This Letter presents intrinsic Fabry–Perot interferometers in the fiber tapers fabricated by the femtosecond laser micromachining technique. The sensing of temperatures as high as 1000°C based on the fiber device is characterized, with a sensitivity of 15.28 pm/°C. A nearly linear refractive index sensing is also obtained by using the fringe visibility to characterize, with a sensitivity of 73.05 dB/RIU. These intrinsic Fabry–Perot interferometers in fiber tapers may be useful in applications of high-temperature and linear refractive index sensing.