Measurements of growth and decay of radiation induced attenuation during the irradiation and recovery of plastic optical fibres M.S. Kovacˇevic´ a,b,n , S. Savovic´ a,b , A. Djordjevich b , J. Bajic´ c , D. Stupar c , M. Kovacˇevic´ d , S. Simic´ a a University of Kragujevac, Faculty of Science, Kragujevac, Serbia b City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China c University of Novi Sad, Faculty of Technical Science, Serbia d Vincˇa Institute of Nuclear Sciences, Belgrade, Serbia article info Article history: Received 16 August 2012 Received in revised form 17 September 2012 Accepted 17 September 2012 Available online 12 October 2012 Keywords: Plastic optical fibres Gamma radiation Radiation induced attenuation abstract In this work, we present the experimental study of the radiation-induced attenuation in step-index polymethyl–methacrylate based plastic optical fibre by exposure to low dose rate ionizing radiation. The low dose exposure has been found to induce significant permanent attenuation in plastic optical fibres. Based on the experimental results, the formula between radiation-induced attenuation and radiation dose is obtained accordingly. The recovery properties of plastic optical fibre also were investigated. The fibre begins to recover immediately after irradiation, but it does not fully recover, i.e. the irradiation leads to permanent damage of polymer. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction The growth of Internet traffic in the past decade has led to an increasing demand for data transmission capacity even in local area networks (LANs) and home networks. Silica-based multi- mode optical fibres (MMFs) have been proposed and utilized for Gigabit Ethernet and 10-Gb Ethernet [1,2]. It can provide such a high-speed network with a lower cost than by single mode silica fibres. On the other hand, plastic optical fibres (POFs) having much larger core (120–1000 mm) than silica fibres is expected to be the office- and home-network medium because its large core and great mechanical flexibility allow an easy network installa- tion. The attractiveness of POFs is due chiefly to their low cost, flexibility and ease of handling and interconnecting, while their relatively high attenuation limits the range of systems using them [3]. The main types of POFs, their manufacturing and possible present and expected future applications have been reported [4,5]. The status of POF development over the past half century of focusing on the loss reduction and bandwidth enhancement has been presented by Koike and Koike [6] and Koike and Asai[7]. Fibre–optic characteristics can be classified as linear and nonlinear. Linear characteristics include attenuation, chromatic dispersion, polarization mode dispersion and optical signal-to-noise ratio. Nonlinear characteristics are influenced by parameters, such as bit rates, channel spacing, and power levels. Many studies have been conducted to research the nonlinear characteristics including self-phase modulation, cross-phase modulation, four-wave mixing, stimulated Raman scattering and stimulated Brillouin scattering [8–12]. Effects of radiation on sensing and data transmission of optical fibres are of great interest in many applications including space application, nuclear industry, nuclear medicine, high energy phy- sics experiments and military. It is well-known that plastic optical fibres can be very sensitive to ionizing radiation [13–15]. Even at low total doses, the optical attenuation of the fibre can significantly increase. Radiation-induced attenuation (RIA) is primarily due to the main chain scission and cross linking in the fibre core. These degradations give rise to the radiation-induced optical attenuation. The radiation-induced attenuation depends on fibre type, fibre temperature, wavelength and intensity of the injected light, and irradiation conditions (especially dose rate and total dose). The influence of low dose radiation-induced attenuation on data transfer using multimode POFs is of great interest in high energy physics experiments, nuclear medicine and military. The use of the RIA as a radiation sensing principle has already been proposed [16,17]. All of these applications of fibre systems should consider influence from irradiation and their hardness against optical attenuation induced by irradiation. In recent years, the behaviour of optical fibres under g rays irradiation has been actively inves- tigated [18–21]. Fundamentals about theory of radiation induced absorption in optical fibres can be found in [22–24]. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/optlastec Optics & Laser Technology 0030-3992/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.optlastec.2012.09.019 n Corresponding author at: University of Kragujevac, Faculty of Science, Kragujevac, Serbia. Tel.: þ381 34 336 223; fax: þ381 34 335 040. E-mail address: kovac@kg.ac.rs (M.S. Kovacˇevic´). Optics & Laser Technology 47 (2013) 148–151