Constructing $N$ -to- $N$ Shared Optical Queues With Switches and Fiber Delay Lines

All-optical router has been considered as a natural choice to keep pace with growing fiber link capacity. One main research issue of all-optical router is the design of optical queues with the same flexibility as their electronic counterparts, and some recent works have proved the feasibility of using optical switches and fiber delay lines (SDL) to emulate the electronic queues. In this paper, we focus on the SDL-based construction of N -to- N shared optical queue, a more efficient queue structure in comparison with the dedicated input and output queues. The construction we consider consists of a crossbar switch of size (N + M) × (N + M), where N inputs (outputs) are reserved for external arrivals (departures), and M fiber delay lines are connected from the remaining M outputs back to the remaining M inputs. We first show that by setting the length r_i of fiber delay line i as r_i = 1 + [(1 - 1) mod N], i = 1, . . . M, and scheduling packets properly among these delay lines, such a construction can work as a non- idling first in first out (FIFO) shared queue of size B = Σ_i=1^M r_i. We further extend our work to the design of more general shared buffer, where the packets can be stored for an arbitrary time and may depart in a non-FIFO order.