Thin-Film filters are widely used in fiber-optic telecommunication networks. Important applications include channel and band selection, gain-flattening, and pump isolation/combining. As telecommunications networks evolve toward more spectral efficiency and higher data rates, filter manufacturers will be challenged to produce thin-film filters with better performance at a lower cost. This talk will detail the evolution of filter performance and complexity, and report on recent progress toward the development of extremely thick filters with very low stress. Such filters enable very good performance at a low cost. Some of the most significant results of this research will be presented, including the characteristics and resulting optical performance of a 94+ micrometer thick "8-skip-0 100GHz" filter for DWDM bandsplitting applications.