A detailed investigation of the frustrated-total-internal-reflection (FTIR) phenomenon in silica-glass-based optical fibers and its application to simple intensity-modulated strain and pressure sensors is presented. Such sensors may be readily fabricated with silica-based fibers and can be easily modified with sapphire fibers for high-temperature industrial applications where conventional silica-based fiber sensors are not feasible. We present the all-fiber FTIR sensor and show good correlation between theory and experiment. We also present results for the design and implementation of a prototype FTIR-based fiber pressure sensor. (C) 1997 Optical Society of America.