Paparao Palacharla

Intra-Node Contention in Dynamic Photonic Networks

Dynamic photonic networks rely on colorless, non-directional Reconfigurable Optical Add/Drop Multiplexer (ROADM) nodes to enable rapid re-routing of wavelength channels without optoelectronic conversion. We report numerical simulations of the wavelength contention that can occur in such multi-degree ROADM nodes. Intra-node blocking rates and transponder utilization are computed for node designs with and without a client-side fiber cross-connect, and both are compared to results predicted for an ideally contention-free ROADM.

Intra-node contention in a dynamic, colorless, non-directional ROADM

Using numerical simulation of a dynamic network, we quantify the intra-node blocking occurring in colorless, non-directional Reconfigurable Optical Add/Drop Multiplexers (ROADMs). Designs including a client-side fiber cross connect are shown to offer lower blocking probability.

Traffic grooming and regenerator placement in impairment-aware optical WDM networks

In this paper, we address the problem of traffic grooming and regenerator placement in a WDM optical network in which lightpaths are hop-constrained by physical impairments. The efficient placement of regenerators and electronic grooming equipment at ROADM nodes for a given network topology is required such that all traffic demands can be supported with minimum cost. We present a detailed ROADM node architecture together with an associated cost model, and we propose an auxiliary-graph-based heuristic for jointly placing regenerators and electronic grooming equipment in the network. The numerical results show that combining the grooming problem with the placement of regenerators reduces the network cost significantly compared to the cases in which traffic grooming and regenerator placement are handled separately.

Blocking performance in dynamic optical networks based on colorless, non-directional ROADMs

We show that blocking in dynamic networks of colorless, non-directional ROADMs is tolerant to intra-node contention when contention-aware routing/wavelength assignment (RWA) algorithms are used. An optional client-side cross-connect enables low blocking with simpler RWA variants.

Service Velocity: Rapid Provisioning Strategies in Optical ROADM Networks

The advent of reconfigurable optical add/drop multiplexers with colorless and non-directional add/drop ports enables transponders and regenerators to be pre-deployed, without a priori knowledge of which wavelength or direction they will eventually serve. We study pre-deployment of optical regenerators as a means to drastically reduce the provisioning time, using Monte Carlo simulation of an optical backbone network. With appropriate placement strategies, regenerators can be efficiently pre-deployed so that new connections can be established rapidly, without the delays caused by service visits to intermediate network nodes.

Performance of colorless, non-directional roadms with modular client-side fiber cross-connects

We study the impact of partitioning client-side fiber cross-connects on the blocking performance of colorless, non-directional ROADM based dynamic optical networks. Simulations show that smaller fiber cross-connects (16×16, 48×48) can achieve low blocking.

Free space optical interconnect at 1.25 Gb/s/channel using adaptive alignment

Free space optical backplanes have previously required precision mechanics or moving parts. An adaptive alignment technique is described, using redundant VCSEL and detector arrays for real-time mapping of parallel 1.25 Gb/s data channels to aligned links.

Survivable virtual optical network mapping in flexible-grid optical networks

In this paper, we study the problem of survivable impairment-aware virtual optical network mapping in flexible-grid optical networks (SIA-VONM). The objective is to minimize the total cost of transponders, regenerators, and shared infrastructure for a given set of virtual optical networks, which can survive single link failures. We first provide the problem definition of SIA-VONM, and then formulate the problem as an integer linear program (ILP). We also develop a novel heuristic algorithm together with a baseline algorithm and a lower bound. Numerical results show that our proposed heuristic achieves results that are very close to those of the ILP for small scale problems, and that our proposed heuristic can solve large scale problems very well.

Survivable impairment-aware traffic grooming and regenerator placement with connection-level protection

In this paper, we address the problem of survivable traffic grooming and regenerator placement in optical wavelength division multiplexing (WDM) networks with impairment constraints. The working connections are protected end to end by provisioning bandwidth along a sequence of lightpaths through either a dedicated or a shared connection-level protection scheme. We propose an auxiliary-graph-based approach to address the placement of regenerators and grooming equipment for both working and backup connections in the network in order to minimize the total equipment cost. Simulation results show that the proposed algorithms outperform lightpath-level protection algorithms, in which each lightpath is protected separately. We also show the performance of connection-level protection under both dedicated and shared protection schemes in terms of the network cost, along with the effect of different cost models on equipment placement and performance for networks with different line rates. The restoration time of dedicated and shared connection-level protection is also investigated.

Reliable resource allocation for optically interconnected distributed clouds

In this paper, we study the reliable resource allocation (RRA) problem of allocating virtual machines (VMs) from multiple optically interconnected data centers (DCs) with the objective of minimizing the total failure probability based on the information obtained from the optical network virtulization. We first describe the framework of resource allocation, formulate the RRA problem, and prove that RRA is NP-complete. We provide an algorithm, named Minimum Failure Cover (MFC), to obtain optimal solutions for small scale problems. We then provide a greedy algorithm, named VM-over-Reliability (VOR), to solve large scale problems. Numerical results show that VOR achieves results close to optimal solutions gained by MFC for small scale problems. Numerical results also show that VOR outperforms the resource allocation through random DC selection (RDS).