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.

An optical module includes an optical fiber component, a wavelength division multiplexing (WDM) filter, at least one isolator, a mirror and an optical detecting component. The optical fiber component, the WDM filter, the at least one isolator, the mirror and the optical detecting component are configured to prevent a signal light which is before an EDF component and an amplified signal light after the EDF component from counter transmission with a simplified structure and compact size.

An optical amplifier that amplifies an incident WDM signal and includes cores having an amplification medium, the optical amplifier includes: a wavelength demultiplexer configured to demultiplex the incident WDM signal into wavelength bands and introducing the demultiplexed WDM signals into the cores separately; a wavelength multiplexer configured to multiplex amplified optical signals propagated through the cores and outputting the multiplexed signal; and an wavelength demultiplexing controller configured to monitor an amplification rate of a specific wavelength band of an amplified WDM signal or a scale associated with an amplification rate of a specific wavelength band, demultiplexing, from the incident WDM signal, an optical signal of a wavelength band having relatively-small optical amplification efficiency according to a monitoring result, and controlling demultiplexing performed by the wavelength demultiplexer in such a way as to amplify, with a relatively-large amplification rate, the optical signal of the wavelength band having relatively-small optical amplification efficiency.

An optical amplifier includes at least two stages of optical amplifier systems, an optical switch, a dynamic gain equalizer (DGE), and a control circuit. An input end of the optical switch is separately coupled to an output end of a first-stage optical amplifier system and an output end of a second-stage optical amplifier system, and an output end of the optical switch is separately coupled to an input end of the second-stage optical amplifier system and an input end of the DGE. The optical switch is configured to set at least two gain modes of the optical amplifier. The control circuit is configured to adjust an attenuation spectrum of the DGE based on the at least two gain modes set by the optical switch. The DGE is configured to perform, based on an adjusted attenuation spectrum, power attenuation processing on signals of different wavelengths in a received optical signal.

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.

Apparatus for providing optical radiation (9), which apparatus comprises; a first seed source (1) for providing first seeding radiation (11); a second seed source (2) for providing second seeding radiation (12); a coupler (3) connected to the first seed source (1) and the second seed source (2) for coupling the first seeding radiation (11) and the second seeding radiation (12) together; and at least one amplifier (4) for amplifying the first seeding radiation (11) and the second seeding radiation (12).

An EDFA may include an input photodiode configured to generate a control signal based on an input signal. The EDFA may include a blind stage configured to generate an amplified signal based on the control signal and the input signal. The EDFA may include a non-blind stage configured to generate an output signal based on the amplified signal within the blind stage, the control signal, and a feedback signal. The EDFA may include a filter configured to generate a filtered signal based on the output signal. The EDFA may include an output photodiode configured to generate the feedback signal based on the filtered signal. The EDFA may include an alarm device. A signal within the non-blind stage may be generated based on the feedback signal and the control signal. The alarm device may be configured to generate an alarm signal when the signal exceeds a threshold value.

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 adjusting a target gain on the basis of a first offset gain to obtain the post-initial-adjustment target gain; when the actual power of the pump laser reaches target power determined on the basis of the post-initial-adjustment target gain, obtaining, on the basis of a first signal optical power and a second signal optical power, a second offset gain and a first offset slope through calculation; adjusting again the post-initial-adjustment target gain according to the second offset gain to obtain a adjusted target gain; and adjusting a target slope according to the first offset slope to obtain a adjusted target slope. This solution can provide high precision control for the gain and the slope of the optical fiber amplifier.

A Raman amplifier includes a first light source that outputs a primary pumping light, which propagates in a same direction as a propagation direction of a signal light, to an optical transmission line for Raman amplification, a second light source that outputs a secondary pumping light, which pumps and amplifies the primary pumping light and propagates in the same direction as the propagation direction, to the optical transmission line, and a control unit that controls a gain for the signal light by adjusting power of the secondary pumping light.

An optical signal amplifier using a praseodymium doped fiber is described. The optical signal amplifier includes a signal laser, a first optical isolator, a second optical isolator a pump laser, a wave division multiplexer, a silica based glass optical fiber, a second optical isolator, an optical power meter, and an optical spectrum analyzer (OSA). The signal laser generates a signal laser beam. The pump laser generates a pumped laser beam. The wave division multiplexer combines the signal laser beam and the pumped laser beam and generates a combined laser beam. The silica based glass optical fiber has a preferred concentration of praseodymium ions of about 5010.sup.24 ions/m.sup.3 and a length of about 5.7 m. The silica based glass optical fiber receives the combined laser beam, amplifies photons in the combined laser beam, and generates an amplified laser beam.