Abstract: An optical communication system suitable for a coherent optical satellite communication is configured to include an optical transmission device having a laser signal generator, a first reference laser signal generator having a first local oscillating laser signal generator and an automatic frequency controller, an optical receiving device, and a second reference optical signal generator having a second local oscillating laser signal generator. The first reference local oscillating laser signal generator and the automatic frequency controller are used to generate a fixed beat reference optical signal, and thus the optical receiving device is capable of locking the transmitted laser signal according to the fixed beat reference laser signal in a way of heterodyne receiving so as to demodulate the transmitted signal frequency accurately and resolve the problem of laser frequency drifting.

Abstract: A tracking system and method in an optical communications system utilizing an optical communications beam. In one embodiment, the disclosed optical communications system includes a communications receiver circuit and a tracking circuit. The optical communications system generates a communications signal. The tracking system includes a tracking detector having a plurality of regions coupled to a corresponding plurality of tracking channel circuits. Each of the tracking channel circuits includes an optical detector coupled to receive the optical communications beam. The peak-to-peak amplitude modulation in the optical communications beam is measured by substantially reducing or removing a direct current (DC) offset present in the optical communications beam. In one embodiment, after the DC offset is substantially reduced or removed, the signal is then amplified, mixed with the communications signal and then filtered.

Abstract: An infrared transmission/reception apparatus and a method thereof in which an infrared transmission output is changed to transmit a plurality of station finding commands, and an infrared transmission output for such a station finding command out of the plurality of station finding commands as returning a station finding response from a secondary station is used to perform a subsequent communication. Thus, communication can be performed with the minimum infrared output regardless of the opposite apparatus.

Abstract: A device for interactively transmitting optical signals in a first wavelength and receiving optical signals in a second wavelength both through a one-core optical fiber, includes a first photodiode that converts a received optical signal into a first electric signal, a second photodiode that converts an optical signal into a second electric signal, a first amplifier connected between the second light-electricity signal converter and the coherent light remover, a second amplifier connected to the second light-electricity signal converter, and a differential amplifier that subtracts the second electric signal from the first electric signal.

Abstract: An optical transmission system including at least one optical transmitter configured to transmit at least one signal wavelength and a tuning wavelength, an optical receiver including an optical filter having a filter bandwidth including the at least one signal wavelength and a percentage of the tuning wavelength and an optical to electrical signal converter configured to receive the at least one signal wavelength from said filter, a first tuning optical to electrical converter configured to receive a first portion of the tuning wavelength stopped by said filter, a second tuning optical to electrical converter configured to receive a second portion of the tuning wavelength passed by said filter, and a filter controller configured to tune the filter bandwidth based on the relative proportion of first and second portions of the tuning wavelength provided to the first and second tuning optical to electrical converters.

Abstract: A monitoring system useful for monitoring the state of a fiber communication channel in which a portion of the fiber signal is tapped and detected by a photodiode. The dark current of the photodiode and other DC offsets of the system may be compensated by passing a known signal through the photodiode and extracting the component due to the known signal. The known signal may be a locally generated optical signal having a predetermined harmonic signature. Optionally, the fiber signal may be selectively attenuated before being combined with the known signal so only the known signal is detected. The known signal may also be a dark signal induced by selectively attenuating the fiber signal. The system may include a temperature sensor which allows the compensation to be performed against stored temperature dependent compensation values while the fiber signal is not attenuated.

Abstract: A tracking system and method in an optical communications system utilizing an optical communications beam. In one embodiment, the disclosed tracking system includes a tracking detector having a plurality of regions coupled to a corresponding plurality of tracking channel circuits. Each of the tracking channel circuits includes an optical detector coupled to receive the optical communications beam. The peak-to-peak amplitude modulation in the optical communications beam is measured by substantially reducing or removing a direct current (DC) offset present in the optical communications beam. In one embodiment, after the DC offset is substantially reduced or removed, the signal is then amplified and converted into an all positive signal, which is then filtered. The filtered signal is one of a plurality of tracking signal outputs, which are input to an alignment circuit.

Abstract: All-optical bit phase sensors that utilize nonlinear interferometers are described. An all-optical bit phase sensor that utilizes an optical fiber and a detector optically coupled to the core of the fiber, perpendicular to the longitudinal direction of the core, is described. In addition, an electrooptic bit phase sensor that utilizes a semiconductor diode and an electrical detector electrically coupled to the active layer is described. Electrooptical and all-optical phase lock loops, optical processors, and optical networks that utilize these bit phase sensing are also described.

Abstract: A system and method of varying the control loop gain of an optical wireless communication link between a transmitting station and a receiving station as an inverse function of distance between the transmitting station and the receiving station to allow the optical wireless communication link to be used reliably over a wide range of distances.