Femto-strain resolution fiber-optic sensing with an ultra-simple white-light round trip filtering method

In the past decade, laser-driven resonant fiber-optic sensors (RFOSs) have been reported touching their ultimate resolution limit. The practicability of these high-performance sensors is, however, discounted because of high system complexity and dependence on narrow-linewidth lasers. In this paper, a novel, to the best of our knowledge, white-light-driven RFOS is established based on a round trip filtering (RTF) method. Via measuring the RTF loss of an add-drop fiber ring resonator (FRR) sensor, strain signal can be read out with an ultra-simple open-loop configuration. In the sensing experiment, even a resolution of several femto-strain around 1 kHz is demonstrated, representing the highest resolution level of RFOS to date. Thanks to the obvious superiority in both resolution, simplicity, and cost over traditional laser-driven RFOSs, the proposed white-light-driven RFOS is believed to be a milestone in the development of fiber-optic strain sensors.