Abstract: A method and apparatus is described that use an index-of-refraction profile having a significant central dip in refractive index (or another tailored index profile) within the core of a gain fiber or a gain waveguide on a substrate. The benefits of this central dip (more power with a given mode structure) are apparent when an input beam is akin to that of a Gaussian mode. In some embodiments, the invention provides a fiber or a substrate waveguide having an index profile with a central dip, but wherein the device has no doping. Some embodiments use a central dip surrounded by a higher-index ring in the index of refraction of the core of the fiber, while other embodiments use a trench between an intermediate-index central core portion and the ring, or use a plurality of rings and/or trenches. Some embodiments use an absorber in at least one core ring.

Abstract: The present invention relates to an optical module that has a structure for protecting a pumping light source at a low cost. The optical module comprises an amplification optical fiber, an optical coupler, a pumping light source, a delay optical fiber, a seed light source, an optical fiber, a photodetector, an optical fiber, an optical isolator, an optical isolator, and a control section. Through the insertion of the delay optical fiber between the pumping light source and the optical coupler, the timing of the output control of the pumping light source which is carried out after the photodetector detects return light leads the timing with which the return light enters the pumping light source. Hence, the time with which the return light enters the pumping light source is shortened and the accumulative damage time of the pumping light source is reduced.

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

Abstract: The invention provides an optical fiber amplifier which assures stable operation of a pump light source and efficiently makes use of residual pump power to achieve improvement in conversion efficiency. The optical fiber amplifier includes a rare earth doped fiber. Pump light from a pump light source is introduced into one end of the rare earth doped fiber by way of a first optical coupler, and residual pump light originating from the pump light and arriving at the other end of the rare earth doped fiber is applied to the other rare earth doped fiber amplifier or the loss compensation of a dispersion compensating fiber by Raman amplification.

Abstract: A doped superfluorescent fiber source (SFS) has an enhanced mean wavelength stability. A method stabilizes the mean wavelength of a SFS. The method includes providing an SFS including a doped fiber. The method further includes pumping the SFS with pump light from a pump source having a wavelength dependent on the temperature of the pump source and dependent on the power of the pump light. The method further includes optimizing the length of the fiber to reduce the influence of the pump light wavelength on the stability of the mean wavelength.

Abstract: An optical amplifier is provided with a controlling unit for controlling a gain of the optical amplifier based on input light power and output light power of the optical amplifier, as well as a gain control amount variable unit for changing the gain control amount of the optical amplifier by the controlling unit according to at least one of the input light power and the output light power. Thereby, optical communication, which can follow the change in the input power of the optical amplifier in high speed and also is stable, can be realized, without causing the occurrence of an oscillation phenomenon, the large size of the optical amplifier, and the increase in power consumption and heating.

Abstract: Provided is a hybrid optical amplifier using a gain-clamped semiconductor optical amplifier enabling Raman amplification. The hybrid optical amplifier comprises a spool of optical fiber used as transmission line in the optical communication, a GCSOA amplifying optical signal input via the optical fiber and generating a self-oscillation laser beam for gain-clamping through the gain medium, and a backward pumping Raman optical amplifier inducing Raman amplification by emitting the self-oscillation laser beam generated by the GCSOA into the optical fiber. Therefore, the Raman amplification can be obtained with a relatively simple structure using the GCSOA.

Abstract: A fiber amplifier is configured such that its spontaneous emissions are filtered out at the instant of creation. The fiber optic amplifier combines the gain medium of the fiber optical amplifier with a continuous filter to filter out the spontaneous emissions to prevent spontaneously emitted photons from stealing gain from signal photons. The photonic crystal fiber has a central core doped with a gain medium such as erbium, ytterbium or thulium ions. The central core of the photonic crystal fiber is surrounded by a cladding region having an array of holes or air voids that may be filled with materials with refractive index different from that of the central core. The array of holes are configured to restrict the wavelength range within which light can propagate inside the central core thereby providing continuous filtering functionality. The fiber amplifier has a pump operative to generate pump energy that is coupled to the photonic crystal fiber simultaneously with the signal.

Abstract: The present invention relates to an optical fiber amplifying module equipped with a structure for stably attaining a high gain even when amplifying light having a low duty cycle. The optical fiber amplifying module comprises at least three amplification optical fibers successively arranged from an input connector to an output collimator. A bandpass filter is arranged between the first- and second-stage amplification optical fibers. Control means having a structure constituted by optically passive components alone or a feedback structure functions so as to render an upper limit to a gain for input light in the first-stage amplification optical fiber, thereby preventing the deterioration in performances such as destruction of the bandpass filter from occurring in optical components positioned on the upstream side of the final-stage amplification optical fiber.

Abstract: An optical system adapted to amplify an input signal includes an optical pump supporting the input signal and an optical pump beam. The optical pump includes an input port, a first active medium coupled to the input port, and a pump output coupled to the first active medium. The optical amplifier includes an amplifier input optically coupled to the pump output and adapted to receive the input signal after passing through the optical pump, a second active medium coupled to the amplifier input, and an amplifier output adapted to output the amplified input signal.

Abstract: A method is described for detecting aging effects in components of an optical fiber amplifier wherein a broadband signal is amplified by means of a pump source in conjunction with at least one amplifying fiber. Input and output powers or, as the case may be, photon flows are determined at the input of the first amplifying fiber and at the output of the last amplifying fiber. Photon balancing from which an effective pump power of the pump source is calculated taking account of the characteristics of components of the optical amplifier at the beginning of life is calculated is carried out using the input and output powers or, as the case may be, photon flows in the case of a present operating status. Conclusions can be drawn about the aging of components in the optical fiber amplifier depending on the nature of the difference between the current and effective pump powers. An associated monitoring device is presented for implementing the method according to the invention.

Abstract: A plurality of pump light sources generate plural variations of pump light having different frequencies. A modulation circuit intensity-modulates the plural variations of pump light in the predetermined periods, respectively. A pump light pair whose frequency difference equals a Raman shift frequency are modulated such that they cannot simultaneously enters an emission state. A wavelength-multiplexer wavelength-multiplexes the plural variations of pump light modulated by the modulation circuit. A optical guide device guides the plural variations of pump light wavelength-multiplexed by the wavelength-multiplexer to an optical fiber.

Abstract: An optical fiber communication system is provided which uses remote pumping that is capable of improving pumping efficiency and reducing a noise figure. A coupler (20) of a linear repeater (18) couples signal light to pumping light outputted from a pumping light source (19). The outputted signal light and pumping light reach a linear repeater (25) through transmission fibers (22 to 24) and remote pumping modules (27F and 27R). A coupler (30) of the linear repeater (25) couples the signal light to the pumping light supplied from a pumping light source (29), to output the signal light and the pumping light to the transmission fiber (24). The remote pumping module (27F) divides the pumping light propagated in the transmission fiber (22), from the signal light. The remote pumping module 27F branches the divided pumping light in two directions with a predetermined ratio. After branching, each of the branched pumping light is coupled to the signal light to be supplied to both ends of an erbium-doped fiber.

Abstract: The present invention relates to an optical fiber for amplification, an optical amplifying apparatus, and so on, having a structure for enabling increase of power of output light, suppression of occurrence of nonlinear optical phenomena, and compact storage all together. The optical amplifying apparatus comprises an optical fiber for amplification amplifying input light inputted together with pumping light from a pumping light source. The optical fiber for amplification comprises a core region doped with a rare-earth element, and a cladding region provided on an outer periphery of the core region and having a refractive index lower than that of the core region. The core region has an outer diameter of 10 ?m or more but 30 ?m or less, and has a relative refractive index difference of 0.5% or more but 2.0% or less with respect to the cladding region. The cladding region has an outer diameter of 75 ?m or more but 200 ?m or less.

Abstract: This invention relates to optical fibres, fibre lasers, fibre laser arrays and sensor systems comprising fibre laser arrays. Conventional fibre laser sensor arrangements comprise a plurality of fibre lasers arranged in series along a length of optical fibre. A pump light source is located a one end of the fibre and supplies pump light energy to each of the fibre lasers in turn. Such sensor systems experience a number of disadvantages. Firstly, there is an uneven distribution of pump power along the length of the fibre which effectively limits the number of laser devices that can successfully be incorporated into the optical fibre array. Secondly, the manner in which existing sensor systems are constructed often results in back reflections, optical losses and mechanical weaknesses. The present invention provides a fibre laser which mitigates the above problems with fibre laser sensor arrays.

Abstract: A fiber gain medium assembly is provided. The fiber gain medium assembly includes a fiber gain medium, which in turn, includes a longitudinally extending inner core. The fiber gain medium also includes a cladding layer and a photo-emitting conductive polymer, both of which surround the inner core and extend longitudinally therealong. In this regard, the photo-emitting conductive polymer can surround the cladding layer to thereby surround the inner core. Alternatively, the cladding layer can comprise the photo-emitting conductive polymer. The fiber gain medium assembly can also include an electrical system electrically coupled to the photo-emitting conductive polymer. The electrical system is capable of providing an electric field to thereby excite the photo-emitting conductive polymer to emit photons capable of propagating into the inner core and producing gain for the signals propagating through the inner core.

Abstract: The present invention relates to a fiber having a core of crystal fiber doped with chromium and a glass cladding. The fiber has a gain bandwidth of more than 300 nm including 1.3 mm to 1.6 mm in optical communication, and can be used as light source, optical amplifier and tunable laser when being applied for optical fiber communication. The present invention also relates to a method of making the fiber. First, a chromium doped crystal fiber is grown by laser-heated pedestal growth (LHPG). Then, the crystal fiber is cladded with a glass cladding by codrawing laser-heated pedestal growth (CDLHPG). Because it is a high temperature manufacture process, the cladding manufactured by this method is denser than that by evaporation technique, and can endure relative high damage threshold power for the pumping light.

Abstract: A semiconductor-based Raman ring amplifier is disclosed. A method according to aspects of the present invention includes directing a pump optical beam having a pump wavelength and an input pump power level from an optical waveguide into a ring resonator. The optical waveguide and ring resonator are comprised in semiconductor material. A signal optical beam having a signal encoded thereon at a signal wavelength is directed from the optical waveguide into the ring resonator. The pump optical beam is resonated within the ring resonator to increase a power level of the pump optical beam to a power level sufficient to amplify the signal optical beam via stimulated Raman scattering (SRS) within the ring resonator. A free carrier concentration in the optical waveguide and the ring resonator is reduced to reduce attenuation of the pump optical beam and the signal beam.

Abstract: An optical terminal apparatus includes a plurality of signal light units that transmits and receives a signal light having a predetermined wavelength; at least one pumping light unit that emits a pumping light having a predetermined wavelength to perform Raman amplification for the signal light transmitted; and an optical multiplexer/demultiplexer that multiplexes/demultiplexes the signal light and the pumping light, the optical multiplexer/demultiplexer having one end connected to an optical transmission path and other end connected to the signal light units and the pumping light unit.

Abstract: A bi-directional configuration is employed to implement a hybrid ultra long haul (ULH)/long haul (LH) optical transmission system. The link carries ULH channels and LH channels in opposite directions in different bands. Raman amplification is employed for the ULH band while Erbium-doped fiber amplification (EDFA) is used for both the LH and ULH bands. Optical circulators are employed for multiplexing and demultiplexing. This solution does not incur the ripple penalty of prior art solutions based on interferential filters while providing excellent isolation between the ULH and LH channels and bi-directional communication within a single fiber.

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: Control of average wavelength-converted power and/or wavelength converted pulse energy is described. One or more seed pulses may be generated and amplified with an optical amplifier to produce one or more amplified pulses. The amplified pulses may be wavelength converted to produce one or more wavelength converted pulses characterized by an average wavelength-converted power or pulse energy. Wavelength-converted power or pulse energy may be controlled by adjusting wavelength conversion efficiency without substantially changing the amplified power or pulse energy. Average wavelength-converted power may be controlled over a time scale comparable to a pulse period of the amplified pulses without adjusting an average power of the amplified pulses over the time scale comparable to a pulse period of the amplified pulses.

Abstract: An optical amplifier is disclosed having a substantially uniform spectral gain. In an exemplary embodiment, the optical amplifier comprises a planar waveguide including a substrate, which includes a region doped with rare earth element. The optical amplifier also comprises an optical fiber including a core doped with the rare earth element. The optical fiber is optically coupled to the planar waveguide.

Abstract: A WDM optical source, in adopting a spectrum-sliced method, advantageously needs neither an optical source with specific generation wavelength nor a wavelength-stabilizing circuit for stabilizing wavelength. Affording high power and a very narrow line width, the WDM optical source can provide a broadcasting service without signal distortion by a chromatic dispersion effect and also avoids the expense of an amplifier and/or external modulator, thereby relieving subscribers of the economical burden. The practical use of WDM-PON and of WDM-PON using an inventive WDM optical source can therefore be brought to fruition and broadcasting service can be provided economically.

Abstract: A semiconductor laser module has a semiconductor laser device; a package for housing the semiconductor laser device; a PBC fixed in the package for polarization-synthesizing two laser beams output from the semiconductor laser device; a depolarizing element fixed in the package for depolarizing a synthesizing light output from the PBC; and an optical fiber for receiving a light output from the depolarizing element.

Abstract: A reliable optical transmission system with an improved signal control mechanism that avoids abrupt power variations of light beams, thereby preventing optical supervisory channel (OSC) signals from experiencing errors. An optical amplifier amplifies main signals under the control of an optical amplifier controller, which spends a first predetermined time to raise the output power of the optical amplifier up to a desired level. A pump light source produces a pump beam for injection to a fiber-optic transmission line so as to make it serve as an amplifying medium. The pump light source is controlled by a pump light source controller that spends a second predetermined time to raise the pump beam to a desired power level. This stepwise start-up process of the amplifier power and pump beam power prevents OSC signals from experiencing abrupt power variations.

Abstract: A large mode area, gain-producing optical fiber is configured to support multiple transverse modes of signal radiation within its core region. The fiber is a hybrid design that includes at least two axial segments having different characteristics. In a first axial segment the transverse refractive index profile inside the core is not radially uniform being characterized by a radial dip in refractive index. The first segment supports more than one transverse mode. In a second axial segment the transverse refractive index profile inside the core is more uniform than that of the first segment. The two segments are adiabatically coupled to one another. Illustratively, the second segment is a terminal portion of the fiber which facilitates coupling to other components. In one embodiment, in the first segment M12>1.0, and in the second segment M22<<M12. In a preferred embodiment, M12>>1.0 and M22˜1.0.

Abstract: A method for remodulation of a modulated optical signal is disclosed which uses a disturbed line signal and an optical clock signal derived from the undisturbed original line signal modulated with the bitrate frequency feeding both signals in a Raman amplifying fiber connected to at least one Raman pump running the clock signal as Raman pump wavelength for the line signal.

Abstract: An optical fiber arrangement has at least two optical fiber sections, each optical fiber section defining an outside longitudinally extending surface. The outside longitudinally extending surfaces are in optical contact with each other. The invention further provides for an amplifying optical device have an optical fiber arrangement as just described, and a pump source. The amplifying optical device is configured such that the pump source illuminates the amplifying optical fiber. A amplifying arrangement is also disclosed. The amplifying arrangement includes a plurality of amplifying optical devices as just described, and each amplifier also has at least one input fiber and a first multiplexer connected to the input fiber. Each amplifier is configured such that at least one of the amplifying optical fibers is connected to the first multiplexer. The amplifying arrangement also has a second multiplexer connected to each of the first multiplexers.

Abstract: The invention is in the field of distributed Raman amplification for digital and analog transmission applications and other applications, e.g., instrumentation and imaging applications, including HFC-CATV applications. In particular, the invention uses a high power broadband source of amplified spontaneous emission (ASE) as the Raman pump source for improved system performance. The invention also includes methods for constructing such a high-power broadband Raman pump.

Abstract: The invention provides an optical fiber laser apparatus. In the invention, an excitation light source outputs light of a given wavelength. A first optical fiber generates light of a plurality of wavelengths including light of a first wavelength by up-conversion from the output light. Also, a first resonator includes first and second mirrors provided on both ends of the first optical fiber, respectively. The first resonator selects the first wavelength light to output via the second mirror. Further, a second optical fiber amplifies an output of the first wavelength light incident from the first resonator. In addition, the first and second mirrors have higher reflexivity for the first wavelength light than the second wavelength light having higher gain per length of the optical fiber. The first fiber has a length set such that the first wavelength light oscillates preferentially over the second wavelength light.

Abstract: The specification describes an optical fiber device wherein a LOM is converted to an HOM prior to entering the gain section. The gain section is a few mode fiber that supports the HOM. The output from the gain section, i.e. the HOM, may be utilized as is, or converted back to the LOM. With suitable design of the few mode fiber in the gain section of the device, the effective area, Aeff, may be greater than 1600 ?m2. The large mode separation in the gain section reduces mode coupling, allowing greater design freedom and reducing the bend sensitivity of the optical fiber.

Abstract: An optical transmission system accomplishes optical transmission over a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission over a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-toelectric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, and with no use of any optical booster amplifier and optical preamplifier in multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.

Abstract: An optically active linear single polarization device includes a linearly birefringent and linearly dichroic optical waveguide (30) for propagating light and having single polarization wavelength range (48). A plurality of active dopants are disposed in a portion (34) of the linearly birefringent and linearly dichroic optical waveguide (30) for providing operation of the waveguide in an operating wavelength range (650) for overlapping the single polarization wavelength range (48).

Abstract: An optical amplifier system comprises an optical gain medium receiving an input optical signal and outputting an amplified optical signal and a pump laser optically coupled to an input of the optical gain medium, wherein the pump laser emits a series of pulses to the optical gain medium, the pulses being emitted during coherence collapse operation of the pump laser, the time between pulses being shorter than an excited state lifetime of the optical gain medium.

Abstract: An optical system couples laser light into an optical fiber, such as a optical amplifier fiber, from the side of the fiber by side-pumping of the fiber that is in contact with the laser such that refracted laser light is redirected into and through the fiber using direct attachment of a laser, such as a high-power laser diode, to the inner cladding of a fiber.

Abstract: Optical transmission systems of the present invention include at least one optical amplifier configured to provide optical amplification of one or more information carrying optical signal wavelengths. At least one optical amplifier is controlled based on an in situ performance characterization of the at least one optical amplifier and the transmission fiber. The in situ, or installed, performance characteristics of the optical amplifier can be characterized based on relative gain measurements over the signal wavelength range as a function of the supplied pump power. The installed characterization allows the optical amplifier performance and gain profiles to be tightly controlled over the signal wavelength range in the transmission system.

Abstract: An EDF amplifier comprises two EDF loops separated by optical isolators and pumped with light by pump laser diodes under the control of an output power control system. To achieve the required output power the current supplied to the pump supplying light to the input loop is set to the maximum drive current Imax for the pump laser, and the pump currents of all pumps not supplying light to the input loop, that is the pumps supplying light to the further loop or loops, are adjusted to achieve the required output power. To avoid a very high MPI, the inversion of all loops is never so low that the gain in the first loop has to compensate for loss in the following loop or loops. This is done by providing a minimum pump power to the second loop and any following loops. This ensures that the loops are always inverted enough, and that they do not exhibit too much loss. The required minimum pump current is obtained by modelling and experimental verification.

Abstract: An EDFA with integrated input and output modules is presented. The integrated input module has a packaged pump laser diode mounted to the metal EDFA package to provide a heat sink for the pump laser diode which sends the pump laser light over a optical fiber section connected to the amplifying erbium-doped optical fiber section. The fiber section is formed from an optical fiber which better matches the transmission modes in the erbium-doped optical fiber section and has an end subsection of the single mode fiber for a larger numerical aperture. Collimating lenses also increase the coupling efficiency of the laser diode to the erbium-doped fiber section. The integrated output module has a photodiode with a tap filter to monitor the output power of the EDFA, an optical isolator to prevent interference in the erbium-doped optical fiber section. With a twin optical isolator, the integrated input and output modules can be arranged in different ways and combinations with the erbium-doped optical fiber section.

Abstract: A method and apparatus is presented which reduces noise degradation in the shorter wavelength band by using modulation of one/multiple pumps plus multiple-order Raman amplification. Such a scheme is very suitable for the case of SSMF fiber where pump—pump induced four-wave mixing (FWM) effects are negligible. Further, a group Time Domain Multiplexing (TDM) configuration is provided to simultaneously reduce the amplified spontaneous emission (ASE) noise and pump—pump induced FWM effects for the case of NZ-DSF fiber.

Abstract: A dual-port broadband light source with independently controllable output powers includes a broadband light source having a first gain medium pumped by an input pump light in order to output a first amplified spontaneous emission through both ends thereof. A second gain medium pumped by another input pump light in order to output a second amplified spontaneous emission through both ends thereof. A reflector disposed between the opposite ends of the first and second gain mediums to reflect the input first and second amplified spontaneous emissions. The first and second amplified spontaneous emissions output from the first and second gain mediums are then output to the outside through first and second output terminals.

Abstract: A planar waveguide optical amplifier includes a substrate and an active waveguide formed on the substrate for imparting gain to an optical signal propagating therethrough. The active waveguide has an input port for receiving an optical signal to be amplified and an output port on which an amplified optical signal is directed. A plurality of coupling elements are formed on the substrate and are adapted to couple pump power to the active waveguide. The plurality of coupling elements are located at predetermined positions along the active waveguide.

Abstract: An optical pulse testing apparatus incorporating an optical pulse generator composed of low cost components. The optical pulse testing apparatus comprises: a ring optical path including an optical fiber 30 with a rare earth element added to; an excitation light source 32 which enters excitation optical pulses into the optical fiber 30; an optical branching filter 38 for branching the circulating optical pulses circulating through the ring optical path to emit output optical pulses; and a photodetector 40 for detecting the circulating optical pulses circulating through the ring optical path to obtain signals indicative of a light intensity and a generation timing of the circulating optical pulses. Thus, the optical pulse generator, and the optical pulse testing apparatus and method using the optical pulse generator require no expensive optical parts and complicated device control.

Abstract: An amplification architecture for WDM receiver systems. The WDM channel grid is divided into groups of adjacent channels. A separate optical amplifier is provided for each channel with a single pump being shared among the channels of each group. The gain experienced by channels of a given group may be adjusted by varying the power of the group's pump. This approach allows equalization of received channel power such that all channels fall within the desired dynamic range. The amplification architecture may be implemented in a space-efficient manner at low cost.

Abstract: A long-throw, tight focussing optical coupler has a first passive optical element capable of coupling light between an optical source and an optical destination and a second passive optical element, capable of coupling light between the optical source and the optical destination, located between the first passive optical element and one of the optical source or the optical destination such that, a light beam from the optical source will be transferred to the optical destination when the optical source and optical destination are spaced apart by a distance.

Abstract: An optical transmission system ensuring high-quality monitor control even if an optical fiber fault occurs. A monitor instruction sending unit sends a monitor instruction. An operating condition recognizing unit receives a response signal and recognizes the operating condition. A filtering unit filters the monitor instruction and the response signal. A monitor control unit monitors the operating condition of its own repeater in response to the monitor instruction, and generates resultant response information. A pump unit generates a pump light to cause Raman amplification within an optical fiber transmission medium. A regeneration control unit performs a regeneration control of the response signal to thereby create a regenerated signal. A modulation control unit modulates the pump light by the response information or the regenerated signal to thereby generate the response signal.

Abstract: An improved device and method to pump fiber lasers in order to enhance performance and reliability is provided. A fiber laser is bent into a coil having a moderate curvature so as to avoid radiation losses. A cladding is partly polished to produce coupling surfaces along the length of the spring-like coil. Radiation emitters are imaged with one or more micro lenses that are attached to the coupling surface. In a preferred embodiment, banks of high power laser diodes are utilized as pump sources. Coupling surfaces are preferably created along the length of the fiber at intervals where pump radiation from the previous pump edge has been absorbed. Although the system may be used to pump single mode fibers, the preferred application is to pump multimode fibers, having greater core diameters and higher luminescent capacity, wherein only a single cladding can be used.

Abstract: An automatic gain controller for controlling gain values of an optical fiber amplifier. The automatic gain controller includes a first opto-electric conversion unit for converting a portion of optical signals that are input into the optical fiber amplifier into electrical signals to output the converted electrical signals. A second opto-electric conversion unit converts a portion of output optical signals output from the optical fiber amplifier into electrical signals and then outputs the converted electrical signals. A transient suppressing unit generates pulse typed waveforms when a change in channel number is generated during monitoring outputs of the first opto-electric conversion unit, and a comparing unit compares the sum of output signals of the transient suppressing unit and output signals of the first opto-electric conversion unit with output signals of the second opto-electric conversion unit.

Abstract: The present invention discloses a long-band Erbium doped-fiber amplifier including: a first Erbium doped fiber with a predetermined length, coupled to a first pumping light source through a first wavelength-selective coupler, for amplifying a C-band optical signal by supplied pumping light; a second Erbium doped fiber with a predetermined length for amplifying an L-band optical signal by a second pumping light source; a feedback loop for recycling a specific C-band wavelength generated in the amplification of the first Erbium doped fiber as the second pumping light source of the L-band optical signal; a tap coupler formed between the first and second Erbium doped fibers, for dividing the optical power amplified in the first Erbium doped fiber, for supplying a predetermined ratio of optical power to the second Erbium doped fiber, and for re-inputting the residual optical power to the feedback loop; and, a second wavelength-selective coupler for coupling the signal light transmitted from the tap coupler to the