The range of the structural parameter values required to design the optical devices for ITU-T G 694.1 Dense Wavelength Division Multiplexing (DWDM) systems are numerically examined over the wavelength range of DWDM from 1470 nm to 1610 nm. The Photonic Band Gap structure is employed to know the required values. Further, the change in PBG in accordance with radius of the rod, lattice constant or period, refractive index difference, total number of rods used in the structure and arrangement of rods or phipattern are investigated through simulation. The Bandsolve simulator of Rsoft is utilized to calculate PBG which is derived using Plane Wave Expansion (PWE) method.