Optical communication system and master station

An optical communication system comprising:

• a plurality of slave station devices that are connected to a loop path in parallel;
• and
• a master station device that is connected to the loop path and configured to perform communication with each of the slave station devices,
• wherein communication paths between the master station device and each of the slave station devices include:
• a normal path that extends along the loop path from the master station device to each of the slave station devices in a first direction, and
• a backup path that extends along the loop path from the master station device to each of the slave station devices in a second direction that is opposite to the first direction,
• the master station device is configured to execute communication control processing for controlling communication with each of the slave station devices based on an RTT (Round Trip Time) between the master station device and the slave station device,
• a normal path RTT is the RTT in a case of communication performed via the normal path,
• a backup path RTT is the RTT in a case of communication performed via the backup path,
• a first slave station device is one of the slave station devices,
• a first normal path RTT is the normal path RTT between the master station device and the first slave station device,
• a first backup path RTT is the backup path RTT between the master station device and the first slave station device,
• a second slave station device is a slave station device that cannot perform communication via the normal path, among the plurality of slave station devices,
• a second normal path RTT is the normal path RTT between the master station device and the second slave station device,
• a second backup path RTT is the backup path RTT between the master station device and the second slave station device,
• the master station device holds the normal path RTT for each of the slave station devices and the first backup path RTT,
• if the second slave station device does not exist, the master station device executes the communication control processing with respect to the slave station devices based on the normal path RTTs, and
• if the second slave station device is detected, the master station device calculates the second backup path RTT based on the first normal path RTT, the first backup path RTT, and the second normal path RTT, and resumes the communication control processing with respect to the second slave station device based on the calculated second backup path RTT.