Sivasankara Pillai,V N; Radhakrishnan, P; Nampoori, V P N; Girijavallabhan, C P; Suresh, Kumar P(Journal of Optics : A Pure and Applied Optics, March 8, 2002)
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Abstract:
A fibre optic technique for detecting trace amounts of nitrite compounds in
water is described. The off-line fibre optic sensor outlined here is based on
evanescent field absorption in a test solution formed by the reaction of nitrite
compounds in water with suitable chemical reagents. A short unclad portion
of a plastic clad silica fibre acts as the sensing region. The experimental
results clearly establish the usefulness of the present technique for detecting
very low concentrations of the order of 1 ppb (parts per billion) of nitrite
compounds with a large dynamic range of 1–1000 ppb. Such a high
sensitivity enables the present device to be used for measuring the nitrite
content in drinking water.
Optical fiber based laser induced fluorescence (LIF)
measurements were carried out using Rhodamine B to analyze
two different species of bacteria , a Gram-positive bacteria
namely Bacillus smithii , and fibrin alginolvticus, a Gram-
negative bacteria . The fiber sensor was clearly able to distinguish
between the two species of bacteria . Quenching effect of the dye
Rhodamine B by Bacillus smithii was observed . The effect of dye
on the samples was also studied in detail.