A study of the reliability of optical switching nodes for high capacity telecommunications networks

Abstract: The use of optical fibers and optical network componentsallows aggregating the bit streams in order to minimize theequipment that is necessary for transmission and switching. Inthis way, however, the robustness of the network totransmission failures is decreased, i.e., number of servicesthat can be affected magnifies the effect of failure.Thus, the reliability issues are of great importance inattempting to introduce photonics in a broader context incommunications, e.g. for cross-connects, ATM switches etc.These questions are becoming of high significance with theimminent introduction of more photonic functionality in thenetworks and have received scant attention in the past.The aim of this thesis is thus to investigate reliabilityperformance of optical switching nodes in order to define theirusefulness for application in high capacity telecommunicationnetworks. The work has been focused on demonstrated nodearchitectures. The limitations of these architectures have beeninvestigated, originating from reliability data for optical,electro-optical, and opto-mechanical components.The introductory part of the thesis describes the researchtopic, aim and motivation for the thesis project, basics forsystem reliability modeling and summarizes the originalresearch work. The main results are presented in sixpublications, which are reproduced in the thesis.In this thesis the reliability performance of severaloptical ATM switches and optical cross-connect nodes has beeninvestigated. Some original solutions have been proposed bothfor the node architectures and, for the choice of components inorder to improve the reliability of the switching nodes.It is shown that all of the considered photonic ATMswitching systems have to be modified in order to meetreliability and performance requirements. The improvement ofthe reliability performance of photonic ATM switching systemshas been investigated. It is shown that for the configurationsconsidered, introducing inherent redundancy is not enough andproviding a multiplane structure is required in order tosatisfy the reliability and ATM service standards.Considerable attention is paid in this thesis to the opticalcross-connects (OXCs) because they are considered as imminentand basic optical networking elements, allowing morefunctionality to the transparent optical networks. The OXCsstudied in this thesis are characterized by differentarchitectures and component technologies.It is shown in this thesis that in most published cases, thereliability performance is very far from that requested, in theproposed configurations. A novel strictly non-blockingarchitecture of the optical cross-connect has been proposed inorder to improve the reliability of the optical cross-connectnodes to an acceptable level.