Multi-mode planer optical waveguides have been fabricated on PDMS coated glass substrate using off stoichiometry thiolene- epoxy (OSTE+) polymer thin film, by an optical photolithography technique. The light wave-guiding phenomena has been observed in this novel OSTE+ polymer waveguide using prism coupling method. Four discrete propagating optical modes have been observed, upon monochromatic light (635 nm) excitation. These modes were recorded using a USB camera at different angular positions. The evanescent wave absorption of these modes has been exploited for refractive index based photonic sensing applications.