In incoherent-injected WDM-PONs, it is shown through simulations and experiments that Flat-band athermal AWGs with channel spacing of 100GHz have improved performance in terms of BER than their Gaussian-shape counterpart, due to the effect of signal filtering. At a BER of 10-9, the power penalty is 2 dB for Flat-band AWGs and more than 4 dB for Gaussian AWGs, which do not reach the required BER. In addition, the effect of AWG detuning in the WDM-PON systems is investigated. It is shown that by detuning the two Flat-band AWGs by 40GHz from their center wavelength, an additional 0.5dB power penalty is induced.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.