portion 42 is unjacketed to the core and treated to form a chemical sensor a reactive chemical such as 3 aminopropyltrimethoxysilane can be used as an adhesion promotor that bonds derivatized pah 39 s i e sulfonated perylene to the optical fiber a preferred method of bonding the pah 39 s to the optical fiber is through an entrapment mechanism a polymer solvent mixture is used to solubilize and entrap pah compounds then used as a coating on the optical fiber to form the chemical sensor the fluorescence of the chemical sensor is excited by light transmitted through the fiber and subsequently detected by light monitoring means such as a spectrometer through window 32 as in fig2 when the particular explosive molecules enter the chamber 20 the airborne explosive molecules interact with the pah and reduce the fluorescence the reduced fluorescence on the tip 42 is detected by the light sensing means the relative decrease in fluorescence can be extrapolated into a relative quantity of explosive mixture molecules in the airstream directed through chamber 20 in fig3 a quenching plot of the chemical sensor optical fiber due to tnt exposure is shown in this plot the fluorescent intensity of the encapsulated pah coating is plotted as a function of time a baseline fluorescent intensity is established in the region indicated by a at point b the sensor is exposed to tnt vapor in the region indicated by c the fluorescent intensity decreases as a result of interaction of the tnt with the encapsulated pah coating at point d tnt.