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In this paper an adaptive mapping technique (AMT) is proposed for spectral amplitude coding-optical code division multiple access (SAC-OCDMA) system. The main purpose of the proposed technique is to construct codes whose length varies adaptively with the number of users. This task can be easily accomplished by successive offsets of the basic code m...
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... Multiple Access Interference (MAI) has emerged as a major cause of optical system performance declination in OCDMA due to the overlap created between optical codes having the same optical chip positions, which leads to the emergence of multi-user interference (MUI) and phase-induced intensity noise (PIIN), which limits the multiplexing capacity and makes it adapt to a low cardinality (Nisar et al. 2021;Hacini and Aissaoui 2022). ...
This study investigated a novelty system known as optical code division multiple access-free space optics (OCDMA-FSO) based on a new two-dimensional successive weight (2D-SW) code. The proposed approach is developed to be employed in incoherent wireless optical networks to improve channel capacity, support a large number of concurrent users, accommodate a high bits rate, and eliminate the effect of electromagnetic and multiple access interferences. A new mathematical analysis for the proposed system has been detailed, including the expression of signal-to-noise ratio (SNR) and bit error rate (BER). Accordingly, the numerical outcomes of the mathematical analysis at a total data rate of 260 Gbps revealed that the proposed system enhanced the channel capacity to 2.04, 1.6, 3.32, 1.47, 1.68, 1.33, and 2.29 times than those of the systems based on the two-dimensional codes family including perfect difference (2D-PD), both diluted perfect difference (2D-DPD) and dynamic cyclic shift (2D-DCS), hybrid flexible cross-correlation/modified double weight (FCC/MDW), hybrid zero cross-correlation/multi-diagonal (2D-ZCC/MD), modified prime code (2D-MPC), hybrid prime code (2D-HPC), and one-dimensional successive weight (1D-SW), respectively. It can save − 4.9 dBm, − 2.9 dBm, − 4.3 dBm, and − 2.2 dBm of received power in comparison to both 2D-DPD, 2D-DCS, 2D-ZCC/MD, 2D-MPC, and 2D-HPC codes respectively, and it keeps − 6.2 dBm when moving from 1D-SW to 2D-SW. Moreover, the suggested network is also studied using Optisystem software at 30 Gbps of each channel, where it achieves a low BER value reaching \(1.72\times {10}^{-33}\) with a high transmission quality reaching 11.99 at a lengthy range attaining 1.3 km. Consequently, the results demonstrate that the proposed system can satisfy optical communication needs and be implemented in the next generations of wireless optical networks.
... En fait, ces systèmes souffrent de nombreux défis qui dégradent principalement les performances du système, premièrement, l'interférence d'accès multiple (MAI) ou soi-disant interférence multi-utilisateur (MUI) est définie comme la collision entre les utilisateurs transmettant simultanément dans le même canal [24][25][26]. Deuxièmement, le bruit d'intensité induit par la phase (PIIN) est un facteur qui dégrade principalement les performances au niveau du récepteur, ce bruit apparaît grâce au chevauchement des spectres optiques des différents utilisateurs, ce type de bruit est lié au MAI [27][28][29] De plus, l'augmentation de la capacité de multiplexage est liée à la longueur du code spectral, ce qui signifie que l'augmentation du nombre d'utilisateurs est proportionnelle à la longueur du code. Par conséquent, un code optique long nécessite une consommation d'énergie élevée et provoque un taux d'erreur élevé au niveau du récepteur, ce qui limite le nombre d'utilisateurs simultanés [30,31]. ...
In the framework of improving the performance of optical communication systems, the spectral amplitude coding - optical code division multiple access (SAC-OCDMA) has become a key technology to be able to improve the performance in terms of multiplexing rate, data rate, reduce power consumed, and synchronous /asynchronous transmission. It allows several subscribers to transmit their information simultaneously and securely by assigning a specific code to each user, which leads to good use of the transmission medium. Incoherent OCDMA systems in particular are affected by the phase induced intensity noise (PIIN) effect which is defined by the overlaps produced between codes which lead to multiple access interference (MAI) at the receiver. This phenomenon has become a dominant factor that leads to degraded performance of multiple OCDMA access systems. Thus, the right choice of code with zero crosscorrelation is required to overcome these drawbacks; moreover, the exploitation of the bandwidth is not perfect which induces a low spectral efficiency. In this thesis, a new hybrid model for the SAC-OCDMA system using advanced digital modulation OFDM (Orthogonal Frequency Division Multiplexing) has been investigated to overcome these drawbacks and improve the performance in terms of the number of available users, power consumption, data rate, and spectral efficiency. The suggested system is based on a new code having zero cross- correlation called Variable Weight Zero Cross-Correlation Code (VWZCC) characterized by simple construction, high security, simple coder/decoder design, and flexible weight. A new mathematical development is detailed to find a new equation of signal-to-noise ratio (SNR) and deduce the equations of bit error rate (BER), quality factor (Q), and error-vector magnitude (EVM) based on a spectral direct detection (SDD) technique using a single photo- detector (PD). The numerical results obtained from our hybrid system demonstrate an outperformance in comparison with OCDMA systems and hybrid systems based on Modified Double Weight (MDW), Flexible Cross-Correlation (FCC), shift-ZCC (shift-ZCC), and multi- diagonal (MD) codes. Hybrid network performance has been successfully verified using
𝑂𝑝𝑡𝑖𝑠𝑦𝑠𝑡𝑒𝑚𝑇𝑀 software for four users when the data rate is fixed at 622 Mbps, the eye diagram interpretation shows that our hybrid network offers a very low BER range and high- quality transmission when transmitting over long distances.
In the context of increasing the cardinality of a three-dimensional (3D) multiple access system by mainly eliminating the MAI effect and reducing the impact of PIIN noise, a 3D-OCDMA system has been developed in order to satisfy the large capacity of optical communication and reduce code length. Therefore, in this examination, a new spectral/temporal/spatial coding called variable weight zero cross-correlation (3D-VWZCC) code has been suggested. As clarified in Chapter 5, its construction is based on the extension of the previously proposed one-dimensional code where its corresponding mathematical analysis has been also detailed here. The numerical analysis results carried out indicates that the 3D-VWZCC code presents better performance compared to the 3D-Perfect difference (PD), 3D-Perfect difference/multi diagonal (PD/MD), and 3D-Dynamic cyclic shift/multi diagonal (DCS/MD) codes. It supports a massive number of simultaneous users of up to 317 users when power consumption is reach -10dBm as well as accommodates a high data rate of up to 2Gbps in the optical communication threshold (10−9). In addition, 3D-VWZCC system planning was also implemented using 𝑂𝑝𝑡𝑖𝑠𝑦𝑠𝑡𝑒𝑚𝑇𝑀 software for eight users to enrich the numerical simulation results. The network simulation when the data rate is fixed at 1Gbps gives excellent results in terms of evaluating the opening of the eye diagram. The system offers a low BER rate of up to 1,99 × 10−31 with a high transmission quality of 11.56. As a result, the outcomes prove that the proposed code can be used in the next generation of large multiplexing capacity multiple access optical networks since it satisfies optical communication requirements and improves performance criteria.
Briefly, these contributions could be a promising solution to high-quality optical access networks due to their various advantages such as overcoming PIIN noise, ignoring the MAI effect, improving access cardinality, increasing spectral efficiency and reinforcing data security, reducing power consumption and code size, as well as supporting very high data rate,...etc. These features provided solve the major obstacles that limit the progress of optical communications which makes these systems as an emerging challenge for future generations of high-speed optical networks.
... When increasing the number of users, the codes with ZCC property are not always favorable candidates because of the low efficiency of bandwidth utilization due to their long length [9,13]. In fact, codes with an optimal IPCC are considered reasonable solutions because of their suitable length when increasing the cardinality [14]. On the other hand, several detection schemes have been invented for SAC-OCDMA systems based on optimal IPCC codes to alleviate the impact of PIIN, such as modified-AND subtraction detection [15], single photodiode detection (SPD) [16], modified multi-photodiode balance detection [17], and normal spectral partition detection [18]. ...
This paper aims to enable the two-keying approach in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system that employs modified double weight (MDW) code. To achieve this goal, two-keying subtraction detection (TKSD) is suggested, which also declines the impact of multiuser interference (MUI) and phase-induced intensity noise (PIIN). The results of simulation test demonstrate that the TKSD is efficient in realizing the two-keying detection feature in SAC-OCDMA system with superior bit-error rate (BER) performance, security, and transmission rate.
... Spectral Amplitude Coding (SAC) is one of the techniques developed for OCDMA systems that have received much attention due to the reduction of multiple access interference, simplicity, and low cost of production (Kitayama 2014;Aissaoui and Hacini 2020). Accordingly, many studies have discussed the performances of SAC-OCDMA systems in the optical fiber scenario Norazimah et al. 2011;Hacini and Aissaoui 2022). Search for appropriate codes for these systems occupies an important part of the studies where various codes have been proposed (Aissaoui and Hacini 2020;Anuar et al. 2009;Imtiyaz et al. 2016). ...
A spectral amplitude coding-optical code division multiple access (SAC-OCDMA) system over the FSO channel is highly advantageous in providing high-speed communications with lower bit error rate (BER) and minimum multiple access interference (MAI). This work can be considered as an improvement over previous works published in the literature. This is due to the fact that a proper study of the performance of a SAC-OCDMA-FSO system has been carried out using Latin square code (LSC). This code, recently proposed, has a zero cross-correlation value and a short code length that reduces the number of used wavelengths. These properties make it better than other codes already proposed in previous works related to SAC-OCDMA-FSO systems. The performance of this system has been numerically evaluated, under fog attenuation conditions, in terms of BER with respect to different parameters such as: power transmitted, data rate, and FSO link range. For this, the maximum range of the FSO link, for a BER = \(10^{-9}\), has been determined for different cases of parameter values. The simulation results prove that the transmitted signal quality depends significantly on the attenuation conditions. So that, at a data rate of 1 Gbps and a transmitted power of 10 dBm, a maximum range of 2.34 km is obtained in clear weather, 1.56 km in haze, 496 m in light fog, 350 m in moderate fog, and 69.5 m in dense fog.
To overcome the multi-path effect in Visible Light Communication (VLC) Quasi-Synchronous (QS) Optical Code Division Multiple Access (OCDMA) system, Optical Zero Correlation Zone (OZCZ) code set pair have been proposed. In this article, new two methods for constructing OZCZ codes based on the Double Weight (DW) and the Zero Cross Correlation (ZCC) matrix are presented. The newly proposed methods are based on ZCC constructions that allow generating code sequences having all ZCC and OZCZ properties, ideal for use in VLC-QS-OCDMA transmission. The structure of the proposed ZCC-OZCZ code is simple, less complex, and their construction is more flexible than proposed DW-OZCZ and existing construction. In addition, the performance evaluation of the system adopting the proposed constructions, in terms of Bit Error Rate (BER), show that the proposed codes significantly reduce MAI compared to ZCC, and give the same performance as unipolar OZCZ codes with more simple and flexible construction.
