The use of real time cylinder pressure information in advanced diesel engine monitoring and control techniques offers the potential for improved engine reliability and performance as well as reduced levels of emissions. This paper reports the design and performance of Optrand high-temperature, long-life, and miniature fiber-optic pressure sensor that has been specifically developed for engine control and monitoring applications. For use in automotive diesel engines the sensor is preferably integrated with a fuel injector or a glow plug. Laboratory and various engine tests are reported here for small and large diesel engines demonstrating a typical +/-0.5% total error due to non-linearity, hysteresis, and thermal shock. In various engines the sensor has already demonstrated the unprecedented lifetime of 0.8 Billion-pressure cycles.