Optical fiber sensor for temperature measuring

Abstract

ABSTRACT Simple fiber-optic sensor for temperature measuring, based upon the temperature-dependent bend losses in plastic clad silica optical fibers, is being proposed. The quantity of light energy transmitted along the fiber depends on the numericalaperture of the fiber, i.e. the refractive index difference between the silica core (nj) and the plastic cladding (no). On theone hand, the refractive index of polymer cladding n0 for plastic clad silica optical fibers exhibits considerable temperature dependence. On the other hand, local aperture in fiber bend region also changes at strong curvature, which reduces the number of guided modes and respectively decreases the transmitted light power. Interaction of these two effects produces great dependence of light output energy on temperature. High sensitivity over a wide temperature range (at least from - 20°C to +60°C) can be obtained.1. INTRODUCTIONIn recent years, research and development into optical fiber sensors has made rapid progress. Accordingly, many studies ofapplication of optical fibers for industrial measurements utilizing their excellent properties have been carried out.