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.

An optical amplification system that includes a combiner and an active fiber. The combiner is configured to receive and combine an input signal and an excitation signal. The active fiber is configured to receive the input signal and the excitation signal from the combiner and generate an amplified input signal. The active fiber is directly coupled to the combiner.

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 is connected to the wavelength level adjuster. The controller includes a first input end and a control output end. The first input end is configured to receive an input optical signal, 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 in a separate manner based on the adjustment control signal.

In order to solve the problem that the power consumption of optical amplifiers is not optimized over the life time of a network whose capacity in use varies, an optical amplifier according to an exemplary aspect of the invention includes a gain medium for amplifying a plurality of optical channels, the gain medium including a plurality of cores through which the plurality of optical channels to propagate respectively and a cladding area surrounding the plurality of cores; monitoring means for monitoring the plurality of optical channels inputted into the gain medium and producing a monitoring result; a first light source configured to emit a first light beam to excite the cladding area; a second light source configured to emit a plurality of second light beams to excite each of the plurality of cores individually; and controlling means for making a decision as to whether each of the plurality of cores to transmit one of the plurality of optical channels based on the monitoring result, and controlling the first light source and the second light source based on the decision.

Disclosed is a method of Controlling a gain of an optical amplifier comprising a gain medium and at least one pumping device. The method comprises the following steps: determining or predicting a change of input signal power to the amplifier, changing the pump power from an initial pump power level to a new pump power level at a first time instant, the initial pump power level being the pump power level applied to the amplifier prior to the change in input signal power, setting the pump power to a second pump power level at a second time instant, wherein the pump power level is varied in an oscillatory manner for at least one period of time starting at a third time instant and ending at a fourth time instant, wherein said third time instant is identical with or later than said first time instant and said fourth time instant is identical with or earlier than said second time instant.

A dual output laser diode may include first and second end facets and an active section. The first and second end facets have low reflectivity. The active section is positioned between the first end facet and the second end facet. The active section is configured to generate light that propagates toward each of the first and second end facets. The first end facet is configured to transmit a majority of the light that reaches the first end facet through the first end facet. The second end facet is configured to transmit a majority of the light that reaches the second end facet through the second end facet.

A dual output laser diode may include first and second end facets and an active section. The first and second end facets have low reflectivity. The active section is positioned between the first end facet and the second end facet. The active section is configured to generate light that propagates toward each of the first and second end facets. The first end facet is configured to transmit a majority of the light that reaches the first end facet through the first end facet. The second end facet is configured to transmit a majority of the light that reaches the second end facet through the second end facet.

A system comprising a recirculating loop configured to store an electromagnetic wave signal, the recirculating loop comprising a transmission medium and a plurality of transceivers configured to introduce the electromagnetic wave signal into the transmission medium and retrieve the electromagnetic wave signal from the transmission medium, and a signal conditioning system comprising a plurality of signal conditioners coupled to the transmission medium, the plurality of signal conditioners configured to amplify or regenerate the electromagnetic wave signal traveling in the transmission medium, one or more pump laser sources, wherein at least one of the one or more pump laser sources is configured to provide a pump laser beam to at least two of the plurality of signal conditioners, and one or more control circuits for controlling the plurality of signal conditioners, wherein at least one of the one or more control circuits is configured to control and monitor at least two of the plurality of signal conditioners, is disclosed.

A method for realizing precise gain control for a hybrid fibre amplifier, and a hybrid fibre amplifier, in which by an erbium-doped fibre amplifier firstly outputting a constant power, a comparable source signal optical power is provided for a raman fibre amplifier of a next stage. A feedback for the gain control may be formed by comparing a source signal optical power calculated after starting pumping of the Raman fibre amplifier and a source signal optical power detected after pumping stops, thereby greatly improving gain control precision of the Raman fibre amplifier. Moreover, the erbium-doped fibre amplifier parts of all the hybrid fibre amplifiers may simultaneously output a constant optical power, and the Raman amplifier parts of all the hybrid fibre amplifiers may simultaneously start calibration, so that the time for starting operation of the entire system may be improved greatly.

A cascade control system of an optical fiber amplifier includes a target setting parameter module, a primary controller, at least one controlled module and a secondary controller corresponding to the controlled module. The control system adopts two or more cascade control loops so that disturbance entering into the secondary loop can be overcome quickly, thereby the dynamic characteristics of the system may be improved. The primary controller aims to coarse adjustment and overall target control, and the secondary controller aims to fine adjustment and quick convergence of a short-term target, so that the control quality of the cascade control system may be further improved. The cascade control system may define the overall control target directly in the primary loop and avoid impact of aging characteristics of some special parameters on the application.