Femtosecond point-by-point inscription of fiber Bragg gratings through the polyimide coating

The paper presents the results on Bragg gratings inscription in non-photosensitive optical fibers through the polyimide protective coating by femtosecond radiation with the wavelength of 1026 nm. The Bragg gratings inscribed by a point-by-point method in specialized optical fibers: high-temperature resistant Fibercore SM1500(9/125)P and hydrogen resistant Fibercore SM1500SC(9/125)P have reflectivity 50-90%.