This paper contains the investigation of 8-channel wavelength-division-multiplexed passive optical network by using spectrum-sliced amplified spontaneous emission (ASE) source as a seed light with arrayed-waveguide gratings (AWGs). There are investigated the impact of signal filtering for Gaussian and Flat-top type AWGs on the overall optical system’s performance. It is shown that Gaussian type AWG’s with channel interval 100 GHz are not suitable for SS-WDM PON systems with high data rate - 2.5 Gbit/s because of wide spectral shape and high channel crosstalk. Numerically it is proved that best solution for 8 channel SS-WDM PON system which provides high performance over the passive fiber optical link length up to 10 km with BER < 1e-10 are AWG’s with Flat-top spectral shape. It has been investigated that Flat-top AWG unit shows high OSNR because of its amplitude transfer function that provides excellent channel separation and filtering at the same time passing sufficient high optical power from spectrally sliced ASE broadband light source.