Measurement range enlargement in Brillouin optical correlation-domain reflectometry based on double-modulation scheme.

We have demonstrated a double-modulation scheme to enlarge the measurement range of Brillouin optical correlation-domain reflectometry for fiber-optic distributed strain sensing. In this scheme, the frequency of the laser output is simultaneously modulated with two different frequencies. In the experiment, 53-cm resolution and 1.5-km measurement range were simultaneously obtained. Furthermore, 27-cm resolution and 1.5-km measurement range were also simultaneously achieved when a noise-floor compensation technique was employed.