Abstract Measurement of temperature changes is very important in the fields of physics, chemistry, biology, and industrial applications. The development of temperature sensors also continues to be developed both on an electric and optical basis. In this research, the detection of temperature changes based on optics is successfully detected using optical fiber splitter 1 × 2 by utilizing a plane mirror as a reflector and by stripping the cladding at the end optical fiber. Measurement of the power transmission of reflection to changes in temperature using an optical spectrum analyzer (OSA) at wavelength 1550 nm. This research showed that a linear relationship between transmission power and temperature increase from 40°C to 200°C on the sensor probe with a stripping length of 35 mm.