Strain sensing with parallel air-cavity Fabry-Perot interferometers based on Vernier Effect

We proposed and investigated Vernier Effect (VE) based strain sensor, which comprises two parallel air cavity Fabry-Perot Interferometers (FPI). The sensor involves simple fabrication techniques, such as cleaving and fusion splicing. A small section of Double Side Hole Fiber (DSHF) is cleaved and spliced between two pieces of Single Mode Fiber (SMF). The core of the SMF-1 and the air core of the DSHF are aligned by a minor lateral offset to make an air cavity FPI. During the strain measurement, the sensor exhibits the strain sensitivity of 36.7 pm/mu epsilon. The sensor improves the sensitivity with the highest amplification factor of 10. In addition, the proposed strain sensor shows the temperature sensitivity of only 1 pm/degrees C in the temperature range of 30 degrees C-100 degrees C, which has temperature cross-sensitivity of 2.72 x 10-2 mu epsilon/degrees C, and appear to be insensitive to temperature. The proposed device has high strain sensitivity, low temperature cross-sensitivity, simple fabrication, and low cost. Therefore, it has many applications in different engineering fields, for example, structural health monitoring and civil engineering.