A review of fiber optic displacement transducer using optical fiber bundle is given as developed by author and co-workers. The transducer consists of an optic lever formed with illuminating fiber and receiving fibers, and an operational amplifier, which can measure up to $10^{-9}$ m range. Recent improvements to the probe are described in this study, which show greater linearity, sensitivity, and flexibility when compared to the original fiber optic lever displacement transducer. The improved transducer performance is examined by using small accelerometer and a typical measurement is performed on a 2-for-1 twister spindle for comparison of vibration response.