To obtain an optical communication system of which the fault resistance is more enhanced as compared with a conventional system.

In the optical communication system, when receiving a signal from the outside of a bidirectional ring network, a relay apparatus (5) copies the received signal and relays the copied signal to two directions on the bidirectional ring network. A primary connection apparatus (3) copies one of normally received signals on an upstream ring in two bidirectional ring networks to which the apparatus (3) itself belongs, and then relays the copied signal to two directions on a downstream ring. A secondary connection apparatus (4) selects one normally received signal out of a first signal received on the upstream ring without passing through the primary connection apparatus (3) and a second signal received on the downstream ring through the primary connection apparatus (3), and relays the selected signal in a direction opposite to the direction of receiving the second signal on the downstream ring.

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