Optical frequency combs are used for a wide range of applications, some of which require precise control of the amplitude and phase of individual comb teeth. A technique is provided for tooth-level optical frequency comb control. A frequency comb may include a plurality of comb teeth that are separated from one another by a comb frequency spacing. This technique includes generating a train of control pulses, each of the control pulses being frequency-locked to a corresponding tooth of an optical frequency comb to be controlled. The tooth-level control of the frequency comb is enabled via stimulated Brillouin scattering using the train of control pulses.

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.

A method for realizing precise gain control for a hybrid fibre amplifier, and a hybrid fibre amplifier, in which by an erbium-doped fibre amplifier firstly outputting a constant power, a comparable source signal optical power is provided for a raman fibre amplifier of a next stage. A feedback for the gain control may be formed by comparing a source signal optical power calculated after starting pumping of the Raman fibre amplifier and a source signal optical power detected after pumping stops, thereby greatly improving gain control precision of the Raman fibre amplifier. Moreover, the erbium-doped fibre amplifier parts of all the hybrid fibre amplifiers may simultaneously output a constant optical power, and the Raman amplifier parts of all the hybrid fibre amplifiers may simultaneously start calibration, so that the time for starting operation of the entire system may be improved greatly.

The embodiments of the present invention disclose a method and an apparatus for determining a gain of a Raman optical amplifier and a Raman optical amplifier. The method includes: acquiring present gain parameter information of a Raman optical amplifier; and determining a present gain of a monitoring channel of the Raman optical amplifier according to the present gain parameter information and a correspondence between a gain of the monitoring channel of the Raman optical amplifier and gain parameter information. According to the method and apparatus for determining a gain of a Raman optical amplifier and the Raman optical amplifier that are in embodiments of the present invention, a present gain of a monitoring channel can be accurately determined; therefore, a gain spectrum of the Raman optical amplifier can be accurately monitored, and the gain of the Raman optical amplifier can be accurately adjusted to a target gain.

A multicore optical fiber amplifier according to an exemplary aspect of the present invention includes a multicore optical fiber amplification medium including, in a clad, a plurality of cores doped with a rare earth element; signal light introduction means for introducing, into each of the plurality of cores, signal light with a wavelength included in a gain band of the multicore optical fiber amplification medium; excitation light introduction means for introducing, into the clad, excitation light for exciting the multicore optical fiber amplification medium; and control light introduction means for introducing control light into each of the plurality of cores, wherein the control light introduction means introduces the control light into a non-signal core into which the signal light is not being introduced, among the plurality of cores, only when the excitation light is being introduced.

An optical amplifier of the present disclosure includes an optical resonator that includes an amplification fiber capable of amplifying signal light having one or more propagation modes and resonates at least one propagation mode of the signal light amplified by the amplification fiber; an excitation light source that outputs excitation light for exciting the amplification fiber; and a multiplexer that multiplexes the signal light and the excitation light, in which the optical resonator includes a gain clamp setting unit which sets gain clamp for at least one propagation mode out of a plurality of propagation modes resonating in the optical resonator.

Methods and laser systems are disclosed for generating amplified output laser pulses with individually specified pulse energies and/or pulse shapes at individually specified time points at an output by providing a first pulse sequence of input laser pulses with a same pulse energy and a same temporal pulse distance smaller than a temporal pulse distance between adjacent output laser pulses, selecting input laser pulses arriving at the output at or close to the specified time points to form a second pulse sequence of input laser pulses, coupling at least one sacrificial laser pulse (energy balance or temporal balance) into the second pulse sequence, amplifying the second pulse sequence of input laser pulses with the sacrificial laser pulse, and coupling out the amplified sacrificial laser pulse from the amplified second pulse sequence upstream of the output to obtain the amplified output laser pulses.

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.

An optical amplification device includes: a laser medium that amplifies input light to generate output light; an excitation light source that supplies excitation light used for amplifying the input light, to the laser medium; a resonator that includes a pair of first optical elements and disposed to optically face each other with the laser medium interposed between the first optical elements and that resonates generated light generated in the laser medium through the supply of the excitation light; and an optical switch disposed on an optical path of the resonator between the pair of first optical elements.

There is the problem that, in a multicore optical fiber amplifier based on a clad excitation method, it is difficult to suppress the occurrence of an optical surge due to input of signal light into a core with no signal light, without the occurrence of fluctuation in the gain of a core into which signal light is inputted; therefore, a multicore optical fiber amplifier according to an exemplary aspect of the present invention includes a multicore optical fiber amplification medium including, in a clad, a plurality of cores doped with a rare earth element; signal light introduction means for introducing, into each of the plurality of cores, signal light with a wavelength included in a gain band of the multicore optical fiber amplification medium; excitation light introduction means for introducing, into the clad, excitation light for exciting the multicore optical fiber amplification medium; and control light introduction means for introducing control light into each of the plurality of cores, wherein the control light introduction means introduces the control light into a non-signal core into which the signal light is not being introduced, among the plurality of cores, only when the excitation light is being introduced.