Fábio Renan Durand

Impact of PMD on hybrid WDM/OCDM networks

In this work, we investigated the impact of polarization-mode dispersion (PMD) in optical networks using the hybrid technology of wavelength-division multiplexing and optical code-division multiplexing. In these networks, virtual paths based on code/wavelength channels (VCP/VWP) are dynamically established to attend the traffic demand. We use a routing channel assignment based on genetic algorithm to establish the VCP/VWPs. The main results show that the network blocking probability caused by PMD depends on parameters of optical orthogonal codes like weight and length.

Distributed SNIR Optimization Based on the Verhulst Model in Optical Code Path Routed Networks With Physical Constraints

In this work, the performance of a distributed power control algorithm (DPCA), based on the Verhulst model for signal-to-noise plus interference ratio (SNIR) optimization in optical code path (OCP) routed networks, was investigated. These networks rest on 2-D codes (time/wavelength) to establish the OCP. The DPCA can be effectively implemented in each node because it uses only local parameters. The SNIR model considers multiple-access interference, amplified spontaneous emission at cascaded amplified spans, group velocity dispersion, and polarization mode dispersion. Numerical results have shown SNIR convergence at power penalties of 7.94 and 11.51 dB for 2.5 and 10 Gbps, respectively. These results could be utilized for adjustment of either the transmitted power to a transmitter node or the gain to dynamic intermediary amplifiers.

The effects of power control on the optical CDMA random access protocol

Abstract In this work, the performance of the hybrid system that combines the distributed power control algorithm (DPCA) with the random access protocol as a novel and simple scheme of achieving a high performance in decentralized optical code division multiple access (OCDMA) networks has been investigated. The multiple access interference (MAI) and the near–far problem effects have been considered. The DPCA’s advantage lies in its characteristics being effectively implemented to each node, since only local parameters are necessary. The principal results have shown that the network throughput and delay are strongly affected by the near–far problem and the DPCA works to solve this problem. Hence, the introduction of a certain level of the power control to the random access temporally coded (1D) or the time-wavelength coded (2D) OCDMA networks has demonstrated profitability of the throughput increase and the delay reduction. As a consequence, the proposed system configuration with the DPCA using a very low number of iterations has resulted in a better throughput and simultaneously in a delay decrease when compared to the system without power control mechanisms.

Energy-efficient power allocation for WDM/OCDM networks with particle swarm optimization

In this paper, an optical network optimization based on particle swarm intelligence is described. The particle swarm optimization (PSO) algorithm is evocated in order to solve the problem of resource allocation (RA) based on the signal-to-noise plus interference ratio optimization in a hybrid wavelength division multiplexing/optical code division multiplexing network with quality-of-service restrictions. The RA optimization based on the PSO strategy allows the regulation of the transmitted power in order to maximize the energy efficiency. For the network optimization context, a system model is described, figures of merit are presented, and a suitable model for the heuristic optimization approach is developed, with emphasis on the optimization of input parameters and network performance. Afterward, extensive numerical results for both optimization problems are discussed, taking into account realistic network operation scenarios.

The effects of polarization mode dispersion on 2D wavelength-hopping time spreading code routed networks

In this study, we investigate the effects of multiple access interference (MAI) and polarization mode dispersion (PMD) in 2D wavelength-hopping time spreading optical code paths. The main results show the MAI effects and PMD constraint at the outage probability. The contribution of these sources of interference is analysed to choose the better design of code parameters in order to increase the performance of networks based on optical code paths. These results could be applied to determine the parameters design in code/wavelength routed networks.

WDM/OCDM Energy-Efficient Networks Based on Heuristic Ant Colony Optimization

The ant colony optimization for continuous domains (ACOR) approach is deployed in order to solve two resource allocation (RA) optimization problems associated to the signalto-noise plus interference ratio metric with quality-of-service constraints in the context of hybrid wavelength-division multiplexing/ optical code-division multiplexing networks. The ACOR-based RA optimization strategy allows optimally regulating the transmitted optical powers, as well as maximizing the overall energy efficiency (sum EE) of the optical network. In this context, a suitable model for heuristic optimization approach is developed, with emphasis on the network performance under optimized ACOR input parameters. Extensive simulation results for both power allocation and EE optimization problems are discussed taking into account realistic networks operation scenarios. Computational complexity analysis is performed in order to obtain a suitable, yet sturdy, algorithm regarding the robustness versus complexity tradeoff. The performance and complexity of the proposed heuristic approach are compared with a disciplined convex optimization approach based on CvX tools.

Design of multi-rate optical code paths considering polarisation mode dispersion limitations

The authors propose an original design based on multi-rate optical code paths (OCPs) for transport in advanced wavelength-division multiplexing/optical code division multiplexing (WDM/OCDM) networks. The authors utilise multi-length optical orthogonal codes (OOC) to obtain multi-rate OCPs. The performance of the proposed scheme is analysed and the impact of multiple access interference (MAI) and polarisation mode dispersion (PMD) over these OCPs is evaluated. Results show that not only multi-rate operation can be achieved but also MAI effects can be reduced, while mitigating PMD effects.

Performance analysis of optical code switching router

In this work we study and evaluate the performance of an optical code switching router (OCSR), intended to be utilised in hybrid wavelength-division multiplexing/optical code-division multiplexing (WDM/OCDM) networks. This OCSR can transport and route efficiently user data over optical code paths without departing from the optical domain. Limitations of the proposed OCSR are investigated and its superior performance demonstrated based on non-coherent prime codes. Our results indicate that our solution is useful in showing the effects of the optimum threshold level on the OCSR performance. We propose a continuous adjustment of the optimum threshold level based on the measurement of the mean optical power before the decoder. The influence of various parameters of the optical codes on the OCSR performance are also considered and evaluated. Copyright

Mitigation of environmental temperature variation effects in OCDMA networks using PSO power control

In this paper, a mitigation of environmental temperature variation effects in optical code division multiple access (OCDMA) networks based on power control is described. The temperature changes would adversely affect 2D wavelength-hopping time-spreading optical code by causing a reduction in the expected height of the autocorrelation peak. Environmental temperature variation is usually difficult to accurately determine and compensate for due to its dynamic nature and fluctuations. Furthermore, the power control strategy allows the regulation of the transmitted power in order to dynamically mitigate the effects of temperature variation. The particle swarm optimization (PSO) algorithm is evocated to solve the problem of power control based on the signal-to-noise plus interference ratio optimization to mitigate the environmental effects. Afterward, numerical results are discussed taking into account the code parameters, such as the code weight and spectral spacing.

Effects of multiple access interference and PMD on optical code lightpaths

In this work we investigate the effects of multiple access interference (MAI) and polarization mode dispersion (PMD) in optical code division multiplexing (OCDM) lightpaths. These paths are determined by the data encoding with non-coherent optical orthogonal codes (OOC), using a sequence inversion keying (SIK) optical correlator system. Our results show the impact of MAI effects and PMD constraint on the packet error rate, which depends on OOC parameters like weight and length. These parameters in turn depend on MAI and PMD effects. The results obtained can be used as input parameters for the design of OOC in virtual code/ wavelength path (VOCP/ VWP) routed networks.