Cost Benefit Analysis of Elastic and Mixed Line Rate Optical Network Models

<div>Network traffic continues to grow at more than 30 percent per year and we either have to install new optical infrastructures or upgrade our optical networks to meet the increasing demands. Installing new fibers seems very costly the network operators considering the heterogeneity of optical networks with some consumers requiring low bit rate and others requiring high bit rate demands. As an alternative, we can use the existing fiber infrastructure to meet the traffic demands by aggregating both high and low bit rate demands or using a single type of rate-tunable technology to handle the increasing demands. This paper analyzes the two planning strategies-all period planning and incremental planning- for allocating resources in an increasing traffic and shows the pros and cons that a network operator may experience in case of using either elastic or mixed line rate optical networks.</div>

Cost Benefit Analysis of Elastic and Mixed Line Rate Optical Network Models

<div>Network traffic continues to grow at more than 30 percent per year and we either have to install new optical infrastructures or upgrade our optical networks to meet the increasing demands. Installing new fibers seems very costly the network operators considering the heterogeneity of optical networks with some consumers requiring low bit rate and others requiring high bit rate demands. As an alternative, we can use the existing fiber infrastructure to meet the traffic demands by aggregating both high and low bit rate demands or using a single type of rate-tunable technology to handle the increasing demands. This paper analyzes the two planning strategies-all period planning and incremental planning- for allocating resources in an increasing traffic and shows the pros and cons that a network operator may experience in case of using either elastic or mixed line rate optical networks.</div>

On the performance of switching methods in space division multiplexing based optical networks

In the current work, for Space Division Multiplexing based Optical Networks (SDM-b-OTNs), we investigate the performance of various switching methods with a variation in traffic evolution over different time frame periods. Initially, comparison of the existing methods viz., independent switching (InSw), frequency switching (FqSw), and space switching (SpSw) demonstrates that (i) over longer periods of time frame, FqSw provisions low network usage, and (ii) SpSw offers low network usage for shorter periods of time frame; however, as time frame increases to longer periods, SpSw starts to outperform InSw. Next, we investigate a hybrid switching (HySw) method which begins by implementing InSw and then shifts to the use of SpSw after the activation of specific numbers of space channels. HySw is observed to provision substantial savings on the costs incurred for switching, and with lower space channel values it also offers a balance in the trade-off which occurs between the costs associated for activating the space channels and that incurred for switching. Lastly, a comparison of InSw, SpSw, and HySw considering mixed line rate (MLR) demands shows that the space channels assigned in the ‘in-between’ periods of time frame can be reduced by shifting from InSw to SpSw in the starting periods of time frame.Overall, from the results it is inferred that the network performance only slightly depends on the MLR traffic, and over longer periods of time frame, in comparison to InSw, the significant benefits of SpSw and HySw remains conserved.

Effect of Channel Spacing on the Design of Mixed Line Rate Optical Wavelength Division Multiplexed Networks

The ever increasing heterogeneity and growing traffic volume has resulted in significant innovations and paradigm shifts within the telecom backbone networks. In order to cost-effectively respond to the diverse variety of traffic requirements having heterogeneous service demands, wavelength division multiplexed (WDM) optical networks have adopted the mixed line rate (MLR) strategy. In MLR networks, many wavelength channels with various line rates can co-exist within the same fiber which, however, raises many important design issues; one of them being the choice of the channel spacing. The quality of signal is affected by the channel spacing in terms of the bit-error rate (BER), which in turn affects the maximum optical reach of the lightpaths that depends on the line rates. In regard to the aforementioned, different methods can be adopted in order to set the width of the channel spacing, viz., (a) choice of a 50 GHz uniform fixed channel spacing specified by the ITU-T grid, (b) exploring various channel spacing values for different line rates so as to optimize the usage of the fiber spectrum, or (c) seek for an optimal value of the channel spacing which results in the minimum network cost. In the current work, we evaluate the MLR network cost for various channel spacings; hence, we find an optimal value of the channel spacing that leads to the minimum MLR network cost. The simulation results reveal that, for a MLR network, even with the assumption of uniform channel spacing, optimal values of the channel spacing for a minimum cost network can be identified.

Performance Evaluation of OOK, DPSK and Duo-binary Modulation Format based Mixed-Line-Rate (MLR) Optical Network

With the steady increase in the heterogeneous Internet traffic, the optical wavelength division multiplexed (WDM) networks based on a mixed line rate (MLR) strategy have emerged as an efficient-solution. Also, with the migration from the legacy to the higher line rate(s), the advanced modulation format(s) (MF) is/are required. However, use of appropriate MF(s) for the higher line rate(s) still remains an open problem. In this article, we compare the performance of an On-Off Keying (OOK), Differential Phase Shift Keying (DPSK) and Duo-binary (DB) MF based MLR network in the presence of various physical layer impairment(s) (PLIs) for which, we propose a mathematical model based on various MFs. As a novelty, we validate the proposed theoretical model’s results by comparing them with the results obtained through simulations from OptSim, which has not been conducted in any existing study(s) thus far. Our simulation results show that the DB MF is perfectly suitable for high spectral-efficient MLR systems owing to its high resistance to various PLIs.