Waveguide-based optical devices are finding important applications in optical communications, optical signal processing, and optical sensors. Among the many waveguide materials, polymer possesses a number of distinct advantages. First, it is easy to form and process polymer thin films and low-cost processes, such as imprinting and hot embossing, for mass production of polymer planar lightwave circuits are available. Second, polymer is compatible with practically any optical materials, which makes it possible to form hybrid devices with enhanced performance. Third, the dimensions of polymer waveguides and optical fibers are well matched, which can ease device packaging. Fourth, optical polymer is in general photosensitive, which allows the development of fast and inexpensive laser/UV-writing methods for the fabrication or post-processing of polymer waveguide devices. Fifth, the large thermo-optic coefficient of polymer can be explored to realize effective thermally tunable devices. Last, but not the least, it is easy to form multilayer and hence three-dimensional (3D) waveguide structures with polymer. 3D waveguide optics not only leads to more compact devices, but also provides more flexibility in the device design. This feature of polymer has become particularly useful for the development of mode (de)multiplexers, which are the key components in the emerging mode-division -multiplexing fiber communication technology. The availability of special polymer materials, such as electro-optic polymer, can further widen the scope of applications with optical polymer. While the stability of optical polymer is often questioned, highly stable polymer materials are commercially available. Nowadays, optical polymer waveguides can be embedded in printed circuit boards with a lamination process that involves both high pressure and high temperature. In this talk, the speaker will provide a review of the polymer waveguide technology with some of the devices fabricated in his laboratory as examples.