An acoustic vibration sensor is investigated and demonstrated by using a tapered triple cladding fiber (TCF). It is
fabricated by tapering a length of 2 cm TCF which is spliced between two single mode fibers (SMF). The TCF consists of
core, inner cladding, middle cladding and outer cladding. After the tapering process, this structure becomes a tapered
coaxial fiber coupler which presents a periodic filtering transmission spectrum. The surrounding vibration perturbation can
be directly demodulated by intensity detection of the transmission power at a particular wavelength. The experimental
result shows that the maximum frequency response of 700 kHz is achieved.