Simple ring-type passive optical network with two-fiber protection scheme and performance analysis

A simple passive optical network with ring-type distributed optical networking units (ONUs) is proposed. The ring protection is performed by a clockwise and a counterclockwise circulating fiber. The protection-and-restoration time is measured to be less than 5 s, and depends on the optical switching and the autodiscovery process time. In spite of additional devices for protection, the system reliability is enhanced so that the expected downtime decreases from 41.3 to 28.9 min/yr. The optimum condition to support the maximum number of ONUs is derived and verified by an optical link simulation.