Provided are a low-cost and low power-consumption optical fiber amplifier, an optical fiber amplifier control method, and a transmission system. The optical fiber amplifier comprises: an optical fiber to which pumping light is supplied and which amplifies an optical signal, the optical fiber including a plurality of cores in a cladding; a light source which outputs the pumping light; a combining means which supplies the pumping light from the light source to the cladding of the optical fiber and causes the pumping light to be combined with the optical signal; a collect means which collects, without collecting the signal light, pumping light among the supplied pumping light that has not been absorbed by the optical fiber; a monitor means which monitors residual pumping light that has passed through the optical fiber and collected by the collect means; and a control means which controls the state of the pumping light.

Example fiber amplifiers and gain adjustment methods for the fiber amplifiers are described. One example fiber amplifier includes a first power amplifier, a wavelength level adjuster, and a controller, where the first power amplifier and the wavelength level adjuster are sequentially connected. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal of the fiber amplifier, and the control output end is configured to output a first amplification control signal to the first power amplifier, and output an adjustment control signal to the wavelength level adjuster. The wavelength level adjuster is configured to perform power adjustment on each wavelength based on the adjustment control signal.

An optical amplifier includes an input port for receiving an input optical signal; a wavelength division multiplexer (204) having a first input coupled to the input port, a second input coupled to a pump source (206), and an output coupled to an amplification fiber (208); and an integrated component (210) configured to provide output monitoring and isolation, wherein the integrated component (210) is configured to separate a first portion of a light signal received from the amplification fiber (208), direct the first portion to a photo detector, direct a second portion of the input light from the amplification fiber (208) to an output port, and attenuate light signals received from the output port.

Described herein are methods for developing and maintaining pulses that are produced from compact resonant cavities using one or more Q-switches and maintaining the output parameters of these pulses created during repetitive pulsed operation. The deterministic control of the evolution of a Q-switched laser pulse is complicated due to dynamic laser cavity feedback effects and unpredictable environmental inputs. Laser pulse shape control in a compact laser cavity (e.g., length/speed of light<1 ns) is especially difficult because closed loop control becomes impossible due to causality. Because various issues cause laser output of these compact resonator cavities to drift over time, described herein are further methods for automatically maintaining those output parameters.

A fiber-based master optical power amplifier (MOPA) is configured to utilize a pump source that operates in pulse mode with the arrival time of the pump pulses coordinated with the arrival time of the input pulses. The width of the pump pulses is also controlled, thus providing a mechanism for controlling both the amount of pump energy injected into the fiber amplifier, as well as the overlap in time between the pump pulse and the seed pulse. As the pulse repetition interval (PRI) of the input seed pulse changes, the timing of the pump pulses and their width are also changed so that a constant gain environment is created within the amplifying medium, providing an essentially constant energy output pulse, regardless of differences in ASE generated during different PRIs.

The de-multiplexing unit 2 de-multiplexes an inputted optical wavelength multiplexed signal into a first optical wavelength multiplexed signal having a first wavelength band and a second optical wavelength multiplexed signal having a second wavelength band in a longer wavelength band than the first wavelength band. The first optical amplifier 3 amplifies the first optical wavelength multiplexed signal. The second optical amplifier 4 amplifies the second optical wavelength multiplexed signal. The multiplexer 5 multiplexes the amplified first optical wavelength multiplexed signal and the amplified second optical wavelength multiplexed signal and outputs the multiplexed signal to a Raman amplifier 6. The first optical amplifier 3 adjusts the amplification rate of the first optical wavelength multiplexed signal so that the intensity of light in the second wavelength band is compensated for by the Raman effect in the Raman amplifier 6.

A system for pumping laser sustained plasma is disclosed. The system includes a plurality of pump modules configured to generate respective pulses of pump illumination for the laser sustained plasma, wherein at least one pump module is configured to generate a train of pump pulses that is interlaced in time with another train of pump pulses generated by at least one other pump module of the plurality of pump modules. The system further includes a plurality of non-collinear illumination paths configured to direct the respective pulses of pump illumination from the plurality of pump modules into a collection volume of the laser sustained plasma.

A laser apparatus according to the present disclosure includes an excitation light source configured to output excitation light, a laser crystal disposed on an optical path of the excitation light, a first monitor device disposed on an optical path of transmitted excitation light after having transmitted through the laser crystal to monitor the transmitted excitation light, a temperature adjustment device configured to adjust a temperature of the excitation light source to a constant temperature based on a temperature command value, and a controller configured to change the temperature command value based on a result of monitoring by the first monitor device.

A fiber-based master optical power amplifier (MOPA) is configured to utilize a pump source that operates in pulse mode with the arrival time of the pump pulses coordinated with the arrival time of the input pulses. The width of the pump pulses is also controlled, thus providing a mechanism for controlling both the amount of pump energy injected into the fiber amplifier, as well as the overlap in time between the pump pulse and the seed pulse. As the pulse repetition interval (PRI) of the input seed pulse changes, the timing of the pump pulses and their width are also changed so that a constant gain environment is created within the amplifying medium, providing an essentially constant energy output pulse, regardless of differences in ASE generated during different PRIs.

A MOPA laser system that includes a seed laser configured to output pulsed laser light, an amplifier configured to receive and amplify the pulsed laser light emitted by the seed laser; and a pump laser configured to deliver a pump laser beam to both the seed laser and the amplifier and a variable attenuator configured to eliminate missing Q-switched pulses.