High-speed and high-precision torsion sensor based on polarization-induced microwave photonic phase shift measurement

We propose and experimentally demonstrate a technique to achieve high-speed and high-precision torsion sensing based on polarization-induced microwave photonic phase shift measurement. In the proposed system, a section of single-mode fiber (SMF) is used as a sensor that is incorporated into a microwave photonic phase shifter (MPPS). The MPPS consists of a laser source, a polarization modulator (PolM), an optical bandpass filter (BPF), a SMF, a polarizer, and a photodetector (PD). The phase shift of the microwave signal is a linear function of the twist angle of the SMF. An IQ detection module is utilized to measure the microwave phase shift. The performance of the proposed torsion sensor is experimentally evaluated. A measurement range of over 180° and a sensing accuracy of 0.03° are realized at an ultrahigh speed of 1 MHz, with low strain and temperature cross-sensitivity.