A method to measure and report electromagnetic radiation power includes receiving electromagnetic radiation and generating an electrical signal having a magnitude based on the power of the electromagnetic radiation. An adjustable gain may be applied to the electrical signal to generate an amplified electrical signal that may be sampled to generate a digital sample. The adjustable gain may be controlled based on the value of the digital sample and the digital sample may be associated with a gain value. One or more calibration factors may be selected based on the gain value associated with the digital sample and the selected calibration factor(s) may be used to calculate the power of the electromagnetic radiation.

The present disclosure provides a trans-impedance amplifier, comprising: an inverting amplifier circuit, having an input end and an output end. The input end is coupled to an optical diode and is used for accessing an input voltage signal, and the output end is used for outputting an amplified voltage signal. The inverting amplifier circuit comprises at least three sequentially-connected amplifier units. Each of the amplifier units comprises two mutually-coupled N-type transistors, wherein one N-type transistor is used for receiving an input voltage, and the other N-type transistor is used for receiving a DC voltage signal. A common connection end of the two N-type transistors is used for outputting an amplified voltage signal, and the N-type transistor used for receiving the DC voltage signal adopts a native NFET. The trans-impedance amplifier further comprises a feedback resistor coupled to the input end and the output end of the inverting amplifier circuit.

A wideband transimpedance amplifier circuit is provided. The wideband transimpedance amplifier circuit includes a common-gate transistor, a bias current controlling circuit and an amplifier circuit. The bias current controlling circuit is coupled to a source of the common-gate transistor. The amplifier circuit is coupled to a drain of the common-gate transistor. The bias current controlling circuit adjusts the input impedance of the wideband transimpedance amplifier circuit according to the output signal of the amplifier circuit.

An apparatus is described which uses directly modulated InGaN Light-Emitting Diodes (LEDs) or InGaN lasers as the transmitters for an underwater data-communication device. The receiver uses automatic gain control to facilitate performance of the apparatus over a wide-range of distances and water turbidities.

A visible light audio system is operable to enable free space optical communication of audio signals via transmission of modulated light intensity at a light source to a photo diode being operably engaged with a demodulator and audio output device. Embodiments of the visible light audio system may be utilized, for example, in commercial, residential, or church buildings to transmit audio signals to occupants via the overhead lighting of the building. Embodiments of the present disclosure may be utilized in any commercial application where line of sight transmission of an audio signal is required or beneficial for occupants of an interior structure to receive a location-specific audio message.

A wideband transimpedance amplifier circuit is provided. The wideband transimpedance amplifier circuit includes a common-gate transistor, a bias current controlling circuit and an amplifier circuit. The bias current controlling circuit is coupled to a source of the common-gate transistor. The amplifier circuit is coupled to a drain of the common-gate transistor. The bias current controlling circuit adjusts the input impedance of the wideband transimpedance amplifier circuit according to the output signal of the amplifier circuit.

Methods and systems for process and temperature compensation in a transimpedance amplifier using a dual replica and servo loop is disclosed and may include a transimpedance amplifier (TIA) circuit comprising a first TIA, a second TIA, a third TIA, and a control loop. The first TIA comprises a fixed feedback resistance and the second and third TIAs each comprise a configurable feedback impedance. The control loop comprises a gain stage with inputs coupled to outputs of the first and second TIAs and with an output coupled to the configurable feedback impedance of the second and third TIAs. The circuit may be operable to configure a gain level of the first TIA based on the fixed feedback resistance and a reference current applied at an input to the first TIA, and configure a gain level of the second and third TIAs based on a control voltage generated by the gain stage.

An apparatus for automatic amplifier gain setting of an optical amplifier, said apparatus comprising an optical channel counter, OCC, unit configured to detect a number of channels present in an optical transmission spectrum; a determination unit configured to determine an average power per channel calculated by dividing a measured total power of a signal input and/or signal output of the optical amplifier by the number of channels detected by said optical channel counter, OCC, unit and a gain adjustment unit configured to adjust the amplifier gain of said optical amplifier automatically depending on a calculated power difference between a predetermined desired power per channel and the determined average power per channel provided by said determination unit.

A light detection and ranging (LIDAR) system includes an automatic gain control (AGC) unit to reduce the dynamic range, reducing processing power and saving circuit area and cost. The system detects a return beam of a light signal transmitted to a target, having a first dynamic range in a time domain. An analog to digital converter (ADC) generates a digital signal based on the return beam. A processor can perform time domain processing on the digital signal, convert the digital signal from the time domain to a frequency domain, and perform frequency domain processing on the digital signal in the frequency domain. The AGC unit can measure a power of the return beam, and apply variable gain in the frequency domain to reduce a dynamic range of the return beam to a second dynamic range lower than the first dynamic range.

An apparatus, e.g., an optical signal receiver, includes a trans-impedance amplifier (TIA) circuit. The TIA circuit includes a variable gain amplifier (VGA) having a tunable tail current source. The TIA circuit is configured to tune the tail current source to stabilize a DC current to a load resistor of the VGA over an operating gain range of the TIA circuit.