Sensing characteristics of long period grating by writing directly in SMF-28 based on 800 nm femtosecond laser pulses

摘要

A long period grating is fabricated in standard SMF-28 fibers without hydrogen loading by adopting point-by-point direct writing based on femtosecond laser pulses with 800 nm wavelength and 100 fs pulse width. Its sensing characteristics is investigated and the sensing sensitivities to temperature, external refractive index (RI) and strain are systematically examined as well. The experimental results show that the sensing sensitivity of the long period grating to temperature, RI and strain is about 124 pm/degrees C with a linearity of 0.989 within temperature ranging from 20 degrees C to 800 degrees C, -582.5 nm/RIU (refractive index unit) with a linearity of 0.998 in the RI ranging from 1.342 to 1.380, and -9.45 x 10(-4) dB/mu epsilon with a linearity of 0.98 in the strain ranging from 0 to 2925 mu epsilon, respectively. The high sensitivity of prepared LPG will have potential application values in sensing measurement of multi-parameters and in the field of high temperature and harsh environments detection.