The impact of filter concatenation effects on the performance of wavelength-division-multiplexing (WDM) metropolitan area transparent optical networks utilizing cost-effective 10-Gb/s transmitters is investigated with recirculating loop experiments. We considered directly modulated lasers and electroabsorption modulator integrated distributed feedback lasers (electroabsorption-distributed feedback) as cost-effective 10-Gb/s transmitters. The filter concatenation performance for thin-film multilayer interference filters designed for dense WDM networks with both 200- and 100-GHz channel spacing is studied.