Abstract: The invention relates to a pump coupler (2) and a manufacturing method. The pump coupler (2) comprises a least one signal fiber (50) for outputting optical energy, multiple pump fibers (31) for inputting optical energy into the signal fiber (50), and a coupling structure (40) for coupling the optical energy of the pump fibers (31) into the signal fiber (50). A signal feed-through fiber (32) goes through the coupling structure (40). In accordance with the invention the coupling structure (40) is a tapering capillary tube (40) having a first wide end (65) and a second narrow end (70), the pump fibers (31) are connected to the wide end of the capillary tube (40), and at least the narrow end (70) of the capillary tube (70) is collapsed around the signal fiber (32).

Abstract: A method of operating a fiber amplifier characterized by a spectral gain curve includes providing an input signal at a signal wavelength. The signal wavelength lies within an in-band portion of the spectral gain curve extending from a first in-band wavelength to a second in-band wavelength, the in-band portion being characterized by a first amplitude range. The method also includes providing pump radiation at a pump wavelength. The pump wavelength is less than the signal wavelength. The method further includes coupling the pump radiation to the fiber amplifier and amplifying the input signal to generate an output signal. All portions of the spectral gain curve at wavelengths less than the first in-band wavelength and greater than the pump wavelength are characterized by a second amplitude less than or equal to 10 dB greater than the first amplitude range.

Abstract: An optical amplifier amplifies signal light and includes a pump light source that outputs pump light of a wavelength different from that of the signal light; a combining unit that combines the signal light and the pump light output by the pump light source, to output combined light; an amplifying unit that has non-linear optical media that transmit the combined light to amplify the signal light, the amplifying unit further removing, in the non-linear optical media, idler light generated from the signal light and the pump light, and outputting light that results; and an extraction filter that extracts the signal light from the light output by the amplifying unit.

Abstract: The present invention relates to a light source apparatus that has a base structure capable of generating SC light and further having a structure that enables the shaping of the spectral waveform of the SC light, power adjustment of the SC light, or adjustment of the frequency of repetition of the pulse train that contains the SC light. For example, a light source apparatus that enables shaping of spectral waveforms comprises a seed light source that emits seed light which is a pulse train or continuous light; an optical fiber that generates SC light from the seed light, and spectrum shaping means for completely or partially changing the spectral waveform of the SC light. The shaping of the spectral waveform changes the maximum power of the seed light by changing the optical coupling efficiency of the seed light source and optical fiber, for example, thereby suitably deforms the spectrum of the SC light.

Abstract: The invention relates to an optical waveguide, in particular an optical fibre comprising a core, formed from a material based on rare-earth-ion-doped silica, covered by an optical cladding. Nanoparticles, at least some of which are metal nanoparticles, are dispersed in the material of the core. The optical devices, such as especially optical amplifiers, comprise an optical fibre having a core formed, from a material based on rare-earth-ion-doped silica covered with an optical cladding, nanoparticles, at least some of which are metal nanoparticles, being dispersed in the material of the core, and a pumping source delivering electromagnetic excitation radiation, which propagates in the core.

Abstract: There are provided an amplification optical fiber, and an optical fiber amplifier and a resonator using the same capable of outputting light of high beam quality even when a higher-order mode that is axially symmetric is excited in addition to LP01 mode. An amplification optical fiber 50 includes: a core 51; a clad 52 coating the core 51; and an outer clad 53 coating the clad 52, wherein the core 51 has a larger refractive index than the clad 52, the core 51 allows light having a predetermined wavelength to propagate in at least LP01 mode and LP02 mode, and in the core 51, active element that stimulates to emit light of the predetermined wavelength is doped at a higher concentration at a position where an intensity of the LP02 mode becomes zero than center of the core 51.

Abstract: Embodiments of auto-cladded optical fibers are described. The fibers may have a refractive index profile having a small relative refractive index change. For example, the fiber may include an auto-cladded structure having, e.g., a trough or gradient in the refractive index profile. A beam of light propagating in the fiber may be guided, at least in part, with the auto-cladded structure. In some embodiments, the optical fiber may be all glass. In some embodiments, the optical fiber may include a large-core or an ultra large-core.

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: Provided is a double clad fiber device. The double clad fiber device includes a double clad fiber, a pump combiner, at least one first laser diode, and at least one second laser diode. The double clad fiber includes a core and a clad. The pump combiner provides pump light to the core and the clad through one end of the double clad fiber, respectively. The at least one first laser diode provides first pump light to the clad through the pump combiner. The at least one second laser diode provides second pump light to the core through the pump combiner.

Abstract: The various laser architectures described herein provide increased gain of optical energy as well as compensation of optical phase distortions in a thin disk gain medium. An optical amplifier presented herein provides for scalable high energy extraction and gains based on a number of passes of the signal beam through a gain medium. Multiple, spatially separate, optical paths may also be passed through the same gain region to provide gain clearing by splitting off a small percentage of an output pulse and sending it back through the amplifier along a slightly different path. By clearing out the residual gain, uniform signal amplitudes can be obtained.

Abstract: An all-fiber optical pulse compression arrangement comprises a concatenated arrangement of a section of input fiber (e.g., a single mode fiber), a graded-index (GRIN) fiber lens and a section of pulse-compressing fiber (e.g., LMA fiber). The GRIN fiber lens is used to provide mode matching between the input fiber (supporting the propagation of chirped optical pulses) and the pulse-compressing fiber, with efficient pulse compression occurring along the length of the LMA fiber. The dispersion and length of the LMA fiber section are selected to provide the desired degree of pulse compression; for example, capable of reconstituting a femtosecond pulse as is used in supercontinuum generation systems.

Abstract: A multi-channel optical amplifier arrangement operating over a particular bandwidth is provided. The amplifier arrangement includes at least one optical amplifier stage that includes a rare-earth doped optical waveguide, at least one pump source for supplying optical pump energy to the doped optical waveguide, and at least one coupler for coupling the optical pump energy to the doped optical waveguide. The amplifier arrangement also includes a dynamic range enhancer (DRE) having an input and an output and a plurality of distinct optical paths each selectively coupling the input to the output. At least two of the optical paths produce different gain spectra across the particular operating bandwidth. The DRE further includes an optical path selector for selecting any optical path from among the plurality of optical paths such that for all channels in the particular bandwidth the selected path optically couples the input to the output of the DRE.

Abstract: The present invention embraces an amplifying optical fiber having a central core adapted to convey and amplify an optical signal and a cladding that surrounds the central core to confine the optical signal conveyed in the central core. The central core is formed of a core matrix in which nanoparticles are present. The nanoparticles themselves include a nanoparticle matrix and rare-earth-dopant elements. The core matrix may also include one or more additional dopants (i.e., in addition to nanoparticles). The amplifying optical fiber possesses a small numerical aperture and is suitable for use in high-pump-power applications without a degraded gain shape.

Abstract: A laser apparatus with all optical-fiber includes a plurality of pumping light sources in different wave bands and an optical-fiber laser system. The optical-fiber laser system includes an optical fiber at least doped with erbium (Er) element and doped with or not doped with ytterbium (Yb) element according to a need. The optical-fiber laser system outputs a laser light through the pumping light source.

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 method and apparatus use a photonic-crystal fiber having a very large core while maintaining a single transverse mode. In some fiber lasers and amplifiers having large cores problems exist related to energy being generated at multiple-modes (i.e., polygamy), and of mode hopping (i.e., promiscuity) due to limited control of energy levels and fluctuations. The problems of multiple-modes and mode hopping result from the use of large-diameter waveguides, and are addressed by the invention. This is especially true in lasers using large amounts of energy (i.e., lasers in the one-megawatt or more range). By using multiple small waveguides in parallel, large amounts of energy can be passed through a laser, but with better control such that the aforementioned problems can be reduced. An additional advantage is that the polarization of the light can be maintained better than by using a single fiber core.

Abstract: A method of operating a fiber amplifier characterized by a spectral gain curve includes providing an input signal at a signal wavelength. The signal wavelength lies within an in-band portion of the spectral gain curve extending from a first in-band wavelength to a second in-band wavelength, the in-band portion being characterized by a first amplitude range. The method also includes providing pump radiation at a pump wavelength. The pump wavelength is less than the signal wavelength. The method further includes coupling the pump radiation to the fiber amplifier and amplifying the input signal to generate an output signal. All portions of the spectral gain curve at wavelengths less than the first in-band wavelength and greater than the pump wavelength are characterized by a second amplitude less than or equal to 10 dB greater than the first amplitude range.

Abstract: The present invention generally relates to the operation of optical network equipment such as optical amplifiers. In one aspect, a method of operating an optical amplifier is provided such that output of the optical amplifier avoids the effects of operating an optical gain medium in a non-linear (kink) region of an L-I curve. The method generally includes operating an optical gain medium in a fully off state or fully on state above the kink region with a PWM signal. In another aspect, the effects of the kink region may be compensated for by utilizing a lookup table. A sample of the optical power of an amplified optical signal may be used to select an entry in the lookup table that compensates for non-linearities in the kink region. In yet a further aspect, a lookup table may be used to control a pulse modulator to compensate for non-linearites in the kink region of the L-I curve.

Abstract: An optical connector having a plurality of directional taps and connecting between a plurality of optical waveguides (e.g., such as a connector between a waveguide that is part of, or leads from, a seed laser and/or an initial optical-gain-fiber power amplifier, and a waveguide that is part of, or leads to, an output optical-gain-fiber power amplifier and/or a delivery fiber), wherein one of the directional taps extracts a small amount of the forward-traveling optical output signal from the seed laser or initial power amplifier (wherein this forward-tapped signal is optionally monitored using a sensor for the forward-tapped signal), and wherein another of the directional taps extracts at least some of any backward-traveling optical signal that may have been reflected (wherein this backward-tapped signal is optionally monitored using a sensor for the backward-tapped signal).

Abstract: According to an aspect of the embodiment of the invention, an optical amplifier including an input port, an output port, a plurality of amplifying parts, an optical attenuator, a gain controller and an optical attenuator controller. The plurality of amplifying parts includes an optical amplification medium and a pumping light source for generating pump light. The optical attenuator is optically connected between the amplifying parts. The gain controller controls the pump light power of the pump sources, respectively, in such a way that the ratio decreases in accordance with the gain set value increasing and the ratio interpose between a first threshold level and a second threshold level. The optical attenuator controller controls attenuation of the optical attenuator in order to maintain the sum of generating gains of the amplifying parts in the gain set value in accordance with a state of the signal light inputted into the input port.

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: The present disclosure provides an approach to more efficiently amplify signals by matching either the gain materials or the pump profile with the signal profile for a higher-order mode (HOM) signal. By doing so, more efficient energy extraction is achieved.

Abstract: The present invention relates generally to devices for the generation and amplification of electromagnetic energy. The present invention relates more particularly to optical fiber devices, such as lasers and amplifiers, useful for generating and amplifying optical energy.

Abstract: Various embodiments described herein comprise a laser and/or an amplifier system including a doped gain fiber having ytterbium ions in a phosphosilicate glass. Various embodiments described herein increase pump absorption to at least about 1000 dB/m-9000 dB/m. The use of these gain fibers provide for increased peak-powers and/or pulse energies. The various embodiments of the doped gain fiber having ytterbium ions in a phosphosilicate glass exhibit reduced photo-darkening levels compared to photo-darkening levels obtainable with equivalent doping levels of an ytterbium doped silica fiber.

Abstract: A controller monitors output level variation rate of excitation light outputted by a light source in accordance with a drive current of the light source and provided to a rare-earth doped amplifying medium so that a signal light is amplified as the signal light travels through the amplifying medium. In an embodiment, the controller decreases the drive current when the monitored output level variation rate is larger than a threshold value, to thereby reduce power level of the outputted excitation light and thereby delay progress of degradation of the light source indicated by the monitored output level variation rate being larger than the 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: A stable, single mode fiber amplifier is described. The amplifier consists of a seed source, a passive single clad multimode fiber, an active double clad multimode fiber or a multimode fiber horn and a semiconductor laser pump source. The passive fiber is packaged on a mandrel with a compound radius of curvature such that high order modes in the fiber are stripped from the core leaving only the fundamental mode. This fiber is then spliced to a multimode active fiber of similar core diameter. By exciting only the fundamental mode of this active fiber, stable single mode amplification is achieved.

Abstract: A remotely optically amplified passive optical network (PON) system, an optical line terminal, and a remote node, and an optical amplification and gain-clamping methods of the PON system are provided. The PON system generates pump light and transmits the generated pump light to an optical transmission line, amplifies primarily an optical signal by the pump light which pumps the optical transmission line, and amplifies secondarily the optical signal by the transmitted pump light which pumps a gain medium of a remote node while maintaining a gain of the optical signal by applying a gain-clamping method to the remote node.

Abstract: Guided adiabatic bend transitions for multimode fibers are presented to preserve the power of guided light in the fundamental mode while guiding from one level of curvature to another for improved operation of mode filters and fiber amplifiers. A method is provided to find the guidance path. Implementations of these transducers include modal power back converters, and guidance paths into and out of higher order mode filtering devices which work on bending. A spiral structure is shown to incorporate adiabatic bends for a forward-pumped fiber amplifier.

Abstract: At an optical transmission system that uses plural light sources for Raman amplification, even when a failure occurred in a pumping light source in one of the light sources for Raman amplification, the signal light output level and its wavelength characteristic are not deteriorated at the final stage, and the number of components in the system is not made to be large and the cost of the system is not made to be high. This optical transmission system is provided. At an optical transmission system using “n” light sources for Raman amplification, a first to “n?1”th light sources for Raman amplification do not provide spare pumping light sources, and an “n”th light source for Raman amplification provides the spare pumping light sources. When a pumping light source in one of the “n” light sources for Raman amplification had a failure, the spare pumping light source in the “n”th light source for Raman amplification corresponding to the failure occurred pumping light source is worked.

Abstract: An integrated optical-amplification module includes a housing member, a first input optical terminal configured to receive an optical signal, a second input, optical terminal that can receive a pump light, and an output optical terminal that can output a combined optical signal comprising at least a portion of the optical signal and a portion of the pump light. The integrated optical-amplification module also includes an optical combiner fixedly installed relative to the housing member. The optical combiner can receive the pump light and the optical signal and an optical prism fixedly installed relative to the housing member. The optical combiner can merge the pump light and the optical signal to form the combined optical signal. The optical prism can direct at least a portion of the optical signal through free space to the optical combiner.

Abstract: An optical fiber for optical amplification has: a core portion doped with at least erbium and aluminum; a cladding portion formed around the core portion and having a refractive index smaller than that of the core portion; a peak value of absorption coefficient of 35 dB/m or greater at a wavelength around 1530 nanometers; normal dispersion characteristics and an effective core area of 20 ?m2 or larger, at a wavelength of 1550 nanometers; and a power conversion efficiency of a conversion from pumping light to amplified light having a wavelength of 1550 nanometers is 30% or more.

Abstract: The invention consists in an amplifying optical fiber comprising a core containing a dopant and a cladding, wherein said core comprises a monomode core intended to propagate an optical signal, quantum dots of a semiconductor material being disposed in or near said monomode core, and a multimode core surrounding the monomode core, intended to receive a pumping signal.

Abstract: The specification describes optical devices and related methods wherein an input mode is converted by multiple LPG mode transformers to produce an output with multiple predetermined modes.

Abstract: There is provided a light source apparatus including at least a excitation light source and a photocoupler, a light source medium formed of one kind of a single, rare-earth element doped fiber that is excited by the excitation light source and has two terminals, and an output end formed of an optical fiber, the light source apparatus being characterized in that an optical component having at least one of reflection, branching or attenuation function is provided in anywhere of an optical circuit from the light source medium to the output terminal and that it is possible to output lights of different wavelengths derived from different spontaneous emission light peaks that are generated from rare-earth element ions added to the rare-earth element doped fiber, and that at least one of the lights to be obtained is visible light.

Abstract: An apparatus includes a first optical amplifier that uses a rare-earth-doped optical medium, an isolator that inputs amplified light amplified by the first optical amplifier, a second optical amplifier that uses a rare-earth-doped optical medium to amplify a light output from the isolator, and a first light router that routes amplified spontaneous emission light generated by the first optical amplifier or the second optical amplifier to input, by a second light router, the routed amplified spontaneous emission light to the optical rare-earth-doped medium other than the optical rare-earth-doped medium where the routed amplified spontaneous emission light is generated.

Abstract: The present invention provides an amplified spontaneous emission fiber optic source having high optical power (>20 mW) and a spectral broadband emission (>70 nm) centered near a wavelength of 1060 nm. In an embodiment of the invention, the fiber source comprises a combination of Yb-doped and Nd-doped silica fibers in a dual-pumping configuration. The Yb-doped optical fiber has a peak absorption coefficient of 350 dB/nm at 977 nm band, and the Nd-doped fiber used has a dopant concentration of 500 ppm-wt in a glass host of aluminum-germano-phospho-silicate. A combination of these two doped-fibers along with optical spectral filtering provides a broadband spectrum giving coherence length <7 ?m (in air), which is well suited for optical coherence imaging.

Abstract: An optical fiber amplifier apparatus and optical signal amplification method are provided. In one example, the amplifier apparatus comprises an optical combiner that is configured to receive an input optical signal to be amplified and a pump light beam. The optical combiner combines for output the input optical signal and the pump light beam. A first cladding pumped optical fiber in which Erbium is the only optically active dopant is coupled to the optical combiner to receive the pump light beam and the input optical signal. The first cladding pumped optical fiber pre-amplifies the input optical signal and passes the pre-amplified input optical signal and power of the pump light beam not absorbed by the first cladding pumped optical fiber. A second cladding pumped optical fiber is provided that is coupled to the first cladding pumped optical fiber. Erbium and Ytterbium are optically active dopants in the second cladding pumped optical fiber.

Abstract: An optical fiber amplifier pumping technique based on multiple stimulated Raman scattering (SRS) for optical communication systems includes a plurality of pump signals with increasing wavelength which are injected into a fiber. The wavelengths of such pump signals are such that, in cascade, each pump signal of the plurality is amplified by the pump signal of wavelength immediately shorter, while it amplifies that with the wavelength immediately higher with the pump signal of highest wavelength which, in turn, pumps a remote rare earth doped optical fiber amplifier.

Abstract: An all-fiber optical pulse compression arrangement comprises a concatenated arrangement of a section of input fiber (e.g., a single mode fiber), a graded-index (GRIN) fiber lens and a section of pulse-compressing fiber (e.g., LMA fiber). The GRIN fiber lens is used to provide mode matching between the input fiber (supporting the propagation of chirped optical pulses) and the pulse-compressing fiber, with efficient pulse compression occurring along the length of the LMA fiber. The dispersion and length of the LMA fiber section are selected to provide the desired degree of pulse compression; for example, capable of reconstituting a femtosecond pulse as is used in supercontinuum generation systems.

Abstract: [Object] An optical fiber coupler in which damage to an pumping light source can be suppressed even if signal light leaks and an optical fiber amplifier using the optical fiber coupler are provided. [Solving Means] An optical fiber coupler 100 includes: a first optical fiber 10 having a core 11 and a clad 13 coating the core 11; a second optical fiber 20 having a core 21; and a fusion-drawn portion 110 formed by arranging the first optical fiber 10 and the second optical fiber 20 so that their longitudinal directions are in the same direction and fusing the clad 13 of the first optical fiber 10 and the core 21 of the second optical fiber 20. The clad 13 of the first optical fiber 10 has a larger refractive index than the core 21 of the second optical fiber 20.

Abstract: A fiber optical device 1A includes an amplification optical fiber 10, a seed light source 15 for supplying pulse seed light to the optical fiber 10, excitation light sources 21 to 25 for supplying excitation light, a bleaching light source 40 for supplying bleaching light for reducing a light transmission loss caused by photodarkening, and a control device 50 that controls the operations of individual portions. The control device 50 divides a period between a first output light pulse and a succeeding second output light pulse into a first period which includes a time point immediately after the output of the first output light pulse and during which the population inversion is unsaturated, and a second period which includes a time point immediately before the output of the second output light pulse, and, to the optical fiber 10, supplies the bleaching light in the first period and supplies the excitation light in the second period.

Abstract: An optical direct amplifier lowers the power consumption with a simple structure at a low cost. This amplifier includes an optical amplification medium (e.g., optical fiber) that carries out an optical amplification function in response to optical excitation by an exciting light source (e.g., semiconductor laser); a temperature controller for controlling the temperature of the amplification medium; a heat radiating member for radiating the heat generated by the light source; and a heat transmission regulator (e.g., Peltier module) for allowing the heat to flow into the amplification medium from the light source and for preventing the heat from flowing into the light source from the amplification medium. The amplification medium is heated by application of the heat generated by the light source by way of the heat radiating member and the heat transmission regulator.

Abstract: In a light amplification system, a fiber-based oscillator, amplifier, and cascaded Raman resonator are coupled together in series. The oscillator output is provided as an input into the amplifier, the amplifier output is provided as a pumping input into the cascaded Raman resonator, and the cascaded Raman resonator provides as an output single-mode radiation at a target wavelength. A loss element is connected between the oscillator and amplifier, whereby the oscillator is optically isolated from the amplifier and cascaded Raman resonator. A filter is coupled between the isolator and the amplifier for filtering out backward-propagating Stokes wavelengths generated in the cascaded Raman resonator. The oscillator is operable within a first power level range, and the amplifier and cascaded Raman resonator are operable within a second power level range exceeding the first power level range.

Abstract: An optical amplifier for determining the attenuation of a length of optical fibre (7) to which it is adapted to be connected comprising means (5) to receive an input signal from the optical fibre (7), means (6) to output an amplified signal to the optical fibre (7), a gain medium (2) and a pump means (3) arranged to generate the amplified signal from the input signal, the amplifier (1) further comprising means (13) to measure the optical power of the signal leaving the gain medium and means (14) to measure the optical power of the signal backscattered from the optical fibre (7), wherein the pump means (3) is controlled by a control means (4), the control means (4) being adapted to modulate the pump means (3) with a determination signal, the control means (4) being adapted to change the frequency of the determination signal over a plurality of determination frequencies while keeping the amplitude of the determination signal constant, the control means (4) further being adapted to calculate the attenuation of t

Abstract: A parametric process for producing light at a second wavelength and a fourth wavelength including pumping an optical parametric oscillator with input light at a first wavelength of less than one micron, wherein said oscillator consists of an optical fibre having each end closed by a dichroic mirror.

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 high power integrated fiber laser system includes cascaded amplifiers that utilize low numerical aperture fiber amplifiers. The system is rugged and lightweight.

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: It is desirable to provide a semiconductor optical amplifier from which it becomes able to obtain a higher output power. A semiconductor optical amplifier in comprises an active wave guiding layer which comprises a passive core region that is formed of a semiconductor, and active cladding regions that are located at both sides of the passive core region and each of that is comprised of an active layer which is formed of a semiconductor and which has an index of refraction to be lower than that of the passive core region, wherein a light is wave guided with being amplified in the active wave guiding layer. Moreover, it is desirable for the active wave guiding layer to be formed of a compound semiconductor, and to be formed by integrating the passive core region and the active cladding regions to be monolithic on to a substrate that is formed of a compound semiconductor by making use of a process of a butt joint growth.