An avalanche photo-diode (APD) circuit includes a first APD and a bias circuit. The first APD is configured to detect light. The bias circuit is configured to control a gain of the first APD. The bias circuit includes a second APD, a reference voltage source, a bias voltage generation circuit, and a metal layer configured to shield the second APD from the light. The reference voltage source is configured to bias the second APD. The bias voltage generation circuit is configured to generate a bias voltage for biasing the first APD based on dark current output by the second APD.

An optical communication apparatus according to an embodiment of the present invention includes: a light emitting element; a transmission driver that drives the light emitting element; a light receiving element capable of changing a multiplication factor by a bias voltage; a temperature sensor; a computing unit that calculates a drive rate of the transmission driver; and an adjusting unit that adjusts the bias voltage applied to the light receiving element. The adjusting unit adjusts the bias voltage by linear computation using a plurality of target values of the bias voltage for combinations of a plurality of temperatures and a plurality of drive rates, based on a temperature detected by the temperature sensor and a result of calculation of the drive rate.

An apparatus embodiment includes a remote control interface unit configured to accept an appliance control code carried in a radio frequency signal transmitted from a smart phone, extract the appliance control code from the radio frequency signal, send the extracted appliance control code to an optical frequency interface, and initiate transmission of an optical frequency signal including the appliance control code to an appliance configured to receive signals from an optical remote control.

In one embodiment, stable and controlled circuit element biasing is provided in a circuit comprising a voltage source operable to output a first voltage, a reference voltage source operable to output a reference voltage, a circuit element biased, during operation, by the first voltage at a first end and by a second voltage at a second end, a voltage controller coupled to the second end of the circuit element, wherein the voltage controller is operable to adjust the second voltage based on a gain output, a gain controller operable to receive the reference voltage as a first input and the second voltage as a second input, wherein the gain controller is operable to generate, at an output of the gain controller, the gain output based on the second voltage and the reference voltage, and a feedback loop that extends from the output of the gain controller, through the voltage controller, and to the second input.

Described herein is an electronic device, including a pixel and a turn-off circuit. The pixel includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage node and an anode selectively coupled to ground through an enable circuit, and a clamp diode having an anode coupled to the anode of the SPAD and a cathode coupled to a turn-off voltage node. The turn-off circuit includes a sense circuit coupled between the turn-off voltage node and ground and configured to generate a feedback voltage, and a regulation circuit configured to sink current from the turn-off voltage node to ground based upon the feedback voltage such that a voltage at the turn-off voltage node maintains generally constant.

Apparatus and associated methods relate to an open-loop control circuit (OLCC) configured to determine a photodiode element (PDE) drive voltage as a function of a commanded photodiode gain level and a measured temperature signal. In an illustrative example the OLCC may receive a current temperature of an APD element. The OLCC may, for example, receive a commanded gain for the APD relative to a predetermined reference gain. The OLCC may, for example, retrieve a predetermined efficiency characteristic (PEC) of the APD based on the current temperature. If the temperature corresponds to a substantially non-linear portion of the PEC, the OLCC may, for example, determine the drive voltage as a function of the temperature and the commanded gain based on the PEC. Various embodiments may advantageously provide direct control of output gain of photodiodes over a wide dynamic range of temperature associated with the photodiode.

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.

Apparatuses include (among other components) a first gain device connected to receive an initial voltage, a second gain device in series with the first gain device and connected to receive output of the first gain device, differential gain devices connected to receive outputs from the first gain device and the second gain device (the differential gain devices provide opposite voltage outputs from the apparatus) and high-frequency compensation feed-forward paths connected to the first gain device and the second gain device.

Optical signal receivers, systems, and methods of operating the same include a non-line of sight optical signal receiver configured to receive and detect a complex modulated optical signal through a non-line of site propagation path from an optical transmitter, comprising an optical resonator configured to receive the complex modulated optical signal through the non-line of sight propagation path, and to convert the complex modulated optical signal to an intensity modulated signal, and a detector configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and to provide a detected signal.

A communication device effectively transmits high-speed data while being less affected by restrictions of an environment by adjusting a communication channel depending on an optical communication environment.