A simple optical fiber cantilever vibration sensor consisting of two opposite aligned bare optical fibers sealed in a quartz capillary is presented.The fiber with the longer bare section is suspended in air and acts as a cantilever. By detecting the transmission power of the sensor directly, the environmental vibrational frequencies and amplitudes may be obtained. By adjusting the cantilever's natural deflection angle, the sensor can achieve high sensitivity, good response linearity, and a wide dynamic range. Coupling conditions are optimized to minimize temperature effects by simply setting an appropriate air gap between the bare fibers.