We propose a new multiwavelength almost all-optical switch architecture cal
led the lambda-scheduler that uses wavelength division multiplexing (WDM) i
nternally to fold the switch architecture in both the space and time domain
s to reduce the hardware complexity and to improve the signal characteristi
cs through the switch. The lambda-scheduler preserves the packet order for
a given input-output pair, is consistent with virtual circuit switching, an
d when combined with appropriate connection and flow control protocols, pro
vides lossless communication for bursty (or nonconstant rate) traffic, prov
ided the traffic satisfies certain smoothness properties. The lambda-schedu
ler uses novel scheduling and wavelength assignment algorithms, in conjunct
ion 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-s
cheduler, the N internal wavelengths are used to fold the architecture in t
he time domain, which reduces the total number of delay blocks for the swit
ch by 2N log N, In the collapsed lambda-scheduler, the N internal wavelengt
hs 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 implementatio
ns and discuss the tradeoffs between the reduction in overall component cou
nt and the improvement in the signal characteristics.