State-of-the-art of this technology are Brillouin Optical Time-Domain Analyser (BOTDA) based on Stimulated Brillouin Scattering (SBS). The basic working scheme of a BOTDA is presented in Figure 1 and works as follows:
Figure 1: BOTDA Setup
(1) a pulse of “pump” light is injected at a first end of the sensing fibre and creates a travelling virtual sensor that moves along its length, while at the opposite end of the fibre (2) the “probe” light having a specific wavelength is continuously injected. When the “travelling” sensor (3) sweeps a region of the sensor that has the temperature (or strain) characteristics tested by the specific “probe” wavelength in use, the probe light results perturbed by stimulated Brillouin amplification. Perturbed light (4) is then analyzed in the time-domain in order to locate the position and length of the perturbed region along the sensor.