Influence of Brillouin Slow Light on Distributed Brillouin Fiber Sensor due to Depletion of Pump Beam

Abstract

The influence of Brillouin slow light on distributed Brillouin fiber sensors is studied. We demonstrate Brillouin slow light for a 1.2 ns pulse with peak power from 3.3 to 56.2 mW at the depletion of the pump power from 1.3 mW to 83.2 mW in conventional optical fibers (SMF-28). Our experimental results show that when the depletion of the pump power is not negligible (pump and probe powers are comparable, which is the optimized distributed Brillouin fiber sensor regime), for a given pump power the Brillouin gain and delay time of a pulse decrease when the pulse peak power increases in a long length (≥10 km) sensing fiber. The strong depletion of the pump beam resulting from the strong interaction between pump and probe in the fiber provides accurate local temperature and strain information at high spatial resolution. Our study reveals that for a nanosecond pulse at low pump power, the spatial resolution error caused by pulse delay for a distributed Brillouin fiber sensor with centimeter spatial resolution is less than 5% of the pulse length, which is within experimental uncertainty.