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This paper presents a comprehensive investigation of a wide range of protection strategies against all single link failures in all-optical WDM networks based on mesh and multi-ring architectures. In the mesh architecture, three protection strategies, namely, minimal cost, single link basis and disjoint path protection strategies are investigated. In the multi-ring architecture, the distribution and non-distribution traffic multi-ring design strategies are extensively examined. Although, the concepts of mesh and multi-ring designs have previously been perceived to be fundamentally different, in this paper we explain and show that these two architectures can be systematically related and viewed as a unified concept. This new way of looking at the fully survivable network design helps understand clearly the mechanisms and performance of each protection strategy. To minimize the system cost of 100% protection WDM networks, mathematical models based on the integer linear programming (ILP) are derived as the tool for achieving optimal path placement, wavelength assignment and ring selection simultaneously. Apart from the mathematical model, the main contributions of this paper are the analysis and comparison in aspects of the spare capacity requirement and ease of operation and practical feasibility amongst these protection strategies. However, the emphasis is on the multi-ring protection schemes. In addition, the influence of the number of multiplexed wavelengths per fiber to design outcomes and the benefit of having wavelength conversion capability in WDM network environment are also studied.