Silica-based planar lightwave circuits (PLC) are key components of functional devices designed for use in optical fiber communication systems because, compared with bulk optics devices, they offer compactness, excellent stability and reliability in addition to high functionality. This talk reviews the current status of PLC development. The fabrication process, basic characteristics, packaging and reliability are presented, many device applications are described, and experimental results related to optical switches, interleave filters, chromatic/polarization dispersion compensators, gain spectrum equalizers and wavelength multiplexers are reported. Finally, the history of PLC development is summarized, and future target devices are described along with the kind of development needed for such devices designed for use in the next generation of optical communication systems.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.