Abstract

Advances in the technology of compact single- mode near-infrared lasers have stimulated interest in laser Doppler velocimetry (LDV) systems for optical air data measurements. This paper reports on the performance of a cw 1.06-μm LDV device in Mach-Zender configuration. At a fundamental level, laser temporal coherence (linewidth) determines the maximum possible signal strength in coherent LDV. In practical systems, additional circumstantial factors including system alignment, propagation effects, and speckle effects degrade signal levels. The Mach-Zender configuration provides flexibility in mode matching signal and local oscillator. In tests with a diffusely scattering hard target, this design produced a normalized mutual coherence of 0.8 (on a scale of 0-1) between local oscillator and collected signal. Wavefront curvature mismatch of ~13% accounts for the observed departure from ideal performance.

© 1991 Optical Society of America