Optical fiber ph sensor

Abstract

An optical fiber pH sensoris described, where a transducer mechanically couples a Bragg grating to a pH-sensitive hydrogel, said sensor comprising a central partwhere are placed the optical fibercontaining a Bragg grating, the pH-sensitive hydrogel set of discs, and the mechanical transducer which is a springa beamor still the optical fiber itself, the mechanical transducer assuring the strain on the Bragg grating. The change in hydrogel hydrodynamic volume resulting from a change of the pH of the medium introduces a force that is sufficient to cause a strain in the Bragg grating. The measure of the pH change is retrieved using the usual techniques for wavelength measurement. The pH sensorof the invention is useful for the indirect evaluation and control of corrosion in petroleum wells and is suitable for multiplexing with other optical fiber sensors measuring the same or different parameters.