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 correlationdomain reflectometry (BOCDR) for fiber-optic distributed strain sensing. In this scheme, the frequency of the laser output is simultaneously modulated with two different frequencies. A resolution of 27 cm was achieved with 1.5-km measurement range when a noise-floor compensation technique was used.