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 s/degrees C in the sensing range of 30 similar to 70 degrees C and 0.1553 mu s/cm(-1) in the sensing range of 0.8696 similar to 1.0526 cm(-1). The experimental results agree well with the theoretical predictions.