This article reports the design and deployment of two optical-fiber temperature sensors based on the fiber Fabry-Perot etalon. The first involved the use of an extrinsic fiber Fabry-Perot sensor, but in this instance, the coefficient of thermal expansion of the reflector and/or capillary was chosen to offer a mismatch. Hence, the cavity length could increase or decrease according to the coefficient of thermal expansion of the fiber and/or capillary. For comparison, single-mode and multimode optical-fiber Bragg gratings were also used as temperature sensors. The Fabry-Perot sensors operated from -50 to 410degreesC. The accuracy of the measurements was up to 0.5degreesC with a low-cost charged-coupling-device spectrometer. The sensors also worked effectively in a microwave oven and in a composite panel in an autoclave. (C) 2004 Wiley Periodicals, Inc.