A method of propagating a laser signal through an optical waveguide and a waveguide laser system provide a novel way of stabilizing the beam emitted by a fiber laser system above the mode instability threshold wherein the beat length of two or more interfering transverse modes of the laser signal in the optical waveguide is modulated in time.

A system includes a laser system having a master oscillator and a planar waveguide (PWG) amplifier having one or more laser diode pump arrays, a PWG pumphead, input optics, and output optics. The PWG pumphead is configured to receive a low-power optical beam from the master oscillator and generate a high-power optical beam. The PWG pumphead includes a laser gain medium, a cartridge, and a pumphead housing. The cartridge is configured to receive and retain the laser gain medium, and the cartridge includes one or more cooling channels configured to transport coolant in order to cool the laser gain medium. The pumphead housing is configured to receive and retain the cartridge, where the cartridge is removable from the housing.

A laser system includes a multipass amplifier for amplifying laser light and providing an amplified output beam, and a control unit. The multipass amplifier includes a laser-active medium. The control unit is configured to keep a thermal load on the laser-active medium substantially constant over a range of a laser output power of the output beam. The thermal load is determined by at least two different power sources.

A Raman pump laser control apparatus comprises a wavelength division multiplexer, a tap coupler, a photoelectric detector, an analog amplification processing circuit, an analog-to-digital converter, a fast Raman pump control unit, an digital-analog converter, and a Raman pump laser. The fast Raman pump control unit, after having known anticipated output light power of the Raman pump laser, based on a direct relationship between a current anticipated output light power of the Raman pump laser and input digital quantity that is needed by the digital-analog converter, uses a feedforward control mechanism so that actual output light power of the Raman pump laser fastly approximates the anticipated output light power thereof, and then synchronously combines with a feedback control mechanism so that the actual output light power of the Raman pump laser is precisely locked on the anticipated output light power, thereby achieving fast and precise control of the Raman pump laser.

A distributed Raman amplifier comprises a loss-measuring device that measures losses in an optical fiber transmission line; a signal processing circuit that compares the measured losses to a threshold, below which a pumping light source is permitted to pump the transmission line; a control circuit responsive to a control signal from the signal processing circuit for controlling operation of the pumping light source; and a spool of fiber configurable to be optically coupled between the pumping light source and optical point-loss sources in the transmission line when the losses are above the threshold. The spool of fiber has a fiber of sufficient length to offset aggregated losses, which prevents the distributed Raman amplifier from shutting down while also allowing the distributed Raman amplifier to achieve entitled gain by pumping the fiber in the spool.

An optical transceiver that includes an optical modulator of a Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified spontaneous emission in regions out of the wavelength band of the light.

A light amplifying device includes, a light amplifying fiber to amplify a seed beam from a seed light source with an excitation beam from an excitation light source, and a controller. The controller causes the seed light source to emit the seed beam in an emission period in which the light amplifying fiber outputs the amplified light beam, causes the excitation light source to emit the excitation beam having first-level power in a non-emission period immediately before the emission period, and changes the excitation beam power to a second level higher than the first level at a beginning of the emission period. The controller increases the excitation beam power to a third level higher than the second level after starting of the emission period, and decreases gradually the excitation beam power from the third level to the second level.

A smart spool is configured to be optically coupled between a pumping light source and optical point-loss sources in an optical fiber transmission line. The smart spool comprises a probe signal transmitter that transmits an optical probe signal into the transmission line. An optical detector receives probe signals scattered in the transmission line. A loss-measuring device is coupled to the optical detector and operable to measure aggregate losses in the transmission line and report the aggregate losses to a network manager. The spool comprises a fiber of sufficient length to offset the aggregated losses to enable a distributed Raman amplifier to pump the transmission line. The smart spool prevents the distributed Raman amplifier from shutting down and allows the distributed Raman amplifier to achieve entitled gain by pumping the fiber in the spool.

An optical transceiver that installs an optical modulator with the Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified stimulated emission in regions out of the wavelength band of the light.

A switchable optical amplifier includes: a first optical amplifier; a second optical amplifier; and an optical switch which includes first and second input ports and first and second output ports, the optical switch that switches between a first connection state where the first input port and the first output port are in an optical connection and the second input port and the second output port are in a no optical connection and a second connection state where the first input port and the second output port are in an optical connection and the second input port and the first output port are in an optical connection, wherein an output of the first optical amplifier is optically coupled to the first input port of the optical switch, an input of the second optical amplifier is optically coupled to the second output port of the optical switch.