Optical Fiber Fabry-Perot Temperature Sensors

Abstract

Optical fiber Fabry-Perot (FP) interferometric sensors are simple, accurate, and sensitive. While the basic principle of FP sensors is well known, the interpretation of experimental results is not very simple. If the simple fringe counting technique is employed, one cannot, however, distinguish the temperature rise from temperature drop. Additional information is needed to determine the direction of temperature change. Yoshino et al [1] observed the temporal order of two propagating modes with distinguishable light intensity ratio in a fiber FP arrangement as a means for determining the direction of temperature change. Their method depends critically on the fiber length, the fiber characteristics, and the temperature range. Complicated electronics have been used by Ito [2] to compare optical signals at two different instants to extract the instantaneous temperature. In this work, a simple scheme of determining the temperature change and the direction of temperature change is reported. The experimental results are in excellent agreement with independent, thermocouple measurements.