White-Light-Driven Ultrahigh-Resolution Fiber Ring Resonator Array Based on Frequency Division Multiplexing Technology

Resonant fiber optic sensor (RFOS) is an important branch of fiber optic sensors due to its ultrahigh sensitivity and resolution. However, the multiplexing of RFOSs usually suffers from high system complexity and maintenance costs. In this article, we proposed an RFOS array based on frequency division multiplexing (FDM) technology. Using a broadband light source as the driving light source, the multiplexed system is characterized by low cost, simple system, ultrahigh-resolution, and no observable crosstalk between channels. In the proposed system, fiber ring resonators (FRRs) with different free spectral ranges are connected to form an array, serving as different sensing channels. The sensing mechanism of the system is based on detecting the round-trip filtering loss of the FRR sensors, and channel separation is achieved through modulating the frequency of an acousto-optic modulator (AOM). Using a 1 km delay fiber and an ultra-simple configuration, an experimental strain resolution of 361 f $\varepsilon /(\text {Hz})^{1/2}$ at 1 kHz is achieved without observable crosstalk between channels.