Impairment Aware RWA based on a K-Shuffle Edge- Disjoint Path Solution (IA-KS-EDP) Chirag Taunk 1 , Sarvesh Bidkar 1 , Chava. V. Saradhi 2 and Ashwin Gumaste 1 1 Indian Institute of Technology, Bombay, India.400076 2 Create-Net, eNTIRE Department, Via Alla Cascata 56C, Trento 38123, Italy Email: {chiragtaunk, sarvesh.bidkar}@iitb.ac.in, {saradhi, ashwing}@ieee.org Abstract: We propose an IA-RWA algorithm called IA-KS-EDP, which evaluates multiple routing combinations considering the effects of OSNR, CD, PMD and using edge-disjoint paths to satisfy multi-line-rate traffic demands with minimum wavelengths. OCIS codes:(060.0060) Fiber optics and optical communications; (060.4251) Networks, assignment and routing algorithms 1. Introduction With the advancements in optical switching technologies and multi-degree ROADM architectures, the transport networks are moving towards all-optical (i.e., transparent) networks. However, due to non-ideal properties of optical components, the Physical Layer Impairments (PLIs) accumulate along an optical-path in the absence of OEO regeneration. Optical amplifiers introduce Amplified Spontaneous Emission (ASE) noise, which degrades the OSNR of the signal. Higher line-rate channels also suffer from Chromatic Dispersion (CD) and Polarization Mode Dispersion (PMD) leading to Inter Symbol Interference (ISI). These PLIs degrade the signal quality leading to high BER. Hence, we need to consider the effects of PLIs in the Routing and Wavelength Assignment (RWA) solution. In this paper, we propose an RWA algorithm called as Impairment Aware K-Shuffle Edge-Disjoint Path (IA-KS- EDP) where routing is based on our earlier K-shuffle Edge-Disjoint Path (EDP) pool approach (KS-EDP) [2]. In KS-EDP, we consider edge-disjoint paths for routing different connections, which significantly reduces the total number of wavelengths required to satisfy the given set of connections. We consider K different EDP routing combinations by shuffling the connection-list K times, each time picking up the random sequence of connections. This increases the chance of selecting an optimal routing combination. The wavelength assignment algorithm is a variation of First-Fit approach [3], which considers the possible sharing of Add-Drop Multiplexing (ADM) cards and transponders at a node. This leads to efficient usage of the network equipment. In this paper, we extend our work on KS-EDP algorithm [2] and consider PMD and OSNR limits in the routing decision on multi-line-rate demands. The connections that are unable to satisfy these limits are blocked. The routing combination is selected based on the least blocking probability. 2. Problem Statement and High Level Solution We consider the RWA problem in mesh topologies with limited number of available wavelengths and no converters and assume that the static traffic demands are given a-priori. The problem statement is as follows: a network graph G (V, E, T) is given; where V is the set of nodes, E is the set of bidirectional optical links, and T is a traffic matrix. Every   is a connection between source i and destination j, which can have multiple traffic demands of different line-rates.    (≥ 0) is the number of traffic demands of granularity k for the connection   . Each traffic demand of granularity k requires equivalent capacity wavelength along the route. We let k be one of the different granularities amongst 1Gbps, 2.5Gbps, 10Gbps, and 40Gbps, selected based on a given traffic distribution. The objective is to minimize the blocking probability and the number of wavelengths required to satisfy all the traffic demands. The classical RWA problem does not assume any power loss at the optical components such as fiber loss, insertion and pass-through loss of the nodes as well as neglects ASE noise and dispersion. In our Impairment Aware RWA solution, we consider the ASE noise effects to the OSNR, as the predominant contributor to OSNR degradation. The OSNR for an amplifier stage is calculated as:  ݐݏ =   ×××∇ and the OSNR at the receiver node is calculated as: 1   = 1  ݐݏ1 + 1  ݐݏ2 + ⋯ + 1  ݐݏ [4]. In addition, we also consider Chromatic dispersion (CD) and Polarization Mode Dispersion (PMD) introduced in signals of line-rate ≥ 10 Gbps. CD is calculated as: ܦܥ= ܦܥ ݋ݐݏ ݐ × ܮ  and PMD for a link is calculated as  ܦܯ  =  ܦܯ ݋ݐݏ ݐ ×  ܮ  . PMD of the lightpath is calculated as ( ܦܯ  ) 2 [1]. We assume the same link model as considered in [1] for OSNR, CD and PMD calculation. The in-line amplifiers and DCUs are placed on the fiber links to fully compensate for the power loss and CD. However, due to the absence of efficient in-line PMD