SNR and Spectral Broadening in Turbulence Structure Measurement Using a cw Laser

Abstract

A symmetrical method of optical heterodyning of the doppler shifted signal has been developed possessingminimal instrumental spectral broadening and high SNR. These advantages can be gainfully employed in measuringturbulence structure using a cw laser. The method employs two beams incident on the moving scatterer. Thedoppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperturebroadening. Typical values of signal-to-noise ratio are around 30 dB for a signal strength of 3 x 10(-9) W. Optical alignment is simple. Relative merits of this technique compared to the localoscillator heterodyning method are briefly described.