Design and characterization of a plastic optical fiber pH sensor

Licínio Ferreira; Pedro Simões; Rui S. Carvalho; Paulo Lopes; Mário Ferreira

doi:10.1117/12.2027505

18 November 2013 Design and characterization of a plastic optical fiber pH sensor

Licínio Ferreira, Pedro Simões, Rui S. Carvalho, Paulo Lopes, Mário Ferreira

Proceedings Volume 8785, 8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications; 8785FA (2013) https://doi.org/10.1117/12.2027505
Event: 8th Ibero American Optics Meeting/11th Latin American Meeting on Optics, Lasers, and Applications, 2013, Porto, Portugal

Abstract

In this paper are present the design and characterization of a pH sensor using plastic optical fiber (POF) technology and a material produced by the sol-gel process with TEOS (tetraethyl orthosilicate) to immobilize universal indicator of pH (comprised of Thymol Blue, Methyl Red, Bromothymol Blue and Phenolphthalein) inside the silica matrix. This matrix is positioned between two extensions of plastic optical fiber tightly positioned at each side with both fibers aligned and sharing a common optical axis. This set will work as a pH sensor since the matrix embedded with indicator and in the presence of a solution (basic or acid solution) will change the optical transmittance properties. The optical source is a superluminescent white LED and the receiver is a photodiode having a good and linear responsivity in the visible spectrum. This pH sensitive matrix has large pores which allow the diffusion of the surrounding fluid molecules into the matrix and thus the close contact of these to the indicator molecules. This contact causes the change of color of the whole matrix allowing proper colorimetric detection by the photodiode. This variation of color associated with the detector wavelength linear response is the base of operation of the proposed device. This pH sensor presents many advantages over the standard and commercial pH meters namely, lightweight, portability and a low cost.

Citation Download Citation

Licínio Ferreira, Pedro Simões, Rui S. Carvalho, Paulo Lopes, and Mário Ferreira "Design and characterization of a plastic optical fiber pH sensor", Proc. SPIE 8785, 8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications, 8785FA (18 November 2013); https://doi.org/10.1117/12.2027505

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KEYWORDS

Sensors

Phase only filters

Photodiodes

Polymer optical fibers

Molecules

Sol-gels

Light emitting diodes

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