The present access services like video on demand, live streaming, online gaming etc. require enormous amount of bandwidth and traditional digital subscriber line technology fails to meet up this requirement. The next generation networks, in particular, hybrid WDM-TDM Long-Reach Passive Optical Networks provide the required bandwidth and reduce the operational expenditure. Laser sources used at the Optical Network Units increase the cost due the extra equipment required for stabilizing the operating wavelength. To overcome this, a centralized source is installed at the Optical Line Terminal and the signal is reflected and intensity-modulated at the ONU, by using a special optical device Reflective Semiconductor Amplifier (RSOA), thus making the end receiver unit “colourless”. The analytical model for RSOA has been described in detailed in this book. The primary objective of this enitre work is to examine the feasibility of hybrid WDM-TDM LR-PON physical layer uplink setup consisting of reflective ONUs with due consideration to the BER performance in presence of realistic and non-ideal characteristics of optical and optoelectronic devices used in the setup.