| 摘要 |
PROBLEM TO BE SOLVED: To attain communication between a master set and slave sets without setting an identification number to a plurality of slave sets by providing a function of changing a transmission level with respect to each slave set to the master set. SOLUTION: A master set 1 is provided with a function to change a transmission level to each of slave sets 2a, 2b, 2c,..., and each of the slave sets 2a, 2b, 2c,... is provided with a function that accepts transmission information from the master set 1 only in the case of reception in a range of a preset reception level and that does not accept transmission information from the master set 1 in the case of reception at the outside of the range of the set reception level. Then the master set 1 sends an optical signal at a specific level, and the optical signal is being propagated while receiving a loss specific to an optical fiber and reaches a branching device 3a. The optical signal is branched at the branching device 3a and fed to the slave set 2a. In this case, the optical signal receives a loss called a coupler loss at the branching device 3a. |
