A double-cladding fiber curvature sensor based on the extrinsic Fabry-Perot interferometer

Based on the principle of Fabry-Perot (F-P) interference, a new type of optical fiber curvature sensor is presented, which is fabricated by single-mode fiber (SMF), ceramic tube and double-cladding fiber (DCF). And the curvature sensing properties are analyzed, and the double-peak method is used to demodulate the cavity length. The experimental results show that the F-P interference spectrum shifts toward long wavelengths with increasing the curvature. And the sensors are placed in different positions on the cantilever to get their different curvature sensitivities. Smaller initial cavity length gives greater sensor sensitivity. The best curvature sensitivity is achieved as 2 554.53 pm/m -1 in 0.71—1.18 m -1 . By demodulating the length of the F-P cavity, the cavity length of sensor 4 is changed by 0.08 mm. Therefore, the sensor has some potential for measure the small displacement.