Prestressed Fiber Bragg Grating With High Temperature Stability

A prestressed fiber Bragg grating with high temperature stability has been successfully fabricated by use of 800 nm femtosecond laser pulse irradiation through high-temperature annealing, followed by a rapid cooling treatment. The reflectivity and the resonant wavelength of the grating are maintained constants for more than 26 h in an isothermal measurement up to 1200°C, showing significant improvement over conventional femtosecond laser pulse induced fiber gratings. Longitudinal tension tests demonstrate that the prestressed fiber exhibits enhanced mechanical robustness compared with the residual stress relaxed fiber. This paper reveals that residual stress plays an important role and essentially provides a new solution to enhance the thermal stability of fiber gratings at elevated temperatures and offering high reliability.