Using distributed feedback laser diode (DFB-LD) in a high-speed transmission system, the chirp effect in the LD is a factor limiting transmission span length. We discussed the impact of fiber chromatic dispersion on this system performance at 10-Gb/s due to LD chirp effect. For the dispersion range of −3.51 to 2.97 ps/nm·km, negative power penalties have been observed due to the pulse compression effect, which is resulted from a low chirp of DFB-LDs. We evaluated 10-Gb/s directly modulated DFB-LDs wavelengths from 1275-nm to 1350-nm of power penalties versus transmissible standard single-mode fiber (SMF) distance. The calculated power penalties are less than 1 dB for 20-km SMF transmission. Furthermore, we also achieve a bidirectional CWDM-PON system covering a wide wavelength of 1.3-µm and 1.5-µm with an aggregated data rate of 40-Gb/s is proposed and experimented. Four uncooled direct-modulated DFB-LDs with wavelengths of 1275-nm, 1300-nm, 1325-nm, and 1350-nm are adopted for the upstream transmission to lower the installation cost and dispersion effect. Another four external-modulated lasers by LiNbO 3 modulators with wavelengths of 1510-nm, 1530-nm, 1550-nm, and 1570-nm are deployed for the downstream transmission to minimize the chirp effect. These lasers are operated at 10-Gb/s simultaneously for transmission over 10-km SMF. Downstream and upstream data of high capacity are operated at 10-Gb/s per channel simultaneously. This CWDM-PON network enables client's maximum subscribing bit rate to 10-Gb/s and the splitting ratio can vary from 1:4 to 1:64.