A novel fiber optic pH sensor is experimentally demonstrated by coating multilayers of poly(acrylic acid) (PAA) and poly(diallyldimethylammonium chloride) (PDDA) on a tilted fiber Bragg grating (TFBG) with the layer-by-layer (LbL) electrostatic self-assembly method. The utilization of PDDA/PAA pH sensitive polymeric coating presents a variation of the thickness with the pH of the solution, which introduces the wavelength shift and transmission change in the spectrum of TFBG. Using fast Fourier transform (FFT) analysis on a selected bandwidth of the transmission spectrum, it is found that the peak amplitude of the dominant spectral fringes increases with the increasing pH value with an near-linear sensitivity of 117 arbitrary unit (a.u.)/pH unit (in the range of pH 4.66 to pH 6.02). The dynamic response of the sensor also has been studied (10 s rise time and 18 s fall time).

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Keywords Fourier transform, Layer by layer, pH sensor, Polymeric coatings, Self-assembly, Tilted fiber Bragg grating
Persistent URL dx.doi.org/10.1117/12.974898
Conference 22nd International Conference on Optical Fiber Sensors
Shao, L.-Y, Yin, M.J., Tam, H.Y., & Albert, J. (2012). Fiber optic pH sensor with self-assembled multilayer nanocoatings on tilted FBG. Presented at the 22nd International Conference on Optical Fiber Sensors. doi:10.1117/12.974898