OPTICAL RING NETWORK SYSTEM, OPTICAL NODE UNIT, METHOD OF MAKING OPTICAL RING NETWORK SYSTEM REDUNDANT

摘要

PROBLEM TO BE SOLVED: To obtain an optical ring network system which continues communication even in the event of a fault to improve the reliability and reduces the number of optical transmission lines for connecting optical node units to reduce the cost. SOLUTION: A center optical node unit 1 and a plurality of remote optical node units 2-1 to 2-N are connected in a ring by a single optical fiber 7, the center node unit 1 transmits a optical down signal Sig1 in the right and left directions to each remote node unit 2-1 to 2-N, and the remote node units 2-1 to 2-N receive the optical down signal Sig1 in a direction where no fault occurs and transmit optical up signals Sig2-1 to Sig2-N in the direction the signal was received.