A communication system of a passive optical communication network includes an optical line terminal (OLT) system including a first OLT, a second OLT, and an OLT control device that controls the first OLT and the second OLT, a plurality of splitters that connects between the first OLT and the second OLT with an optical communication path, and an optical network unit (ONU) that is connected to each of the plurality of splitters with an optical communication path.