Concatenated high wavelength isolation WDM and 4×4 wavelength-flattened coupler

A novel WDM (wavelength division multiplexer) with high wavelength isolation integrated with three WDMs, and a 4×4 single-mode wavelength-flattened star coupler integrated with four 2×2 wavelength flattened couplers (WFCs), as single assemblies, are presented. These assemblies are fabricated by fusing the couplers or WDMs directly at the same fibers. Without any splices, and packaging in small compact packages, these integrated assemblies not only show better performance, less excess loss, and smaller package dimension with no additional splices than the concatenated ones, but also have environmental stability and reliability similar to that of the single fused components