Calibration of Optical Fiber Refractive Index Sensor with Potential for Structural Corrosion Monitoring

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Title: Calibration of Optical Fiber Refractive Index Sensor with Potential for Structural Corrosion Monitoring

Author(s): C.C.C. Lam, M. Rajesh, T. Sun, K.T.V. Grattan, S.K.T. Grattan, S.E. Taylor, and P.A.M. Basheer

Publication: Special Publication

Volume: 252

Issue:

Appears on pages(s): 73-84

Keywords: chloride; fiber optic sensor; interferometer; long period grating; structural health monitoring

Date: 3/1/2008

Abstract:
There is a need in industry for new devices for the monitoring of chloride ion ingress in structural concrete. This work reports on the development of a reflective, gold-coated long period grating-based senor for the measurement of chloride ions in solution, with potential for evaluating the corrosion condition of concrete structures. The sensor scheme is based around a long period fibre grating (LPG)-based Michelson interferometer where the sensor was calibrated and evaluated in the laboratory using sodium chloride solutions, over a wide range of concentrations, from 0.01 M to 4.00 M. The grating response yields shifts in the spectral characteristic of the interferometer, due to the change of refracting index of the solution surrounding it. It was found that the sensitivity of the device could be enhanced over that obtained from a bare fibre by coating the LPG-based interferometer with gold nanoparticles.