United States of America As Represented by the Administrator of Nasa

Pacific Wave Industries, Inc.

Serge Dubovitsky

Joseph Michael

Harold R Fetterman

William H Steier

Oliver P Lay

The present invention relates to a heterodyne interferometer system with a pre-processing of the target signal to isolate and remove self-interference signals using a known phase modulation of the carrier signal's frequency. Where self-interference signals do not include a time delay inherent in the target signal that travels to the target reflector, by selecting a modulation frequency tuned to the time delay and then filtering the resultant signal the target beam can be isolated and the self-interference signal can be effectively removed The system includes a modulation unit to apply a phase modulation to the carrier signal, and a mixing unit that demodulates the target signal at the modulation frequency to isolate the target beam.

Heterodyne interferometer with a phase modulated source

A method for suppressing distortion in a multi-wavelengths system which uses a Mach Zehnder optical modulator includes adjusting an internal path length mismatch of the modulator and changing an applied voltage, V , such that the combination biases the modulator to the required &pgr;/2 phase bias.

Method for suppressing distortion in mach-zehnder optical modulators with a chirped or variable operating wavelength

The present invention is an improved distance measuring interferometer that includes high speed phase modulators and additional phase meters to generate and analyze multiple heterodyne signal pairs with distinct frequencies. Modulation sidebands with large frequency separation are generated by the high speed electro-optic phase modulators, requiring only a single frequency stable laser source and eliminating the need for a first laser to be tuned or stabilized relative to a second laser. The combination of signals produced by the modulated sidebands is separated and processed to give the target distance. The resulting metrology apparatus enables a sensor with submicron accuracy or better over a multi-kilometer ambiguity range.

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Los Angeles, CA, United States of America

Serge Dubovitsky