Abstract: Coupled fiber-optic, evanescent-wave biosensors are improved through the use of configurations which detect changes in polarization for enhanced sensitivity. The inventive approach forms the necked-down region by heating and pulling the fibers without twisting them. As such, when polarized light is introduced, including randomly polarized light, the outputs will exhibit a split based upon polarization orientation as well. One or more bindings partners are then attached to the necked-down region and within the evanescent field for very specific and direct detection of minute concentrations of an analyte of interest. The invention is applicable to any type of organic/inorganic material, so long as the interaction of one component causes a change in any optical property detectable by the apparatus. The biomolecule may be linked to the surface of the fusion joint by means of a spacer molecule. Polarizing beam splitters are employed to detect the based upon polarization orientation.