A forward Raman amplifier includes a plurality of pumping light sources with different wavelengths and the forward Raman amplifier, according to a fiber type or a zero-dispersion wavelength of the fiber, changes the number of pumping light sources to be emitted, changes a power ratio between the plurality of pumping light sources with the different wavelengths or changes wavelength characteristics of a gain, according to a fiber type.

A reconfigurable optical add/drop multiplexer (ROADM) includes a plurality of interconnected ROADM blocks. Each ROADM block includes an ingress switchable-gain amplifier, an output power detector coupled to an output of the ingress switchable gain amplifier, and a wavelength-selective switch coupled to the output of the ingress switchable gain amplifier. Each ROADM block includes a plurality of add/drop blocks coupled to the wavelength-selective switches of the plurality of ROADM blocks. The ROADM includes a controller configured to receive an indication of an output signal power from the output power detector and adjust gain and equalization parameters of the ingress switchable-gain amplifier based on the received indication of the output signal power.

A data storage system is disclosed that includes a recirculating loop storing data in motion. The data may be carried by a signal via the loop including one or more satellites or other vessels that return, for example by reflection or regeneration, the signals through the loop. The loop may also include a waveguide, for example an optical fiber, or an optical cavity. Signal multiplexing may be used to increase the contained data. The signal may be amplified at each roundtrip and sometimes a portion of the signal may be regenerated.

An optical receiver includes an optical filter that transmits signal light to be received from wavelength-multiplexed signal light, a light source that outputs local oscillation light, a 90-degree hybrid circuit that causes the local oscillation light output from the light source to interfere with the signal light transmitted through the optical filter to output interference signal light, a converter that converts the interference signal light into an electrical data signal, a spectrum detector that detects a frequency spectrum of the electrical data signal based on the electrical data signal, and a controller that controls a center frequency of a passband of the optical filter based on a shape of the frequency spectrum.

A system has a plurality of non-linear circuit stages and an intervening linear circuit stage. An input signal is provided to a first non-linear circuit stage, and from the first non-linear circuit stage, to the linear circuit stage. The first non-linear circuit stage applies a second-order distortion to the input signal and provides the resulting signal to the linear circuit stage. The resulting signal that is output from the linear circuit stage is inverted with respect to the input signal and suitably linearly processed (attenuated or amplified). This signal is then provided to a second non-linear circuit that applies a second-order distortion and outputs a signal that has an overall reduction in second-order distortion.

An optical amplifier may include an erbium-doped fiber and an optical coupler coupled to the erbium-doped fiber. In some embodiments, a length of the erbium-doped fiber may be selected for an amplification gain applied by the optical amplifier. The optical coupler may be configured to multiplex one or more optical data signals and an optical pump signal from an optical pump onto the erbium-doped fiber such that the erbium-doped fiber may amplify a first continuous range of wavelengths of the optical data signals. The optical amplifier may further include a filter coupled to the erbium-doped fiber and configured to attenuate a second continuous range of wavelengths. In some embodiments, the second continuous range may be less than the first continuous range and positioned within the first continuous range.

A reconfigurable optical add/drop multiplexer (ROADM) includes a plurality of interconnected ROADM blocks. Each ROADM block includes an ingress switchable-gain amplifier, an output power detector coupled to an output of the ingress switchable gain amplifier, and a wavelength-selective switch coupled to the output of the ingress switchable gain amplifier. Each ROADM block includes a plurality of add/drop blocks coupled to the wavelength-selective switches of the plurality of ROADM blocks. The ROADM includes a controller configured to receive an indication of an output signal power from the output power detector and adjust gain and equalization parameters of the ingress switchable-gain amplifier based on the received indication of the output signal power.

A system has a plurality of non-linear circuit stages and an intervening linear circuit stage. An input signal is provided to a first non-linear circuit stage, and from the first non-linear circuit stage, to the linear circuit stage. The first non-linear circuit stage applies a second-order distortion to the input signal and provides the resulting signal to the linear circuit stage. The resulting signal that is output from the linear circuit stage is inverted with respect to the input signal and suitably linearly processed (attenuated or amplified). This signal is then provided to a second non-linear circuit that applies a second-order distortion and outputs a signal that has an overall reduction in second-order distortion.

A reconfigurable optical add/drop multiplexer (ROADM) includes a plurality of interconnected ROADM blocks. Each ROADM block includes an ingress switchable-gain amplifier, an output power detector coupled to an output of the ingress switchable gain amplifier, and a wavelength-selective switch coupled to the output of the ingress switchable gain amplifier. Each ROADM block includes a plurality of add/drop blocks coupled to the wavelength-selective switches of the plurality of ROADM blocks. The ROADM includes a controller configured to receive an indication of an output signal power from the output power detector and adjust gain and equalization parameters of the ingress switchable-gain amplifier based on the received indication of the output signal power.

An electrical circuit includes a sensor configured to generate a current signal comprising a first portion comprising a contribution from a target source and/or a second portion comprising a contribution from sources other than the target source, a trans-impedance amplifier that amplifies the current signal and generate a low noise signal, and a high pass filter that converts the low noise signal into an AC signal having a positive amplitude, a negative amplitude, and a zero cross-over point between the positive and negative amplitudes. The circuit also includes a positive integrating amplifier that receives the positive amplitude of the AC signal and generates a positive integrated value over an integration period, and a negative integrating amplifier that receives the negative amplitude of the AC signal and generates a negative integrated value over the integration period. The circuit further includes at least one analog-to-digital converter that receives the integrated values.