Research on COTDR for measuring distributed temperature and strain

The coherent optical time domain reflectometer (COTDR) based distributed temperature and strain sensing is studied in this paper. The sensing principle is analyzed and discussed in detail. Rayleigh backscattering in a single-mode optical fiber is measured by COTDR with a precisely frequency-controlled light source, and the cross-correlation of the Rayleigh backscattering is calculate to detect the frequency changes of the cross-correlation peak caused by the changes of temperature and strain. We perform simulations on the COTDR based sensing system by computer and draw some conclusions.