A Miniature high-temperature fiber-optic sensor based on tip-packaged Fabry-Perot interferometer

In this paper, we propose and demonstrate a miniature high-temperature fiber-optic sensor based on tip -packaged Fabry-Perot interferometer which is insensitive to changes in external refractive index and can maintain good temperature sensing characteristics. The sensor is built by splicing a piece of a suspended-core optical fiber (SCF) to single mode fiber (SMF). In addition, we propose two packaging methods. One is pack-aged by a section of hollow core fiber (HCF) whose the other end is discharged to form a tapered structure and the other is packaged by a section of SMF. The temperature sensitivities of these two sensors increase from 11.10 pm/ degrees C to 20.10 pm/ degrees C and 10.93 pm/ degrees C to 20.75 pm/ degrees C over the temperature range of 25-1000 degrees C due to the thermo-optic coefficient (TOC) of silicon is not linear, respectively. Besides, repeatability and stability are verified by heating and cooling the FPI another two times and the hysteresis errors are analyzed. These sensors with the merits of repeatability and stability over a large temperature range are available for many practical engineering applications.