Dense wavelength division multiplexing-direct scheme with two thin film filters (full width half maximum bandwidth 100 and 200 GHz) for broadband access has been realized to evaluate the minimal channel interval for each thin film filter needed for a satisfactory bit error ratio. From the results, the minimal channel interval has been established for both thin film filters that ensure reliable data transmission and higher spectral efficiency of the whole system. It was found that for the dense wavelength division multiplexing-direct system for broadband access with 200 GHz thin film filter, a satisfactory performance is achieved with a 100 GHz channel interval at the 10 Gbit/s data transmission speed and the spectral efficiency was raised from 0.05 to 0.1 bit/s/Hz.