Fiber-Optic Michelson Interferometer with Faraday Mirrors for Acoustic Sensing using a 3 × 3 Coupler and Symmetric Demodulation Scheme

For the past 40 years, acoustic sensing has been a major avenue for the growth of interfero- metric fiber-optic sensors. Fiber-optic acoustic sensors have found uses in military, commer- cial, and medical applications. An interferometric fiber-optic acoustic sensor is presented utilizing the Michelson interferometer configuration with Faraday mirrors to eliminate po- larization fading. A 3 × 3 coupler is used as the beamsplitting component, and a symmetric demodulation algorithm is applied to recover the phase signal. This sensor has a theoretical resolution of 5.5 pico-strains and room to improve. Such improvements are discussed in the conclusion.