Micromachining of an in-fiber extrinsic Fabry-Perot interferometric sensor by using a femtosecond laser

The fabrication of a micromachining extrinsic Fabry-Perot (F-P) interferometer (MEFPI) within a conventional single-mode fiber (SMF) by using a 800 nm femtosecond laser was reported in this paper. The strain and temperature characteristics of the MEFPI are investigated. The experimental results show that the strain sensitivity is 0.006 nm/με, and linearity is 99.69% at the range of 0 to 350 με. Furthermore, the interference fringe of the MEFPI shifts about 0.15 nm to the short wavelength while the temperature rises from 20°C to 100°C, Such kind of in-fiber interference sensors has many advantages, such as compact size, good reliability, low cost, easy fabrication and mass-production, which offers great potential for sensing applications.