Methods, systems, and devices for free-space optical communications. An aircraft includes a flat optical communication terminal on an external surface of the aircraft, the flat optical communication terminal being configured to communicate with a ground station via a free-space optical communication link.

A diverged beam optical transmitter is provided that includes a laser source configured to emit a light beam, and one or more lenses. The diverged beam optical transmitter also includes a diffuser placed between the laser source and the one or more lenses, and configured to increase an intrinsic divergence of the light beam and to fill some portion of the one or more lenses such that the light beam is eye safe after the one or more lenses.

A diverged beam optical transmitter is provided that includes a laser source configured to emit a light beam, and one or more lenses. The diverged beam optical transmitter also includes a diffuser placed between the laser source and the one or more lenses, and configured to increase an intrinsic divergence of the light beam and to fill some portion of the one or more lenses such that the light beam is eye safe after the one or more lenses.

An Optical Wireless Communication (OWC) receiver configured to receive an incoming optical beam modulated with data and output an output signal including the modulated data. A lens receives the incoming optical beam. Photodiodes positioned at a distance from the lens and proximal to the focal plane of the lens receive a fraction of the incoming optical beam and generate a photocurrent in correspondence with photons received. The photodiodes are provided in a two-dimensional array including rows and columns wherein outputs of the columns are combined and their photocurrents are summed. An amplifier connected to the combined output of the columns converts the summed photocurrents into an output signal. Interconnections of the photodiodes form at least two parallel branches wherein each branch includes a cascade of at least two photodiodes forming a combined photodetector surface.

An Optical Wireless Communication (OWC) receiver configured to receive an incoming optical beam modulated with data and output an output signal including the modulated data. A lens receives the incoming optical beam. Photodiodes positioned at a distance from the lens and proximal to the focal plane of the lens receive a fraction of the incoming optical beam and generate a photocurrent in correspondence with photons received. The photodiodes are provided in a two-dimensional array including rows and columns wherein outputs of the columns are combined and their photocurrents are summed. An amplifier connected to the combined output of the columns converts the summed photocurrents into an output signal. Interconnections of the photodiodes form at least two parallel branches wherein each branch includes a cascade of at least two photodiodes forming a combined photodetector surface.

Proposed is a receiving UE for receiving a signal in optical wireless communication, according to the present disclosure. The receiving UE may include: a transceiver for receiving an optical signal of an orbital angular momentum (OAM) mode from a transmitting terminal; a demodulator composed of at least one phase shifter; a photoelectricity converter composed of at least one photodiode; and a processor connected to the transceiver, the demodulator, and the photoelectricity converter. In addition, the at least one phase shifter may convert an optical signal of the OAM mode into an optical signal of a Gaussian mode, and the at least one photodiode may convert an optical signal of the Gaussian mode into an electrical signal.

Proposed is a receiving UE for receiving a signal in optical wireless communication, according to the present disclosure. The receiving UE may include: a transceiver for receiving an optical signal of an orbital angular momentum (OAM) mode from a transmitting terminal; a demodulator composed of at least one phase shifter; a photoelectricity converter composed of at least one photodiode; and a processor connected to the transceiver, the demodulator, and the photoelectricity converter. In addition, the at least one phase shifter may convert an optical signal of the OAM mode into an optical signal of a Gaussian mode, and the at least one photodiode may convert an optical signal of the Gaussian mode into an electrical signal.

Disclosed is an optical window cleaning device, including: a cleaning brush; and a wiper arm. The wiper arm includes a first link, a torsion mechanism, a second link and a wiper arm drive system. A second end of the first link is hinged to a first end of the second link. The cleaning brush is hinged to a first end of the first link, a rotation trajectory of the cleaning brush and a rotation trajectory of a hinge joint between the second end of the first link and the first end of the second link are both located in a first plane. A rotation trajectory of the second link and the rotation trajectory of the hinge joint are located in the first plane. The torsion mechanism provides the first link and the second link with a force that rotates the first link relative to the second link.

An invisible light communication system can communicate using infrared or ultraviolet light signals to provide more secure communications. The system includes a software definable and hardware configurable transmitter that uses an input, an encoder, an invisible light source, and an optic to transmit an invisible light signal. The system also includes a software definable and hardware configurable receiver that receives the invisible light signal using an optic, a detector, a detector, and an output. Applications for the invisible light communication system include fixed, deployable, vehicle, and wearable configurations for voice, video and data transmission and receipt in support of a variety of use cases: remote sensing; data exfiltration; remote control, ordnance detonation; tactical chat/messaging; point-to-point and point-to-multipoint audio communications; and full motion video.

A method of RF signal processing comprises receiving an incoming RF signal at each of a plurality of antenna elements that are arranged in a first pattern. The received RF signals from each of the plurality of antenna elements are modulated onto an optical carrier to generate a plurality of modulated signals that each have at least one sideband. The modulated signals are directed along a corresponding plurality of optical channels with outputs arranged in a second pattern corresponding to the first pattern. A composite optical signal is formed using light emanating from the outputs of the plurality of optical channels. Non-spatial information contained in at least one of the received RF signals is extracted from the composite signal.