Physical layer security is a crucial step towards fully secure communications systems. The flexibility and ubiquity of digital signal processors in modern wireless and optical communication systems ...open up a clear path for the development of discrete-signals encryption techniques, which can be implemented relatively cheap. In this paper, we show the fundamental role of amplitude and phase encoding in the security and practical implementation of linear discrete signal cryptography (DSC). We focus on the spectral implementation of these encoding schemes and consider the equivalence between spectral amplitude encoding (SAE) and spectral scrambling (SS). Numerical simulation results show that 16-quadrature amplitude modulation (16-QAM) signals encrypted by SS and spectral phase encoding (SPE) can be recovered only if eavesdroppers know the exact position of <inline-formula> <tex-math notation="LaTeX">\sim ~95 </tex-math></inline-formula>% of the scrambled samples with a maximum phase error of <inline-formula> <tex-math notation="LaTeX">\pm ~7^{\circ } </tex-math></inline-formula> for all samples. The number of brute force attacks to break such encrypted signals far exceeds the one provided by the widely deployed data ciphering algorithm Advanced Encryption Standard (AES). Physical layer results reveal that the bit error ratio (BER) associated with the encrypted signals is 0.50 regardless of the deployed signal format and DSC scheme. The BER vs. signal-to-noise ratio performance of the encrypted/ decrypted signal is the same as that of signals not encrypted. Finally, the paper proposes the adoption of pseudo-random dynamic keys (PRDKs) to promote encryption randomness, diffusion, and confusion to the encrypted signals. A new numerical methodology shows this strategy outperforms AES diffusion and confusion properties.
Flexible optical network (FON) architectures are considered a very promising solution where spectrum resources are allocated within flexible frequency grids. These architectures must handle the ...spectrum more efficiently and must support on-demand elastic bandwidth provisioning. However, when multi-bandwidth services coexist without a suitable bandwidth management, blocking of wider spectrum calls increases compared to narrower spectrum calls. This unfairness effect limits FONs' performance, not fulfilling much of the promise they hold. In this letter we present a new specific variant of trunk reservation policies that can effectively deal with fast on-demand bandwidth provisioning. Through network simulations we show that trunk reservation is able to guarantee fairness and to equalize the performance of an entire network in terms of blocking probability and link utilization with different flexible spectrum allocation policies.
We propose a novel digital signal processing (DSP) technique that encrypts multiple baseband signals by dividing them into several spectral slices, which are then shuffled. Afterwards, the shuffled ...signals modulate optical carriers and are propagated through transparent optical communication systems. Simulation results reveal that the reach of shuffled signals is ~ 90% of that of unshuffled ones. We also evaluate a scenario where the shuffled signals are transmitted through multiple routes to increase security and investigate the robustness of the technique against brute force and chosen plaintext attacks.
Routing and wavelength assignment (RWA) problem has been an attractive problem in optical networks, and consequently several algorithms have been proposed in the literature to solve this problem. The ...most known techniques for the dynamic routing subproblem are fixed routing, fixed-alternate routing, and adaptive routing methods. The first one leads to a high blocking probability (BP) and the last one includes a high computational complexity and requires immense backing from the control and management protocols. The second one suggests a trade-off between performance and complexity, and hence we consider it to improve in our work. In fact, considering the RWA problem in a wavelength routed optical network with no wavelength converter, an improved technique is proposed for the routing subproblem in order to decrease the BP of the network. Based on fixed-alternate approach, the first k shortest paths (SPs) between each node pair is determined. We then rearrange the SPs according to a newly defined cost for the links and paths. Upon arriving a connection request, the sorted paths are consecutively checked for an available wavelength according to the most-used technique. We implement our proposed algorithm and the least-hop fixed-alternate algorithm to show how the rearrangement of SPs contributes to a lower BP in the network. The numerical results demonstrate the efficiency of our proposed algorithm in comparison with the others, considering different number of available wavelengths.
Hitherto, several algorithms have been proposed for routing and wavelength assignment (RWA) problem on single or multifiber wavelength routed optical network (WRON) with or without wavelength ...converters. However, due to budget limit, we may equip only a few links in the network with multi fibers, and hence we have a sparse multifiber WRON (SM-WRON). Here, we consider the RWA problem on an SM-WRON without wavelength conversion. Different number of links are considered to equip with multi fibers to make an SM-WRON. Two basic techniques to select the required links to make them multifiber are random-choice and first-choice. The earlier one selects some links randomly and the later one selects the first numbered links. Here, in order to propose an improved algorithm, we define a cost for every link in the network, and then equip the most expensive links with multi fibers. The numerical results made on the well known benchmark networks, i.e., ARPANET and NSF topologies, show the proposed technique to be more efficient than the basic ones taking the blocking probability into account.
In this paper, it is proposed and numerically tested a 4 −THz guard-band-less integrated all-optical wavelength converter (iAOWC) with two four-wave mixing (FWM) stages. The nonlinear media used in ...each stage is a waveguide with a tellurite core that is buried into a SiO2 substrate. The core is shaped as two interleaved spirals connected in their centers by two arcs of a circle to minimize bend loss. The iAOWC can continuously shift a 4 −THz WDM bandwidth from the C- to the L-band and vice versa. In the physical layer simulations, 80×28−GBaud, as DP-QPSK and DP-16QAM, 50-GHz-WDM signals were propagated, respectively, through typical distances found in ultra-long-haul and long-haul transmission systems. For up to four wavelength conversions, the penalties imposed on the signals bit-error-ratios by the iAOWCs were negligible. In the network layer simulations, blocking probabilities were estimated in the CORONET and PANEUR topologies supposing an incremental traffic scenario. Physical layer results were fundamental for the parameters (route lengths, wideband conversion, and spectral shift) considered in the network layer analysis. All network links could carry up to 160 wavelengths that extended from C- to L-band. It is shown that by using an iAOWC with bandwidth of 4-THz instead of 1-THz, both with the same spectral shift capability, to match the blocking probabilities achieved with OEOWCs, this would lead to a reduction of 50% and 40% in the number of required devices for the CORONET and PANEUR topologies, respectively. Finally, this is the first time that it is reported a joint analysis of the physical and network layers regarding the impact of wideband wavelength conversion on the performance of optical networks, specially using an integrated all-optical device and under real-world traffic scenarios.
•A wideband integrated all-optical wavelength converter was numerically tested.•Wavelength converter can operate with dual-polarization WDM signals.•Wavelength converter imposes negligible penalty on the WDM signals BER.•Physical and network layers analysis on the impact of wavelength conversion.•The wider the wavelength converter band, the fewer the required devices.
In this work, a new methodology to compute the blocking probability in wavelength-routed optical networks is presented. The proposal is based on an interactive procedure, named Interactive Matrix ...Methodology (IMM), that executes actualization of the network traffic distribution in order to reach a precise blocking performance. The IMM updates an initial network link load continuously and computes the blocking probability for each output link considering that the traffic among the links is dependent and related with all links and nodes in the network, not only with all links in a given path or route. The simulation results obtained in the same conditions and in several optical network scenarios match very well with the theoretical approximation achieved with this methodology. The advantage of this theoretical methodology is to be fast, accurate and applicable in low load regions, where a discrete event simulation is not precise. Furthermore, this method can be used to compute the estimative of blocking probabilities per node and in the network, including the cases where the number of wavelengths is different on each node.
In this work, we propose and investigate numerically a two-stage one-pump four-wave mixing (FWM) device for guard-band-less wavelength conversion. This device can convert all signals within the ...C-band to the L-band and, afterwards, return them to the C-band. The nonlinear medium for FWM is a spiral-shaped tellurite waveguide with a footprint of 2.5 mm 2 . Our simulation results indicate, after wavelength conversion (C- to L-band and back to C-band at the destination) 80×56-Gb/s quadrature phase shift keying signals could be propagated in networks with diameters as large as 640 km.
In this study, we investigate the performance of optical packet/burst switched (OPS/OBS) architectures connected as mesh and as ring topologies for future optical metropolitan networks. Network ...throughput and protection to link failure under uniform traffic distribution for all nodes are investigated to evaluate the sensitivity of OPS/OBSN performance. Our data are based on analytic results and computer simulations that include a comparison between various mesh and ring topologies. We also consider detailed traffic distributions over the network links and the impact caused by failure of more or less loaded links, thus providing a method to select links that require protection, which can be very useful in network planning.
The performance of a hybrid WDM/OCDM technology is investigated under impairments of Multiple Access Interference. We employed analytical models of Optical Orthogonal Codes to evaluate the switching ...network resources, such as the number of optical codes carried on each wavelength. Moreover, we propose and analyze a few optical code and wavelength conversion switching architectures, in order to scale the number of codes and wavelength converters and obtain a minimum burst blocking probability. The results demonstrate that architectures comprising Sparse-Partial Optical Code Converters with Sparse-Partial Wavelength Converters provide better performance. The network resources utilization are improved with number of converters, hence reaching a better cost benefit.
