Polarimetric multilongitudinal-mode fiber laser sensor for strain, temperature, and fiber birefringence measurement

Abstract

In this paper, we proposed a multi-parameter sensing system based on a polarimetric multilongitudinal-mode fiber laser sensor and beat frequency signal interrogation technique. The polarimetric fiber laser consists two fiber Bragg gratings and a piece of Erbium-doped-fiber. Since the linear birefringence exists in any real fiber duo to its core deviating from a circular shape, two types of beat frequency signals exist in the fiber laser: longitudinal mode beat frequency and polarization mode beat frequency signals. They have different sensing characteristic to external perturbations such as temperature or strain change, so the polarimetric fiber laser can distinguish simultaneously the change of strain, temperature and the birefringence change. We theoretically analyzed the principle for measurement of temperature, strain and fiber birefringence, and experimentally studied the sensing performance of temperature, strain and fiber birefringence. The proposed multi-parameter sensing system just consists a polarimetric fiber laser sensor and a beat frequency demodulation equipment, so it shows the advantages of simple structure, portability, high sensitivity, and low cost.