(IIHFWRIFRPELQHGJDPPDQHXWURQUDGLDWLRQRIPXOWLSOH[HGILEHU%UDJJ JUDWLQJVHQVRUV Andrei GUSAROV a,b,*1 , Alberto FERNANDEZ FERNANDEZ b,d , Francis BERGHMANS b,e , Sergei VASILIEV c , Oleg MEDVEDKOV c , Marc DÉCRETON b , Olivier DEPARIS a , Patrice MEGRET a , Michel BLONDEL a a Faculté Polytechnique de Mons, bd. Dolez 31, B-7000 Mons, Belgium b SCK·CEN, Belgian Nuclear research Centre B-2400 Mol Belgium, c Fiber Optic Research Center, Vavilov str.39, Moscow, Russia d ULB, 50 av. F.D. Roosevelt, CP165/41, B-1050 Bruxelles, Belgium e Vrije Universiteit Brussel, Pleinlaan 2, B-1050, Brussel, Belgium Optical fiber technology is considered now for communication and sensing applications in various radiation environments, like space and nuclear industry. We report on results from an on-going experimental program, which aims at using multiplexed Fiber Bragg gratings (FBGs), essential photonic components, for in-pile temperature monitoring in a nuclear reactor. To the best of our knowledge, its is the first time that multiplexed FBG-sensors are used in such conditions. Radiation effects, photonic components, optical fiber sensors, fiber Bragg gratings Optical fibre sensors (OFS) are developed to replace conventional electro-mechanical sensing systems. The advantages of OFS include immunity to electromagnetic interference, intrinsic safety, mechanical simplicity, small size, a possibly high sensitivity, multiplexing capabilities, and remote interrogation. These features make OFS an interesting alternative for application in nuclear industry. However, the necessary safety regulations make nuclear industry very conservative. In contrast to electro-mechanical sensors, which are well established, have proven their reliability and can be manufactured at known cost, the reliability of OFS is still an issue. As a result, the number of practical implementations of OFS in nuclear environments remains very limited. The main goal of our experimental study is to asses the radiation hardness of a particular type of OFS – fibre Bragg grating-based sensors. The most obvious effect of radiation action on an optical fibre is an increase of the attenuation 1 . It was recently demonstrated that failure of commercial-off-the-shelf optical fibre sensors under radiation is related to this induced attenuation and the sensors have to be redesigned to withstand radiation 2 . The advantage of a FBG-sensor is that the information about the measured parameter is encoded in a narrow band (1-2 nm) and, therefore, should be insensitive to broad-band (bandwidth > 100 nm) radiation-induced losses. A FBG is an all-fiber device, which originates from a periodic fiber index modulation. Such periodic modulation may couple different waveguide modes, and in particular forward and backward propagating modes in a single-mode fibre thus resulting in reflection. The reflection spectrum is peaked around the Bragg wavelength λ B , defined by the Bragg condition: λ B = 2n eff Λ, where n eff is the refractive index of the guided mode and Λ is the grating pitch. The use of a FBG as a sensor is 1 Corresponence: E-mail: gusarov@telecom.fpms.ac.be, Fax: +32 65374199, Photonics for Space Environments VII, Edward W. Taylor, Editor, Proceedings of SPIE Vol. 4134 (2000) © 2000 SPIE · 0277-786X/00/$15.00 86 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 12/18/2013 Terms of Use: http://spiedl.org/terms