Adaptive Interferometry for High-Sensitivity Optical Fiber Sensing

Adaptive holographic interferometry is a promising method for high-sensitivity phase modulation measurements in the presence of slow perturbations from the environment. This technique is based on the use of a nonlinear recombining medium. Here, we report the use of an adaptive holographic interferometer based on an optically addressed spatial light modulator. Owing to the physical mechanisms involved, the interferometer adapts to slow phase variations within a range of 5-10 Hz. Moreover, owing to the basic principle of holography, this technique can be used with complex wave fronts such as the speckled field reflected by a highly scattering surface or the optical field at the output of a multimode optical fiber. We demonstrate both theoretically and experimentally, that using a multimode optical fiber as sensing element, rather than a single mode fiber, allows improving the interferometer phase sensitivity. Finally, we present a phase-OTDR optical fiber sensor using the adaptive holographic interferometer.