Fiber Lateral Stress Sensor Based on Michelson Interference and Optical Vernier Effect

In this paper, an ultra-sensitive optical lateral stress sensor with the Optical Vernier effect (OVE) is successfully fabricated, and its feasibility is also experimentally demonstrated. The fundamental structure of this sensor is an optical fiber Michelson Interferometer (MI) based on an optical coupler. One arm of the MI is built up by the single mode fiber (SMF) with a well-cleaved end. The other arm is built up by the Panda polarization maintaining fiber (PMF) with a well-cleaved end. Because of the fiber end reflection and the birefringence effect, there are three reflected lights from the two arms. By adjusting the length difference between the two arms to a proper value, the three reflected lights can interfere with each other, generating an extensive envelope modulation with enhanced sensing capabilities on the output spectrum. The experimental results show that the proposed sensor can respond linearly to the lateral stress variation from 0 to 7.5 kPa with a sensitivity of 3.76 nm/(kPa·m). The temperature cross-sensitivity of the proposed sensor is about ∼0.56 kPa/℃. After compensating temperature cross-sensitivity by a fiber Bragg grating (FBG), the proposed sensor can work ideally with the permitted error range on a broader temperature range.