PROBLEM TO BE SOLVED: To enable inter-ONU communication having high reliability equivalent to (1+1) protection with neither addition of a special device nor increase of delay caused by electrical processing.SOLUTION: A representative node 11A has a DWBA function unit 27A for controlling to set three independent logical paths Y11 to Y13 on a route among ONUs via OLT 21A. When setting and controlling the three paths Y11 to Y13, the DWBA function unit 27A controls to set three paths Y11 to Y13 on different three routes out of at least four routes obtained by combining at least two routes between ONU and OLT 21A along which data are directed from the ONU to the OLT 21A via two optical fibers 16 and 17 in opposite directions, and at least two routes between OLT 21A and ONU along which data returned at OLT 21A are directed to ONU via two optical fibers 16 and 17 in opposite directions.SELECTED DRAWING: Figure 1
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