An optical fiber amplification. system includes: a first optical fiber amplifier including a first optical amplifying fiber including a core portion doped with a first rare-earth. element, a first input unit configured to receive first signal light, an excitation-light source configured to output pump light, a pump light combiner configured to input the pump light to the first optical amplifying fiber, and a residual pump light recovery device configured to recover residual pump light; and a second optical fiber amplifier including a second optical amplifying fiber including a core portion doped with a second rare-earth. element, a second input unit configured to receive second signal light, and a residual pump light combiner configured to input, to the second optical amplifying fiber, the residual pump light recovered by the residual pump light recovery device.

A device for the generation of ultrashort pulses, wherein an oscillator is formed by: a first and a second non-overlapping transmission band-pass filter, which can serve as reflecting end element of the oscillator; optically transparent means with non-linear Kerr coefficient χ.sup.(3) different from zero configured to achieve a spectral broadening by self-phase modulation of the signal transiting through these means; an optical waveguide that produces a positive gain; a node configured to receive a trigger signal designed to activate the operation of the oscillator; a trigger signal generating device comprising: a laser source, for example a microchip, configured to generate a laser pulse, preferably with a minimum bandwidth, having a duration of hundreds of ps, up to the ns; a coupling system designed to introduce the pulse of the trigger laser into a waveguide made of an optically transparent material characterised by a non-linear Kerr coefficient χ.sup.(3) different from zero, which is configured to produce two distinct effects in order to spectrally broaden the pulse of the trigger laser, and precisely: a) self-phase modulation four-wave mixing; the output of the waveguide supplies the trigger signal to the node. The pulses produced by the oscillator typically have a duration of the order of the picosecond and are easily reduced to the Fourier limit of circa 100 femtoseconds by means of a dispersive device.

A broadband optical amplifier for operation in the 2 μm visible wavelength band is based upon a single-clad Ho-doped fiber amplifier (HDFA). A compact pump source uses a combination of discrete laser diode with a fiber laser (which may be a dual-stage fiber laser) to create a pump output beam at a wavelength associated with creating gain in the presence of Ho ions (an exemplary pump wavelength being 1940 nm). The broadband optical amplifier may take the form of a single stage amplifier or a multi-stage amplifier, and may utilize a co-propagating pump and/or a counter-propagating pump arrangement.

An optical fiber may include a core in which core-guided light generated by one or more light sources propagates along a length of the at least one optical fiber, one or more claddings, surrounding the core, to guide cladding-guided light generated by the one or more light sources along the length of the at least one optical fiber, and a reflector structure machined into the at least one optical fiber. The reflector structure may include multiple angled facets arranged at one or more respective angles relative to an axis of the optical fiber to reflect at least a portion of the core-guided light and/or the cladding-guided light passing through the optical fiber.

The present invention makes it possible to improve excitation efficiency in a fiber laser device provided with a TFB having an injection optical fiber not connected to an excitation light source. This fiber laser device is provided with: a plurality of excitation light sources, at least one fiber bundle that injects excitation light from the plurality of excitation light sources from a plurality of injection optical fibers and couples the excitation light to one optical fiber; and a cavity that introduces the excitation light coupled by the fiber bundle and amplifies and emits laser light. The number of the plurality of injection optical fibers of the fiber bundle is larger than the number of the plurality of excitation light sources, and a loop part is configured by connecting surplus injection optical fibers to which the excitation light is not injected among the plurality of injection optical fibers of the fiber bundle.

A fiber amplifier is provided, including a pump laser (202), a pump and signal combiner (203), and a few-mode doped fiber (204). The pump laser (202) is configured to output pump light. The pump and signal combiner (203) is configured to couple input few-mode signal light and the pump light into the few-mode doped fiber (204). Refractive indexes of a fiber core of the few-mode doped fiber (204) are distributed to be gradient along a radial direction of a cross section, the fiber core is etched with periodic gratings along an axial direction, and periods of the gratings satisfy a phase matching condition. The fiber amplifier achieves strong coupling and co-amplification between optical signal modes, thereby reducing a differential gain between mode groups.

The present invention addresses the problem that, when an optical amplification device having a plurality of optical transmission paths, such as multi-core optical fibers, is used for bidirectional communication, it is difficult to construct an optical transmission system optimized for all of signal lights having different transmission directions. The optical amplification device of the present invention comprises: an optical guide means having a plurality of optical transmission paths including an optical amplification medium having a gain in the wavelength band of a signal light; an excitation light introducing means for introducing excitation light for exciting the optical amplification medium into the optical guide means from both ends of the optical guide means; and a residual excitation light introducing means for introducing residual excitation light output from both ends of the optical guide means and having a wavelength component of the excitation light into the optical guide means.

There is described a fiber laser system generally having a pump laser generating a pump laser beam; and a length of optical fiber optically coupled to the pump laser, the length of optical fiber having: a laser cavity having a cavity path, a first fiber Bragg grating having a first reflectivity profile, a second filter having a second filter profile, and an optical gain region between the first fiber Bragg grating and the second filter along the cavity path, the first reflectivity profile being spectrally detuned from the second filter profile, the first fiber Bragg grating having a first refractive index profile comprising a full width at half maximum bandwidth of at least 0.2 nm and a Gaussian-like apodization, wherein, upon pumping of the optical gain region with the pump laser beam and mode locking of the laser cavity, optical pulses are circulated along the cavity path; and an output.

An object is to provide an optical amplifier with a cladding pumped configuration that improves amplification efficiency. The optical amplifier according to the present invention includes a pump light conversion fiber 11 that converts first pump light L1 with a first wavelength propagating in a cladding into second pump light L2 with a second wavelength, an amplification fiber 13 that is connected to the pump light conversion fiber 11 and optically amplifies signal light Ls with the second pump light L2 supplied to the cladding from the pump light conversion fiber 11, and an oscillator 12 that causes the second pump light L2 to be reflected on two reflectors 15 and to reciprocate within the claddings of the pump light conversion fiber 11 and the amplification fiber 13 to cause laser oscillation of the second pump light L2.

An optical-resolution photoacoustic microscopy (OR-PAM) system for visualizing water content deep in biological tissue uses an all-fiber 1930-nm hybrid optical parametrically-oscillating emitter. The emitter includes a tunable laser source whose output is amplified by a first erbium-doped fiber amplifier (EDFA). The output of the first amplifier is modulated with a Mach-Zehnder amplitude modulator that receives an RF signal with a nanosecond pulse width and a multiple kilohertz repetition rate. A second EDFA further amplifies the signal and passes it to a fiber circulator that in turn delivers it to a 1950/1550 mm fiber wavelength-division-multiplexing coupler WDM. The coupler introduces the signal to a cavity that includes a spool of highly nonlinear fiber and a Thulium-doped fiber amplifier TDFA. From the TDFA the signal reaches a 50/50 fiber coupler that sends part to a second output TDFA and guides part back to the cavity through a port of the WDM.