Hyun-Kyu Jung

Gamma-Ray Radiation Effect on Non-Resonant Third-Order Optical Nonlinearity of Germano-Silicate Optical Fiber

Gamma-ray radiation effect on the non-resonant third-order optical nonlinearity of the germano-silicate optical fiber has been investigated by the continuous-wave self-phase modulation method. The nonlinear refractive index, n2, of the gamma-ray irradiated optical fiber was found to increase linearly with the increase of the gamma-ray induced absorption. The increased n2 has been mainly ascribed to the NBOs and Ge-realted radiation-induced defects having hyperpolarizabilities.

Gamma-Ray Irradiation-Induced Optical Attenuation in Co/Fe Co-Doped Alumino-Silicate Optical Fiber for Dosimeter Application

Dose dependence of radiation-induced optical attenuation (RIA) at 1310 nm of the Co/Fe co-doped alumino-silicate optical fiber was investigated under gamma-ray irradiation at dose rates from 6.7 to 78.3 Gy/min. From the measured RIA, radiation dose sensitivity (ΔRIA/ΔDose) and rate of RIA change with irradiation time (ΔRIA/ΔTime) at the different dose rates were estimated. RIAs at various wavelengths (800 to 1600 nm) of the optical fiber were also measured and the RIA characteristics at 800 and 1310 nm under discrete gamma-ray irradiation were investigated. The measured RIA of the Co/Fe co-doped fiber showed very high dose sensitivity regardless of the dose rates and the ΔRIA/ΔTime was found to show linear response with respect to the dose rate. The significantly large RIA was attributed to Co, Fe, and Al-related defects in the fiber core which were formed by the irradiation, and it became larger at shorter wavelength. The high radiation dose sensitivity, linear response of the ΔRIA/ΔTime with respect to dose rate, and the high reproducibility of the dose dependence of RIA under the discrete irradiation clearly indicate that the Co/Fe co-doped fiber is able to provide highly accurate information of not only total accumulated dose but also dose rate of the radiation with irradiation time.

Radiation-induced optical attenuation of Co/Fe co-doped alumino-silicate optical fiber for radiation dosimeter application

Possibility of a Co/Fe co-doped alumino-silicate optical fiber as a radiation dosimeter application was investigated from the measurement of radiation-induced optical attenuation (RIA). The RIA at 1310 nm of the optical fiber upon gammaray irradiation was found to increase linearly with the radiation dose. The extent of the RIA increase to 11,900 dB/km at radiation dose rate of 20 Gy/min for 1 hour was 70 times larger than that of the reference single mode fiber and the RIA remained almost constant after 5 minutes of the irradiation termination.

Gamma-Ray Dose-Rate Dependence on Radiation Resistance of Specialty Optical Fiber with Inner Cladding Layers

A germano-silicate glass optical fiber with inner cladding layers of pure silica buffer and boron-doped silica was fabricated to enhance photosensitivity of fiber Bragg grating (FBG) maintaining the radiation resistance for sensing applications. The gamma-ray dose-rate dependence on the radiation-induced attenuation (RIA) and the peak shift of the FBG inscribed in the core of the fiber was investigated. As the γ-ray irradiation on the fiber with the FBG increased to 22.86 kGy/h, the reflected peak power increased together with small temperature increase but the transmitted power at 1550 nm decreased. While the Bragg reflection wavelengths were shifted toward longer wavelengths during the γ-ray irradiation, the FWHM bandwidth remained unchanged. The Bragg peak shift of the FBG was found to saturate at a 78 pm level and the RIA of 1.345 dB/m at 1550 nm was obtained with the accumulated dose-rate of 22.86 kGy/h.