The need for higher communication medium is endless as the newer technologies have been came so far, and there is always a search for a more efficient and promising scheme as compared to the present system. The current communication system is the most modern mode of communication. Today, most of the transmission takes place in 1550 nm window. So, the purpose of this paper is to present the simulation of Wavelength Division De-Multiplexing using a Photonic Crystal four-Channel Drop filter, and design it for multi channel Add-Drop filter with Wavelength Division Multiplexing and De-multiplexing, as it can provide the result in 1530 nm to 1570 nm window, which is quite ideal for
present optical communication system. A crystal is a periodic arrangement of atoms and molecules and the pattern which the atoms and molecules are repeated in space is the crystal lattice. In the PhC, the atoms or molecules are replaced by macroscopic media with differing dielectric constants and the periodic potential is replaced by a periodic dielectric function. The Wavelength Division Multiplexing (WDM) is considered to be a propitious scheme for high capacity optical interconnects and communications.