Over the past several years, many groups have been carrying out research in the area of fiber optic sensor technology, and many types of fiber sensors have been developed. Two of the most promising fiber optic sensor types will be discussed in this talk: phase-modulated single mode interferometric sensors and intensity modulated multimode fiber sensors. Phase-modulated sensors, which utilize an all fiber Mach-Zehnder interferometer, have high sensitivity and geometric versatility. Since the phase sensitivity of a fiber depends primarily on its coating, different fiber coatings can be utilized to detect various physical perturbations, such as acoustic, magnetic, electric, and thermal. The intensity modulated sensor is based on microbending losses which depend on the amplitude of the bend of a multimode fiber. The microbend sensor has moderate sensitivity, simple optical and electronic construction, and utilizes available multimode technology. If the fiber deformer mechanical design is tailored to a given external perturbation, various fields, such as acoustic, pressure, acceleration, and magnetic can be detected. In this talk, the transduction mechanism of each sensor type will be discussed and mechanical designs for detecting various fields will be presented.