Implementation of interrogation systems for fiber Bragg grating sensors

Abstract

The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating (FBG) sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG, and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.

Keywords

Fiber Bragg grating / interrogator / reflected power / strain and temperature measurement

References

[1] Udd E, Lawrence C, Nelson D. Development of a three axis strain and temperature fibre optic grating sensor. Proc. SPIE, 1997, 3042, 229-236.

[2] Lee C H, Kim M K, Kim K T, Lee J. Enhanced temperature sensitivity of fiber Bragg grating temperature sensor using thermal expansion of copper tube. Microwave and Optical Technology Letters, 2011, 53(7): 1669-1671.

[3] Kersey A, Davis M A, Patrick H J, Leblanc M, Koo K P, Askins C G, . Fiber grating sensors. Journal of Lightwave Technology, 1997, 15(8): 1442-1463.

[4] Shu X, Zhang L, Bennion I. Sensitivity characteristics of long-period fiber gratings. Journal of Lightwave Technology, 2002, 20(2): 255-266.

[5] Xu M G, Reekie L, Chow Y T, Dakin J P. Optical in-fiber grating high pressure sensor. Electronics Letters, 1993, 29(4): 398-399.

[6] Zhao I Y, Huang H, Wang Q. Interrogation technique using a novel spectra bandwidth measurement method with a blazed FBG and a fiber-optic array for an FBG displacement sensor. Sensors Actuators A: Physical, 2011, 165(2): 185-188.

[7] Liang W, Huang Y, Xu Y, Lee R K, Yariv A. Highly sensitive fiber Bragg grating refractive index sensors. Applied Physics Letters, 2005, 86(15): 151122-1-151122-3.

[8] Yeo T L, Sun T, Grattan K T V, Parry D, Lade R, Powell B D. Characterization of a polymer-coated fiber Bragg grating sensor for relative humidity sensing. Sensors and Actuators B: Chemical, 2005, 110(1): 148-155.

[9] Measures R M. Smart composite structures with embedded sensors. Composites Engineering, 1992, 2(5–7): 597-618.

[10] Zhou G, Sim L M. Damage detection and assessment in fiber-reinforced composite structures with embedded fiber optic sensors-review. Smart Materials and Structures, 2002, 11(6): 925-939.

[11] Silva A F, Carmo J P, Mendes P M, Correia J H. Simultaneous cardiac and respiratory frequency measurement based on a single fiber Bragg grating sensor. Measurement Science and Technology, 2011, 22(22): 075801.

[12] Yin S, Ruffin P B, Yu F T S. Fiber optic sensor, 2008, England: Press Taylor & Francis Group

[13] Kutaran S, Kilickaya M S. The modeling of fibre Bragg grating. Optical and Quantum Electronics, 2007, 39(8): 643-650.

[14] Li H N, Li D S, Song G B. Recent applications of fiber optic sensors to health monitoring in civil engineering. Engineering Structures, 2004, 26(11): 1647-1657.

[15] Majumder M, Gangopaadhyay T K, Chakraborty A K, Dasgupta K, Bhattacharya D K. Fiber Bragg gratings in structural health monitoring — present status and applications. Sensors and Actuators A: Physical, 2008, 147(1): 150-164.

[16] Fallon R W, Zhang L, Everall L A, Williams J A R, Bennion I. All-fiber optical sensing system: Bragg grating sensor interrogated by a long period grating. Measurement Science and Technology, 1998, 9(12): 1969-1973.

[17] Song I C, Lee S K, Jeong S H, Lee B H. Absolute strain measurement made with fiber Bragg grating sensors. Applied Optics, 2004, 43(6): 1337-1341.

[18] Kim S, Kim S, Kwon J, Lee B. Fiber Bragg grating strain sensor demodulator using a chirped fiber grating. IEEE Photonics Technology Letters, 2001, 13(8): 839-841.

[19] Kashyap R. Fibre Bragg grating, 1999, London: Academic Press

[20] Gupta B D. Fibre optic sensors principles and applications, 2006, New Delhi: New India Publications

[21] Chuang K C, Ma C C. Multidimensional dynamic displacementandstrain measurement using an intensity demodulation-based fiber-Bragg grating sensing system. Journal of Lightwave Technology, 2010, 28(13): 1897-1905.