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.

An optical module includes a board including a first surface and a second surface, a light-receiving element mounted on the first surface of the board, a capacitor mounted on the first surface of the board and connected to the light-receiving element, an optical waveguide attached to the second surface of the board and configured to transmit light, and a housing that covers the board. A recess is formed in an area of the inner surface of the housing to face the capacitor.

An optical apparatus includes a first light receiving unit including a first avalanche photodiode, a second light receiving unit including a second avalanche photodiode whose light receiving surface is shielded from light, and a voltage control unit configured to apply a first reverse bias voltage to the first avalanche photodiode and a second reverse bias voltage to the second avalanche photodiode. The voltage control unit controls the first reverse bias voltage based on the second reverse bias voltage.

An apparatus comprises a laser emitter configured to transmit laser energy across an air gap to a separate device, and a driver circuit electrically coupled to the laser emitter and to an electrical interface. The driver circuit is configured to detect voltage levels at the electrical interface including a first voltage level, a second voltage level, and a third voltage level, and drive the laser emitter at a first power level when detecting the first voltage level, drive the laser emitter at a second power level when detecting the second voltage level, and drive the laser emitter at a third power level intermediate the first and second power levels when detecting the third voltage level.

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.

The present disclosure provides an optical module comprising: a photoelectric conversion unit, a first demodulation circuit, and a second demodulation circuit; the first demodulation circuit and the second demodulation circuit are respectively connected to the photoelectric conversion unit; the photoelectric conversion unit is configured to convert the received optical signal into an electrical signal; the first demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a high-frequency electrical signal; the second demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a low-frequency electrical signal.

A communication system includes an optical receiver that receives a modulated optical signal and converts same back to electrical form by a photodiode. The photodiode includes an optical input and a dc bias input, and outputs a photocurrent. The optical communication system includes a photodiode linear operation point feedback loop communicating with the photodiode based on an intermodulation distortion contour plot corresponding to the photodiode. The intermodulation distortion contour plot includes a plurality of linear operation points for the photodiode. The photodiode linear operation point feedback loop operates the photodiode at a respective operation point of the plurality of linear operation points. Optionally, the photodiode linear operation point feedback loop includes a voltage-biasing feedback loop receiving the photocurrent and outputting to the dc bias input a bias voltage based on the intermodulation distortion contour plot, and/or an optical power regulating feedback loop communicating with the optical input.

An apparatus comprises a laser emitter configured to transmit laser energy across an air gap to a separate device; a photodiode configured to detect laser energy received across the air gap from the separate device; and logic circuitry configured to initiate recurrent transmission of a laser pulse by the laser emitter; and end the recurrent transmission in response to detecting laser energy received by the photodiode from the separate device.

A system includes a communication interface including separate electrical connectors configured to communicate power and ground using electrical conductors, the communication interface includes a free-air optical interconnect including at least one of: a laser emitter configured to transmit laser energy across an air gap to a separate device; or a photodiode configured to detect laser energy received across the air gap from the separate device.

An operation voltage testing circuit includes a voltage generating circuit, a current-to-voltage conversion circuit, and a processing circuit. The voltage generating circuit is configured to generate a first voltage signal according to a first current signal, such that a photoelectric conversion unit generates a second current signal corresponding to the first voltage signal. The current-to-voltage conversion circuit is configured to generate a second voltage signal corresponding to the second current signal. The processing circuit is configured to receive the second voltage signal and to selectively adjust and output the first current signal according to the second voltage signal and a threshold value, such that the voltage generating circuit selectively adjusts the first voltage signal according to the first current signal.