Abstract
Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF) called the random hole opticalfiber (RHOF) has been recently developed. The RHOFs can be made in many differentforms 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 ofapproximately 20 μm. The fiber structure contains thousands of air holes surrounding thecore with sizes ranging from less than 100 nm to a few μm. We present the first study ofthe behavior of RHOF under gamma irradiation. We also propose, for the first time to ourknowledge, an ionizing radiation sensor system based on scintillation light from ascintillator phosphor embedded within a holey optical fiber structure. The RHOF radiationresponse was compared to normal single mode and multimode commercial fibers(germanium doped core, pure silica cladding) and to those of radiation resistant fibers (puresilica core with fluorine doped cladding fibers). The comparison was done by measuringradiation-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 60Co source (with an exposure rate of 4x104 rad/hr) at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values less than 106 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.
Highlights
Use of optical fibers in environments with significant radiation exposure potential may allow operation of optical fiber sensors and optical communication/data links in situations where conventional electronic systems may fail
Photonic crystal fibers (PCF), which belong to a class of fibers known as microstructured optical fibers (MOF) or “holey fibers”, were first reported in [1] and have been the subject of intensive research since the 1990s
We report the first study of the behavior of the new random hole optical fiber (RHOF) under gamma irradiation and propose an ionizing radiation sensor system based on luminescence from a scintillator phosphor embedded within the RHOF microstructure
Summary
Use of optical fibers in environments with significant radiation exposure potential may allow operation of optical fiber sensors and optical communication/data links in situations where conventional electronic systems may fail. A wide variety of different PCF structures has been proposed (mainly differing in the size, spacing and number of air holes present in the cladding region), including hollow core PCFs. Photonic crystal fibers are known to have ordered holes in which the holes occur in a uniform or regular pattern. A new type of MOF, called the random hole optical fiber (RHOF), has been developed [2] In this type of fiber, thousands of air longitudinal holes which are random in both size and spatial location surround the pure silica core [3]. The size, number and location of the holes occurring in these fibers can be controlled to produce a variety of different properties in the fiber These fibers have been described previously by our group and so will only be reviewed briefly here with respect to the fabrication and resulting microstructures
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