Abstract
A new method of analysis employing the time-dependent response of long-period-grating (LPG) fiber-optic sensors is introduced. The current kinetic approach allows analysis of the time-dependent wavelength shift of the sensor, in contrast to previous studies, in which the LPG sensing element has been operated in an equilibrium mode and modeled with Langmuir adsorption behavior. A detailed kinetic model presented is based on diffusion of the analyte through the outer protective membrane coating into the affinity coating, which is bound to the fiber cladding. A simpler phenomenological approach presented is based on measurement of the slope of the time-dependent response of the LPG sensor. We demonstrate the principles of the kinetic methods by employing a commercial Cu+2 sensor with a carboxymethylcellulose sensing element. The detailed mathematical model fits the time-dependent behavior well and provides a means of calibrating the concentration-dependent time response. In the current approach, copper concentrations below parts per 106 are reliably analyzed. The kinetic model allows early-time measurement for low concentrations of the analyte, where equilibration times are long. This kinetic model should be generally applicable to other affinity-coated LPG fiber-optic sensors.
© 2005 Optical Society of America
Full Article | PDF ArticleMore Like This
Rong Chen, Wenli Liu, Guojia Huang, Daoyuan Wang, Xiang Qin, and Wenlin Feng
Appl. Opt. 57(33) 9755-9759 (2018)
Zhiyong Wang, J. R. Heflin, Rogers H. Stolen, and Siddharth Ramachandran
Opt. Express 13(8) 2808-2813 (2005)
Sergiy Korposh, Stephen W. James, Seung-Woo Lee, Stephen Topliss, Sammy C. Cheung, William J. Batty, and Ralph P. Tatam
Opt. Express 18(12) 13227-13238 (2010)