This presentation will discuss advancements in thin-film filter technology for telecommunications applications in the following key topic areas: <b>Narrow Band Channel Spacing: </b>Several years ago, it was thought by industry analysts that thin-film filter technology would not be practical for channel spacings below 100 GHz due to loss and center wavelength stability requirements. Thin-film solutions for 50 GHz and 25 GHz channel spacings have been demonstrated with state of the art low-loss thin-film fabrication and new packaging strategies. Chromatic dispersion and dispersion power penalty for narrow band filters will also be discussed. <b>Wide band filters with fewer dropped channels and near theoretical performance:</b> Optical Add-Drop Multiplexing (OADM) is a key application for wide-band thin-film filters. Application requirements call for a minimization of the number of dropped channels with very steep filter sidewalls. The reflection notch function must have very deep isolation to minimize coherent cross-talk effects. This class of filter requires advancements in total film thickness, accurate layer thickness control, and center wavelength temperature control. <b>High angle of incidence filters: </b>Filter designs that use fixed angle of incidence in the 8 degree to 15 degree range are enjoying resurgence in popularity especially for CWDM applications. Wavelength tunable optical add/drop filters using angle-tuning methods are also emerging as an important application. Special designs have been created to optimize performance in these applications.