Fiber Bragg gratings inscription with a single UV laser pulse by high-temperature arc pretreatment

This study proposes a high-temperature arc discharge pretreatment method to enhance the photosensitivity of hydrogen-loaded germanium-doped fibers for single-pulse FBG inscription. By coupling hydrogen diffusion dynamics with hydroxyl reaction kinetics, a numerical model based on Fick's law and Arrhenius equations was established. Finite difference analysis revealed that 400°C with 50 ms heating maximizes hydroxyl concentration while suppressing hydrogen escape. In the experiments study, the pretreatment temperature and duration are controlled by adjusting the electrode discharge power and discharge time. The effectiveness of fiber sensitization is verified through single-pulse grating writing using a phase mask and a 248 nm ultraviolet laser. After optimizing the heat treatment parameters, fiber Bragg gratings (FBGs) with a reflectivity exceeding 83.7% were successfully written using a single pulse laser of 160mJ, representing a 130-fold improvement compared to the results obtained without heat treatment. This method not only enhances the efficiency of FBG writing but also fundamentally mitigates the issue of grating erasure, significantly reducing the stability requirements for the writing system.