Dynamic strain measurement based on ultrafast Brillouin collision in the correlation domain

The Brillouin collision rate in a Brillouin optical correlation domain analysis fiber sensor is ultimately limited by the sensing fiber length, which restricts the single point sampling rate in dynamic strain measurement. Here, a time-gated long-phase-sequence-coded pump method is proposed to overcome this limitation. The Brillouin collision rate is limited only by the phonon lifetime, since it governs the building and decaying time of the acoustic wave. For a sensing fiber length of ∼1 km, a Brillouin collision rate as high as 1 MHz is experimentally realized. This further results in a single-point sampling rate of 1 kHz for dynamic strain sensing with a spatial resolution of ∼2 cm and a measurement uncertainty of <33.5 µε.