The characteristics of a fiber Bragg grating (FBG) temperature sensor using thermal expansion of an external tube is presented. For enhancement of the temperature sensitivity of a bare FBG fiber, both sides of the FBG fiber were glued with epoxy to a cylindrical ceramic tube as an external tube and. pulled due to the thermal expansion of the cylindrical ceramic tube, which was made of hard, fracture-tough Zirconia (ZrO(2)) with higher thermal expansion coefficient. The presented FBG sensor was heated on the surface of the hot plate at temperature from -5 degrees C to 100 degrees C and had a response time of 6 seconds/degrees C. The temperature sensitivity of the fabricated FBG temperature sensor was improved 2.84 times when compared to that of a bare FBG fiber. The coupling characteristic of the fabricated FBG temperature sensor was analyzed by using coupled-mode theory.