An optical receiver includes a demultiplexer configured to demultiplex, for each channel, optical signals input through a plurality of channels, a photoelectric converter having a number of light receivers corresponding to the plurality of channels, the photoelectric converter being configured to convert an optical signal into an electric signal for each channel, a monitor circuit configured to monitor, for each channel, an amplitude characteristic of the optical signal converted into the electric signal by the photoelectric converter, and a control circuit configured to control, based on a monitored result of the monitor circuit, a bias voltage to be applied to the light receiver such that an amount of variability in the amplitude characteristic between the channels is minimum or falls within a predetermined range.

High-performance ultra-wideband Phased Array Sensors (PAS) are disclosed, which have unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for a Receive PAS are provided by wafer scale photonic integration including heterogeneous integration of III-V materials and ultra-low-loss silicon nitride waveguides, combining key component technologies into complex PIC devices. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors providing the capability to combine many RF photonic signals with very low loss. The architecture also includes optical down-conversion, as well as digital signal processing to improve the linearity of the system. Simultaneous multi-channel beamforming is achieved through optical power splitting of optical signals to create multiple exact replicas of the signals that are then processed independently.

An avalanche photodiode (APD) bias control method may include acquiring a photocurrent intensity voltage and generating a control signal by superposing the acquired photocurrent intensity voltage and a bias setting signal, wherein the control signal controls a voltage drop between an adjustable power supply output voltage and a voltage of the APD. The APB bias control method may further include adjusting the adjustable power supply output voltage and the bias setting signal simultaneously so that the voltage drop is within a target voltage drop range and the APD bias voltage approaches a bias voltage that corresponds to an APD optical input power. An avalanche photodiode (APD) bias controller and an avalanche photodiode (APD) photoelectric receiver are also provided.

An integrated circuit that includes an optical receiver is described. This integrated circuit may include an optical receiver. The optical receiver may include a photodiode that receives an optical signal and that outputs a corresponding current. Moreover, the optical receiver may include an inductor that is electrically coupled to the photodiode. Furthermore, the optical receiver may include a resistive analog front-end stage that is electrically coupled to the inductor. Note that the inductor may have a resistance per unit length that is greater than a first threshold value (such as 40 m/m), and the inductor may be approximately dispersion-less. For example, a Q factor for inductive peaking associated with the inductor is less than a second threshold value (such as 5).

There is provided a photoelectric converter that converts an optical signal into an electrical signal for amplification, the photoelectric converter including a photoelectric conversion element that converts the optical signal into an electrical signal and outputs the electrical signal from an output terminal, a high-frequency amplifier that includes an input terminal of an electrical signal output from the output terminal and a DC cut-off capacitor which is disposed at an output stage of the input terminal and is serially connected to the input terminal and that amplifies the electrical signal, and an inductance element that is disposed between a bias power supply applying bias voltage or bias current to the photoelectric conversion element and the input terminal and which is connected in parallel to the DC cut-off capacitor.

Aspects of a method and system for feedback during optical communications are provided. In one embodiment, a system for optical communications comprises a predistortion module, a feedback subsystem, a transmit optical subsystem, and an external modulator. The predistortion module is operable to receive an input digital signal and modify the input digital signal to produce a digital predistorted signal. The transmit optical subsystem is operable to generate an optical signal from the digital predistorted signal. The modification of the input digital signal is dynamically controlled by the feedback subsystem according to one or more characteristics of the optical signal as determined by the feedback subsystem. The amplitude of the external modulator output is also dynamically controlled by the feedback subsystem.

A portable transponder device including a receiver having an input frequency range of either but not both of 20 kHz-300 kHz and 3 MHz-30 MHz, the receiver having a plurality of signal input channels, the input frequency range not including an infra-red frequency range, and infra-red frequency range receiving circuitry receiving infra-red frequency range signals modulated by at least one signal in the input frequency range, and providing the infra-red frequency range signals to the receiver through at least one signal input channel of the plurality of signal input channels.

An example system may include a first vertical cavity surface emitting laser (VCSEL) that includes a first integrated polarization locking structure to produce a polarized optical data signal. The system may also comprise a second VCSEL that includes a second integrated polarization locking structure, the second integrated polarization locking structure orthogonal to the first integrated polarization locking structure, to produce an orthogonally polarized optical data signal. Lenses may be disposed on the substrate opposite the first VCSEL, to collimate the polarized optical data signal, and opposite the second VCSEL to collimate the orthogonally polarized optical data signal. A polarization division multiplexer may combine the first collimated polarized optical data signal and the second collimated orthogonally polarized optical data signal.

Disclosed herein is a system comprising: an avalanche photodiode (APD); a bias source configured to supply a reverse bias to the APD; a current meter configured to measure electric current through the APD; a controller configured to reduce the reverse bias to a value below a breakdown voltage of the APD from a value above the breakdown voltage when an intensity of light incident on the APD is above a threshold, and configured to determine the intensity of the light above the threshold based on the electric current through the APD when the reverse bias is below the breakdown voltage.

A sensing pixel includes a single photon avalanche diode (SPAD) coupled between a first node and a second node, with a clamp diode being coupled between a turn-off voltage node and the second node. A turn-off circuit includes a sense circuit configured to generate a feedback voltage based upon a voltage at the turn-off voltage node, a transistor having a first conduction terminal coupled to the turn-off voltage node, a second conduction terminal coupled to ground, and a control terminal, and an amplifier having a first input coupled to a reference voltage, a second input coupled to receive the feedback voltage, and an output coupled to the control terminal of the transistor. A readout circuit is coupled to the SPAD by a decoupling capacitor.