An optical amplifier includes a photodiode configured to measure power of an output light; a converter configured to convert the power of the output light into a voltage signal; and a processor configured to determine whether a difference between a level of the voltage signal and a predetermined potential is equal to or higher than a first predetermined value, change power of excitation light so that the level of the voltage signal approaches the predetermined value, when it is determined that the difference is equal to or higher than the first predetermined value, determine whether the power of the excitation light is equal to or higher than a second predetermined value, after the power of the excitation light is changed, and reduce the power of the excitation light, when it is determined that the power of the excitation light is equal to or higher than the second predetermined value.

A laser diode system includes plurality of laser pumps, each of the plurality of laser pumps including a plurality of laser diode drivers and a plurality of laser diode elements, wherein each of the plurality of laser diode drivers is electrically coupled to power at least two of the plurality of laser diode elements. A combiner electrically is coupled to the plurality of laser diode elements to combine an output of each of the plurality of laser pumps to generate a combined output light. A controller identifies a failed laser pump or a failed laser diode element, receives an encoded key to gain access to the controller, and disables the failed laser pump or the failed laser diode element based at least in part on authenticating the encoded key.

A laser system including a seed laser and an optical amplification subsystem, receiving an output of the seed laser and providing an amplified laser output, the optical amplification subsystem including a first plurality of amplifier assemblies, each of the first plurality of amplifier assemblies including a second plurality of optical amplifiers, and phase control circuitry including phase modulating functionality associated with each of the first plurality of amplifier assemblies.

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 amplifier (1), and a related optical amplification method, comprising an optical path (2) having an input end (3) and an output end (4), a first erbium doped optical fiber (5) placed along the optical path, a first gain flatting filter (6) placed along the optical path downstream the first erbium doped optical fiber, a second erbium doped optical fiber (7) placed along the optical path downstream the first gain flatting filter, a second gain flatting filter (8) placed along the optical path downstream the second erbium doped optical fiber, a third erbium doped optical fiber (9) placed along the optical path downstream the second gain flatting filter, and an optical pump (10) optically coupled to the optical path so as to optically pump at least the first and the third erbium doped optical fiber.

An arrayed optical amplifier includes: at least one first amplifier including a first excitation light source controlled to a first temperature; at least one second amplifier including a second excitation light source controlled to a second temperature different from the first temperature; and a control circuit coupled to the at least one first amplifier and the at least one second amplifiers.

A laser system including a seed laser and an optical amplification subsystem, receiving an output of the seed laser and providing an amplified laser output, the optical amplification subsystem including a first plurality of amplifier assemblies, each of the first plurality of amplifier assemblies including a second plurality of optical amplifiers, and phase control circuitry including phase modulating functionality associated with each of the first plurality of amplifier assemblies.

The present embodiment relates to an optical amplifier which can perform an amplification operation equivalent to a normal operation even with an increase of dark current in a PD forming a part of a light detection circuit for monitoring signal light as an amplification object. In the optical amplifier, a detection controller performs an anomaly determination on a light detection circuit due to an increase of dark current in the PD based on a difference between temporal change amounts of a signal component of a voltage of output signal from a light receiving unit including the PD, and a voltage component in a high frequency region included in the signal component. An amplification controller can perform suitable switching of control on a drive current to a pumping light source, based on the result of the determination.

A Raman pump laser control apparatus comprises a wavelength division multiplexer, a tap coupler, a photoelectric detector, an analogue amplification processing circuit, an analogue-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 semiconductor laser device includes: a semiconductor laser that contains aluminum or gallium arsenide in an active layer; a detector that detects a shift of a wavelength of emission light from the semiconductor laser toward a short wavelength side; and a judger that makes a judgment about a sign of a sudden failure of the semiconductor laser based on a detection result by the detector.