Duplex system configuration in passive double star system

The paper proposes a new passive double star (PDS) duplex configuration that enables either single or duplex wiring in customer buildings. The automatic protection switching algorithm using this duplex configuration is also discussed. The paper also proposes an orderly and quick round trip delay control algorithm of plural optical network units (ONUs) of the PDS system. The control algorithm is required in the activation process of an automatic protection switching, since the new duplex configuration requires a cold stand-by mechanism in the transmission equipment. This algorithm uses only one shared channel by ONUs to minimize the waste of transmission capacity.