In this work an 8-channel DWDM demultiplexer is proposed with multiple designs and numerical analysis. Photonic crystal ring resonators of airholes on a 220 nm thick silicon slab are used as wavelength selective elements. Demultiplexers of three different designs are considered and their characteristics are analyzed. For all the three designs, the resolved wavelengths are in the range of 1530–1540 nm, where Erbium Doped Fiber Amplifiers are applicable. For the optimized device, the average coupling efficiency, cross talk are found to be 70.4% and − 16.76 dB, respectively. Maximum and minimum coupling efficiencies of 79% and 56% are achieved. Photonic bandgap computation is performed by using plane wave expansion method and spectral characteristics are obtained by applying 3D finite difference time domain method.