Ahmed Nabih Zaki Rashed

Optical Image Encryption Based on Chaotic Baker Map and Double Random Phase Encoding

This paper presents a new technique for optical image encryption based on chaotic Baker map and Double Random Phase Encoding (DRPE). This technique is implemented in two layers to enhance the security level of the classical DRPE. The first layer is a pre-processing layer, which is performed with the chaotic Baker map on the original image. In the second layer, the classical DRPE is utilized. Matlab simulation experiments show that the proposed technique enhances the security level of the DRPE, and at the same time has a better immunity to noise.

High efficiency wireless optical links in high transmission speed wireless optical communication networks

Power link budgets are prepared for wireless optical communication systems to illustrate the optical losses that happen during transmission. This paper has presented optical wireless links, which offer ultra multi gigabit per second data rates and low system complexity. For ground space and/or terrestrial communication systems, these links suffer from atmospheric loss mainly due to fog, and scintillation. Optical wireless links provide high bandwidth solution to the last mile access bottleneck. However, an appreciable availability of the link is always a concern. Wireless optical links are highly weather dependent, and fog is the major attenuating factor reducing the link availability. Link margin, received signal power, transmission bit rate, bit rate distance product, signal-to-noise ratio, and BER are the major interesting design parameters in the current study. Copyright

Performance Evaluation of Short Range Underwater Optical Wireless Communications for Different Ocean Water Types

This paper has presented our interesting in wireless underwater communications for different ocean water types. Recent interest in ocean exploration has brought about a desire for developing wireless communication techniques in this challenging environment. Due to its high attenuation in water, a radio frequency (RF) carrier is not the optimum choice. Acoustic techniques have made tremendous progress in establishing wireless underwater links, but they are ultimately limited in bandwidth. In traditional communication systems, constructing a link budget is often relatively straight forward. In the case of underwater optical systems the variations in the optical properties of ocean water lead to interesting problems when considering the feasibility and reliability of underwater optical links. The main focus of this paper is to construct an underwater link budget which includes the effects of scattering and absorption of realistic ocean water. As well as we have developed the underwater optical wireless communication systems to have shorter ranges, that can provide higher bandwidth (up to several hundred Mbit/s) communications by the assistant of exciting high brightness blue LED sources, and laser diodes suggest that high speed optical links can be viable for short range application. The received signal power, signal to noise ratio, bit error rate, transmitted signal bandwidth, and transmission bit rates are the major interesting parameters for different ocean water mediums as a criteria of the best signal transmission characteristics of short wireless optical communications over wide range of the affecting parameters.

Transmission Characteristics Evaluation Under Bad Weather Conditions in Optical Wireless Links with Different Optical Transmission Windows

Optical wireless links offer gigabit per second data rates and low system complexity. For ground space and or terrestrial communication systems, these links suffer from atmospheric loss mainly due to fog, scintillation and precipitation. Optical Wireless link provides high bandwidth solution to the last mile access bottleneck. However, an appreciable availability of the link is always a concern. Wireless Optics links are highly weather dependent and fog is the major attenuating factor reducing the link availability. Optical wireless links offer gigabit per second data rates and low system complexity. For ground space and or terrestrial communication scenarios, these links suffer from atmospheric loss mainly due to fog, scintillation and precipitation signals and then to upgrade the transmission bit rate distance product for ultra long transmission links. This paper has presented the bad weather effects such as rain, fog, snow, and scattering losses on the transmission performance of wireless optical communication systems. It is taken into account the study of bit error rate, maximum signal to noise ratio, maximum transmission optical path lengths and maximum transmission bit rates under these bad operating conditions.

Optical Wireless Communication Systems Operation Performance Efficiency Evaluation in the Presence of Different Fog Density Levels and Noise Impact

The free space optical communication technology tries to fulfill rising need for high bandwidth transmission capability link along with security and ease in installation. The free space optics uses beam of light to provide optical connection that can send and receive video, voice, and data information. In this paper a model analytical description of optical wireless communication systems operation performance efficiency evaluation in the presence of different fog density levels and noise is constructed. It is used for quantitative determination of the maximum range between transmitter and receiver depending on the signal transmission quality. Link margin, signal transmission, signal quality, received signal power, particle size distribution, optical depth, transmission data rate, signal time delay spread, signal noise and signal attenuation are deeply studied over wide range of the affecting parameters. Signal time delay spread and signal to noise ratio are deeply studied with using on-off keying modulation technique and are compared with their results with using binary phase shift keying in Li et al. (IEEE Trans Commun 55:1598–1606, 2007).

Optical fibre communication cables systems performance under harmful gamma irradiation and thermal environment effects

One problem in the application of fibre optics to military systems is that nuclear (and space) radiation is known to produce colour centres in optical materials, causing a reduction of light transmission over a spectrum of wavelengths. These radiation effects could cause permanent or temporary disruption of a fibre optics transmission system. Thus, the study has investigated the harmful effects of gamma irradiation on fibre communication system links under thermal environment effects over a wide range of operating parameters. Both the ambient temperature and the irradiation dose have severe effects on the system transmission link characteristics and consequently the performance characteristics of optical communication systems. It is also to be noted that the model has deeply developed the modelling basics of transmission communication systems, which may be used to analyse total pulse dispersion, transmitted signal bandwidth, transmission bit rates, radiation induced loss and optical received power by using the soliton transmission technique after different gamma irradiation doses and irradiation times.

Transmission Performance Simulation Study Evaluation for High Speed Radio Over Fiber Communication Systems

Radio over fiber communication system technology modulation techniques are presented in this study in order to enhance the performance behavior of optical fiber communication systems. The proposed modulation techniques used to meet this aim mainly consist from a mixture of traditional modulation technologies. The proposed modulation technologies include merging modulation techniques such as pulse amplitude frequency modulation, quadrature amplitude frequency modulation, differential phase shift keying amplitude modulation, offset quadrature phase shift keying amplitude modulation and frequency phase modulation are applied on different optical communication system models. The different types of modulation techniques are illustrated and discriminated in current research paper that provides measured quantities details that namely received power, maximum Q-factor and minimum bit error rate regarding to simulation results. Optiwave Simulation Version 13 software is the basic tool which is used to study proposed models.

Performance enhancement of IM/DD optical wireless systems

Due to the fast development of telecommunications and the great demand of bandwidth, optical wireless communication (OWC) has become a promising trend. OWC offers flexible networks for both indoor and outdoor communications providing high security, high speed and a license free spectrum. Data transmission over indoor OWC systems with diffused channel model at high speed will extend the channel impulse response over several symbol periods with many reflections causing inter-symbol interference. This interference distorts the data symbols being transmitted and affects the signal recovery at the receiver side. This paper studies error control coding for OWC systems over additive white Gaussian noise and ceiling bounce channel models. It considers Hamming coding and channel equalization for unipolar optical orthogonal frequency division multiplexing (OFDM) system. The objective is to mitigate the channel distortion, and hence achieve reliable transmission and correct detection at the receiver side.

Optical Cross Connect Performance Enhancement in Optical Ring Metro Network for Extended Number of Users and Different Bit Rates Employment

Optical cross connect (OXC) is important device that play a vital role in switching high speed optical signals and in our case as high speed switch to open the first ring to the second ring to become one ring in case of path failure or during maintenance in any node in this path and also if the failure path get in service it switch the two ring again to become isolated from each other. This paper has presented different enhancement techniques to increase number of users at different bit rates and also increased the transmission distance between nodes. Its main advantages have made it to disaster path in case of any failure cause in any node or path between two optical cross connect OXC. That is no doubt that crosstalk, dispersion and noise are produced when OXC separates incoming optical signals onto different output paths.

Performance Evaluation of SAC-OCDMA System in Free Space Optics and Optical Fiber System Based on Different Types of Codes

In this paper, the Spectral Amplitude Coding-Optical Code Division Multiple Access (SAC-OCDMA) system performance is investigated both in Free Space Optics (FSO) and Optical Fiber Systems (OFS) scenarios focusing on different types of codes. The codes having low cross correlation such as Random Diagonal (RD) and Khazani-Syed (KS), and zero cross correlation such as Zero Cross Correlation (ZCC) and Multi-Diagonal (MD) are used. In the FSO scenario, moderate turbulence and hazy weather conditions are considered. In the OFS scenario, nonlinear effects, attenuation, and dispersion are taken into consideration. Also, the performance of various codes is evaluated under different rain attenuation conditions. The simulation results show that the SAC-OCDMA codes performance is media-dependent. The ZCC codes give better performance than low cross correlation codes in both FSO and OFS scenarios. The MD code gives the best code performance in both scenarios with the ZCC code following. The RD code provides better performance than the KS code in the OFS scenario. However, in the FSO scenario, the KS code performs better than the RD code under the turbulence effect. Furthermore, the MD code performance under different bit rates is investigated to support tri-play services. Its security performance is also investigated.