High Spatial Resolution BOTDR Based on Differential Brillouin Spectrum Technique

A novel differential-technique Brillouin optical time domain reflectometry with sub-meter spatial resolution is proposed and demonstrated. By analyzing the time-space related property of the pulse excited backward spontaneous Brillouin scattering light, a weighting factor distribution of the Brillouin spectrum along the fiber is obtained. Based on this distribution, a two-step-subtraction technique is proposed. A pulse pair with slightly width difference is employed as the probe pulse. At each corresponding location, for each pulse of the pulse pair a Brillouin-spectrum pair is extracted with two different time sequence length. By performing a two-step subtraction on these two Brillouin-spectrum pairs, the differential Brillouin spectrum is theoretically and experimentally proved to be spatially related with the width difference of the pulse pair. A spatial resolution of 0.4 m utilizing 60/56 ns pulse pair is experimentally achieved over 7.8-km sensing length with 4.1-MHz Brillouin frequency accuracy.