The present invention provides, in one aspect, an optical device, a method of manufacture therefor, and an optical system including the same. The method that includes transducing a power frequency current flowing through a power line, into a power frequency voltage, via an inductive coupler that couples a communications signal from the power line, separating the power frequency voltage from the communications signal, and determining a value of a parameter of the power frequency current from the power frequency voltage. The addition of the preheating devicestep significantly improves the ability of hot air heat-setting machines to maintain continuous operation during texture setting of BCF yarns and makes the hot air heat-setting method commercially viable for this application. The gelled composition contained on the applicator is applied to the nasal membrane.