Fresnel-reflection-based fiber sensor for on-line measurement of ambient temperature

A fiber sensor with a simple structure for measuring the environment temperature is presented. The sensor uses only a diode laser as light source, three couplers, two photodetectors and two sensing fiber ends with protective cladding. One of the sensing fiber ends is covered by solidified epoxy resin with a metal cover. The measurement principle is based on relative Fresnel reflective intensity. Various ambient temperatures are measured in the setup. The measured data is fitted to linear equation very well with the value of R2 of 0.9982. Applying the relative technique, the errors resulted from fluctuation of light source and other influences of environment are effectively eliminated, and the stability for long time measurement can be improved.