Switch with large optical buffers (SLOB) for ATM traffic

ABSTRACT Recently, optical ATM switches, composed of optical switches, fiber delay lines and other devices, have been proposed by researchers world-wide as a way of overcoming the EMI, pinout and interconnection problems that would be encountered in future large electronic switch cores. Attaining the size of buffers (buffer depth) in optical ATM fabrics that would be required in practice is a major problem; in this paper, an architectural solution is presented. A technique is introduced for cascading many small switches to form a bigger switch with a larger buffer depth. A special feature of this scheme is that the number of cascaded switches is proportional to the logarithm of the buffer depth, providing an economical and feasible hardware solution. Architectural concepts are discussed and justified mathematically, and an electronic control scheme is introduced. Cell loss and delay performance, and buffer dimensioning are considered. The performance in terms of crosstalk and noise will be covered in a companion paper. In conclusion, it is clear that optical switching elements, with a buffer depth of several hundred required for bursty traffic, can be constructed using fewer components than other schemes, and, by implication, better noise and crosstalk performance.