ABSTRACT Fiber Bragg Grating (FBG) has been widely applied in optical materials for measuring temperature and strain, such as measuring the temperature of the human body. The FBG used were singlemode FBG and a Bragg wavelength of 1550 nm with a reflectivity variation of 10% to 90%. This study aims to analyze changes in human body temperature using a measuring instrument thermometer and FBG. Th…