MODELING OF DIRECT-DETECTION DOPPLER WIND LIDAR - II - THE FRINGE IMAGING TECHNIQUE

A simple analytic model is developed for the shot-noise-limited measur ement precision of Doppler wind lidars based on the fringe imaging tec hnique by use of either molecular or aerosol atmospheric backscatter. The model leads to etalon design parameters for an instrument optimize d for precision. The ultimate measurement precision possible is two to four times the limit for a perfect, lossless receiver. The correspond ing result for the double-edge Doppler analyzer was a ratio of 2.5, sh owing that the two methods are little different in this respect. For a erosol backscatter instruments, the wind speed dynamic range of the fr inge imager is substantially greater than that for the edge detector. The etalon aperture needed to meet system etendue requirements is deri ved and shown to be approximately half that of each of the two etalons required by the double-edge technique. A comparison with more detaile d modeling of fringe imaging Doppler-shift analyzers shows good agreem ent for the Rayleigh model and fair for the aerosol version, confirmin g the validity of this simpler technique for analyzer design and perfo rmance prediction. (C) 1998 Optical Society of America.