Optical Fiber Mach-Zehnder Interferometric Strain Sensor Basedon Concatenating Two Micro Cavities Fabricated by A Femtosecond Laser

An optical fiber Mach-Zehnder interferometer (MZI) is proposed by concatenating two micro cavities that are fabricated by a femtosecond laser. The interferometer is applied for strain sensing with a sensitivity of -664.2 nm/specialeqno=”A2” which is comparable to long period fiber grating and taperbased strain sensors. Also, it exhibits a good reversibility in loading and unloading processes. The relationship between intensity variation and applied strain is a quadratic function. The refractive index dependence and temperature dependence of the interferometer are also investigated. Further, this structure is more robust than taper- or trench-based fiber sensors because of no reduction in fiber diameter direction.