Hiroaki Mukai Yoshifumi Hotta Tetsuya Yokotani Akira Takahashi Kiyoshi Shimokasa PON with Automatic Protection switching for high reliable communication. 163-170 2009 6 Optical Switching and Networking 3 http://dx.doi.org/10.1016/j.osn.2009.04.002 db/journals/osn/osn6.html#MukaiHYTS09