Abstract

Interferometric spectrum analyzers offer improved performance over power spectrum analyzers but not without a substantial increase in complexity. In this paper a technique for improving the performance of power spectrum analyzers is presented. The intensity profile of the input light beam controls the level of the sidelobes in the detection plane as well as the resolution of the analyzer. This profile, together with acoustic attenuation also controls the instantaneous dynamic range by suppressing acoustic nonlinearities. The most common criterion used for determining the resolution of an acoustooptic spectrum analyzer is the Rayleigh criterion. The application of this criterion requires two signals of the same power, a condition which rarely occurs in practice. A condition more likely to occur is that the signal powers vary extensively and require a large dynamic range. It is for this reason that the use of the Rayleigh criterion in spectrum analysis is not recommended. A different criterion is suggested and shown to be more appropriate. The most general weighting function used is Gaussian. This function is evaluated by using the suggested criterion for resolution shown not to be optimal. An optimal weighting function is determined incorporating the effect of acoustic attention and acoustic nonlinearities. This is shown to exert an appreciable influence on system specifications and design.

© 1989 Optical Society of America