Fiber-optic vibration sensors have the potential to replace conventional technology based on magnetic pick-up coils. Advantages of this technology include immunity to electromagnetic interference, small size and light weight for better coupling, wide bandwidth, large dynamic range, high sensitivity, and potentially low cost. A fiber-optic vibration sensor based on single-mode fiber technology has been built and evaluated for comparison with conventional technology. The device is a grating-based unit designed for quadrature detection. This unit is mounted onto a conventional vibration sensor, and comparisons of the output of the two devices are made.