Liquid-level sensing method based on differential pulse-width pair Brillouin optical time-domain analysis and a self-heated high attenuation fiber

Abstract

A liquid-level sensing method based on differential pulse-width pair Brillouinoptical time domain analysis (DPP-BOTDA) combining with a self-heated high attenuationfiber (HAF) is proposed, where the principle is to locate the temperature abruption position atthe interface between liquid and air caused by their different thermal diffusion rates. A Pandapolarization-maintaining fiber is used as the sensing optical fiber, which is tightly gluedalongside a laser-powered HAF. Heated by a high-power laser, the temperature of the HAFcan increase and exhibits approximately exponential attenuation with the light propagationdirection, which induces a similar temperature distribution over the sensing fiber. By using a5-cm spatial resolution DPP-BOTDA and a 1.4-W heating light, temperature distributions ofthe sensing fiber are measured for different water levels, and the results indicate thatdistributed liquid-level sensing with a range of 20 cm and a resolution of 1 cm is realizedusing our method.