BOTDR based on a self-sweeping fiber laser

Fiber sensing systems based on the Brillouin scattering are one of the most advanced types of distributed measurements, allowing the analysis of strain and temperature in fiber lines with length of tens of kilometers. Brillouin optical time domain reflectometry (BOTDR) systems are of particular importance since they require access to sensing lines from one side only. Typically, such systems involve the use of heterodyne detection techniques based on tunable radiation. In turn, generation of highly coherent tunable radiation often requires the use of electro-optical modulators and expensive microwave electronics elements. In this study, we present the first demonstration of a BOTDR system based on a selfsweeping fiber laser. Such lasers simplify greatly generation of highly coherent tunable radiation because of passive wavelength tuning (without external control). So, the BOTDR system itself can be simplified by applying suitable selfsweeping fiber laser. We used an Er-doped continuous-wave self-sweeping fiber laser with a sweeping step of 6.2 MHz and range of about 20 pm (2.5 GHz) near the wavelength of 1565.2 nm. A BOTDR system based on the self-sweeping fiber laser was constructed and the Brillouin frequency shift was recovered in a 25-km-long sensing line. The spatial resolution was estimated to be about 10 m. The here-proposed approach to construct BOTDR systems on the basis of continuous-wave self-sweeping lasers can make it possible to create less complicated and less expensive systems for distributed temperature and strain measurements.