Yousef Fazea

Multidiameter optical ring and Hermite–Gaussian vortices for wavelength division multiplexing–mode division multiplexing

Abstract. Optical vortices are high-capacity data carriers for mode division multiplexing (MDM) in multimode fiber (MMF). This paper reports on the MDM of a combination of helical-phased optical vortices comprising donut modes and Hermite–Gaussian (HG) modes for different radial offsets from the MMF axis. A data rate of 44 Gbps is achieved for wavelength division multiplexing–MDM of two pairs of helical-phased donut mode and HG mode at wavelengths 1550.12 and 1551.72 nm for a MMF length of 1500 m.

40Gbit/s MDM-WDM Laguerre-Gaussian Mode with Equalization for Multimode Fiber in Access Networks

Abstract Modal dispersion is seen as the primary impairment for multimode fiber. Mode division multiplexing (MDM) is a promising technology that has been realized as a favorable technology for considerably upsurges the capacity and distance of multimode fiber in conjunction with Wavelength Division Multiplexing (WDM) for fiber-to-the-home. This paper reveals the importance of an equalization technique in conjunction with controlling the modes spacing of mode division multiplexing-wavelength division multiplexing of Laguerre-Gaussian modes to alleviate modal dispersion for multimode fiber. The effects of channel spacing of 20 channels MDM-WDM were examined through controlling the azimuthal mode number and the radial mode number of Laguerre-Gaussian modes. A data rate of 40Gbit/s was achieved for a distance of 1,500 m for MDM-WDM.

Investigation of channel spacing for Hermite-Gaussian mode division multiplexing in multimode fiber

Mode division multiplexing (MDM) may be used to increase the capacity of multimode fiber interconnects for data centers. This paper demonstrates the importance of controlling the channel spacing of a MDM system capitalizing on Hermite-Gaussian (HG) modes in order to mitigate modal dispersion and minimize the average system bit-error rate. The effect of channel spacing of a 25-channel hybrid MDM-wavelength division multiplexing (WDM) system was examined through the x-index and y-index separations of Hermite polynomials of HG modes for different MMF lengths. Simulations prove that by controlling the index separations of the Hermite polynomials, acceptable BER was achieved for 25Gb/s data transmission for a distance of 800 meters for a 25-channel HG-based MDM-WDM system at a center wavelength of 1550.12nm. The optimal x-index and y-index Hermite polynomial separations for the HG modes are 2, 3 and 4.

Mode division multiplexing of spiral-phased donut modes in multimode fiber

Mode division multiplexing (MDM) is a promising technology for alleviating network traffic congestion in order to future proof current local area network infrastructure. In view of the capacity limits of multimode fiber in the advent of tremendous data growth, various dimensions for multiplexing and modulating data have been commercially deployed in the intensity, phase, wavelength and time domains. The eigenmode dimension, however, has been relatively untapped. This paper models the MDM of spiral-phased donut modes of different diameters in MMF for increasing the data capacity. A data rate of 40Gbit/s up for a distance of 1500 meters is achieved. Analyses of the power coupling coefficients and modal delays at the photodetectors are analyzed for different mode vortex orders.

Space Division Multiplexing in Multimode Fiber for Channel Diversity in Data Communications

Space division multiplexing (SDM) has recently gained eminence as a means to alleviate data traffic congestion to future-proof current network infrastructure. This paper reports on SDM of a new spiral-phased wavefront comprising modified Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) modes on a wavelength of 1550.12 nm over a 2 km-long MMF. Power coupling coefficients, degenerate mode group delays and bit-error rates are analyzed for different vortex orders.

From grids to clouds: Recap on challenges and solutions

Grid Computing is a set of resources; the separate computational power of these resources has combination to execute a huge task. Usually, in a Computational Grid environment, the main resource is the Central Processing Unit (CPU), mostly used in research fields that demand high computational power to perform massive and complicated calculations. Cloud Computing is a promising computing pattern which offers facilities and common resources on demand over the Web. The implementation of cloud computing applications has high priority, especially in the modern world, for example in providing adequate funding for social services and purchasing programs. In this paper, we discuss the implementation of cloud computing over a Smart Grid: reliable, guaranteed and efficient with low cost, it is expected to offer Long Term Evolution (LTE). This allows larger pieces of the spectrum, or bands, to be used, with greater coverage and less latency. The third technology is the Vehicular Network, an important research area because of its unique features and potential applications. In this survey, we present an overview of the smart grid, LTE and vehicular network integrated with cloud computing. We also highlight the open issues and research directions in implementing these technologies with cloud computing in terms of energy and information management for smart grids; applying cloud computing platforms for 4G networks to achieve specific criteria; and finally architectural formation, privacy and security for vehicular cloud computing.

PAPR Reduction in OFDM Signal by Incorporating Mu-Law Companding Approach into Enhanced PTS Scheme

Abstract Orthogonal Frequency Division Multiplexing (OFDM) is a potential transmission approach for high capacity communication systems. Despite the many advantages of OFDM, the major downside is the high peak-to-average power ratio (PAPR) which increases the system complexity, reduces the efficiency of the system, causes degradation in BER performance, and makes OFDM sensitive to nonlinear distortion in the transmission. Various methods have been proposed to deal with the PAPR problem, including the partial transmit sequence (PTS) that has attracted considerable attention. Hence, this paper presents a hybrid approach combining an enhanced PTS technique with Mu-Law companding. The PTS technique was enhanced through improving its sub-block partitioning scheme, where the enhanced partitioning scheme consolidated a conventional interleaved partitioning into an adjacent partitioning scheme. This incorporation of Mu-Law characteristic in time domain for PAPR reduction in OFDM essentially enhances the PAPR reduction performance, based on using numerical simulation results. Consequently, though the pseudorandom sub-block partition method obtains better PAPR reduction more than the other sub-block partition schemes (interleaved and adjacent) of ordinary PTS, it is quite difficult to be designed. The findings show that the enhanced PTS technique with Mu-Law companding, while maintaining low computational complexity, performs significantly better than the pseudorandom partitioning PTS on various types of modulation formats and subcarriers.

ISCP: In-depth model for selecting critical security controls

Abstract The primary goal of all organizations worldwide is to reduce potential threats and vulnerabilities. An information security control assessment is a far-reaching way to deal with control analysis that can help organizations to measure the adequacy and effectiveness of their present and planned security controls. Availability of adequate resources and proper risk analysis practices should be considered in preventing security breaches in order to achieve returns on security investments. Nonetheless, and despite the necessity for a competent security analysis framework, present frameworks and methodologies for security control analysis lack practical guidelines and mostly depend on subjective judgment and qualitative approaches. This paper proposes an information security control prioritization (ISCP) model that can determine the critical vulnerable controls based on a number of assessment criteria. The model uses techniques from the Order Performance by Similarity to Ideal Solution (TOPSIS) method, which is a sub-method of multiple attribute decision making. The proposed model provides clear guidelines on how to accomplish control analysis in a structured, self-organizing and constituent manner, with minimal overlap. Evaluation of information security controls using TOPSIS as the prioritization method involves a cost-effectiveness analysis, an effective and efficient assessment in terms of testing and selecting information security controls in organizations.

Performance of a Direct-Detection Spot Mode Division Multiplexing in Multimode Fiber

Abstract Multimode fiber (MMF) regarded as an excellent choice for providing large capacity and high-speed for applications such as data centers due to its adaptability and unwavering quality. The ceaseless development and the increase of Internet users that emphasis on increasing data capacity have promoted mode division multiplexing (MDM) as a promising contender for providing further level of multiplexing freedom by propagating several and dissimilar channels in different mode stream. This paper investigates and analyzes the effects of launching MDM spot mode with various vortex order using vertical-cavity surface-emitting laser array in conjunction with equalization scheme. A capacity of 40 Gbit/s transmitted over MMF long distance of 1500 m has been achieved at a wavelength of 1550.12 nm.

Mitigation of Atmospheric Turbulences Using Mode Division Multiplexing based on Decision Feedback Equalizer for Free Space Optics

Abstract In mode division multiplexing (MDM) free space optical (FSO) communication system, the atmospheric turbulences such as fog, rain, and haze cause adverse effects on system performance. This paper investigates the mitigation of atmospheric turbulences of FSO using MDM and decision feedback equalizer (DFE) with minimum mean square error (MMSE) algorithm. The implementation of the MMSE algorithm is used to optimize both the feedforward and the feedback filter coefficients of DFE. The proposed system comprises three parallel 2.5Gbit/s channels using Hermite–Gaussian modes. A data rate of 7.5Gbit/s over 40 m, 800 m, 1400 m, and 2km under medium fog, rain, haze, and clear weather, respectively, has been achieved. In addition, it is noticed that the link distance is reduced while increasing the attenuation. The simulation results revealed that a DFE improves the performance MDM FSO system while maintaining high throughput and desired low bit error rate.