Optical transmitters, receivers, and transceivers implemented using a plurality of surface-coupled optical devices that can be manufactured on the same planar substrate and then post-processed to provide some of the devices with different respective partially transparent front mirrors compatible with and/or customized for different respective optical functions. When appropriately electrically biased and driven, different subsets of such devices can operate as lasers, optical modulators, optical amplifiers, and photodetectors, respectively. In this manner, an integrated array of such devices can be customized to provide the optical functions needed for the intended product. For example, an optical transmitter can be constructed using an integrated array that comprises three surface-coupled optical devices configured to operate as a laser, an optical modulator, and an optical amplifier, respectively. An optical receiver can be constructed using an integrated array that comprises two surface-coupled optical devices configured to operate as an optical amplifier and a photodetector, respectively.

An amplification device includes an element for splitting an input optical signal into first and second optical signals having first and second polarization modes, first and second amplification stages each including polarized SOAs for amplifying the first and second optical signals depending on driving currents, an intermediate processing stage for compensating optical characteristics of the optical gain bandwidth of the first amplification stage depending on driving currents, an element for combining the first and second optical signals outputted by the second amplification stage to produce an output optical signal, and a control means producing the driving currents depending on information representative of powers of the first and second optical signals before the polarized SOAs of each amplification stage and on a targeted power of the output optical signal.

An optical device includes an optical coupler that inputs an optical signal received from a light source, a semiconductor optical amplifier that amplifies the optical signal received from the optical coupler, and a light receiving element that receives spontaneous emission light received from the semiconductor optical amplifier. The optical coupler includes a first input port to which the optical signal received from the light source is input, a second input port that is connected to an input stage of the light receiving element and that is different from the first input, and an output port that is connected to an input stage of the semiconductor optical amplifier, and that outputs optical signal received from the first input port to the semiconductor optical amplifier. The light receiving element receives, via the output port and the second input port, spontaneous emission light received from the semiconductor optical amplifier.

A method of controlling an optical amplifying system that processes an optical signal with the PAM4 mode is disclosed. The optical amplifying system includes variable optical attenuator (VOA) and a semiconductor optical amplifier (SOA). The VOA attenuates the optical signal such that maximum optical power thereof corresponding to one of the physical levels of the PAM4 signal becomes equal to a preset optical level for which the SOA may linearly operable. The SOA may amplify thus attenuated optical signal with a fixed optical gain.

Phase modulation of an output optical signal from a phase-sensitive amplifier may be used to perform phase adjustment for optimal phase-sensitive amplification. Specifically, when the optical pump is phase modulated to suppress SBS, a second phase modulator may be used to counter dither the first phase modulator. Both phase modulators may be controlled by a phase shifter. Intensity modulation of the output optical signal may also be performed to reduce noise. In this manner, the OSNR of the output optical signal may be increased.

Consistent with the present disclosure, a transceiver is implemented as a photonic integrated circuit (PIC) that includes a transmitter and a receiver. A laser is also provided that provides light to a splitter, which supplies a first portion of the light to the transmitter and a second power of the light to the receiver. Semiconductor optical amplifiers (SOAs) are provided at one or more locations on the PIC. In one example, at least one SOA is provided in the transmitter so that the transmitted optical signal has a desired power, and at least another SOA is provided in the receiver so that the local oscillator signal has a desired power. In a further example, an SOA is provided in the receiver to boost the power of the received optical signal. Preferably, the transceiver, including the SOAs, is monolithically integrated on a substrate, such as a substrate including indium phosphide (InP). Moreover, the SOA can be readily controlled via a low voltage current source consuming minimal electrical power.

An amplification device includes an element for splitting an input optical signal into first and second optical signals having first and second polarization modes, first and second amplification stages each including polarized SOAs for amplifying the first and second optical signals depending on driving currents, an intermediate processing stage for compensating optical characteristics of the optical gain bandwidth of the first amplification stage depending on driving currents, an element for combining the first and second optical signals outputted by the second amplification stage to produce an output optical signal, and a control means producing the driving currents depending on information representative of powers of the first and second optical signals before the polarized SOAs of each amplification stage and on a targeted power of the output optical signal.

An optical amplifying apparatus and a method to control the same are disclosed. The apparatus includes a semiconductor device that integrates a variable optical attenuator (VOA) with a semiconductor optical amplifier (SOA). The VOA evaluates the optical power of an incident beam from a photocurrent generated therein. The attenuation of the VOA and the optical gain by the SOA are optionally determined based on the detected input power.

Described herein are photonic integrated circuits (PICs) comprising a semiconductor optical amplifier (SOA) to output a signal comprising a plurality of wavelengths, a sensor to detect data associated with a power value of each wavelength of the output signal of the SOA, a filter to filter power values of one or more of the wavelengths of the output signal of the SOA, and control circuitry to control the filter to reduce a difference between a pre-determined power value of each filtered wavelength of the output signal of the SOA and the detected power value of each filtered wavelength of the output signal of the SOA.

An optical level control apparatus includes an input port, an output port, an optical device to assume a state of outputting light inputted to the input port from the output port and a state of not outputting the light inputted to the input port from the output port; a detector to detect an intensity of the light inputted to the input port, and a control unit to detect an input of an optical burst signal to the input port on the basis of a result of detecting the intensity of the light and to control the optical device so that the signal, in which to eliminate a field extending up to an elapse of a period of first time equal to or shorter than laser ON time period of the signal from a head of the signal with its input being detected, is output from the output port.