Enhanced temperature characteristics of strain-assisted fiber Bragg gratings inscription by femtosecond laser pulses

Abstract

A strain assisted fiber Bragg grating (S-FBG) has been fabricated by using femtosecond laser mask phase method. The spectral characteristics of the FBG with different pre-stress has been investigated. It was found that the wavelengths of the S-FBGs shift linearity towards shorter wavelength direction as the applied strain increases and show a sensitivity of 0.1596 pm/με and 0.8796 pm/με before and after the stress released, respectively. Moreover, the S-FBGs show better temperature characteristics than the normal FBG, including smaller decay rate of the reflection intensity, smaller wavelength hysteresis effect and better high temperature stability. Meanwhile, the temperature test has demonstrated that the S-FBG with larger pre-stress shows better temperature characteristics. In addition, the S-FBG has advantages of compact size, easy fabrication and high reflection, which is of high interest in developing high temperature sensing platforms.