Provided are a monitoring device, a monitoring method, an optical amplifier, and an optical transmission system that are adapted for an increase in the number of cores in a multi-core optical fiber transmission path, and that are suitable for crosstalk monitoring. The monitoring device monitors a multi-core optical fiber transmission path comprising a plurality of use core and at least one or more non-use cores. The monitoring device comprises: an applying means for applying dithering to signal light propagating in the use cores; a monitoring means for monitoring the power of the non-use cores; and a separating means for separating a monitoring result from the monitoring means into power components from the plurality of use cores.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

A system includes a master oscillator configured to generate a low-power optical beam. The system also includes a planar waveguide (PWG) amplifier configured to receive the low-power optical beam and generate a high-power optical beam having a power of at least about ten kilowatts. The PWG amplifier includes a single laser gain medium configured to generate the high-power optical beam. The single laser gain medium can reside within a single amplifier beamline of the system. The master oscillator and the PWG amplifier can be coupled to an optical bench assembly, and the optical bench assembly can include optics configured to route the low-power optical beam to the PWG amplifier and to route the high-power optical beam from the PWG amplifier. The PWG amplifier could include a cartridge that contains the single laser gain medium and a pumphead housing that retains the cartridge.

A single-laser light source system for cold atom interferometers, comprising: a reference light module including a narrow-bandwidth laser and a frequency stabilization module and an optical frequency shift module including a first electro-optic modulator and a first narrow-bandwidth optical-fiber filter. The first electro-optic modulator is connected to the first narrow-bandwidth optical-fiber filter by an optical fiber, and the first electro-optic modulator is connected to the laser by an optical fiber. The first electro-optic modulator receives an initial light from the laser, modulates the initial light by a modulation signal with a preset frequency, and generates sidebands with the preset frequency. The first narrow-bandwidth optical-fiber filter filters the optical signal at the output of the first electro-optic modulator to obtain a frequency-shifted light as the +1-order sideband. The frequency-shifted light is used for modulation to obtain a measurement and control light of the cold atom interferometer.

A method for providing spectral beam combining (SBC) including generating a plurality seed beams each having a central wavelength and a low fill factor profile, where the wavelength of all of the seed beams is different; amplifying the seed beams; causing the amplified beams to expand as they propagate so as to be converted from the low fill factor profile to a high fill factor profile where the high fill factor profile tapers to a lower value at a perimeter of each beam; causing a wavefront of the converted beams to flatten to provide a plurality of adjacent SBC beams having different wavelengths with minimal overlap and a minimal gap between the beams; collimating the SBC beams; and directing the collimated SBC beams onto an SBC element that spatially diffracts the individual beam wavelengths and directing the beams in the same direction as a combined output beam.

An example device may include an optical configuration configured to transmit a transmitted optical beam and receive a received optical beam, an optical modem, and an optical amplifier. An example optical amplifier may include an optical gain medium and an optical bandpass filter. The transmitted optical beam may have a transmit wavelength selectable from a plurality of transmit wavelength, and may have a different wavelength from the received optical beam. In some examples, the optical configuration may include at least one dichroic element. Various other devices, systems, and methods are described.

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 system has fiber amplifiers that amplify a seed signal into a high power signal. Control circuity drives the fiber amplifiers. An auxiliary broad-linewidth signal can be selectively introduced to mitigate the onset of Stimulated Brillouin Scattering (SBS) when the primary input seed source does not meet the requirements of power and/or linewidth. To determine whether to mitigate SBS, an input photodiode can detect the seed signal, and the control circuity can detect an operational parameter associated with a detected signal indicative of an onset of SBS on the optical path. In response to the detection, the control circuitry introduces an auxiliary broad-linewidth signal from a broad-linewidth source, which can mitigate the onset of SBS on the optical path.

Disclosed are a control method and an optical fiber amplifier. The optical fiber amplifier is configured to execute the control method. The method comprises: initially correcting a target gain on the basis of a first compensation gain to obtain an initially corrected target gain; when the actual power of the pump laser reaches target power determined on the basis of the initially corrected target gain obtaining, on the basis of a first signal optical power and a second signal optical power, a second compensation gain and a first compensation slope through calculation; correcting the initially corrected target gain again according to the second compensation gain to obtain a corrected target gain; and correcting a target slope according to the first compensation slope to obtain a corrected target slope. This solution can provide high precision control for the gain and the slope of the optical fiber amplifier.

A system and method for communicating supervisory information between amplifier nodes in an optical communication network utilizes modulation of an included pump source to superimpose the supervisory information on through-transmitted customer signals (or ASE associated with the amplifier if no customer traffic is present). The supervisory information (which may include monitoring messages, provisioning data, protocol updates, and the like) is utilized as an input to an included modulator, which then forms a drive signal for the pump controller. In a preferred embodiment, binary FSK modulation is used.