Today's optical networks must meet the unprecedented capacity requirements of 5G communications and provide such capacity under strict cost constraints. Filterless Optical Networks (FONs) (i.e., optical networks where optical nodes are solely based on passive splitters and combiners) are emerging as an outstanding solution to reduce network cost while supporting capacity growth. Due to FONs' specific design criteria (the network topology must be divided into edge-disjoint filterless fiber trees), traditional network problems, such as, e.g., routing and wavelength assignment and virtual network mapping, shall be tackled adopting distinct approaches with respect to stateof-the-art filtered optical networks networks. In this paper, we investigate the problem of survivable virtual network mapping (SVNM) in FONs. We propose an Integer Linear Programming model to establish fiber trees and provide survivable mapping of virtual networks, while minimizing cost of additional equipment and spectrum. We show that joint optimization of filterless trees and survivable mapping significantly decreases transceivers and spectrum cost compared to a disjoint solution where the tree establishment does not consider SVNM constraints.

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Filterless Optical Networks (FONs) (i.e., optical networks where switching nodes are solely based on passive splitters and combiners) enjoy features that are highly appreciated by network operators, such as their low cost and their energy efficiency, posing them as an alternative solution to filtered Wavelength-Switched Optical Networks (WSON) based on active switching nodes. Due to FONs' specific design criteria (the network topology must be divided into link-disjoint filterless fiber trees to avoid laser loops), traditional network problems, such as survivable virtual network mapping, shall be revisited and tackled adopting novel solutions with respect to state-of-theart filtered WSONs. In this paper, we investigate the problem of survivable virtual network mapping (SVNM) in FONs with the aim of evaluating the cost of survivability when adopting FON technology. We first model the problem as an Integer Linear Program to establish fiber trees and provide survivable mapping of virtual networks, while minimizing cost of additional network equipment and spectrum with respect to WSON. We then propose multiple heuristic and meta-heuristic approaches to tackle large problem instances. In our numerical evaluations, we consider three scenarios: FON, WSON, and FON with preestablished fiber trees. Results show that in FON, where SVNM is jointly optimized with fiber tree establishment, the investment in additional network equipment can be largely minimized, and even avoided in some cases. In contrast, in FON with pre-established trees, amount of additional network equipment needed to guarantee survivability is significant (up to 60% with respect to WSON).

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In Filterless Optical Networks (FONs), passive splitters and combiners replace the more complex and more expensive Reconfigurable Optical Add-Drop Multiplexers (ROADMs) based on Wavelength Selective Switch (WSS) in network nodes. The utilization of passive switching elements in network nodes requires to subdivide the network topology into loop-free edge-disjoint fiber trees, consequently constraining physical paths between nodes. In this work, we investigate Virtual Network Mapping (VNM) and Virtual Network Embedding (VNE) with virtual link protection in the context of FONs. To ensure virtual link protection, we propose a strategy based on the placement of additional network equipment to allow mapping virtual links over two fiber trees. We model the problem as an Integer Linear Programming (ILP) formulation with the objective of minimizing network cost in terms of additional network equipment and overall wavelength consumption. Main results show that, when solving VNE, placement of virtual nodes and link mapping can be optimized to avert excessive wavelength consumption, while VNM drains much more network's capacity, since virtual nodes' locations are predetermined. In addition, results show that, when guaranteeing protection of virtual links in FONs, the gain of VNE is further maximized with respect to VNM. Moreover, results show that solving VNM with virtual link protection requires additional network equipment, severely penalizing network cost.