Demodulation algorithm used in single-beam system immune to light power drift.

ABSTRACT

A demodulation algorithm based on the head-tail technique is proposed for single-beam water vapor detection under rough environmental conditions, which is immune to fluctuations of light power. In the head-tail technique, collected data are processed by adding the head and tail data together and gradually approaching the center. The majority of photocurrent attenuation caused by optical loss can be effectively compensated by combining an optical intensity normalization coefficient in the method. The experiment indicates that, when the light power attenuates 4%, the deviation in a single-beam system is 1.29%, which is obviously superior to a dual-beam subtraction system whose deviation is 8.45%. The connection and advantages compared to a previous single-beam detection system have been discussed. The whole arrangement is simply designed without a beam splitter, of which the reliability and validity are fully verified by the experimental results.