Abstract: Methods and systems are provided for generation and detection of rogue waves, including hydrodynamic rogue waves and optical rogue waves. A method for generating an optical rogue wave comprises the steps of generating an input pulse into a nonlinear optical medium, and perturbing the input pulse by directing a narrow-band seed radiation into the input pulse. The seed radiation has a frequency and timing to generate broadband radiation within the nonlinear optical medium.

Abstract: Apparatus and method for amplifying laser signals using segments of fibers of differing core diameters and/or differing cladding diameters to suppress amplified spontaneous emission and non-linear effects such as four-wave mixing (FWM), self-phase modulation, and stimulated Brillouin and/or Raman scattering (SBS/SRS). In some embodiments, different core sizes have different sideband spacings (spacing between the desired signal and wavelength-shifted lobes). Changing core sizes and providing phase mismatches prevent buildup of non-linear effects. Some embodiments further include a bandpass filter to remove signal other than the desired signal wavelength and/or a time gate to remove signal at times other than during the desired signal pulse. Some embodiments include photonic-crystal structures to define the core for the signal and/or the inner cladding for the pump.

Abstract: A fiber-MOPA includes a seed-pulse source followed by fiber amplifier stages. The seed pulse source delivers signal pulses for performing a laser operation and delivers radiation between the seed pulses to maintain the collective average of the seed pulse power and intermediate radiation power constant. Keeping this average power constant keeps the instantaneous available gain of the fiber amplifier stages constant. This provides that the seed pulse delivery can be changed from one regime to a next without a period of instability between the regimes.

Abstract: An optical amplifier using the evanescent light to control the optical output level is provided. The optical amplifier includes: a waveguide path transmitting an optical signal; an optical amplification unit formed on the waveguide path and amplifying the optical signal by an excitation light; an irradiation unit irradiating the excitation light to the optical amplification unit; an optical detection unit generating an electric signal which corresponds to a detected light; a branching unit branching an evanescent light being the optical signal outputted from the optical amplification unit and leaked outside the waveguide path, and focusing the evanescent light on the optical detection unit; a wavelength detection unit detecting a wavelength multiplicity of the optical signal based on the detected evanescent light; and a light amount adjustment unit adjusting a light amount of the excitation light irradiated by the irradiation unit based on the wavelength multiplicity.

Abstract: An optical modulator includes first and second modulation waveguides, a demultiplexer, first and second phase adjustment waveguides that changes phases of a light of the first and second modulation waveguides, a multiplexer that combines light outputs from the first and second phase adjustment waveguides, a gain controller and a modulator bias controller in which voltages of the first and second modulation signals are controlled so that a result of adding light from the first modulation waveguide to light from the second modulation waveguide where light from the first modulation waveguide has a predetermined phase is equal to a result of adding light from the first modulation waveguide to light from the second modulation waveguide where light from the second modulation waveguide has a predetermined phase. A phase-adjustment bias controller that controls phase amounts changed by the first and second phase adjustment waveguides so as to cancel phase errors.

Abstract: A peak value detector detects power of an output light pulse which is output from the light amplifying fiber. A light receiving element receives a group of light pulses including a plurality of pulses and converts the group of light pulses into a current signal. The current/voltage converter circuit converts the current output from the light receiving element to voltage. The integration circuit integrates the voltage output from the current/voltage converter circuit. A programmable gain amplifier (PGA) amplifies the signal output from the integration circuit and provides the signal for the A/D converter circuit. The gain of the PGA is set by a gain setting signal from the signal processing circuit. The signal processing circuit adjusts the gain of the PGA so that the gain increases as the repetition frequency of the group of pulses increases.

Abstract: The invention relates to a pulsed light source capable of effectively utilizing optical power and selecting the pulse width of output pulsed light. A pulsed light source has a MOPA structure, and comprises a seed light source and an optical fiber amplifier. The seed light source includes a semiconductor laser outputting pulsed light. In the optical fiber amplifier, an optical filter branches pulsed light amplified by a YbDF into a first wavelength component including the peak wavelength and the remaining second wavelength component. An optical switch outputs one of the pulsed light of the first wavelength component and the pulsed light of the second wavelength component which are inputted. Another YbDF amplifies the pulsed light outputted from the optical switch.

Abstract: An optical amplifier comprises at least two gain regions, an intermediate region situated between the gain regions, and a transition region situated between the intermediate region and each gain region. The aforesaid regions have claddings that collectively form a path for pump radiation propagating from at least one of the gain regions to the other gain region, and cores that collectively form a path for signal radiation propagating from at least one of the gain regions to the other gain region. The cores in the gain regions support multiple propagating optical modes, including at least one signal mode and at least one non-signal mode. The intermediate region, however, supports fewer propagating core modes than are supported by the gain regions. The transition regions are conformed such that when radiation in propagating non-signal core modes passes from the gain regions into the intermediate region, it is at least partly coupled into cladding modes of the intermediate region.

Abstract: A spatially multiplexed optical link having a plurality of transmission paths, wherein at least one transmission path is configured to carry an optical-pump signal while one or more other transmission paths carry data-bearing signals. Disposed within the optical link are an optical signal-distribution module and an amplifier module. The optical signal-distribution module is configured to couple portions of the optical-pump signal into the data-bearing transmission paths. The amplifier module is configured to amplify the data-bearing signals using these portions of the optical-pump signal as a power source in a suitable all-optical amplification scheme. The optical-pump signal can optionally be tapped and applied to a photovoltaic element configured to directly power a device, e.g., an optical performance monitor, or to charge the battery of that device to enable its autonomous operation if external electrical power is not available where the device is deployed.

Abstract: An ultra-short high-power light pulse source including a first laser pump source (1), a mode-locked laser oscillator (2), a second laser pump source (4), a waveguide (6) capable of inserting spectral phases into the light pulses, and a compressor (8) capable of generating predetermined spectral phases into the light pulses. The waveguide (6) includes an element capable of compensating the predetermined spectral phases generated at least by the compressor (8), the second laser pump source (4) being capable of delivering a second pump light flow (5) having a power PL such that the spectral phases generated by the wave guide (6) are opposed or quasi opposed to the predetermined spectral phases generated by the compressor (8) in order to generate compressed ultra-short light pulses (9) at the output of the compressor (8) with a planar or quasi planar spectral phase.

Abstract: A fiber laser device includes a pumping light source configured to output pumping light having a wavelength ?, and a rare earth-doped fiber, wherein when the intensity change rate of the pumping light with respect to the temperature is denoted by ?P dB/° C., the wavelength change rate of the pumping light with respect to the temperature is denoted by ??p nm/° C., the pumping light absorption change rate of the rare earth-doped fiber per unit wavelength change at the wavelength of ? nm when the wavelength of the pumping light changes is denoted by A?(?) dB/nm, and the pumping light absorption change amount of the rare earth-doped fiber per unit temperature change at the wavelength of ? nm when the temperature of the rare earth-doped fiber changes is denoted by ?A(?) dB/° C., the wavelength ? of the pumping light is such a wavelength ? that ?P, ??p×A?(?) and ?A(?) compensate with each other.

Abstract: A fiber, such as a photonic bandgap fiber, is provided, the fiber including a core and a cladding. The core can extend longitudinally and can have a gain medium configured to provide laser amplification to laser radiation propagating along the core. For example, the gain medium may include a dopant configured to provide amplification, when activated by one or more modes of excitation radiation, of laser radiation propagating along said core. The cladding can be radially exterior to the core, and can be configured to provide a low-loss propagation the one or more modes of excitation radiation and a lossy propagation of all modes of laser radiation along the core, the lossy propagation higher than the low-loss propagation, in particular when the one or more modes of excitation radiation is substantially absent from the core. Associated methods and apparatuses are also provided.

Abstract: Various types of holey fiber provide optical propagation. In various embodiments, for example, a large core holey fiber comprises a cladding region formed by large holes arranged in few layers. The number of layers or rows of holes about the large core can be used to coarse tune the leakage losses of the fundamental and higher modes of a signal, thereby allowing the non-fundamental modes to be substantially eliminated by leakage over a given length of fiber. Fine tuning of leakage losses can be performed by adjusting the hole dimension and/or the hole spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holely fibers have a large hole dimension and spacing, and thus a large core, when compared to traditional fibers and conventional fibers that propagate a single mode. Other loss mechanisms, such as bend loss and modal spacing can be utilized for selected modes of operation of holey fibers. Other embodiments are also provided.

Abstract: A fiber laser of an MOPA type includes an MO which is a laser oscillator for generating seed light, a PA which is a light amplifier connected to a rear stage of the MO, for amplifying and outputting laser light emitted from the MO, and a reflection device which is provided between the MO and the PA. According to the present invention, the MOPA type fiber laser can decrease the peak value of the pulse which is emitted toward the MO or the pump light source by self-oscillation or reflection, and makes it unlikely that the pump light source or the MO will be damaged.

Abstract: A polarization state adjusting optical element is formed by a ½ wavelength plate and a ¼ wavelength plate and its polarization direction and elliptic degree are adjusted. By adjusting the polarization state adjusting optical element in advance, even if the output of a pump light source is changed, the polarization characteristic (polarization direction and elliptic degree) of the output light of an FDFA amplifier will not change or the change is sufficiently small. In this state, a polarization state adjusting optical element adjusts the polarization state of the laser beam coming into a wavelength conversion optical system so that the wavelength conversion optical system has the maximum conversion efficiency. Thus, it is possible to provide an FDFA having a small change of the polarization state of the output light even if the pump light intensity is changed.

Abstract: A semiconductor optical amplifier includes an input-side optical amplifier waveguide section that has a first active core layer. An output-side optical amplifier waveguide section connects to the input-side optical amplifier waveguide section and has a second active core layer that is wider than the first active core layer. The width of the first active core layer and relative refractive index difference between the first active core layer and adjacent clad section in the width direction of the first active core layer, and the width of the second active core layer and relative refractive index difference between the second active core layer and adjacent clad section in the width direction of the second active core layer are set such that the carrier density and optical confinement factor in the first active core layer are higher than the carrier density and optical confinement factor in the second active core layer.

Abstract: A gain-clamped semiconductor optical amplifier comprises: at least one first surface; at least one second surface, each second surface facing and electrically isolated from a respective first surface; a plurality of nanowires connecting each opposing pair of the first and second surfaces in a bridging configuration; and a signal waveguide overlapping the nanowires such that an optical signal traveling along the signal waveguide is amplified by energy provided by electrical excitation of the nanowires.

Abstract: The present invention relates to an optical module having a structure for reducing adverse contingencies such as increased number of fusion splicing points, drops in output, and higher costs associated with a greater number of optical components. The optical module comprises an amplification optical fiber, a transmission optical fiber, and a fusion splicing structure that fusion-splices the amplification optical fiber to the transmission optical fiber, in a state where a cover layer is removed at the tip portions, including the end faces, of these optical fibers. The fusion splicing structure includes a pumping light removing resin that covers directly the tip portions of the amplification optical fiber and the transmission optical fiber from which the cover layer is removed. The pumping light removing resin has a higher refractive index than a first cladding of the amplification optical fiber.

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: An optical amplifier for determining the attenuation of a length of optical fiber (7) to which it is adapted to be connected comprising means (5) to receive an input signal from the optical fiber (7), means (6) to output an amplified signal to the optical fiber (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 fiber (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: An optical amplifier apparatus includes an optical amplifier including an amplification medium doped with an active substance, the amplification medium excited in order to amplify light; a semiconductor optical amplifier arranged after the optical amplifier; a driver for supplying a driving current with respect to the semiconductor optical amplifier in order that the semiconductor optical amplifier has an amplification characteristic with respect to an input light, the amplification characteristic including a gain non-saturated region and a gain saturated region; and an input-light level adjuster for adjusting an out put light of the optical amplifier to the input light level of the semiconductor optical amplifier, the input light level being set up between the gain non-saturated region and the gain saturated region.

Abstract: Disclosed is an amplifying optical fiber having a central core and an optical cladding surrounding the central core. The central core is based on a silica matrix that includes nanoparticles, which are composed of a matrix material that includes doping ions of at least one rare earth element. The amplifying optical fiber can be employed, for example, in an optical amplifier and an optical laser.

Abstract: A method is provided for forming an optical fiber amplifier. The method comprises providing a composite preform having a gain material core that includes one or more acoustic velocity varying dopants to provide a longitudinally varying acoustic velocity profile along the gain material core to suppress Stimulated Brillouin Scattering (SBS) effects by raising the SBS threshold and drawing the composite preform to form the optical fiber amplifier.

Abstract: An optical system including a plurality of fibers each providing a fiber beam and at least one tapered fiber bundle. The tapered fiber bundle includes a plurality of input end fibers, a plurality of output end fibers and a center bundle portion, where each input end fiber is coupled to a separate one of the fibers, and where the bundle portion combines all of the fiber beams received by the input end fibers into a single combined beam and each output end fiber is capable of receiving the combined beam separately from the other output end fibers. The optical system also includes a plurality of optical output channels where each optical output channel is coupled to a separate one of the output end fibers.

Abstract: A fiber laser amplifier system including a plurality of master oscillators each generating a signal beam at a different wavelength. A splitter for each master oscillator splits the signal beam into a plurality of fiber beams to be separately amplified. A separate tapered fiber bundle receives the amplified beam for each master oscillator, where each tapered fiber bundle includes a plurality of input end fibers, a plurality of output end fibers and a center bundle portion, where each input end fiber is coupled to a separate one of the fiber amplifiers, where the bundle portion combines all of the fiber beams received by the input end fibers into a single combined beam and each output end fiber is capable of receiving the combined beam separately from the other output end fibers. A separate optical output channel receives one of the output end fibers from each tapered fiber bundle.

Abstract: An electronic circuit for controlling a laser system consisting of a pulse source and high power fiber amplifier is disclosed. The circuit is used to control the gain of the high power fiber amplifier system so that the amplified output pulses have predetermined pulse energy as the pulse width and repetition rate of the oscillator are varied. This includes keeping the pulse energy constant when the pulse train is turned on. The circuitry is also used to control the temperature of the high power fiber amplifier pump diode such that the wavelength of the pump diode is held at the optimum absorption wavelength of the fiber amplifier as the diode current is varied. The circuitry also provides a means of protecting the high power fiber amplifier from damage due to a loss of signal from the pulse source or from a pulse-source signal of insufficient injection energy.

Abstract: Embodiments of laser systems advantageously use pulsed optical fiber-based laser source (12) output, the temporal pulse profile of which may be programmed to assume a range of pulse shapes. Pulsed fiber lasers are subject to peak power limits to prevent an onset of undesirable nonlinear effects; therefore, the laser output power of these devices is subsequently amplified in a diode-pumped solid state photonic power amplifier (DPSS-PA) (16). The DPSS PA provides for amplification of the desirable low peak power output of a pulsed fiber master oscillator power amplifier (14) to much higher peak power levels and thereby also effectively increases the available energy per pulse at a specified pulse repetition frequency. The combination of the pulsed fiber master oscillator power amplifier and the diode-pumped solid state power amplifier is referred to as a tandem solid state photonic amplifier (10).

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

Abstract: 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: An optical signal processing apparatus includes an input unit to which signal light is input; a wave coupling unit that couples the signal light from the input unit and pump light having a waveform different from that of the signal light; a first nonlinear optical medium that transmits light coupled by the wave coupling unit, the light being the signal light and the pump light; a dispersion medium that transmits the light that has been transmitted through the first nonlinear optical medium; and a second nonlinear optical medium that transmits the light that has been transmitted through the dispersion medium.

Abstract: By compensating polarization mode-dispersion as well chromatic dispersion in photonic crystal fiber pulse compressors, high pulse energies can be obtained from all-fiber chirped pulse amplification systems. By inducing third-order dispersion in fiber amplifiers via self-phase modulation, the third-order chromatic dispersion from bulk grating pulse compressors can be compensated and the pulse quality of hybrid fiber/bulk chirped pulse amplification systems can be improved. Finally, by amplifying positively chirped pulses in negative dispersion fiber amplifiers, low noise wavelength tunable seed source via anti-Stokes frequency shifting can be obtained.

Abstract: A mode filter for eliminating the propagation of higher-order modes along a section of optical multimode fiber comprises a graded index (GRIN) lens, preferably of a quarter-pitch length, and a pinhole element in the form of a small core fiber. This configuration creates a Fourier spatial filter assembly that removes higher order modes propagating along an optical fiber while capturing the fundamental mode of the optical signal. A section of GRIN fiber is preferably used as the lens, with the small core fiber disposed at the output of the GRIN fiber lens to collect substantially only the on-axis fundamental mode of the optical signal. Since the higher order modes are shifted away from the origin by the GRIN fiber lens, only the fundamental mode signal is captured by the small core fiber.

Abstract: The invention relates to an apparatus for coupling light into an optical wave guide, a laser system with such an apparatus, and a preform to manufacture the apparatus for coupling light into an optical wave guide with the aid of a pumping fiber to guide the light, whereby the optical wave guide comprises a core with a cladding and an initial length segment with a second length segment immediately connected to it, whose cross section increases in tapered form with respect to the first length segment.

Abstract: Multi-clad optical fibers and fiber amplifiers are disclosed. Various embodiments include multi-clad, large core fiber amplifiers. In various implementations mixing of pump modes is enhanced relative to that obtainable with conventional double-clad fibers. In some embodiments end terminations are provided with increased length of end-cap fiber. In at least one embodiment a multi-clad fiber is provided, with a pump cladding formed by stacking a layer of low index rods in the preform. Various embodiments include a multi-clad fiber amplifier system. The system includes a pump source to pump said fiber amplifier. The system also includes an optical fiber having a core and a cladding, wherein the cladding includes a pump cladding having a corrugated boundary. In various embodiments the pump cladding is formed by rods in a preform, which are disposed to mix the pump modes and/or scatter or reflect pump energy into the core.

Abstract: According to an aspect of an embodiment, an apparatus includes an optical branching unit for branching an input signal light in four directions, a polarization component extraction unit extracting four polarization components having mutually different polarization parameters from lights branched in four directions by the optical branching unit, and a determination unit determining input/non-input of the signal light based on the four polarization components extracted by the polarization component extraction unit.

Abstract: Apparatus and method for amplifying laser signals using segments of fibers of differing core diameters and/or differing cladding diameters to suppress amplified spontaneous emission and non-linear effects such as four-wave mixing (FWM), self-phase modulation, and stimulated Brillouin and/or Raman scattering (SBS/SRS). In some embodiments, different core sizes have different sideband spacings (spacing between the desired signal and wavelength-shifted lobes). Changing core sizes and providing phase mismatches prevent buildup of non-linear effects. Some embodiments further include a bandpass filter to remove signal other than the desired signal wavelength and/or a time gate to remove signal at times other than during the desired signal pulse. Some embodiments include photonic-crystal structures to define the core for the signal and/or the inner cladding for the pump.

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: An all fiber mid-IR pulse generator is disclosed that may be used to drive an external non-linear converter. The generator comprises fiber laser oscillator and fiber amplifier elements wherein diode lasers are used to cladding pump the different fiber elements depending on different configurations of the pulse generator. Gain switching of the fiber lasers precludes the need for discrete devices such as Q-switches to generate pulses. The fiber laser and fiber amplifier elements are all fused together, along with fiber isolators and reflective gratings, so there is no free space coupling, and there are no optical elements except as may be needed to couple the output of the generator to a non-linear converter. The all fiber implementation has a single transverse mode at the lowest order mode of operation which results in a nearly diffraction limited output which causes non-linear converters to operate more efficiently.

Abstract: A fiber laser amplifier system including a plurality of master oscillators each generating a signal beam at a different wavelength. A splitter is provided for each master oscillator that splits the signal beam into a plurality of fiber beams where a separate fiber beam is sent to a fiber amplifier. A tapered fiber bundle couples the output ends the fiber amplifiers for each wavelength group into a combined fiber providing a combined output beam, where a separate combined output beam is provided for the wavelength for each master oscillator. An end cap is optically coupled to an output end of each of the tapered fiber bundles to expand the combined output beam. A spectral beam combination grating receives the combined beams from the tapered fiber bundles at different angles and outputs an output beam of all of the combined beams as a single beam being directed in the same direction.

Abstract: A pulse laser apparatus includes a laser configured to generate a pulse of a laser beam, a fiber amplifier, and a pulse compressor. The fiber amplifier includes a rare-earth doped fiber that exhibits normal dispersion at a wavelength of the laser beam generated from the laser. The pulse laser apparatus further includes a unit configured to give a loss to energy portions in a wavelength region corresponding to a zero-dispersion wavelength of the rare-earth doped fiber and/or a wavelength region longer than the zero-dispersion wavelength within a wavelength spectrum of the laser beam having been chirped in the fiber amplifier.

Abstract: A laser system for effective injection seeding is configured with a master oscillator lasing a narrowband seed radiation which is characterized by a single longitudinal master mode injected into a slave oscillator so that the latter generates a broadband slave radiation with a dominant slave mode and side slave modes. The slave radiation is coupled into an input of a SM fiber laser amplifier operative to output an amplified radiation with the spectra which is substantially as narrow as the spectra of the slave radiation.

Abstract: A multi-layer optical thin film filter comprising plural deposited optical thin films, wherein optical thin film thickness for each of said optical thin films has a predetermined wavelength spectrum in a predetermined gain equalization band and a predetermined wavelength spectrum in a pumping light transmission band other than said gain equalization band.

Abstract: The invention relates to an apparatus for dynamically controlling the gain of an optically pumped optical amplifier, and the optical amplifier including such apparatus, which utilizes a multiplying digital to analog converter to implement a digitally adjustable analog feed forward control of a source of pump radiation of the optical amplifier.

Abstract: An optical amplifier for amplifying light includes a light source for emitting pump light in accordance with current amount; a rare earth element doped optical fiber doped rare earth element, the rare earth element doped optical fiber pumped by the pump light from the light source; a detector for detecting upconversion light leaked from the rare earth element doped optical fiber; a memory for storing correspondence relationship data of the current amount for the light source and an intensity of the upconversion light in normal state of the light source; a difference calculator for calculating a difference between the intensity of the upconversion light being detected by the detector and an amount being obtained by converting the current amount for the light source by the use of the correspondence relationship data; and a discriminator for discriminating whether the difference calculated at the difference calculator exceeds a predetermined value.

Abstract: Provided is a laser apparatus including: a DFB fiber laser 40 including, as an amplitude medium, a rare earth doped silica optical fiber codoped with a high concentration of aluminum; an optical feedback path 50 formed by a ring-shaped optical fiber; and an optical coupler 70 a) feeding back a part of an output of the DFB fiber laser 40 to the DFB fiber laser 40 via the optical feedback path 50, and b) outputting, to outside, another part of the output of the DFB fiber laser 40, where the optical fiber forming the optical feedback path 50 is longer than a length at which a relaxation oscillation noise in the output to the outside becomes ?110 dB/Hz.

Abstract: Embodiments of optical fiber may include cladding features that include a material (e.g., fluorine-doped silica glass) that may produce a very low relative refractive index difference with respect to cladding material in which the cladding features are disposed. This relative refractive index difference may be characterized by (n1?n2)/n1, where n1 is the index of refraction of the cladding material in which the cladding features are included, and n2 is the index of refraction of the cladding features. In certain embodiments, the relative refractive index difference may be less than about 4.5×10?3. In various embodiments, the configuration of the cladding features including, for example, the size and spacing of the cladding features, can be selected to provide for confinement of the fundamental mode yet leakage for the second mode and higher modes, which may provide mode filtering, single mode propagation, and/or low bend loss.

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: A chirped-pulse fiber amplification method and system operates with large nonlinear phase shifts (as large as ˜20? or more). In this regime, the pulse spectrum is modified by strong self-phase modulation and gain shaping. With large-enough nonlinear phase shift, substantial spectral broadening occurs. The amplified spectrum can therefore be much broader than the spectrum that is obtained with small nonlinear phase shifts. The broader spectrum enables the formation of a shorter pulse, and the bandwidth generated in nonlinear chirped-pulse amplification can in fact be exploited to generate shorter pulses. Ultimately, this allows the generation of pulses shorter than the gain-narrowing limit of a fiber amplifier.

Abstract: Systems and methods are disclosed to process an optical signal using a pre-processor to populate a non-linearity compensation data structure based on a set of predetermined rules in a non-real-time off-line mode; and an amplifier applying said predetermined rules in real-time to one or more channel input data using the data structure to determine a non-linearity compensation output.

Abstract: A cladding-pumped gain optical fiber is provided. The cladding-pumped gain optical fiber includes a core transmitting a signal light; a first cladding covering the core and having an optical-gain dopant; a second cladding covering the first cladding for transmitting a pumping light; and a third cladding covering the second cladding for reflecting the pumping light.