Simultaneous measurement of temperature and ionizing radiation dose based on type-II FBGs inscribed in P-doped optical fibers

A novel approach for the simultaneous measurement of radiation dose and temperature using Type-II fiber Bragg gratings (FBGs) inscribed on phosphorus (P)-doped optical fibers is proposed. For the first time, a Type-II FBG inscribed on a P-doped optical fiber was irradiated within the core of a nuclear reactor, exposing the sensor to both gamma radiation and neutron flux. This work provides new insights into the effects of reactor irradiation on Type-II FBGs in P-doped fibers, demonstrating that the radiation-induced Bragg wavelength shift is only slightly higher compared to FBGs inscribed in pure silica core fibers. Furthermore, the reactor irradiation serves to illustrate the proposed method for simultaneous temperature and radiation dose sensing using a single FBG. The proposed technique can be easily multiplexed along a single optical fiber to provide multiple sensing points, each capable of discriminating temperature and radiation dose. While the method is constrained by the maximum radiation dose at which the P-doped fiber experiences total darkening, it remains applicable for a wide range of environments, including ex-core measurements in nuclear reactors and various locations within particle accelerators.