Abstract: An optical communication system (20) is provided for transmitting a multi-rate data signal between a transmitter (22) and a receiver (24) in a power efficient manner. The optical communication system (20) includes an optical source (32) that supplies an optical carrier signal; an encoder (44) that receives and encodes a data signal; an external phase modulator (42) that modulates the optical carrier signal with the encoded data signal, such that the modulator (42) varies the duty factor of the modulated optical signal based on the encoded data signal; and an optically saturated erbium doped fiber amplifier (36) that amplifies the modulated optical signal prior to transmission by the transmitter (22). In accordance with the present invention, the modulation scheme of the optical communication system (20) varies the duty cycle of the modulation to attain power efficiency during periods of low data demand.

Abstract: An optical communication terminal includes transmit and receive paths along which optical transmit and receive energy passes. The terminal includes a telescope with a housing, a primary mirror and a secondary mirror. The primary mirror directs received beams to a secondary mirror and directs the optical transmit energy out of the telescope in a transmit beam. A secondary mirror is placed confocal to the primary mirror so that optical transmit energy is directed by the secondary mirror to the primary mirror. An annular mirror is positioned along the transmit path and along the receive path. The annular mirror passes the optical transmit energy from the transmit path into a shared path and passes the received optical energy from the shared path into the receive path. Preferably, the secondary mirror is a dichroic lens that reflects optical energy at the wavelength of the receive beam.

Abstract: An apparatus for determining the pointing uncertainty of a satellite communications system comprises a communications terminal coupled to a pointing mechanism which is operative to move and position the communications mechanism. A data storage device is configured to store data from which an actual position of a preselected light source which radiates a reference light can be determined. An acquisition sensor is positioned to move with the communications terminal and is configured to focus incident light onto the acquisition sensor. A control mechanism is coupled to the pointing mechanism and is operative to move the pointing mechanism to a position which would focus the reference light source at a preselected position on the acquisition sensor if the pointing uncertainty were substantially zero. The reference light focusing at a measured position on the acquisition sensor.

Abstract: Method and apparatus for spatially combining a large number of optical signals of different wavelengths carried on optical fibers (12) from laser sources (10). A dispersive optical device, disclosed as a grating (16), combines the multiple signals into a composite beam. Then a sample of the composite beam is analyzed by passing it through tunable etalon (26) and onto a sensor (30). The etalon (16) is successively tuned to passbands, each of which corresponds to the wavelength of each of the optical signals in turn. The sensor (30) measures angular deviation of each beam caused by wavelength changes, and generate control signals (on lines 36) to adjust each wavelength at its laser source. Thus the apparatus provides for reliable multiplexing of a relatively large numbers of laser sources (10), while the etalon (16) and sensor (30) operate in conjunction with a controller (32), which also generates wavelength control signals for the lasers (10), to ensure accurate beam alignment and more efficient multiplexing.

Abstract: A method for reducing smear in video images generated by a frame transfer CCD imaging system having an array of charge coupled devices. The video images comprise successive image frames, each frame including an array of image pixels corresponding to the array of charge coupled devices. The pixel array has a plurality of rows and columns. Each frame is temporally separated from a next successive frame by an integration time interval during which light falling upon the array of charge coupled devices is integrated to produce integrated charge samples representative of image frame pixel values, and by a transfer interval during which the charge samples are transferred from an imaging area to a storage area.

Abstract: An optical wavefront sensor for measuring phase tilt in two dimensions across the cross section of a beam (14), using only a single lenslet array (26) and a single camera sensor array (28). The rectangular lenslet array (26) is oriented at 45 degrees to first and second orthogonal sets of axes defining multiple points of interest (22') in the beam cross section, such that each lenslet subaperture is centered (at 40) between adjacent points of interest on the first and second axes. The points of interest (22') are locations corresponding to the positions of actuators (22) in an adaptive optics system. The camera sensor array (28) has more cells per unit area than there are subapertures per unit area. Only selected cells are activated, to provide for measurements at the approximate mid-points of lines between adjacent points of interest (22') on the first and second orthogonal axes.