The present invention provides a repetition frequency-tunable optical frequency comb generated by basis of optical feedback. The optical frequency comb comprises a single-frequency laser resonant cavity, a wavelength division multiplexer, a single-mode semiconductor pump light source, an optical circulator, a first optical fiber coupler, a second optical fiber coupler, a photoelectric detector, a highly-stable signal source, an error signal processing system, a laser frequency modulation device and a tunable laser-delay module. The present invention performs delay-time processing to the single-frequency laser by the tunable laser-delay module, and achieves an optical feedback by the optical circulator for injecting to the resonant cavity, generating a series of tunable laser longitudinal modes with equal frequency space. Meanwhile, in combination with the highly-stable signal source, the error signal processing system and the laser frequency modulation device, a laser frequency lock is achieved, and the laser frequency comb is generated. The invention obtains a repetition frequency-tunable laser frequency comb with a simple and practical method, having an extensive application prospect and huge application value in fields such as optical fiber sensing and spectroscopy of atom and molecule.

To solve the problem that the power consumption of optical amplifiers is not optimized over the life time of an amplifier, the optical amplifier includes a gain medium for amplifying a plurality of optical channels, the gain medium including a plurality of cores through which the plurality of optical channels to propagate respectively and a cladding area surrounding the plurality of cores, a monitor that monitors the temperature of the optical amplifier and producing a monitoring result, a first light source that emits a first light beam to excite the cladding area, a second light source that emits a plurality of second light beams to excite each of the plurality of cores individually, and a controller that controls the first light source and the second light source based on the produced monitoring result.

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

The present invention discloses a narrow-band, low-noise Raman fiber laser with a random fiber laser pump, pertaining to the technical field of fiber lasers and comprising an ytterbium-doped random fiber laser for producing ytterbium-doped random fiber lasing as the pump of a cascaded Raman random laser; the ytterbium-doped random fiber laser consists of a pump light source, a pump combiner, an ytterbium-doped fiber and a single-mode fiber connected in sequence, as well as a first narrow-band reflector connected to the signal end of the pump combiner. Ytterbium-doped random fiber lasing as the pump of the pump light source disclosed in the present invention is produced by an ytterbium-doped random fiber laser consisting of a narrow-band point reflector, an ytterbium-doped fiber, and a single-mode fiber and further serves as the pump of a Raman light source to achieve random laser output. The Raman fiber laser with a random fiber laser pump provided by the present invention is significantly better in time-domain stability and relative intensity noise than conventional Raman fiber lasers owing to the application of ytterbium-doped random fiber lasing with modeless spectrum as the pump.

An optical amplifier includes a multi-mode pump laser module, a multi-mode waveguide, a multi-mode to multiple single-mode fiber converter module and a plurality of single-mode cores. The multi-mode pump laser module emits pump light having a plurality of modes to the multi-mode fiber or waveguide. The multi-mode waveguide propagates the emitted pump light to the converter module. The converter module receives the pump light and distributes the pump light approximately uniformly to a plurality of single-mode cores.

In some implementations, an optical amplifier system includes a pump system including a pump laser source configured to output multimode pump light at a first wavelength, and a multicore fiber laser having an input end optically coupled to the pump laser source and an output end. The multicore fiber laser may include a multicore active fiber having multiple cores to convert the multimode pump light to multiple single-mode pump light outputs at one or more second wavelengths, where the multiple cores have respective laser cavities defined by fiber gratings on each of the multiple cores. The optical amplifier system may include a fiber amplifier, optically coupled to the pump system, including multiple amplifier components, in one or more active fibers, that are to be pumped by respective cores, of the multiple cores, of the multicore active fiber.