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 that share the same fiber. The output of the Sagnac interferometer is proportional to 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 disturbance magnitude 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.