Optical CDMA System Research Articles

Design and Evaluation of a Hybrid 2D-SWZCC OCMDA System with Multicarrier MM-Wave

This paper presents a hybrid communication system combining optical code division multiple access (OCDMA) and multicarrier millimeter-wave (MM-Wave) architecture operating at 35, 55, 75, and 95 GHz connected to a home network center (HNC) and the end user (EU). Hybrid Link reduces congestion on complex RF networks by combining optical fiber backhaul with radio links. The OptiSystem simulation demonstrates successful data transmission and transmission capacity at 40Gbps over various distances. Furthermore, this new 40G-MM wave OCDMA system that takes advantage of a two-dimensional single-weighted zero cross-correlation (2D-SWZCC) system with a multiplexing scheme of polarization wavelength multiplies the same N channels to M OCDMA code of the MM-Wave system that dramatically increased scalability. The comparative analysis shows that the proposed 2D-SWZCC hybrid algorithm outperforms 1D-SWZCC regarding scalability. This study contributes to developing communication algorithms with high data rates and provides promising solutions for method limitations and scalability in hybrid-MM-Wave-OCDMA architectures.

A 930 m/180 Gbps*User Underwater Coherent Optical Code-Division Multiple-Access Network Based on Hybrid 256-Differential Pulse Position Modulation and Weighted Modified Prime Code Sequence

Currently, there are three types of optical communication networks based on the communication channel between the transmitter and receiver: the optical fiber channel, visible light channel, and optical wireless channel networks. The last type has several advantages for underwater communication, wireless sensors, and military communication networks. However, this type of optical network suffers from weather conditions in free-space communications and attenuation owing to the scattering and absorption mechanisms for underwater communication. In this study, we present a new transceiver architecture of a coherent optical code-division multiple-access (OCDMA) system based on a hybrid M-ary differential pulse position modulation scheme and a spreading code sequence called weighted modified prime code for underwater communication to minimize channel dispersion, increase the transmission rate per second, enhance the network bit error rate (BER) performance, and improve network security. Using an OCDMA system, we can simultaneously expand the network coverage area and increase the number of users sharing the network over the same channel bandwidth. The simulation results in this study proved that the proposed system can accommodate 1310 active users and a network throughput of 180 Gbps*user over a transmission distance of 930 m without any repeater at a 10−9 BER performance, compared to the 45 Gbps*user network throughput and 100 m transmission distance reported in the literature.

Multirate Optical CDMA Systems Combining Generalized Modified Prime Sequence Code and Bi-Orthogonal Code

Multirate Optical CDMA Systems Combining Generalized Modified Prime Sequence Code and Bi-Orthogonal Code

Establishing A Spectral Optical CDMA System Involving The Use Of Two Mutually Orthogonal States Of Polarizations Using 1-D Two-Distinct Codes With Two-Code Keying

Establishing A Spectral Optical CDMA System Involving The Use Of Two Mutually Orthogonal States Of Polarizations Using 1-D Two-Distinct Codes With Two-Code Keying

Performance Analysis of New 2D Spatial OCDMA Encoding based on HG Modes in Multicore Fiber

This paper presents a pioneering 2D spatial Optical Code-Division Multiple Access (OCDMA) encoding system that exploits Mode Division Multiplexing (MDM) and Multicore Fiber (MCF) technologies. This innovative approach utilizes two spatial dimensions to enhance the performance and security of OCDMA systems. In the first dimension, we employ Hermite-Gaussian modes (HG00, HG01, HG11) to modulate each user's signal individually. This unique approach offers a robust means of data transmission while ensuring minimal interference among users. The second-dimension leverages MCF encoding, introducing two incoherent OCDMA codes: the Zero Cross Correlation (ZCC) code (λc=0) and the ZFD code (λc=1). These codes are thoughtfully designed and simulated, taking into account their cross-correlation properties to guarantee minimal interference and heightened data security. To assess the efficiency of this novel OCDMA encoding system, we implemented simulations with three active users using the Opti system software. At the transmitter end, each user's signal is modulated individually by their designated HG mode (HG00, HG01, HG11), resulting in separate channels. Subsequently, at the multicore fiber, each user's data is encoded with a unique code-word, and they are directed through specific core groups, ensuring data isolation and integrity. In this paper, the BER and eye pattern are examined with respect to different parameters such as data rate and distance. At a distance of 5 km and data rate of 10 Gbit/s, a BER value around 10-70 is achieved.

Performance Analysis of New 2D Spatial OCDMA Encoding based on HG Modes in Multicore Fiber

This paper presents a pioneering 2D spatial Optical Code-Division Multiple Access (OCDMA) encoding system that exploits Mode Division Multiplexing (MDM) and Multicore Fiber (MCF) technologies. This innovative approach utilizes two spatial dimensions to enhance the performance and security of OCDMA systems. In the first dimension, we employ Hermite-Gaussian modes (HG00, HG01, HG11) to modulate each user's signal individually. This unique approach offers a robust means of data transmission while ensuring minimal interference among users. The second-dimension leverages MCF encoding, introducing two incoherent OCDMA codes: the Zero Cross Correlation (ZCC) code (λc=0) and the ZFD code (λc=1). These codes are thoughtfully designed and simulated, taking into account their cross-correlation properties to guarantee minimal interference and heightened data security. To assess the efficiency of this novel OCDMA encoding system, we implemented simulations with three active users using the Opti system software. At the transmitter end, each user's signal is modulated individually by their designated HG mode (HG00, HG01, HG11), resulting in separate channels. Subsequently, at the multicore fiber, each user's data is encoded with a unique code-word, and they are directed through specific core groups, ensuring data isolation and integrity. In this paper, the BER and eye pattern are examined with respect to different parameters such as data rate and distance. At a distance of 5 km and data rate of 10 Gbit/s, a BER value around 10-70 is achieved.

A Secure Optical Body Area Network Based on Free Space Optics and Time-Delayed 2D-Spectral/Spatial Optical CDMA

Free space optics (FSO)-based optical body area networks (OBANs) are receiving massive attention as an opportunity to address the limitations of their radio frequency (RF)-based counterparts. This boom in research interests is primarily due to multitude of benefits, including high capacity, immunity to electromagnetic interference (EMI), rapid installation, cost efficiency, and license-free use of spectrum. Securing the transmission of patient health data against interception in OBANs using insecure FSO channels is a challenging task. Therefore, we propose a low-cost, flexible, and secure OBAN based on FSO technology and a time-delayed two dimensional (2D) spectral/spatial optical code-division multiple access (OCDMA) system. The proposed architecture consists of eight sensors attached to the bodies of patients. The sensors operate at a rate of 50 kbps. Electrical data generated from each sensor are used to modulate an optical carrier and then encoded using 2D-spectral/spatial double weight–zero cross correlation (DW-ZCC) code. The 2D encoded optical signals are then time delayed to eliminate the multiple parallel FSO channels between the transmitter and medical center. The combined optical signal consists of eight 2D-encoded time-delayed optical signals transmitted towards a remote medical center over an FSO channel with a range of 1 km. The received signal is decoded and the data from each sensor are recovered after photodetection at the medical center for further analysis. The overall performance of the sensors is analyzed using bit-error rate (BER) and quality factor (Q-factor) plots for different weather conditions and lengths of the FSO channel, considering the log-normal channel model. The capital expenditure (CAPEX) of the proposed architecture is analyzed and compared with the conventional 2D-spectral/spatial FSO system to determine the overall impact of introducing time delay units on the cost of implementation.

A high-speed integrated OFDM/DPS-OCDMA-based FSO transmission system: Impact of atmospheric conditions

Free space optics (FSO) communication systems are preferred due to their high transmission capacity so it can support the ever-increasing volume of online traffic. Optical code division multiple access (OCDMA) is ideal for enhancing capacity by utilizing the same wavelengths for different information transmission. This paper presents a new FSO system based on the combination of orthogonal frequency division multiplexing (OFDM) and OCDMA systems. Three OCDMA channels, employing diagonal permutation shift (DPS) codes, carry 20 Gbps each, modulated by 4-level quadrature amplitude modulation (QAM) and OFDM. To assess performance, the proposed system considers severe climate conditions like rain, fog, and snow. The effectiveness is measured by bit error rate (BER) and received optical power (ROP). In addition, actual meteorological data for the cities of Alexandria, Egypt and Pune, India are evaluated to demonstrate the applicability of the proposed model in a real-world setting. The results reveal successful transmission with an overall capacity of 60 Gbps over a 3600 m FSO range in Alexandria, achieving a 0.27 dBm ROP. In Pune, with higher average rainfall, the maximum FSO link is 2750 m with a −0.06 ROP. Furthermore, the proposed model can propagate up to 850 m under weak turbulence (WT).

Capacity Improvement of 3D-OCDMA-PON Hybrid System Next Generation Using Weight Zero Cross Correlation Code

This paper proposes a novel code for optical code division multiple access (OCDMA) systems, called the three-dimensional (3D) spectral/temporal/spatial single weight zero cross-correlation (3D-SWZCC) code. The proposed code could potentially be used in the next generation of passive optical networks (NG-PONs) to provide a 3D-SWZCC-OCDMA-NG-PON system. The developed code has a high capacity and a zero cross-correlation property that completely suppresses the multiple access interference (MAI) effects that are a main drawback for OCDMA systems. Previously, a two-dimensional (2D) SWZCC code was proposed for two-dimensional OCDMA (2D-OCDMA) systems. It works by devoting the first and second components to spectral and spatial encodings, respectively. However, the proposed code aims to carry out encoding domains in spectral, time, and spatial aspects for the first, second, and third components, respectively. One-dimensional, 2D, and 3D systems can support up to 68, 157, and 454 active users with total code lengths equal to 68, 171, and 273, respectively. Numerical results reveal that the 3D-SWZCC code outperforms codes from previous studies, including 3D codes such as perfect difference (PD), PD/multi-diagonal (PD/MD), dynamic cyclic shift/MD (DCS/MD), and Pascal’s triangle zero cross-correlation (PTZCC), according to various metrics. The system function is provided by exhibiting the architecture of the transmitter and receiver in the PON context, where the proposed code demonstrates its effectiveness in meeting optical communication requirements based on 3D-OCDMA-PON by producing a high quality factor (Q) of 18.8 and low bit error rate (BER) of 3.48 × 10−29 over a long distance that can reach 30 Km for a data rate of 0.622 Gbps.

New Constructions of Optimal Optical Orthogonal Codes Based on Partitionable Sets and Almost Partitionable Sets

Variable-weight optical orthogonal codes (OOCs) were introduced by Yang for multimedia optical CDMA systems with multiple quality of service (QoS) requirements. In this paper, partitionable sets and almost partitionable sets are used to construct variable-weight OOCs. Four new recursive constructions for optimal cyclic packing are presented. Consequently, new infinite classes of optimal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(v,W,1,Q)$ </tex-math></inline-formula> -OOCs are obtained.

Cardinality increasing of SAC-OCDMA system using novel decoder design

Abstract The large number of active users that optical code-division multiple access (OCDMA) offers makes it an attractive technology choice. OCDMA loses its noise immunity due to non-ideal correlation since the maximum auto-correlation and minimum cross-correlation detection technique is required in OCDMA systems. There are several detection techniques like complementary detection, direct detection, etc. This paper presents a new detection technique that is particularly suited for SAC-OCDAM systems with FCZ codes. The simulation results showed that by overcoming the effects of the MAI, significant performance improvements can be achieved.

Two code keying using optical CDMA system with 2D multi-method codes

We propose a novel family of two-dimensional multi-methods with two codes keying (2D MM with TCK) in spectral amplitude coding optical code division multiple access (OCDMA) networks. The idea transfers one code keying (OCK) of one-dimensional (1D) MM codes into two code keying (TCK) of 2D MM codes. The rationale has OCK transferred into TCK, 2D matrix formulations using the 2D MM codes, and modified cross-correlation. The research solution resolves the first item using two OCKs of 2D MM codes to become TCK of 2D MM codes to call 2D MM codes with TCK, the second item using two sets of 1D MM codes to produce 2D matrix formulations using 2D MM codes, and the third item using the cross-correlation to transfer into a modified cross-correlation. The modified cross-correlation eliminates multiuser interference. The proposed analysis utilizes a modified photocurrent to suppress phase-induced intensity noise. In the numerical results, the number of simultaneous users, data transmission rate, and effective source power using 2D MM codes with TCK are 294, 4.72 Gbps, and − 12 dBm, respectively.

Impact of systematically constructed nonorthogonal code shift keying for optical code division multiple access

It is desirable to provide Optical Code Division Multiple Access (OCDMA) systems for practical use in optical wireless communication application systems. Because the data transmission efficiency of the conventional OCDMA system is relatively low, one of the issues encountered with the OCDMA system is increasing the data transmission efficiency. This study proposes the nonorthogonal CSK system in order to clarify the performance improvement of the proposed system on the OCDMA system. Our proposed nonorthogonal CSK system systematically constructs nonorthogonal codes. This paper analyzes the system performances of the proposed system considering the scintillation, background noise, and multiple access interferences to evaluate the fundamental performance of the proposed system. The numerical results show that the proposed system outperforms the conventional OCDMA systems. Our obtained results that the systematically constructed nonorthogonal code is effective for enhancing OCDMA system performance is a useful finding for future research approaches.

Performance analysis of optical spectral amplitude CDMA system unipolar codes with double weight construction design

Abstract Optical Codes Division Multiple Access is a multiplexing approach in which the transmitter a distinguishable optical code is assigned to each user in the communication channel. OCDMA is designed for radio frequency (RF) communication systems and it is a variation of the CDMA system. Subsequently, to develop all OCDMA communication systems, the success of CDMA in wireless networks, as well as the full benefits of fibre optics, such as good security, extremely high bandwidth, low attenuation, and long-haul transmission. In this research Spectral Amplitude Coding-Optical Code Division Multiple Access is proposed. Initially, Modified Double Weight and Zero Cross-Correlation (MDW-ZCC) is proposed in this research to construct the code design of SAC-OCDMA, it produces the best possible autocorrelation and cross-correlation values. Subsequently, a combined Single Photodiode (SPD) and Direct detection technique is introduced to decode the transmitter information and it reduces the noise. Accordingly, a Gaussian approximation technique is presented to estimate the Bit error rate from the eye diagram of BER and Q-factor. Accordingly, the proposed method is simulated using Python software. The performance metrics are Q-factor, and bit error rate and the proposed method is compared with the existing Three-Dimensional Single Weight Zero Cross-Correlation (3D-SWZCC) Code, Two Dimensional Spectral/Spatial Cyclic Shift (2D-SSCS), and Permutation Matrix Zero Cross-Correlation (PM-ZCC) Code. Subsequently, these results exhibit that the proposed method produces the best performance than the other methods and it estimates the BER. Consequently, future work is based on the study of 3D codes with m-sequence code in the spectral/time/spatial OCDMA domain. The approach has elegantly integrated the design of an encoder and a decoder, allowing the system to efficiently create code in 3D bipolar mode, respectively.

New Algorithm for a Fixed Right Shift Code to Support Different Quality of Services in Smart and Sustainable Optical Networks

Smart and sustainable cities require a network that can ensure many exchanges of information. In this sense, the deployment of optical fiber seems essential in order to guarantee urban interconnection. In this work, a new algorithm for the right shift code to be used in optical fiber communication (OFC) is proposed. The algorithm was designed to support different quality of services (audio, video, and data) for smart cities. This algorithm was based on varying the code weight for a certain number of users and transmitting a service to them. This algorithm was used for a spectral amplitude-coding optical code division multiple-access (SAC-OCDMA) system. Two detection scheme approaches were used, which are the single photodiode (SPD) detection technique and the direct detection (DD) technique. The performance was analytically studied for the proposed system in terms of BER, SNR, and the maximum number of users. The obtained results, when our system used SPD, showed an improvement in the number of users, about 2.5% at 622 Mbps and 1.4% at 1.25 Gbps and 2.5 Gbps. It can support a number of users up to 151 for video services at BER = 10−12, 300 for audio services with BER = 10−3, and 162 for data services at BER = 10−9 at a data rate of 1.25 Gbps. Furthermore, the system was simulated and showed transmission distances of 30 km at 1.25 Gbps and 6 km at 2.5 Gbps for video services, 80 km at 1.25 Gbps and 30 km at 2.5 Gbps for audio services, and 44 km at 1.25 Gbps and 13 km at 2.5 Gbps for data services. Our proposed system is suggested to be implemented in a fixed fifth-generation passive optical network (F5G PON).

Improve cardinality with two-dimensional unipolar (optical) orthogonal codes for multiple access interference

Abstract Optical code division multiple access (OCDMA) is one of the promising technologies to be implemented using all-optical networks. The OCDMA system performance is substantially determined by the particular encoding codes. Due to the different transmitter and receiver design considerations, selecting the right code family and code dimension is critical. In this research, 2D codes based on permutation vectors’ (PV) codes are presented to overcome the Multiple Access Interference (MAI) problem and system complexity. Consequently, the research work focused on two-dimensional unipolar codes to mitigate the probability error and cardinality of the optical CDMA system. A fast wavelength-hopping/time-spreading (FWHTS) is introduced as an encoding technique. The FWHTS is used for code construction design, and it achieves cardinality in upper bound theory without sacrificing good auto-and-cross correlation properties. Accordingly, hybrid codes with serial elimination interference receivers are presented to estimate the error probability of 2D optical codes. The proposed method is simulated using Python software. The performance metrics are flexibility, bit rate, minimum temporal length, computational complexity, cardinality and wavelength. The proposed method is compared with the existing 2D balanced incomplete block design (BIBD) technique and multidiagonal (MD) codes. The performance of the proposed method is approximately 4% higher than these existing methods. Subsequently, in the future work, a SAC-OCDMA code construction design shall be presented and the decoding techniques can be introduced, which can reduce the receiver noise and other phase intensity induced noise, respectively.

Visible-Light CDMA Communications Using Inverted Spread Sequences

Visible-light communication (VLC) using light-emitting diodes (LEDs) is gaining attention in the wireless communication field. LEDs can be used as data transmitters without losing their main functionality as lighting devices. In some VLC applications, such as traffic signs and road signals in intelligent transportation systems, high brightness is required to help people recognize the signs and signals conveyed by the light sources. In this paper, the use of inverted modified prime sequence codes (MPSCs) is shown to be efficient for increasing brightness in an optical code-division multiple access (CDMA) system for VLC, while the original MPSCs, namely non-inverted codes, provide much lower brightness. The average light intensity of a system using an inverted MPSC is several times the intensity of a system using an original MPSC, without losing the capabilities of channel multiplexing and multi-user interference canceling. Average light intensity and normalized fluctuation are investigated for the optical CDMA systems with the original and inverted MPSCs. The results show that the systems with the inverted MPSCs provide higher average light intensity and lower normalized fluctuation than the systems with the original MPSCs do. Moreover, the bit error rates of the systems with the inverted MPSCs are evaluated by computer simulation and compared with those of the systems with the original MPSCs.

A Family of Optimal Multiple-Weight Optical Orthogonal Codes for Fiber-Optic Networks.

Optical orthogonal codes (OOCs) were designed for multimedia optical CDMA systems with quality of service requirements in optical fiber networks. Two-dimensional (2-D) multiple-weight optical orthogonal codes have been invested as they can overcome the drawbacks of nonlinear effects in large spreading sequences. In this paper, we reveal the combinatorial properties of optimal 2-D OOCs and focus our attention on the constructions for a family of optimal 2-D multiple-weight optical orthogonal codes by combinatorial methods, such as incomplete difference matrix, h-perfect cyclic packing, and skew starter. In particular, an improved construction of skew starters with multiple weights is also proposed to solve the existence of optimal multiple-weight optical orthogonal codes. Our numerical examples demonstrate that the proposed construction is very helpful for optimizing the utilization of optical network effectively.

Cardinality Enhancement of SAC-OCDMA Systems Using New Diagonal Double Weight Code

Optical code division multiple access (OCDMA) provides another dimension to multiple access systems, in which each user is assigned a unique code. This allows each subscriber to simultaneously access the medium without any contention. However, simultaneous access of multiple users introduce multiple access interference (MAI) which primarily deteriorates the performance of OCDMA systems. This paper proposes a new code called diagonal double weight (DDW) code to elevate the performance and cardinality of spectral amplitude coding (SAC) OCDMA systems. Performance of our proposed code is evaluated using comprehensive analytical analysis followed by simulation analysis. Examination of bit error rate shows that DDW code along with single photodiode detection technique provides efficient performance, with added benefits of simplified design, large cardinality and ease of implementation.

Phase Carrier approach based on Optical Code Division Multiple Access Networks

A technique for optical code-division multiple-access (OCDMA) spectral amplitude coding is proposed and analyzed. The proposed approach is based on combining both OCDMA systems over a phase carrier. Compared with conventional OCDMA systems, this approach exhibits numerous advantages such as simplicity in the system design and cost efficiency. The phase shift based on phase modulation is adopted in the proposed system, and the orthogonal function based on the random diagonal code is applied. The proposed scheme is considered cost-effective because only one laser source is used; which minimizes interference for access network passive optical network applications and improves the system performance of bit-error rate (BER 10-12).