from that port into another port that is coupled to the output of a gain stage. The optical pump(s) then pass from the output to the input of the gain stage while amplifying an optical signal passing from the input to the output of the gain stage. A residual amount of optical pump(s) that exits the input of the gain stage is reflected back into the input of the gain stage. The reflected optical pump(s) then further assists in the amplification of the optical signal. Other embodiments are also disclosed.

Abstract: An optical amplifier configuration for WDM (wavelength division multiplex) systems uses a common pump source connected to an input of an optical splitter deploying pump light via variable optical attenuators to a plurality of optical amplifiers. Control circuits determine individually the output powers of the amplifiers by varying the attenuations of the variable optical attenuators. Amplifier units based on PLC technology are implemented to reduce the size.

Abstract: A system and method for locking the relative phase of multiple coherent optical signals, which compensates for optical phase changes induced by vibration or thermal changes in the environment.

Abstract: The invention provides an amplification module for an optical printed circuit board, the optical printed circuit board comprising plural polymer waveguide sections from independent waveguides, each of the sections being doped with an amplifying dopant, wherein the plural waveguide sections are routed so as to pass through an amplification zone in which the plural polymer waveguide sections are arranged close or adjacent to one another, the amplification module comprising: a pump source comprising plural light sources arranged to provide independently controllable levels of pump radiation to each of the plural waveguide sections. In an embodiment, the amplification module also includes plural polymer waveguide sections corresponding to the plural polymer waveguides of the printed circuit board on which in use the amplification module is to be arranged, each of the sections being doped with an amplifying dopant.

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: The present invention discloses a fiber amplifier, a fabricating method thereof, and a fiber communication system. The fiber amplifier includes at least a pump laser, at least a gain medium and at least an integrated optical component. The integrated optical component includes multiple optical input/output ports, and the optical input/output ports are connected to the pump laser or gain medium directly or indirectly. The present invention may better address problems of unstable performance and difficulty in reducing the size of components in the prior art where fiber amplifiers are formed by a number of discrete components with many fiber fusion splices. In addition, the present invention may reduce the production complexity and costs of fiber amplifiers, and improve the productivity of fiber amplifiers.

Abstract: The fiber laser apparatus comprises an amplifying section for amplifying seed light by cladding-pumping, and has a structure for further using a residual component of pumping light for cladding-pumping in order to heat the object. A guiding optical fiber is provided between an amplifying optical fiber of the amplifying section and an output optical system converging the single-mode amplified seed light on the object, the guiding optical fiber serving to increase the degree of freedom in arranging the output optical system. The guiding optical fiber has a structure enabling the single-mode propagation of the amplified seed light outputted from the amplifying optical fiber and multimode propagation of the residual pumping light. Because the object is irradiated with the converged amplified seed light, while being heated with the residual pumping light outputted from the output optical system, even an object with a complex shape can be subjected to efficient laser processing.

Abstract: A modulator includes an electro-optical substrate and a first and second waveguide formed of a doped semiconductor material positioned on a surface of an electro-optical substrate forming a slot therebetween. A doping level of the semiconductor material being chosen to make the first and second waveguide conductive. A dielectric material is positioned in the slot which increases confinement of both an optical field and an electrical field inside the slot. A refractive index of the semiconductor material and a refractive index of the dielectric material positioned in the slot being chosen to reduce the V?·L product of the modulator.

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.

Abstract: Frequency-multiplied fiber-MOPA apparatus includes one enclosure containing a master oscillator and fiber amplifier stages and another enclosure containing frequency-multiplying stages. Radiation is transmitted between the enclosures by a transport fiber in a flexible jacket or enclosure. The transport fiber functions additionally as a power amplifier fiber, and amplifies the radiation while transporting the radiation between the enclosures. The amplifying transport fiber is energized by diode-lasers in the enclosure containing the master oscillator and fiber amplifiers.

Abstract: There is provided a long-band rare-earth-doped optical amplifier and method for amplifying an optical signal. The optical amplifier has a pre-, a mid- and a post-amplification stage. Only the mid-amplification stage is pumped with a pump light source. The other two are pumped using Amplified Spontaneous Emission (ASE) generated in the mid-amplification stage. An optical coupling device is used to couple the three amplification stages together and to split the ASE generated in the mid-amplification stage and available at one end of the mid-amplification stage. One part of the split ASE is used to pump the pre-amplification stage while the other part is used to pump the post-amplification stage.

Abstract: The present invention relates to an optically active device comprising a plurality of stages of optical amplifying sections cascaded on an input light propagation path, and a structure for effectively preventing an upstream pumping light source from being destroyed by ASE light propagating in a direction opposite to the input light. The optically active device comprises, at least, a front-stage optical amplifying section and a rear-stage optical amplifying section which are adjacent to each other on the input light propagation path. Each of the front-stage optical amplifying section and rear-stage optical amplifying section includes an amplification fiber doped with ytterbium as an optically active material and a pumping light source for supplying the amplification optical fiber with pumping light in the band of 0.98 ?m for pumping the optically active material.

Abstract: An optical pumping device is provided in which a multi-core fiber obtained by bundling up a plurality of optical fibers, which are input ports, and a double clad fiber for optical pumping are spliced through a bridge fiber composed of a double clad fiber having a tapered shape. Accordingly, it is possible to efficiently couple signal light and pumping light to the double clad fiber for optical pumping.

Abstract: An optical component including an acceptance fiber, e.g. a photonic crystal fiber, for propagation of pump and signal light, a number of pump delivery fibers and a reflector element that reflects pump light from the pump delivery fibers into the acceptance fiber. An optical component includes a) a first fiber having a pump core with an NA1, and a first fiber end; b) a number of second fibers surrounding the pump core of the first fiber, at least one of the second fibers has a pump core with an NA2 that is smaller than NA1, the number of second fibers each having a second fiber end; and c) a reflector element having an end-facet with a predetermined profile for reflecting light from at least one of the second fiber ends into the pump core of the first fiber.

Abstract: A system for combining multiple fiber amplifiers, or multiple fiber amplifiers. The system includes a fiber combiner with multiple cores for connecting with the multiple fiber amplifiers and for combining the beams of the fiber amplifiers into a single beam. The fiber amplifiers are aligned, tapered, and stretched. A method for combining fiber amplifiers includes emitting a beam from a tapered fiber combiner and transmitting and coupling a portion of the emitted beam back into the fiber combiner via a feedback fiber. The transmission and coupling of the feedback fiber includes mixing the feedback fiber with the output of an auxiliary laser and boosting the feedback fiber by a pre-amplifier. The feedback fiber is split into a plurality of beams by a fiber splitter. The beams are fed into an array of fiber amplifiers and combined with output of the individual fiber amplifiers to form the tapered fiber combiner.

Abstract: In a laser device, a crystal array includes a laser gain crystal and an optically non-linear frequency conversion crystal. A pump source couples at least two mutually spatially separated pump beams into the crystal array. Between two pump beams, a saw kerf of the crystal array extends parallel to the pump beams.

Abstract: Improved lumped Raman amplification systems are disclosed. A lumped Raman amplification structure provides optimized efficiency, low noise figure over a range of gain settings, and a high saturation threshold. Responsibility for amplifying different portions of the spectrum is divided among multiple stages. In one particular implementation, two outer stages amplify a first band and two inner stages amplify a second band. The two inner stages also apply a small amount of amplification to the first band. A modification improves noise figure in the second band by adding some amplification in the second band to the first stage.

Abstract: High power parallel fiber arrays for the amplification of high peak power pulses are described. Fiber arrays based on individual fiber amplifiers as well as fiber arrays based on multi-core fibers can be implemented. The optical phase between the individual fiber amplifier elements of the fiber array is measured and controlled using a variety of phase detection and compensation techniques. High power fiber array amplifiers can be used for EUV and X-ray generation as well as pumping of parametric amplifiers.

Abstract: Provided is an all-optical gain-clamped fiber amplifier, comprising transmission and isolation means for periodically transmitting an optical signal or reflecting amplified spontaneous emission (ASE) back to a gain medium. The transmission and isolation means can be embodied by an optical interleaver or a number of optical fiber Bragg gratings. Accordingly, an optical signal can be amplified across the entire C-band, and an ASE reflector-based gain-clamped fiber amplifier having a wider dynamic range than conventional amplifiers can be implemented.

Abstract: A method for pumping remote optically-pumped fiber amplifiers (ROPAs) in fiber-optic telecommunication systems is disclosed which uses cascaded Raman amplification to increase the maximum amount of pump power that can be delivered to the ROPA. According to the prior art, high power at the ROPA pump wavelength, ?p, is launched directly into the fiber and the maximum launch power is limited by the onset of pump depletion by Raman noise and oscillations due to the high Raman gain at ˜(?p+100) nm. In preferred embodiments of the present invention, a ‘primary’ pump source of wavelength shorter than ?p is launched into the delivery fiber along with two or more significantly lower-power ‘seed’ sources, among which is included one at ?p. The wavelength and power of the seed source(s) are chosen such that, when combined with the high-power primary source, a series, n, where n?2, of Raman conversions within the fiber ultimately leads to the development of high power at ?p.

Abstract: In one aspect, an optical amplifier including a pump module, preferably for amplifying channels of a WDM-signal is provided. The outlet thereof is connected to an amplifying fibre wherein signal radiation formed by optical signals is amplified. In order to amplify the optical signals with minimum gain spectrum difference, i.e. in the WDM-technique with minimal channel level differences, pump radiation emerging from the pump module has a mode field diameter in the amplification fibre which is selected so that it is smaller than a mode field diameter of the signal radiation.

Abstract: An apparatus is provided comprising a dual optical amplifier. The two optical amplifiers are integrated, in that they share at a set of optical, electrical, or opto-electrical components. The two optical amplifiers may share a pump laser. Alternatively, the optical amplifiers may share photo-detectors. Methods of controlling the signal strength of output signals are also provided. A chip-based integrated optical dual amplifier, using Erbium-Doped Waveguides, is also provided.

Abstract: There is provided an optical amplifier including a Raman amplification medium, a rare earth doped fiber located at a latter stage of the Raman amplification medium, a first pump light outputting unit for outputting pump light with a plurality of wavelengths, a variable distribution element for distributing the pump light with the plurality of wavelengths, outputted from the first pump light outputting unit, to the Raman amplification medium and the rare earth doped fiber in a variable distribution ratio for each wavelength, and a control unit for individually controlling the distribution ratio of the pump light with the plurality of wavelengths in the variable distribution element and the power of the pump light with the plurality of wavelengths from the first pump light outputting unit in accordance with a wavelength arrangement of each of signal lights wavelength-multiplexed into the wavelength-multiplexed signal light.