Distributed Fiber Optic Temperature Sensing

Abstract

This chapter reviews the basic principles of the fiber optic temperature sensing. Distributed temperature sensing (DTS) systems inject a narrow laser pulse into an optical fiber through a directional coupler. The Rayleigh backscattered component is the strongest because of density and composition fluctuations and has the same wavelength as the primary laser pulse. The Raman backscattered components are caused by thermally influenced molecular vibrations from the incident propagating light pulse and their intensity depends on temperature. The Brillouin backscattered components are caused by lattice vibrations from the propagating light pulse. Adopters of the Brillouin technology‐ based DTS systems claim to be capable of providing temperature profiles for open‐ended fiber distances of 100—200km with the aid of optical amplifiers. DTS systems typically have the following five major hardware components: optical fiber; laser; photodetector and optical‐electrical processing unit; controller; optical multiplexing switch allowing temperature profiling of more than one fiber optic cable, at almost the same time.