Heretofore, it was necessary to individually locate an optical switch, an optical switch control circuit, and the like, before and after an optical transceiver that performs optical protection. As a result, costs and the space for implementation increase, and a delay in services is also caused, which...http://www.google.com/patents/US7650075?utm_source=gb-gplus-sharePatent US7650075 - Optical add-drop multiplexer, and optical network equipment using the same
