In this paper, we presented adaptive interferometry as a way to realize distributed fiber optic sensors based on multimode fibers, which enables to improve the interferometer phase sensitivity. We focused on the adaptive interferometer description and evidenced its low frequency cut-off, allowing the filtering of slowly varying perturbations. The interferometer sensitivity is about 200 at about 1kHz corresponding to 1.73pstrain on the sensing fiber. Strain resolution should reach about 0.02pstrain using a highly MMF instead of a single mode fiber. Then, on one hand, we demonstrated SNR enhancement by using a multimode fiber to detect a phase modulation, rather than a single mode one. On the other hand, we presented a localization experiment based on a phase-OTDR in a single mode fiber. Future work will be dedicated to combine AHI and Phase-OTDR into a multimode fiber in order to evaluate the sensitivity and the potential of the overall architecture. Particular attention will be dedicated to enhance spatial resolution and to phase localization at several locations along the sensing fiber simultaneously.