Abstract: A system for directing a communication beam from a transmitter at a first location onto an optical target of a receiver at a second location uses a terrestrial free-space optical data link. The system includes an optical fiber which emanates the communication beam at a first wavelength in the intermediate infrared range onto an optical element of the transmitter. The optical element then collimates and directs the communication beam, together with a beacon beam of a second wavelength in the near infrared range, in a common beam along a path toward the receiver. At the second location, the receiver collects the common beam and focuses it to a focal point. A camera in the receiver then receives scattered light of the beacon beam from the focal point to determine a displacement distance between the focal point and the target. The focal point and target are then aligned with each other to reduce the displacement distance to a null and thereby make the focal point of the common beam incident on the target.

Abstract: A dual mode laser/microwave transceiver for use in line-of-sight communications includes a housing that is formed with a single aperture for receiving both a laser beam and a microwave beam. A turning mirror and a beam splitter are mounted within the housing, and the turning mirror reflects an incoming laser/microwave beam onto the beam splitter which separates the laser beam from the microwave beam. The microwave beam is then directed by the beam splitter toward a microwave feed that is mounted on the housing. On the other hand, the laser beam is directed by the beam splitter toward an optical receiver that is mounted on the housing. Transmitted laser and microwave beams are respectively sent through the transceiver in directions opposite to that of the received beams.

Abstract: A transceiver for a two-way laser beam link in a communications system handles data blocks and stand-down blocks on both in-coming and out-going laser beams. The transceiver includes a detector unit which monitors the in-coming laser beam, and sends an interrupt signal on its out-going beam whenever the quality of the in-coming beam passes a predetermined threshold. Additionally, the transceiver includes an injector for inserting stand-down blocks onto its out-going beam in response to interrupt signals that are received on its in-coming beam. A router is provided at the transceiver for removing stand-down blocks from its in-coming beam. Appropriate buffers are provided at the transceiver so that laser transmissions with other transceivers can be made at a baud rate which is approximately twice as fast as the data signaling rate used on non-laser connections between each transceiver and other components of the system.

Abstract: A device and method for aligning the focal point of a laser beam into coincidence with the active area of a detector includes an optical element for focusing the laser beam to the focal point at a location on the surface of the detector. Also included is a selectively activated light source and a camera which establishes a reference location for the active area within an x-y grid coordinate system whenever the surface of the detector is illuminated by the light source. Further, by using the light that is reflected from the focal point location through a beam splitter, the camera also establishes the location of the laser beam focal point in the same coordinate system. The optical element is then adjusted to move the focal point in the x and y directions, as required, to thereby bring the focal point location into coincidence with the active area.

Abstract: A system and method for establishing a laser link communications system in free space includes first and second terminals which are distanced from each other on an optical path. Each terminal includes a plurality of laser transmitters which together generate a plurality of laser beams, with each of the laser beams carrying a communication signal. Further, each terminal directs its independently generated laser beams along substantially parallel paths. Though their paths are substantially parallel, the transmitted beams generally overlap in the far field, at the other terminal, where they are collected and incoherently summed for reception and analysis of the communication signal.