Abstract: A return-to-zero control signal for controlling a modulator can be generated from two separate streams. A first data stream can include a pulse for each logical one that appears in an input data stream, while a second data stream can include a pulse for each logical zero that appears in the input data stream. The first and second data streams can be combined in a manner that yields the return-to-zero control signal. The first and second data streams can be generated in digital circuitry, such as an FPGA, to minimize the analog path for generating the return-to-zero control signal.

Abstract: A method for determining a pre-selected point-to-point separation between a first craft C1 and a second craft C2 is provided. The method includes the step of providing two laser devices, L1, and L2, onboard each craft, C1 and C2, respectively. Then determining a desired skin location vector S2 of craft C2 in L2 coordinates and translating the skin location vector S2 to L1 coordinates; and then determining skin separation between crafts C1 and C2 in accordance with the translated skin location vector.

Abstract: A liquid crystal variable retarder (LCVR) with automatic gain control for use with an imager-based target tracking application such as a free-space laser communication system. An LCVR is made of two optical windows separated by a gap, typically of a few microns. The gap is filled with nematic liquid crystal material. Electrodes are situated to enable an electric field to be applied between the optical windows and thus across the liquid crystal material. With no voltage applied to the electrodes the liquid crystals lie parallel to the optical windows. In this state of operation, the LCVR exhibits maximum retardation. As voltage is applied to the electrodes the liquid crystal molecules rotate away from the optical windows, becoming perpendicular to the optical windows. In this state of operation, the LCVR exhibits minimum retardation.

Abstract: A method and apparatus for setting the wavelength of a laser beacon in a free-space laser communication system. The invention uses the absorption and transmission attributes of a material, such as cesium, to generate a physical environment at the transmitting transceiver that essentially exactly replicates the environment that governs the physics of an atomic line filter at a receiving transceiver that is based on the absorption and transmission attributes of the same material.

Abstract: For transmitting information via laser beams to and from other similar laser communication transceivers. Each transceiver comprises a wavelength locked beacon laser providing a beacon beam. The transceivers determine the precise location of other transceivers by detecting these beacon beams with beacon receive units comprising atomic line filters matched to the beacon wavelength. Signals are transmitted by imposing an electronic signal on laser beams produced by one or more signal laser devices. These signals are directed with precision at other transceivers, and the signal beams are detected with very narrow field of view signal receive units. In a preferred embodiment, these transceivers are installed on 66 satellites in low earth orbit and on selected mountain tops on earth to provide a global communication system.

Abstract: A laser communication transceiver for transmitting information via laser beams to and from other similar laser communication transceivers. Each transceiver comprises a wavelength locked beacon laser providing a beacon beam. The transceivers determine the precise location of other transceivers by detecting these beacon beams with beacon receive units comprising atomic line filters matched to the beacon wavelength. Signals are transmitted by imposing an electronic signal on laser beams produced by one or more signal laser devices. These signals are directed with precision at other transceivers, and the signal beams are detected with very narrow field of view signal receive units. In a preferred embodiment, these transceivers are installed on 66 satellites in low earth orbit and on selected mountain tops on earth to provide a global communication system.