A Microwave Photonic-Assisted Fiber Loop Ring Down System with Multi-Sensing Function

In this letter, we demonstrate a fiber-loop ring down (FLRD) multi-function sensing system, which is assisted by microwave photonic technique. The temperature and curvature sensing characteristics of the FLRD system are studied. The ring-down curve in the time domain can be acquired by taking the inverse Fourier transform (IFFT) of the frequency response of a microwave photonics filter (MPF). The temperature and curvature information can then be evaluated simultaneously based on the calculated ring-down curves. Compared with the traditional time domain measurement, the system is based on pure frequency domain measurement from a microwave photonic configuration, which reduces the requirements of the light source and has the features of fast responding and easy networking. The sensitivity of the system is measured to be
$0.425~\mu \text{s}/^{\circ }\text{C}$
in the sensing range of 30~70 °C and
$0.1553~\mu \text{s}$
/cm
⁻¹
in the sensing range of 0.8696~1.0526 cm
⁻¹
. The experimental results agree well with the theoretical predictions.