A novel passive protected SONET bi-directional self-healing ring architecture

The authors present a cost-effective implementation for a four-fiber bidirectional self-healing ring architecture (BSHR/4) which uses a totally passive ring as the protection ring of the BSHR/4. The proposed passive protected SONET BSHR/4 uses a SONET ring to carry working traffic, and a passive ring to carry protection traffic in case of network component failures. The passive protection ring, which is composed of optical switches and optical amplifiers, is essentially an optical add-drop protection ring, where optical switches of two ends of the failed facility act as optical add-drop components and optical switches of intermediate ring nodes are used as optical pass-through components. The optical sign add-drop is controlled by SONET add-drop multiplexers. A SONET control scheme for this implementation is discussed. The proposed BSHR/4 is attractive not only because it has a significant cost advantage over conventional BSHR/4 implementations, but also because it can easily evolve from any two-fiber ring, including the two-fiber bidirectional ring, with a minimum capital investment but gaining twice the capacity of the two-fiber ring