Seismic-Physical Modeling Using a Micro Quasi-Michelson Fiber-Optic Interferometer

A microfiber-optic interferometer was proposed and demonstrated experimentally. The device only comprised a fiber-optic taper containing a refractive index modification (RIM) region that was written by a femtosecond laser. The coupling and recoupling of core-to-cladding modes were improved by the RIM to be “window-like.” A well-defined interference spectrum was obtained because of the interference between the recoupled high-order modes based on the quasi-Michelson interference mechanism. Using the spectral-side band filtering technology, the ultrasonic wave (UW) was detected with a high sensitivity by the proposed interferometer. The key to the success of the sensor is that the microtaper sensing fiber is more easily stretched by the UW-induced strain. Moreover, the interferometer was equipped with a cone-shaped horn to further promote the UW sensitivity of the sensor due to its acoustic focusing performance. This sensor offers a better method to realize seismic-physical modeling by scanning detection and reconstructing the echoes.