Abstract

SummaryIn our last paper at NFOEC 2005, we discussed the economic crossover point of the SONET and the DWDM technologies. We understand that each technology has its economic advantage at a different network traffic level. We also pointed out that there have been efforts in integrating the two technologies into a single platform. In this paper, we continue to investigate all the possibilities of merging the two platforms into one. We indicated that the SONET platform, in the form of an add drop multiplexer (ADM), is more granular in grooming the traffic and therefore better utilizing the network capacity, and that the DWDM platform, in the form of an optical add drop multiplexer (OADM), is switching traffic at wavelength levels but more efficient on a per data bit basis when justified by sufficient traffic volume.In the real network deployment, a hybrid design is often desirable with ADM doing the first stage grooming of low speed demands such as DS1, DS3, OC3 and OC12. The ADM then sends the aggregated traffic to an OADM through OC48 and/or OC192 interfaces. The OADM will fulfill the transport of the traffic using wavelengths multiplexed in a single pair of fibers. This leads to the emergence of an integrated platform that is DWM based with the SONET functionality of grooming traffic at STS-1 granularity. The effort is to collapse the overlaid SONET and DWDM networks into a single platform for the benefit of cost reduction in both equipment and network management.In defining an integrated platform of SONET and DWDM, there are two optional architectures. One option is a platform that implements the SONET functionality in a transponder of an OADM. Because a transponder forms a unique wavelength in the DWDM system, this architecture is frequently referred to as "ADM-On-A-Wavelength", or simply ADM-on-WL. The attached figure illustrates a reconfigurable OADM (ROADM) with wavelength selective switching (WSS) and ADM-on-WL. The other option is a DWDM platform with a centralized STS-1 switch fabric (SF). The SONET functionality is built around the SF and OEO (optical-electrical-optical) conversion that is required for traffic in a wavelength that needs to be groomed at sub-wavelength levels. This paper will compare the two options and also compare them with legacy approaches architecturally and economically. Our study shows that the integrated platform has economic advantages over DWDM only and SONET-over-DWDM approaches, and in some cases even over the SONET only approach where traffic warrants a SONET deployment. Therefore, the integration has shifted the economic crossover point to favor DWDM deployment that incorporates SONET functionality.We have two main objectives to achieve in this paper: network design impact with a SONET and DWDM integrated platform; and economic impact of the integrated architectures versus the traditional SONET and DWDM overlay architecture. We will discuss the concepts of SONET network design, DWDM network design and hybrid SONET over DWDM designs. Some real world examples will be used for the analysis of the integrated architectures and the comparison of economic models.Figure 1. ROADM with ADM-on-WL

© 2006 Optical Society of America

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