This study presents the design and analysis of a 5-channel dense wavelength division multiplexing (DWDM) demultiplexer based on a photonic crystal (PC) hexagonal ring resonator (HRR). By varying the radius of a unique hole inside each HRR, the novel method enables exact wavelength control. The apparatus is ideal for applications using Erbium-Doped Fiber Amplifiers (EDFAs) and operates in the wavelength range of 1535 to 1539 nm. With a maximum channel crosstalk of – 15.39 dB and an average channel coupling efficiency of 72.4%, the study shows good signal separation performance. The Plane-Wave Expansion (PWE) approach is used to determine the device’s photonic band gap (PBG), and the Finite-Difference time domain (FDTD) method is used to analyze the electromagnetic (EM) field. This research contributes to the advancement of integrated optical components, showcasing the potential of PC-based devices in enhancing the capacity and efficiency of optical communication systems.