Behavior of Random Hole Optical Fibers under Gamma Ray Irradiation and Its Potential Use in Radiation Sensing Applications

Effects of radiation on sensing and data transmission components are of great interest in many applications including homeland security, nuclear power generation, and military. A new type of microstructured optical fiber (MOF) called the random hole optical fiber (RHOF) has been recently developed. The RHOFs can be made in many different forms by varying the core size and the size and extent of porosity in the cladding region. The fibers used in this study possessed an outer diameter of 110 μm and a core of approximately 20 μm. The fiber structure contains thousands of air holes surrounding the core with sizes ranging from less than 100 nm to a few μm. We present the first study of the behavior of RHOF under gamma irradiation. We also propose, for the first time to our knowledge, an ionizing radiation sensor system based on scintillation light from a scintillator phosphor embedded within a holey optical fiber structure. The RHOF radiation response was compared to normal single mode and multimode commercial fibers (germanium doped core, pure silica cladding) and to those of radiation resistant fibers (pure silica core with fluorine doped cladding fibers). The comparison was done by measuring radiation-induced absorption (RIA) in all fiber samples at the 1550 nm wavelength window (1545 ± 25 nm). The study was carried out under a high-intensity gamma ray field from a (60)Co source (with an exposure rate of 4×10(4) rad/hr) at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values < 10(6) rad, was observed in all fiber samples except in the pure silica core fluorine doped cladding fiber which showed RIA saturation at 0.01 dB. RHOF samples demonstrated low RIA (0.02 and 0.005 dB) compared to standard germanium doped core pure silica cladding (SMF and MMF) fibers. Results also showed the possibility of post-fabrication treatment to improve the radiation resistance of the RHOF fibers.