International Journal of Electrical and Computer Engineering (IJECE) Vol. 10, No. 3, June 2020, pp. 3158~3165 ISSN: 2088-8708, DOI: 10.11591/ijece.v10i3.pp3158-3165  3158 Journal homepage: http://ijece.iaescore.com/index.php/IJECE Design of fiber bragg grating (FBG) temperature sensor based on optical frequency domain reflectometer (OFDR) Nani Fadzlina Naim 1 , Siti Noor Maslizan Sudin 2 , Suzi Seroja Sarnin 3 , Norsuzila Ya’acob 4 , Latifah Sarah Supian 5 1,2,3,4 Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), Malaysia 5 Fakulti Kejuruteraan, Universiti Pertahanan Nasional Malaysia, Malaysia Article Info ABSTRACT Article history: Received Mar 18, 2019 Revised Dec 3, 2019 Accepted Dec 11, 2019 In this paper, the simulation of Fiber Bragg Grating (FBG) as a temperature sensor is conducted. The FBG temperature sensor is designed based on Optical Frequency Domain Reflectometer (OFDR) concept. A continuous wave (CW) laser is used as the optical source and it is transmitted to two FBGs. The two FBGs reflection spectra will produce a beat frequency that can be detected using a Radio Frequency (RF) spectrum analyzer. Any temperature change will shift Bragg wavelength, thus produce a shift for the beat frequency. In this work, an FBG with temperature sensitivity 10 pm/˚C is employed. It is found that by using this technique, a high-resolution temperature sensor can be designed with temperature resolution of 0.1˚C. Keywords: Fiber bragg grating Optical frequency domain Reflectometer (OFDR) RF spectrum analyzer Temperator sensor Copyright © 2020 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Nani Fadzlina Naim, Fakulti Kejuruteraan Elektrik, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia. Email: nanifadzlina@uitm.edu.my 1. INTRODUCTION Nowadays, there is a rapid growth of optical fiber technology, especially on fiber optic sensor. In various smart structures such as pipeline, bridge, aircraft, ship, and others, one of the most important parameters is temperature [1]. This is because most of the structures always been exposed to any physical changes like temperature, strain, and pressure and can result in damage, destruction, and risks to human. Recently, numerous optical temperature sensors have been proposed using various techniques. For instance, temperature sensors based on Long Period Gratings (LPG) [2], fiber tapers [3-4], multimode interference [5] and Fiber Bragg Gratings (FBG) [6-13]. To the best of the authors’ knowledge, FBG is one of the most renowned optical temperature sensors. Theoretically, any temperature change will shift the FBG Bragg wavelength. Commonly, the Bragg wavelength shift of FBG is monitored by using an optical spectrum analyzer (OSA). However, OSA has its own limitations in response time, resolution, weight, size, and cost [14]. To overcome these issues, RF spectrum analyzer is introduced. Hence, Fiber Bragg Grating (FBG) as temperature sensor using RF spectrum analyzer is proposed. In this work, we are focused on technique to be used to designing a high- resolution temperature sensor. Aside from this technique, there are some techniques from another researcher that can relate to FBG temperature sensor. As studied by [15], they develop fiber-optic sensor that have a high-resolution and high-speed temperature measurement based on silicon Fabry-Pérot cavity. The silicon pillar is attached on the tip of a single-mode fiber to fabricate it and have 6×10 -4 °C as the temperature resolution. [16] Has researched the sensor head of FBG to be focused with convex and hand lens, evaluated by varying of focusing elements in harsh environments. They discovered that for both systems, the Bragg