Optical pulse coding in hybrid distributed sensing based on Raman and Brillouin scattering employing Fabry–Perot lasers

We demonstrate simultaneous strain and temperature sensing based on hybrid Raman and Brillouin scattering with enhanced performance thanks to the combined use of standard Fabry-Perot lasers in conjunction with optical pulse coding techniques. The combination of both techniques allows for an improvement of ~8.7 dB in temperature resolution and ~3 dB in strain resolution, with respect to standard distributed feedback lasers, as confirmed by experiments, resulting in a final temperature / strain resolution of ~0.27K / ~30microepsilon over 25-km sensing fiber range, avoiding the use of optical amplification and wavelength averaging techniques.