This work describes the design and fabrication of enhanced polymer waveguide platforms for absorption-based optical chemical sensors and the use of soft lithographic techniques for the fabrication of optical sensor chips. The design of the enhanced polymer waveguide platforms was based on a previously reported theoretical model that was verified experimentally in this work. The platforms were fabricated by micro-injection moulding and subsequently coated with sol-gelderived sensing layers doped with a colorimetric indicator compound. The sensor response to both gaseous ammonia and solution pH was examined using a LEDbased prototype sensor head. Soft lithographic patterning techniques, based on the use of a poly(dimethylsiloxane) (PDMS) patterning element, were employed to produce a variety of sol-gel-based structures with applications in optical sensing. These included discrete sensor spots, surface corrugation grating couplers and ridge waveguides. As a proof of principle, these techniques were applied to the development of an integrated optical oxygen sensor based on the quenching of fluorescence from a sol-gel-encapsulated ruthenium complex that was deposited as a sensor spot onto a ridge waveguide. This work highlights the feasibility of using rapid prototyping technology to fabricate sensitive, mass-producible sensor platforms that employ generic configurations, thereby facilitating their use in a broad range of applications.