Cascaded multiple Fabry-Perot interferometers fabricated in multimode fiber with a waveguide

We demonstrate cascaded multiple Fabry-Perot interferometers in multimode fiber with a waveguide, inscribed by femtosecond laser micromachining. The device can sustain high temperature up to 1000 degrees C, and the temperature sensitivity obtained is 10.1 pm/degrees C and 17.1 pm/degrees C within the temperature region 100-400 degrees C and 400-1000 degrees C respectively. Compared with single-mode fiber, multimode fiber has a larger core diameter and a higher numerical aperture, allowing more optical power to be coupled from the light source. Thus the optical fiber sensors based on multimode fiber do not have high requirements on the light source used, the system cost can be reduced.