A sensitivity enhancement method for an external electro-optic (EO) probing system using a poled polymer as an EO sensor is proposed. A pumping laser, which induces the photo-isomerization effect in a prepoled EO polymer, and a tunable probing laser, which induces Fabry-Pérot effect, are combined to enhance the polymer EO sensor sensitivity. Results of an experiment with an EO sensor made of Disperse Red 1 poly(methy1 methacrylate) that demonstrates this combined effect are reported.