Abstract: Systems, methods, and computer program products are provided for accurately measuring frequency-and/or-phase-related parameters of a sinusoidal signal that varies non-linearly in frequency or phase. A sinusoidal signal is sampled over a finite period of time at a plurality of sample points. The sampled signals are pre-processed, and a Fourier transform is performed on the pre-processed sampled signals. Phases of the pre-processed sampled signals are extracted from the Fourier transform, and a measurement indicative of frequency of the sinusoidal signal is determined from slope of the phases of the pre-processed sampled signals. Range to a target may be determined using the exemplary signal processing described above on laser radar interference signals.

Abstract: The invention performs coordinate measurement employing multiple-frequency intensity-modulated laser radar. A laser diode source is intensity modulated by variation of its excitation current. Its output beam is directed to a target using scanning mirrors or other opto-mechanical means, and the light returned from the target is detected. The modulation frequency is alternated between two or more values, creating a dataset of several relative phase measurements that uniquely determine the distance to the target without ambiguity.

Abstract: A system for tuning a narrow-linewidth semiconductor laser such that the laser produces a laser beam at its output port having a desired frequency. The system includes an optical resonator and an optical system for coupling a portion of the laser beam into the resonator along a feedback optical path. The resonator may comprise a pair of faces, an electro-optic material between the faces, and an electrode for generating an electric field in the electro-optic material in response to a control voltage. The laser beam portion that enters the resonator causes the resonator to produce a feedback beam that is coupled into the input port of the laser, to provide optical feedback that causes the laser to lock to a resonance of the optical resonator. Tuning is accomplished by varying the resonance by applying a voltage to the electrode. The optical feedback also reduces the laser's linewidth. In another embodiment, a fiber-optic cable ring resonator is used to produce the feedback beam.