Abstract: A disclosed spacecraft is provided with: an attitude control actuator configured to control an attitude of the spacecraft; an imaging device configured to receive an optical communication signal from another spacecraft; and an attitude controller configured to control the attitude control actuator, based on a position of the optical communication signal in an image obtained by the imaging device.

Abstract: A method of calibrating a collimating lens system includes transmitting, using an optical transmitter, a beam out of an optical fiber and through a collimating lens of the collimating lens system. The beam is reflected off a perfect flat mirror positioned at an output of the collimating lens and back towards the collimating lens, and received, via the collimating lens, at a power meter connected to the optical fiber. The method also includes adjusting a position of a tip of the optical fiber proximal to the collimating lens while tracking a power reading using the power meter, selecting a calibration position of the optical fiber corresponding to a highest power reading, and securing the optical fiber relative to the collimating lens using the calibration position.

Abstract: This underwater optical wireless communication system (100) is provided with a plurality of moving bodies (1) capable of moving underwater. The plurality of moving bodies each includes a plurality of optical wireless communication units (2) each configured to perform bidirectional communication between the plurality of moving bodies using communication light beams (30) having wavelengths different from each other in a plurality of directions which are mutually opposite directions. The plurality of optical wireless communication units is configured to perform bidirectional communication between the plurality of moving bodies using communication light beams, the communication beams having the same wavelength with respect to each of the plurality of directions.

Abstract: The present disclosure provides a testing method for optical communication module, and a test device. The testing method includes: reading encoded information from the optical communication module to be tested; obtaining a pre-stored optimal test parameter corresponding to the optical communication module, and adjusting test parameter configuration of test device accordingly to the optimal test parameter; obtaining test mode configuration, and performing a test on the optical communication module to obtain first test result; and obtaining a determination result according to the first test result and expected result.

Abstract: A self-organizing network of nodes communicates with uncollimated optical pulses. The nodes use low-power, unmoving, broad-beam optical interfaces, low-power processors, and communication algorithms based on timeslots within a timeframe. Nodes self-organize to form the network by pulsing detectors and sources to find neighboring nodes, confirm connections, transmit and store data, and exchange partner node identities. Two- or three-dimensional networks can thereby self-organize without external awareness of network topology, and can repair themselves when nodes move or fail. Node communication may be synchronous, thereby allowing for images of the environment status, and activation of the environment is possible via node stimulators. After forming a network, a cluster of nodes may be read out to provide data from node sensors.

Abstract: In order to reliably communicate with a communication object even when a relative positional relationship with the communication object cannot be accurately recognized, an inter-mobile-body communication system includes: a control device which performs control of switching between a first mode of transmitting wide-area signal light, and a second mode of transmitting selective signal light toward a communication object in response to response signal light responding to the wide-area signal light transmitted in the first mode, and performs control of selectively receiving the response signal light from the communication object; and a light transmitting/receiving device which transmits the wide-area signal light in the first mode, transmits the selective signal light toward the communication object in the second mode, and selectively receives the response signal light from the communication object, according to control by the control device.

Abstract: A laser communication network implemented with multi-chroic filters that are able to partition signals from a band of wavelengths into different sub-bands that enable more than one relay terminal to interconnect users (i.e., sources and sinks of traffic) is provided. A band of wavelengths may be partitioned to enable users to communicate with relay satellites, and relay satellites to communicate with one another, using a predefined set of transmission and reception wavelengths regardless of which particular relay is in the communication session. In other words, embodiments support both relay satellites and user satellites by constructing distinct passbands for relay-borne terminals and the same passbands for users.

Abstract: An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

Abstract: A beam steering system for a free-space laser communication system in a satellite includes a laser that emits a laser beam, a liquid lens assembly with at least one liquid lens to change the direction of the laser beam, and an amplifying optic to amplify the change in direction of the laser beam. The beam steering system may be used to steer a laser beam transmitted to another satellite or received from another satellite. In one example, a satellite may include two beam steering systems, disposed at opposing ends of a frame, where each steering system is configured to cover a hemisphere such that together, the steering systems can transmit and/or receive a laser beam over a 4? steradian sphere. The beam steering system may include a transmit feedback system and a reception system to monitor the direction and signal of the transmitted beam and the received beam, respectively.

Abstract: Described herein is a satellite communications system that includes: two or more satellites using laser communications, and a communications relay aircraft adapted for flying at altitudes above clouds. The communications relay aircraft includes: a laser communications module to communicate with the satellite using laser communication and a Radio Frequency (RF) communications module to communicate with RF equipment at or near ground level using cloud-penetrating RF communications. The RF communications module is configured to take data received as laser communication and generate a corresponding RF transmission containing the data. The laser communications module is configured to take data received as RF communication and to generate a corresponding laser transmission containing the data.

Abstract: A method for adjusting a radiation direction of an optical communication signal between a communication platform and a remote station includes: starting from an initial position of a beam deflection unit of the platform for steering the optical communication signal, adopting deflection positions of the beam deflection unit along two different lines of movement and in opposite directions along the lines of movement, the deflection positions being consistent with deflection angles having the same absolute value, each deflection position being held for a different period; measuring an intensity of the signal at the station; when an intensity change in the signal is discovered at the station, ascertaining a signal quality change in the signal and recording the duration of this intensity change; determining that intensity change that pertains to the best signal quality change, and the associated duration; changing the intensity of a guidance beam for the duration previously determined.

Abstract: Aspects of the disclosure provide for a method of forming a communication link between two communication devices using a primary search pattern and a secondary search pattern. A misalignment between a first optical system of a first communication device and a second optical system of a second communication device is detected. The first optical system is rotated according to the primary search pattern, and the second optical system according to the secondary search pattern. At the second communication device, a set of frames is captured. Then, it is determined whether a beacon beam transmitted from the first communication device is detected in the one or more of the captured frames. When it is determined that the beacon beam is detected, the communication link is formed between the first communication device and the second communication device.

Abstract: A modular node for an optical communication network includes one or more transceiver modules of a plurality of transceiver modules, and a node core including a plurality of electrical connectors to electrically join up to the plurality of transceiver modules to the node core. At least some of the transceiver modules has an optical transceiver configured to emit optical beams carrying data and without artificial confinement, and detect optical beams emitted and without artificial confinement. The up to the plurality of transceiver modules electrically joined to the node core are spatially separated to provide configurable coverage for optical communication based on their number and placement. And the node core further includes switching circuitry configured to connect the one or more transceiver modules to implement a redistribution point or a communication endpoint in the optical communication network.

Abstract: An aircraft system comprises a first and second transceiver each configured to transmit and receive radio signals in respective first millimeter wave (mmW) frequency band and second mmW frequency band; and a processing unit configured to provide the data signals to the first and second transceivers for transmission and to receive demodulated signals from the first and second transceivers. The processing unit is further configured to output signals to alter the orientation of the first antenna to establish a first point-to-point connection with a first aircraft and to output signals to alter the orientation of the second antenna to establish a second point-to-point connection with a second aircraft; the first point-to-point connection and the second point-to-point connection forming part of a point-to-point aircraft relay ring network communicatively coupling a plurality of aircraft in a shared flight route area to each other.

Abstract: Aspects of the disclosure provide for a method of forming a communication link between two communication devices using a primary search pattern and a secondary search pattern. A misalignment between a first optical system of a first communication device and a second optical system of a second communication device is detected. The first optical system is rotated according to the primary search pattern, and the second optical system according to the secondary search pattern. At the second communication device, a set of frames is captured. Then, it is determined whether a beacon beam transmitted from the first communication device is detected in the one or more of the captured frames. When it is determined that the beacon beam is detected, the communication link is formed between the first communication device and the second communication device.

Abstract: A system includes an optical transceiver configured to transmit/receive at least one optical feed and a beam separator configured to separate the optical feed into a plurality of optical beams, and spatially combine the optical beams into the optical beam. The system also includes a dichroic mirror optically coupled to the beam separator and configured to reflect the optical beams, and allow beacon signals to pass therethrough. A position sensitive detector of the system optically couples to the dichroic mirror and is configured to sense an incidence position of each beacon signal allowed to pass through the dichroic mirror, and output a position error for each optical beam based on the sensed incidence positions. The system also includes a multi-axis optical steering system configured to direct each optical beam based on the corresponding position error outputted from the position sensitive detector and a corresponding transmit/receive target.

Abstract: A moving platform roll sensor system comprises an ellipsometric detector capable of detecting a polarized beam within the detector's line-of-sight, and measuring the beam's polarization state, such that the polarization state indicates the rotational orientation of the moving platform with respect to a predefined coordinate system. The ellipsometric detector comprises a venetian blind component through which the polarized beam passes, arranged such that the intensity of the exiting beam varies with its incident angle with respect to the moving platform, a polarizing beamsplitter which splits the exiting beam into components having orthogonal circular polarizations, the relative intensities of which vary with the relative polarization vector of the beam, and first and second detectors which receive the first and second orthogonal circular components and generate respective outputs that vary with the intensities of their received components.

Abstract: An embodiment of the invention relates to an optical module comprising at least one optoelectronic component capable of generating or receiving radiation; at least one access port for receiving or emitting the radiation; at least one free-space beam path located between the access port and the optoelectronic component; at least one mirror located in said beam path; at least one attenuation unit located in said beam path; the attenuation unit having a reflecting surface section and an absorbing surface section; and, a control unit for adjusting the amount of radiation which is directed towards the absorbing surface section of the attenuation unit by controlling at least one or all of the following: the position of the mirror, the orientation of the mirror, the position of the attenuation unit and/or the orientation of the attenuation unit.

Abstract: An orientation tracking system for a moving platform includes a transmitter which generates an beam having a known polarization with respect to a predefined coordinate system. The moving platform includes an ellipsometric detector capable of detecting the polarized beam when within the line-of-sight of the transmitter, and measuring its polarization state. The polarization state indicates the rotational orientation of the moving platform with respect to the predefined coordinate system. The beam could also be used to convey guidance commands to the platform.

Abstract: An optical communication terminal is configured to operate in two different complementary modes of full duplex communication. In one mode, the terminal transmits light having a first wavelength and receives light having a second wavelength along a common free space optical path. In the other mode, the terminal transmits light having the second wavelength and receives light having the first wavelength. The terminal includes a steering mirror that directs light to and from a dichroic element that creates different optical paths depending on wavelength, and also includes spatially separated emitters and detectors for the two wavelengths. A first complementary emitter/detector pair is used in one mode, and a second pair is used for the other mode. The optical components are arranged such that adjusting an orientation of the steering mirror aligns the terminal to communication over a given free space optical link using either the first or second complementary pair.

Abstract: A laser relay module for free space optical communications including an optical telescope for receiving and transmitting optical beams; an optical diplexer for separating transmitting and received optical beams; an optical amplifier; a modulated beacon laser for line of sight control of a plurality of communicating remote network nodes; a beacon beam detector for detecting an incoming beacon optical beam for line of sight control of the optical telescope and receiving data from other network nodes; and means for inserting an output of the modulated beacon laser into the optical telescope for transmission to another network node, and for transporting the incoming beacon optical beam to the beacon detector.

Abstract: A method, systems, apparatus and device enable high bandwidth satellite communications. An onboard tracking detector, installed in a low-earth orbit satellite, detects a position of an incoming optical beam received/transmitted from a first ground station of one or more ground stations. Tracker electronics determine orientation information of the incoming optical beam based on the position. Control electronics receive the orientation information from the tracker electronics, and control a waveguide drive electronics. The waveguide drive electronics control a voltage that is provided to an electro-optic waveguide beam steering device. The electro-optic waveguide beam steering device steers an outgoing optical beam to one of the one or more ground stations based on the voltage.

Abstract: A satellite test signal reflection apparatus for testing transmitters sending out optical signals, the apparatus includes a plate that is at least partially permeable to optical signals. The plate has a base with a first surface with a residual reflective coating and a second surface. The residual reflective coating is configured to split an optical beam, which penetrates the plate in a first direction from the first surface to the second surface, into a reflective optical beam and a transmitted optical beam.

Abstract: A gearbox IC is incorporated into an optical communications system to enable an optical link that incorporates the system to achieve data rates that are at least double that which are currently achievable in optical links. The gearbox IC performs data rate conversion and phase alignment. In the transmit direction, the gearbox IC receives N lanes of electrical data signals having a data rate of X Gbps and outputs N/2 lanes of electrical data signals having a data rate of 2X Gbps. In the receive direction, the gearbox IC receives N/2 electrical data signals having a data rate of 2X Gbps and converts the N/2 electrical data signals into N electrical data signals having a data rate of X.

Abstract: A system and method in the field of free space optical communications (FSOC) for overcoming atmospheric-induced spatial optical signal variations operates within each of two FSOC terminals that make up a bi-directional FSOC link, with each terminal providing the rapid adaptive beam path method over a much wider field of view than typically used for adaptive optical techniques. Each terminal uses a real-time adaptive beam-steering technique that continuously measures optical power and optical power gradients by the receiver optical detectors; this data is sent to a control system that automatically responds by re-aligning the optical system accordingly by maximizing the optical signal power measured by the optical power receiving detector.

Abstract: A free space optical communication system (100) and method including: several optical beam expanders (414) for receiving incoming optical signals from ground sites and neighboring satellites; several optical preamplifiers (412) for preamplifying the received optical signals; one or more optical main amplifiers (404) for amplifying the preamplified optical signals; and an optical switch (408) for directing respective amplified optical signals to respective destinations via a respective optical beam expander. The respective amplified optical signals are inputted to a respective optical beam expander (414) for transmission to said respective destinations, as outgoing optical signals.

Abstract: A free space optical communication system (100) and method including a constellation of several satellites (102). Each of satellites including: several inter-satellite optical telescopes (204) for optical communication with multiple neighboring satellites, each inter-satellite optical telescope is capable of adjusting its elevation angle; and several up/down link optical telescopes (206) for optical communication with multiple ground sites. As the constellation passes a given ground site, some of the up/down-link telescopes of a given satellite are configured to track at least two respective ground optical telescopes of the given ground site and send data to the ground optical telescope with the clearest line of sight to the given satellite. Moreover, each of the satellites includes optical circuitry (208, 210, 212, 216) for optically processing and switching incoming and outgoing optical signals without converting the optical signals into electrical signals.

Abstract: There is provided a method of eliminating an offset in a spot centroid due to crosstalk. A crosstalk matrix is used to characterize crosstalk characteristics of a multi-pixel spot-centroid detector. Left-multiplication of signals outputted from the multi-pixel spot-centroid detector, which are affected by the crosstalk, by an inverse matrix of the crosstalk matrix can result in a light-intensity-distribution signal with impacts of the crosstalk substantially removed. Based on this light-intensity-distribution signal, it is possible to derive the spot centroid, with the offset in the spot centroid due to the crosstalk substantially eliminated, resulting in an improved accuracy of the spot centroid detection, as compared with conventional methods.

Abstract: An optical transceiver assembly comprises a transmission system, a reception system and a coupling system which directs a part of the signals produced by the transmission system to the reception system. Said part of the transmission signals is detected by a photodetector matrix of the reception system, outside an useful zone of the matrix which is dedicated to the detection of the received signals. A transmission direction may therefore be determined in real time while the received signals are detected. A difference between the transmission direction and a reception direction of the transceiver assembly may then be precisely compensated for at each moment during a tracking step. The transceiver assembly may be a free space laser optical communication terminal.

Abstract: A network device includes a substitutor and a transmitter. The substitutor receives input columns of concurrently received input symbols. Each of the input columns includes one input symbol from each of a plurality of parallel input lanes. The substitutor generates output columns corresponding to the input columns, wherein each of the output columns includes one output symbol for each of a plurality of parallel output lanes. The substitutor replaces the output symbols of a selected column of the output columns with alignment symbols. The selected column is immediately followed by a second column, and the second column is immediately followed by a third column. The substitutor replaces the output symbols of the second column with disposable symbols, and replaces the output symbols of the third column with boundary symbols. The transmitter drives data onto a communications medium in response to the output symbols generated by the substitutor module.

Abstract: A system comprises a transmitter including a laser configured to generate a laser beam directed at a spot on a surface, and a laser driver connected to the laser and configured to modulate input data onto the laser beam. The system may further comprise a receiver including an optical detector configured to decode received light into raw data, a signal processor configured to decode the raw data into the original input data, and telescope optics configured to receive light reflected from the spot on the surface, collimate the light and converge the light onto the optical detector.

Abstract: A method for pointing control of a laser communication terminal on a spacecraft may include measuring a line-of-sight (LOS) error of the laser communication terminal. The method may also include estimating a LOS error of the laser communication terminal based on measurements from a spacecraft gyro and a gimbal gyro onboard the spacecraft. The method may further include switching from a LOS error measurement feedback to a LOS error estimate feedback to control pointing of the laser communication terminal during a power fade condition.

Abstract: Data processing modules including a housing and optical interfaces associated with the exterior of the housing, and systems including the same.

Abstract: In accordance with an aspect of the invention, a system has a transmitter and a receiver, where the transmitter includes a beam source and an optical element. The beam source produces a beam that represents information, and the optical element alters the beam so that the beam has a uniform intensity over a cross-sectional area. The receiver is separated from the transmitter by free space through which the beam propagates and includes an active area positioned to receive a portion of the beam that the receiver converts into a received signal. To accommodate possible misalignment, the cross-sectional area of the beam is larger than the active area by an amount that accommodates a range of misalignment of the receiver with the transmitter.

Abstract: A technique for simultaneously transmitting wide and narrow optical beacon signals includes generating a laser beam and splitting the laser beam into a first signal on a first path and a second signal on a second path via a wavelength-dependent beamsplitter. A wide beacon signal having a first beam divergence is generated from the first signal, and a narrow beacon signal having a second, lesser beam divergence is generated from the second signal. The wavelength of the laser beam determines an allocation of the laser energy between the wide and narrow beacon signals based on transmittance/reflectance characteristic of the beamsplitter at that wavelength. The wide and narrow beacon signals are simultaneously transmitted in a overlaid manner into free space to support acquisition and tracking in a free-space optical communication system. The beamsplitter can simultaneously transmit or reflect substantially all of a data signal at a different wavelength.

Abstract: A transmitter including a plurality of input lanes, a substitutor module, and an interleaver module. The plurality of input lanes is configured to receive input symbols including data symbols and idle symbols, wherein the input symbols are arranged into columns of concurrently received input symbols, and wherein each of the columns includes one input symbol from each of the plurality of input lanes. The substitutor module is configured to, at intervals, replace one of the columns with a column of alignment symbols. The substitutor module is further configured to replace an immediately subsequent one of the columns with a column of disposable symbols; and replace one or more immediately subsequent ones of the columns with columns of boundary symbols uninterrupted by disposable symbols. The interleaver module is configured to interleave symbols from the substitutor module between a first transmit lane and a second transmit lane.

Abstract: Disclosed are methods, devices, and systems for exchanging information between a first wearable electronic device and one of a second wearable electronic device and an account at a remote computing device associated with a user of the second wearable electronic device. The first wearable electronic device intermittently emits directed electromagnetic radiation comprising a beacon signal, and receives, via a receiver coupled to the first wearable electronic device, a signal from the second wearable electronic device identifying one of the second wearable electronic device and the account at the remote computing device. An input may then be detected at the first wearable electronic device, and in response to receiving the signal and detecting the input, the first wearable device may transmit additional data to one of the second wearable electronic device and the remote computing device associated with the second user.

Abstract: A free space optical communication system incorporates a kinematic sensor, such as an accelerometer, proximate an optical signal generator or emitter, such as a laser. Kinematic information generated using an output signal from the kinematic sensor is encoded along with a time signal and transmitted from the sending node to a receiving node. The receiving node receives the kinematic information and determines a future position and orientation of the sending node. The receiving node makes adjustments to receiving optical component hardware in order to better receive the signal based upon the acceleration data and the time signal.

Abstract: According to various embodiments, provided herein is an optical system and method that can be configured to perform image analysis. The optical system can comprise a telescope assembly and one or more hybrid instruments. The one or more hybrid instruments can be configured to receive image data from the telescope assembly and perform a fine guidance operation and a wavefront sensing operation, simultaneously, on the image data received from the telescope assembly.

Abstract: A transmitter modulates a laser beam with data and projects the laser beam. A first and second optical detector indirectly receive a first and second signal (respectively) via light scattered from a first and second segment of the laser beam at a first and second time. The first segment at the first time and the second segment at the second time are modulated with the same data. The receiver phases the first signal and/or the second signal to match their phase and sums the signals. The transmitter and/or the receiver may include a terrain database and/or an order wire for sharing terrain and/or position information. Terrain information and/or position information may be utilized to align the laser beam with the optical detector(s) and/or adjust an aperture of the optical detector(s) to minimize intersymbol interference and maximize communication channel benefits associated with spatial and temporal diversity.

Abstract: A scan acquisition technique for acquiring terminals (62, 64) that does not rely on precise alignment between a sensor (66, 70) and a transmitter (68, 72) associated with the terminals (62, 64). The terminals (62, 64) separate uncertainty regions (76, 78) into a plurality of sections (88, 90). Scan beams (82, 84) include encoded information of what section (88, 90) the scan beam (82, 84) is currently scanning. Each terminal (62, 64) will eventually receive the scan beam (82, 84) of the other terminal (62, 64). When it does, it will encode its scan beam (82, 84) with both the outgoing code and the return code for that section (88, 90), so that when it's scan beam (82, 84) is received by the other terminal (62, 64), that terminal (62, 64) will know what scan section (88, 90) the other terminal (62, 64) is located.

Abstract: Free space optical communication systems, methods, and apparatuses are provided. A system embodiment includes a photodetector for receiving a beacon signal transmitted from a ground communication apparatus, a light source for emitting a light beam toward a source of the beacon signal, where the light beam includes a signal to be transmitted, and a high speed tracking actuator coupled to the light source for moving the light source to maintain the light beam in a direction toward the source of the beacon signal transmitted from the ground communication apparatus.

Abstract: A method and apparatus for achieving high-density and misalignment tolerant short-reach free-space optical interconnects between arbitrary locations in a field, using microlenses, steering elements and a curved reflecting surface.

Abstract: A system for transmission of information between at least two players in a training area comprises means on a first (1) of said players for encoding light pulses and means for transmitting information in the form of such coded light pulses towards at least one second (2-4) of said players, said second player having means for receiving said light pulses and means for decoding the information thereof. Each of said players is provided with a clock, and the system comprises means for keeping said clocks synchronized. The encoding means and the decoding means are adapted to utilize data of times of transmission and receipt of said light pulses for transmitting information from the first player to the second player.

Abstract: An optical interconnect has a plurality of optical data sources, a plurality of optical data receivers, a diffractive optical element configured to diffract an optical beam from at least one alignment optical source to at least one sensor, and an aligning element configured to align optical beams from the optical data sources to said optical data receivers, according to readings from the sensor.

Abstract: This invention pertains to optical fiber transmission networks, and is particularly relevant to transmission of high volume of data and voice traffic among different locations. In particular, the improvement teaches improvements to an optical transport system to allow for efficient and flexible network evolution.

Abstract: A multi-access laser communications terminal is disclosed. The communications terminal includes a deformable mirror whose surface contour is deformable by one or more actuators. The communications terminal further includes a closed-loop tracking system which controls the one or more actuators to change the surface contour of the deformable mirror in accordance with detected movement of an optical beam in order to keep the optical beam optimally locked on a receiver.

Abstract: A method and apparatus for steering energy over a wide field of view is disclosed. The apparatus comprises a beam steering system for directing a first beam from an optical source across an image plane and a WFOV optical system having the image plane, the WFOV optical system mapping the directed first beam incident on the image plane with a second beam extending angularly across the field of view. The method comprises the steps of directing a first beam from a optical source onto an image plane, optically mapping the directed first beam incident on the image plane with a second beam extending angularly across a field of view, and steering the first beam across the image plane.

Abstract: The present invention provides an optical receiving device, in which a portion of an optical signal is deflected for optical axis detection only when the optical axis is misaligned to thereby achieve a high S/N ratio of a received signal. A condensing section 100 condenses a received optical signal. An optical element 110 includes a transmission region 111 and a deflecting region 112, and receives the optical signal, which has been condensed through the condensing section 100. A signal light receiving section 120 receives the transmitted light, which has been transmitted through the transmission region 111. A detection light receiving section 130 receives deflected light, which has been deflected through the deflecting region 112 and performs a photoelectric conversion on the received light to thereby output a detection intensity signal that indicates an intensity of the deflected light.

Abstract: A high-speed optical communications cell is integrated at the interior of a two-dimensional imaging array. The combined receiver and imager carries out both photodetection (converting photons to electrons) and circuit functions (e.g. amplifying and integrating the signals from the photodetectors). The high-speed receiver cell comprises a photodetector and a high-speed amplification circuit, providing an electrical output which can follow a rapidly varying optical signal falling on the photodetector. The imaging array comprises an array of photodetectors and readout circuits, providing an electrical representation of the variation of light with position across the receiver surface. The presence of an imaging array surrounding the communications receiver, and in the same plane as it, allows a single optical path to be used for source acquisition and tracking as well as for data reception.