High-resolution space-domain active fiber cavity ring-down temperature sensors

A high-resolution temperature sensor based on space-domain active fiber cavity ring-down sensing technology was proposed for the first time, to our knowledge. In this scheme, a bidirectional erbium-doped fiber amplifier is employed to compensate for the intrinsic cavity loss, significantly improving the temperature resolution. Meanwhile, a temperature sensing head based on a single-few-single mode fiber structure is utilized to enhance the mode interference effect, thereby effectively increasing the temperature sensitivity. The differential interference signal is captured by a balanced detector and processed via fast Fourier transform to obtain the space-domain ring-down signal, thereby establishing a quantitative relationship between the reciprocal difference of ring-down distance and temperature. Experimental results demonstrate a good linear relationship between the reciprocal difference of ring-down distance and temperature within the range of 90°C to 130°C, with a sensitivity of 0.182km −1 ⋅ ∘ C −1 . Benefiting from the advantages of cavity loss compensation technology and enhanced sensitivity, the proposed sensor achieves a temperature resolution of 0.033°C, which is one order of magnitude higher than traditional time-domain passive cavity ring-down temperature sensors and twice that of space-domain passive fiber cavity ring-down temperature sensors.