We demonstrate a dense wavelength-division-multiplexing passive optical network (DWDM-PON) at 50-GHz channel spacing based on wavelength locked triple-contact Fabry-Perot laser diodes (TC F-P LDs). A transmission distance of 30 km was achieved at 1.25 Gb/s per channel. By controlling injected currents into three electrodes, we can match a lasing mode of the TC F-P LD to an injection wavelength. We also employ a prefilter before amplified spontaneous emission (ASE) injection to enhance the system performance by reducing a filtering effect. The transmission distance was limited by the back scattering. By changing a location of the seed source for upstream signal to the remote node, the transmission distance can be extended up to 60 km.