title: Fiber optic sensor for the measurement of concentration of silica in water with dual wavelength probing.
abstract: The design, development, and characterization of a fiber optic evanescent wave based sensor with selectivity suitable for concentration measurement are presented. The sensor that is made up of a step index plastic multimode fiber can be used for the measurement of silica in water. Generally evanescent wave fiber optic sensors employ a single source and detector that show change in output optical power irrespective of the interacting species, i.e., they lack selectivity. This design employing two sources provides excellent selectivity, and the differential arrangement further enhances sensitivity and repeatability. Advantages of this design include the use of inexpensive and easily available light-emitting diode sources that match the analytical wavelength of the samples. The use of dual wavelength probing topology enhances the selectivity, sensitivity, and repeatability, which cannot be achieved by single source evanescent wave fiber optic sensors.
authors.affiliation: Cochin University of Science and Technology, Cochin, India. benjamin@cusat.ac.in
authors.forename: Benjamin
authors.initials: B
authors.lastname: Varghese P
authors.forename: Satish
authors.initials: S
authors.lastname: John
authors.forename: K N
authors.initials: KN
authors.lastname: Madhusoodanan