WDM-PON activities in Korea including research and development were reviewed. The WDM-PON commercialized in Korea is aimed at delivering a 100 Mbits/s dedicated symmetric bandwidth to each home, based on the prediction of a small statistical gain for future video-centric services. The developed 32-channel WDM-PON based on wavelength-locked Fabry-Perot LDs was qualified by Korea Telecom (KT) and was deployed in KT's networks. Many studies have been conducted with the aim of enhancing the performance of the WDM-PON. High-speed data rate per channel, longer reach, narrow channel spacing, and a high split ratio with the help of subcarrier multiple access or time-division multiple access have been demonstrated. A protection method for feeder fiber fault and OSP fault-monitoring methods were also demonstrated. A gradual upgrade solution from the existing time-division multiplexing-PON to WDM-PON has also been proposed. (c) 2007 Optical Society of America.