A distributed optical fibre dynamic strain sensor based on phase-OTDR

A distributed optical fibre sensor is introduced which is capable of quantifying multiple dynamic strain perturbations along 1 km of a sensing fibre simultaneously using a standard telecommunication single-mode optical fibre. The technique is based on measuring the phase between the Rayleigh scattered light from two sections of the fibre which define the gauge length. The phase is spatially determined along the entire length of the fibre with a single pulse. This allows multiple moving strain perturbation to be tracked and quantified along the entire length of the fibre. The demonstrated setup has a spatial resolution of 2 m with a frequency range of 500–5000 Hz. The minimum detectable strain perturbation of the sensor was measured to be 80 nepsilon.