WDM PON (Wavelength Division Multiplexing Passive Optical Network) is used to increase DAS (Distributed Antenna System) network efficiency applied in existing PON network. The Optical DAS is the best solution for power efficiency in the building. Both DAS and PON use WDM to combine the different optical wavelengths. The simulation network configuration locates the WDM de-multiplexer placed at a distance 18 km from the multiplexer. After 18 km, the optical network is divided into two networks, which are DAS and PON. This paper proposes to use 2×1 WDM PON type for DAS. The experimental DAS and PON configuration system is simulated using Optisystem software. The results of Optisystem simulation shows that photodetector output is -34.071 dBm for DAS. LiNbO3 EOM (Electro Optic Modulator) gives a 4 dB power efficiency in DAS network. While the power input of ONU (Optical Network Unit) in PON network is -21.5 dBm. OSNR (Optical Signal to Noise Ratio) of WDM multiplexer were 69.421 dB for PON and 75.922 dB for DAS. The results comply with the standard of ITU-T G.984.2 for GPON (Gigabit PON) System.