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# Switched delay lines using multiple-length delay lines in optical network

#### Abstract

The lack of optical memories to resolve resource contention in packet switched all-optical networks is addressed in this dissertation through a novel contention resolution architecture. The resulting architecture can be applied to all-optical multi-fiber networks design. Through the combined use of fiber delay lines and 2 $\times$ 2 photonic switches, an approach called Switched fiber Delay Lines (SDL), it is possible to construct an efficient all-optical networks. The efficiency of an SDL-based solution is fundamentally linked to its storage capacity, which in turn is determined by the combined length of the fiber delay lines. In the past, this length was determined by the maximum number of 2 $\times$ 2 photonic switches used, i.e. the number of stages in the switch fabric. These solutions are limited both by the cost, mainly determined by the switch component, and by the signal power loss and crosstalk introduced by each switch, thus limiting the total number of stages. Also the complexity of the control should be minimized in terms of size of switches or size of the input. This dissertation presents and discusses a new solution that makes use of a "multi-buffer" fiber delay lines, so termed since its length allows multiple packets to be concurrently stored (propagated) on each line. In this way the total storage capacity is increased. It is shown that with the proposed design of the SDL, incorporating the multi-buffer delay lines and with the novel switch control, overall network performance can be significantly improved without increasing the number of 2 $\times$ 2 space photonic switches in the system, i.e., its cost. Several different architectures are proposed to realize N $\times$ 1 (N-input single-output) optical packet multiplexers (or receivers), as well as 2 $\times$ 2 space switches. Two conditions are considered in the dissertation depending on the first-in-first-out rule that maintains the same order of the arriving packets when they leave the SDL. The two-stage non-FIFO solution utilizes the full advantage of multiple-length delay lines as its length increases. It performs most of achievable probability of packet loss by using fixed number of control information. On the other hand, the FIFO solution is applied to the $N\ \times$ 1 multiplexer (or receiver). It achieves exponential capacity while keeping non-blocking condition that generates no packet loss within the switch capacity. For all the proposed SDL solutions the complexity of the electronic control required to drive, on a slot by slot basis, the configuration of the photonic switches is shown to be bounded due to the distributed nature of the proposed control strategies.

#### Subject Area

Electrical engineering

#### Recommended Citation

Suh, Chang-Jin, "Switched delay lines using multiple-length delay lines in optical network" (1996). Doctoral Dissertations Available from Proquest. AAI9619445.
https://scholarworks.umass.edu/dissertations/AAI9619445

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