In the DTS system that uses the stimulated Raman
scattering in optical fiber the anti-Stokes part of the spectrum
is the most important part. This part of spectrum
changes its intensity if temperature changes along the optical
fiber – see Fig. 3. The Stokes part, on the other hand, is
independent on temperature. DTS systems are based on the
principle of intensity changes of the anti-Stokes part compared
with the Stokes part: