The hybrid fiber optic interferometers are proposed and experimentally demonstrated. In our schemes, the hybrid fiber optic interferometers are constructed by single mode-multimode-polarization maintaining-single mode optical fiber (SMPS) structure and a Sagnac loop. The temperature and strain characteristics of the hybrid interferometers are studied in experiment, and the sensitivities depending on the length of polarization maintaining optical fiber (PMF) and multimode optical fiber (MMF) are detailedly investigated in experiment. The experimental results have demonstrated that the PMF and MMF lengths have low affect on the strain sensitivity but has great influence on the temperature sensitivity. The achieved strain sensitivity is 37.2pm/με for 10cm PMF and 12cm MMF. The achieved strain sensitivity is 38.0pm/με for 12cm PMF when the length of MMF is fixed at 15cm, and is 37.2 pm/με for 12cm MMF when the length of PMF is fixed at 10cm. The obtained temperature sensitivities is 1.723nm/°C when the length of MPF is 8cm with the fixed length of 15cm MMF, and the obtained temperature sensitivities reach 1.848nm/℃when the length of MMF is 12cm with the fixed length of 10cm PMF.
A high sensitivity and low cost all-fiber temperature sensor combined a single-mode-polarization maintaining-single-mode optical fiber (SPS) structure and a Sagnac loop is proposed and experimentally demonstrated. In this sensor, the SPS structure is reeled into a circle is inserted into a Sagnac loop. Experimental results show that the radius of the circle has significant influence on temperature sensitivity. The temperature sensitivity can reach up to 1.678nm/°C for the radius of 3cm.