Development of highly radiation resistant fiber Bragg gratings

Fiber Bragg gratings with a radiation-induced wavelength shift of <5 pm up to gamma doses of 1 MGy were written with a femtosecond IR laser into Ge-free radiation hard optical fibers. At -50°C the wavelength shift is only about a factor of two higher. After a dose of 1 MGy their tensile stress sensitivity decreased by about 4%. However, it is still necessary to improve their stability before they can be used for temperature and stress sensing in high radiation dose environments.