Modified sagnac/mach-zehnder interferometer for distributed disturbance sensing

We propose an alternative configuration for an interferometric distributed fiber optic sensor. The sensor uses a combination of Mach–Zehnder and Sagnac interferometers sharing the same fiber. The output of the Sagnac interferometer is a function of the product of the position where the disturbance was applied and the magnitude of the disturbance. The output of the Mach–Zehnder interferometer is a function of the magnitude of the disturbance only. The position and magnitude of a disturbance applied to the sensing fiber can thus be obtained from these two signals. Results obtained with a 200 m distributed fiber sensor are discussed.