LAUSR

In this article, a fiber‐optic sensing scheme based on Stimulated Brillouin scattering effect in a recirculating fiber ring and frequency down‐conversion is proposed and experimentally demonstrated. By employing the recirculating fiber ring structure, high‐order backscattering Stocks light has been generated. The Brillouin frequency shift will be affected by the environmental variations, such as, temperature changes, and by measuring the frequency shift of the beat signal of the pump light and the backscattering Stocks light, the measurands can be demodulated. Measuring beat frequency of higher‐order light enjoys higher sensitivity. To facilitate the measurement, frequency down‐conversion has been utilized. Temperature sensing has been demonstrated for verification in the experiment, and by detecting the frequency shift of down‐converted signal of the first‐order, second‐order, and third‐order Brillouin beat signal at ~0.5, ~1.0, and ~1.5 GHz, the sensitivities of ~1.11, ~2.41, and ~3.59 MHz/°C have been obtained, respectively.