Efficient shared buffer optical stars for bursty traffic and fault tolerance in 3-stage ATM switches

An efficient buffer sharing approach with a fault-tolerant mechanism between the switch-units of a 3-stage shared buffer ATM switch is proposed to reduce the bursty traffic cell loss ratio, the required buffer size in each switch-unit, and the number of required redundant switch-units in fault-tolerant applications. With the buffer sharing nature, the proposed structure can reduce the cell loss ratio and the required buffer size of a switch unit. The buffer sharing interconnection structure is based on the passive optical star couplers employing the WDM (wavelength division multiplexing) and the multi-bit parallel transmission technologies for accessing cells in the memory buffers of the switch-units, which can reduce the transmission speed requirement and the wire complexity. A practical example in a B-ISDN shows that 7 optical channels are sufficient in the passive optical stars for building a 1024×1024 ATM switch under a bursty-overflow traffic load of 0.2 and cell loss ratio below 10^-6