Rui Manuel Morais

Genetic Algorithm for the Topological Design of Survivable Optical Transport Networks

We develop a genetic algorithm for the topological design of survivable optical transport networks with minimum capital expenditure. Using the developed genetic algorithm we can obtain near-optimal topologies in a short time. The quality of the obtained solutions is assessed using an integer linear programming model. Two initial population generators, two selection methods, two crossover operators, and two population sizes are analyzed. Computational results obtained using real telecommunications networks show that by using an initial population that resembles real optical transport networks a good convergence is achieved.

Generating Realistic Optical Transport Network Topologies

We address the problem of generating physical realistic optical transport network topologies. This type of network has characteristics that differ from scale-free networks, such as the Internet. Based on the analysis of a set of real transport topologies, we identify and assess relevant characteristics. A method to generate realistic topologies is proposed. The proposed method is validated by comparing the characteristics of computer-generated and real-world optical transport networks.

Statistical model for link lengths in optical transport networks

From the analysis of statistical properties of real networks, it is found that general extreme value (GEV) distribution provides an accurate model for link length statistics of optical transport networks (OTNs). The parameters of GEV distribution can be estimated from the average link length of the OTNs. Expressions for average link lengths, based only on the knowledge of network coverage area and number of nodes, are improved for better accuracy. It is shown that the optimized GEV distribution estimates the link statistics of OTNs with good accuracy (Kolmogorov-Smirnov statistic less than 0.18).

Impact of node architecture in the power consumption and footprint requirements of optical transport networks

We evaluate and compare the power consumption and the number of required slots (footprint) of fixed and flexible transport nodes. The node architecture is assumed to comprise a grooming structure, and a reconfigurable optical add/drop multiplexer (ROADM). Fixed grooming is achieved using cascades of muxponders. Alternatively, flexible grooming is achieved with electrical switches. Fixed frequency and fixed direction ROADM, and colorless and directionless ROADM are considered. For all the architectures, we present an accurate dimensioning model that allows computation of the required modules. Results show that to optimize the total power consumption and footprint of the network, the architecture of each node has to be selected according to the amount and pattern of the add/drop and regenerated traffic and the number of pairs of fibers convergent to the node. An optimization method based on simple rules for node type selection is proposed.

Field Experiments With a Grooming Switch for OTDM Meshed Networking

Field experiments of 42.7/128.1 Gb/s wavelength-division multiplexed, optical time-division multiplexed (WDM-OTDM) transmultiplexing and all-optical dual-wavelength regeneration at the OTDM rate are presented in this paper. By using the asynchronous retiming scheme, we achieve error-free bufferless data grooming with time-slot interchange capability for OTDM meshed networking. We demonstrate excellent performance from the system, discuss scalability, applicability, and the potential reach of the asynchronous retiming scheme for transparent OTDM-domain interconnection.

OTDM-to-WDM Conversion based on Wavelength Conversion and Time Gating in a Single Optical Gate

OTDM-to-WDM conversion from 128.1Gbit/s to 3x42.7Gbit/s is achieved by wavelength conversion using side filtering of SPM broadened spectrum in HNLF, followed by a single electro-absorption modulator based optical gate. A maximum 2dB penalty was achieved.

Field trial of WDM-OTDM transmultiplexing employing photonic switch fabric-based buffer-less bit-interleaved data grooming and all-optical regeneration

We report, for the first time, a field trial of a novel 42.7Gbps/128.1Gbps WDM/OTDM grooming node, and confirm node interoperability and the data integrity of asynchronous retiming.

Optical grooming switch with regenerative functionality for transparent interconnection of networks

We demonstrate a regenerative optical grooming switch for buffer-less interconnection of metro/access and metro/core ring networks with switching functionality in time, space and wavelength domain. Key functionalities of the router are the traffic aggregation with time-slot interchanging (TSI) functionality, the WDM-to-ODTM multiplexing and the OTDM-to-WDM demultiplexing of high-speed channel into lower bit-rate tributaries as well as multi-wavelength all-optical 2R regeneration of several higher-speed signals. BER and Q-factor measurements of different switching scenarios show excellent performance with no error floor and Q-factors above 21 dB.

A statistical model for CapEx fast calculation in optical transport networks

We present a statistical model to estimate the CapEx in multi-layer optical networks. This model allows a fast calculation of the CapEx without complete information. The accuracy of the model was evaluated considering practical optical networks. For all the networks considered an error smaller than 10% was obtained, which shows that is possible to estimate the CapEx with good accuracy even without complete information.

2R/3R optical grooming switch with time-slot interchange

We demonstrate a regenerative optical grooming switch for interconnecting 130 Gbit/s and 40 Gbit/s networks with switching functionality in time, space and wavelength domain. Q-factors are above 21 dB.