Fiber Optic Dual-Ring Michelson Interferometer-Based Detection Scheme for the Measurement of Dynamic Signals

A fiber optic dual-ring Michelson interferometer (DRMI) based detection scheme for the measurement of dynamic signals is proposed and experimentally demonstrated. The fiber optic sensor is a single mode fiber between two broadband fiber Bragg gratings (FBGs) with different center wavelengths. The two FBGs are connected to two output ports of a 3 x 3 coupler to compose a DRMI. High responsivity and wide frequency response range can be achieved at the same time. The scheme has high reliability, in which the undesirable external perturbation applied to interferometric arms is removed. A DRMI-based vibration sensor and a DRMI-based acoustic sensor are fabricated and experimentally investigated. For the DRMI-based vibration sensor, a responsivity of 12.8 rad/g is obtained, and the resonant frequency is 825 Hz. The minimum detectable acceleration is 54 mu g / root Hz at 300 Hz. The acoustic sensor is used to detect signals in the frequency range of 0.5-19 kHz. The detection scheme has properties of wide frequency response range, high responsivity, and high reliability.