The latest development in passive optical network systems is evolving toward higher data rates and long-reach transmission distances, where wavelength-division-multiplexed passive optical networks (WDM-PONs) can be very attractive solutions. In order to reduce the cost of WDM-PON systems, many WDM-PON architectures with colorless light sources were proposed. An injection-locked Fabry-Perot laser diode (FP-LD) is a widespread colorless light source to be utilized at an optical network unit. Thus in this thesis we simulated different light sources for injection-locking of FP-LDs and discussed the characteristics such as injected optical power, frequency detune, side-mode suppression ratio (SMSR) and noise. The simulated results indicate that the injected optical power ratio of reusable light source, directly modulated light source and extinction-ratio-enhanced signal light source to continuous-wave light source is about 2.83 at the requirements of 25-dB SMSR and 30-GHz frequency detune. Additionally, the difference in frequency detune between continuous-wave light source and other coherent light sources there is 10GHz at the requirements of 25-dB SMSR and 0.1-mW injected optical power. Excluding continuous-wave light source, the extinction-ratio-enhanced signal light source has the best tolerance of frequency drift and noise compared with reusable light source and directly modulated light source. However, the amplified-spontaneous-emission light source has the worst performance of injection locking among the discussed light sources.