Comparison of temperature distribution measurement methods with the use of the Bragg gratingsand Raman scattering of light in optical fibers

Abstract

Two types of fiber-optical measurement systems are compared: a line with a large number of point sensors based on fiber Bragg gratings (FBGs) interrogated by a tunable continuous fiber laser and a distributed system based on optical time-domain reflectometry (OTDR) of the Raman scattering of radiation of a pulsed fiber laser. Methods for increasing the measurement accuracy with the use of additional calibration of the Bragg wavelength shift over a fiber interferometer in the FBG system and spectral filtration of the Stokes and anti-Stokes components of the Raman scattering with the use of spectral-selective fiber couplers in the OTDR system are proposed and implemented. Physical effects on system parameters are analyzed, compared, and optimized for applications with monitoring of the temperature distribution in turbogenerators and oil wells.