International Journal on Recent and Innovation Trends in Computing and Communication ISSN: 2321-8169 Volume: 2 Issue: 12 4070 - 4074 _______________________________________________________________________________________________ 4070 IJRITCC | December 2014, Available @ http://www.ijritcc.org _______________________________________________________________________________________ A Novel Approach for Simple Distributed Brillouin Scattering Modeling for Temperature and Strain Sensing Abstract— Distributed fiber optic technology offers the capability to measure strain and deformation at thousands of points along a single fiber up to tens of kilometers. This is of particular interest for the monitoring in the geotechnical structures where it allows the detection and localization of ground movements.This paper presents the analysis by simulation of stimulated Brillouin scattering (SBS) in optical fibres. Brillouin scattering refers to the scattering of a light wave by an acoustic wave. When this process occurs in an optical fibre, the back-scattered light suffers a frequency shift (the Brillouin frequency) which is dependent on the temperature and strain of the fibre. The behaviour of stimulated Brillouin scattering in optical fibres are studied through the backscatter signals. The analysis of parameters affecting backscattered signal power is presented. All the developed simulation models exhibit exceptional analysis accuracy as verified through comparison with the published measurement results Keywords-Brillouin scattering; MATLAB; temperature; strain; sensing __________________________________________________*****_________________________________________________ I. INTRODUCTION Optical fiber has advanced rapidly in current technologies and has found many important applications in recent years. Optical fiber is a physical medium that experiences geometrical (size, shape) and optical (refractive index, mode conversion) changes when subjected to perturbation, which become the essence of distributed fiber optic sensing [1]. Of particular interest, temperature and strain can be sensed by optical fiber over long distances. Any change in temperature or strain causes the refractive index of silica (material of optical fibres) to change in response to such variations. At high guided light intensity, a nonlinear effect, namely stimulated Brillouin scattering (SBS), is also be affected by the change in refractive index [1]. This change is registered as a change in Brillouin shift, as well as the backscattered Brillouin power. The distribution of temperature and strain over long distances can thus be obtained by measuring the change in these parameters. Such sensors are also known as distributed fiber sensors. This paper focuses on simulation of intrinsic distributed fiber optic sensors based on Brillouin scattering for temperature and strain sensing. The Brillouin fiber sensor utilises optical time domain reflectometry (OTDR) for sensing signal detection, as illustrated in Fig. 1. The behaviors of the Brillouin and Rayleigh scattering in the OTDR system are studied for various system conditions, such as laser power, line width, in terms of backscattered signal power through computer simulations. The influence of the dominant noise source, which is coherent Rayleigh noise (CRN), is also incorporated in the simulations and thorough analyses are performed to identify ways for improvement to system sensitivity. The characteristics of backscatter signals when affected by the variation in temperature and strain are studied. The simulation results are compared to the published measurement to verify the accuracy of the developed model. Distributed fiber optic sensing has been one of the vital fiber optic technologies developed for sensor applications [2]. Distributed sensing, particularly using Brillouin signal, is highly preferable due to its capability of extracting information such as temperature and strain continuously along the sensing fiber. An accurate model of the device will be a useful tool that enables proper design of a distributed sensor system. This will provide valuable information on the optical and physical limitations, such as the required optical power of laser, optimum sensing fiber length and measurement ranges. Besides SBS, there also exists a linear scattering, called Rayleigh scattering [3]. The nonlinear Brillouin scattering has a power threshold much above the occurrence of the linear Rayleigh scattering. Therefore, the Rayleigh scattering will always present and the coherent fluctuating backscattered signal will corrupt the Brillouin signal. In order to obtain accurate response of the sensor, the influence of the Rayleigh noise should be taken into consideration. Fiber optic sensors have proven to be ideal transducers for structural monitoring. Being durable, stable and insensitive to external perturbations [2], they are particularly interesting for the long-term health assessment of civil and geotechnical structures. Many different fiber optic sensor technologies exist and offer a wide range of performances and suitability for different applications. The most widely used sensing techniques include point sensors (Fiber Bragg Gratings and Fabry-Perot interferometers), long- gauge sensors (SOFO) and distributed sensors (Raman and Brillouin scattering sensors). These sensing technologies are now widely used in routine application for health monitoring of structures such as bridges, buildings, monuments, tunnels, dams, dykes, pipelines, landslides and many others. This contribution reviews these systems and technologies and presents some significant application examples, in particular to Bridges, Buildings, Geostructures and Pipelines. The global energy demand is constantly growing. It forces major actors in the field to access new resources which can be remote, in harsh environment or deeper water depth, and which need to be transported over longer distances. Despite extremely challenging environmental conditions, energy transport structures must show reliability and efficiency. Similarly, civil engineering is also facing monitoring challenges, to survey the evolution and guarantee the safety of existing structures aging Beyond their original design life time or to closely monitor the long term stability of surrounding neighborhood during new Mandeep Kaur Student, M-Tech, ECE IET Bhaddal, roopnagar Punjab, India er.mandeepkaur85@gmail.com Prof. Navpreet Kaur Assistant Prof., Dept. of ECE IET Bhaddal, roopnagar Punjab, India navpreet.ec35@ietbhaddal.edu.in