We have developed organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry, making them excellent candidates for WDM applications. Waveguides are formed lithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser writing. Our waveguides are low loss (0.03 dB/cm at 840 nm multimode) as well as temperature resistant (up to 10 years at 120°C), enabling use in a variety of applications. Single-mode structures such as directional couplers have been made via laser writing. We further discuss the fundamental optical properties of these polymers and as they relate to WDM applications. As an example, we discuss an inorganic multimode WDM sensor that has been developed for aerospace applications and its integration with multimode polymer waveguides.