We propose a new multiwavelength almost all-optical switch architecture called the lambda-scheduler that uses wavelength division multiplexing (WDM) internally to fold the switch architecture in both the space and time domains to reduce the hardware complexity and to improve the signal characteristics through the switch. The lambda -scheduler preserves the packet order for a given input-output pair, is consistent with virtual circuit switching, and when combined with appropriate connection and flow control protocols, provides lossless communication for bursty (or nonconstant rate) traffic, provided the traffic satisfies certain smoothness properties. The lambda -scheduler uses novel scheduling and wavelength assignment algorithms, in conjunction with a series of feed-forward delay blocks, to avoid packet collisions within the switch or at the switch outputs. We present two implementations of the lambda-scheduler when the number of internal wavelengths k equal the number of inputs (and outputs) N to the switch. In the compressed lambda -scheduler, the N internal wavelengths are used to fold the architecture in the time domain, which reduces the total number of delay blocks for the switch by 2Nlog N . In the collapsed lambda-scheduler, the N internal wavelengths are used to fold the architecture in the space domain,which reduces the number of delay blocks and total fiber length used for delays by a factor of N. We examine the insertion loss for both lambda-scheduler implementations and discuss the tradeoffs between the reduction in overall component count and the improvement in the signal characteristics.
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