We investigated the effects of various noises on the performance of extended-reach WDM-PONs based on broadband light sources (BLSs). The maximum reach in BLS based WDM-PONs was analyzed by taking into account the impact of relative intensity noise of optical source, chromatic dispersion of transmission fiber and in-band crosstalk. We confirmed that the system's performance of BLS based WDM-PONs would be strongly dependent on the equivalent optical bandwidth of optical source. From the results, we found that the maximum reach in BLS based WDM-PONs operating at 1.25 Gb/s could be increased to be approximately 70 km of single-mode fiber as long as the chirp and relative intensity noise (RIN) of optical source would be suppressed properly.