Development of A Low Cost Real Time Strain Monitoring System using DSP Technique Deepika Shukla 1 , Dr. S. K. Ghorai 2 1 Birla institute of technology, Mesra, Ranchi, India, Email 1 - rashi090@gmail.com 2 Birla institute of technology, Mesra, Ranchi, India, Email 2 - skghorai12@gmail.com Abstract— This paper illustrates the development of a low cost strain monitoring system, using a FBG and a LPG. A tensile strain is applied on a dual supported beam structure. The FBG used here works as a sensing head and the LPG as an edge filter. The use of edge filter is to modulate the Broadband source. The proposed scheme is based on the intensity measurement; a linear relationship between the intensity and strain is obtained. A photo detector is used for optical to electrical conversion. The converted electrical signal is applied as input to the DSP kit TMS320F2812 for continuous signal monitoring and data logging. The obtained data is processed in MATLAB to extract the information of the applied strain in terms of intensity level, which is then located on the fitted linear curve used as a reference. Results are obtained for different values of strain applied on a dual supported beam structure. Thus we obtain a low cost real time monitoring system to give output directly in terms of applied strain on the structure. I. INTRODUCTION Most of the Fiber Bragg grating (FBG) based sensors use wavelength-shift as the key observation. This wavelength shift is observed using Optical Spectrum Analyzer (OSA). This has been intensively investigated due to their high precision and great potential in measuring various parameters such as strain, temperature, humidity, refractive index, etc. But measuring of these parameters using makes the whole measuring system costly and bulky. The FBG sensors based on the intensity measurement are now mostly accepted in practice because of its low cost and easier installation. Fiber Bragg grating has very wide application in health monitoring of civil structures, aerospace industries, etc. All these fields require the continuous monitoring of the changing parameter like pressure, temperature, humidity etc. and also to store real time data for future analysis. Many methods have been proposed for the intensity based measurements for various parameters. In our paper we propose a real time FBG based signal monitoring system using DSP kit TMS320F2812 which also stores real time data that can be processed and analyzed in future. The optical signal coming out from the FBG sensor is first converted to electrical voltage form using photodetector. The analog output voltage from photodetector is then applied at ADC input of DSP kit. The ADC output gives a quantized value corresponding to the applied input voltage which is processed to obtain the information about the applied strain. II. THEORY A. Fiber Bragg grating Fiber Bragg grating (FBG) sensor has been recognized as a new non-destructive evaluation (NDE) technique to measure the performance of structure this under varying physical conditions like strain, temperature etc. The advantage of using FBG sensor for strain sensing application is that it is able to measure strain locally with high resolution and accuracy. As the physical size of an optical fiber is extremely small compared with other strain measuring components, it enables to be embedded into structures for determining the strain distribution without influencing the mechanical properties of the host materials. A fiber Bragg grating is designed with distributed pattern of dopant materials. The designed pattern has a constant grating spacing of few hundreds nano-meter. The strain variation in the grating region is determined by the reflected wavelength shift from the sensor. According to Bragg's law, the reflected wavelength is given as λ B = 2 η eff Λ (1) Where η eff is the core refractive index and Λ is the grating period of the index modulation. Any changes of the strain in the grating region result in changing of grating period 1 2011 International Conference on Multimedia, Signal Processing and Communication Technologies 9781457711077/11/$26.00 ©2011 IEEE