Fully distributed optical fiber strain sensor with 10−12ε/√Hz sensitivity

Abstract

Advanced optical fiber reflectometry techniques enable spatially distributed measurements of true relative deformations over the length of a conventional optical fiber cable. This methodology is attractive for many applications ranging from intrusion monitoring to seismology. However, accurate quantification of the applied stimulus in general implies sophisticated implementations with poor sensitivity performance. Coherent reflectometry using chirped pulses is an appealing solution, as it provides fast dynamic strain measurements with a simple experimental deployment. Here, we analyze for the first time to our knowledge the lower performance bounds of this technique as a function of the signal-to-noise ratio of the acquired optical signal. We demonstrate that implementations realized so far have been limited by the temporal sampling used instead of the optical signal quality. Through post-processing interpolation approaches, we reach the performance limit for a given set of signal parameters, attaining unprecedented strain sensitivities (∼10−12epsilon/√Hz) for km-length distributed sensors in conventional single-mode fibers.