A bidirectional 80-km-reach 64-channel dense wavelength-division-multiplexing passive optical network with 50-GHz channel spacing based on wavelength-locked Fabry-Perot laser diodes is demonstrated. By changing the position of the broadband light source (BLS) for the upstream channels to the remote node, both the need for a high-power BLS and the power penalties induced by backscattering are overcome. Packet-loss-free transmission is obtained, guaranteeing 125 Mb/s per channel (8-Gb/s capacity in a single direction) without the support of an optical amplifier.