We present for first time the detailed investigation on the effect of MGy (10~6 Gy) dose level of gamma radiation on the parameters of CO_2 laser-written long-period fiber gratings (LPFGs) in B/Ge-doped single-mode fibers with particular attention to lower-order modes and higher order nonturnaround point (non-TAP) modes. Wavelength shifts up to 11 nm for 100 kGy dose and a further shift of 20 nm (1.5 nm/100 kGy) for dose of 900 kGy (total 1 MGy) were observed. Further, the radiation-induced shifts of resonant modes did not saturate up to a 1 MGy dose. No remarkable changes were observed in width and amplitude of the resonant dips during in-situ measurements up to the full dose irradiation. The radiation sensitivity up to 100 kGy was found to be independent of the grating period. This study shows that LPFGs in boron-doped fibers are strong candidates for very high-dose sensing applications such as in super Large Hadron Collider (LHC) and International Thermonuclear Experimental Reactor (ITER).
展开▼
