Distributed Temperature Sensing (DTS) system is ideal for temperature monitoring over long distances. It monitors temperature over long distances; underground and above large surfaces, it could be along power transmission lines, tunnels or pipelines. DTS is a linear system made of thousands of sensors. Actually fiber itself is used as passive sensor. Instead of installing countless numbers of conventional sensors, DTS systems can be used as a single strand of optical fiber as sensor.
When light source (laser) is incident on the optical fiber, it is scattered by the fiber glass molecules as it propagates down the fiber and exchange molecules with lattice vibration. Their occur Raman scattering which has two components; stokes signal and anti-stokes signal. It is reflected back to transmitted end where it is analyzed. The intensity ratio of backscattered anti stokes and stokes signals help in determining temperature at point. Measurement of arriving time at transmitting end is used to get position of temperature reading.