In this paper

the development of a TFF-based flat-top tunable optical filter with 50 GHz channel spacing is introduced

the principle for the angle-tuned interference filter discussed and the design of an ultra-narrow band film stack optimized.The module performance is fully tested

which proves that 96 ITU-T channels can be optionally dropped in the range of 40 nm wavelength

thus providing a dynamic low-cost high-performance wavelength selection scheme for intelligent optical networks.