OCDMA System Research Articles

Design and performance analysis of BPON using transposed modified walsh code

This work is an attempt to design and analyze unidirectional and bidirectional BPON to support communication within and between ONUs via remote access nodes in an OCDMA system. A complete PON system addressing both downstream and upstream communications links will be demonstrated at data rates up to 100 G chips/s. The proposed passive optical network performance is examined in terms of BER for a specific channel utilization factor, and these results are compared with existing OCDMA codes. The proposed architecture using MWC and TMWC reduces the MUI without compromising the sensitivity of the optical receiver and is also able to support a reasonable number of users with low received signal power. The theoretical analysis shows that the system is capable of supporting hundreds of users over a distance of 10 km with a BER value of only 10−70; while the optical receive power is − 34 dBm with unidirectional BPON. The simulation results for unidirectional and bidirectional BPON have a Q factor of 10.674 with a BER value of 8.7 × 10−27, Q factor 10.147 with BER value of 5.18 × 10−24, for a distance of 30 km respectively for upstream transmission. Therefore unidirectional system has a high Q factor and a low BER compared to that of the bidirectional BPON system.

Construction and Characterization of Optical Orthogonal Codes (n,w,1) for Fast Frequency Hopping-Optical Code Division Multiple Access

This paper investigates a new combinatorial construction approach based on cyclic difference packings for the construction of an optical orthogonal code that is suitable as a time spreading sequence for fast frequency hopping optical code division multiple access (OCDM) systems. The proposed construction provides a solution to the electrical decoding delay problem when compared to its optical counterpart, as well as other optimization issues. The criteria for optimizing the performance of such an OCDMA system are provided, namely: the flexibility and simplicity in constructing the optimal code for any length and weight, a reduction in the encoding/decoding complexity that complies with changes in the fast frequency hopping system, and the provision of system transfer transparency, a decoding rule that exploits the embedded asymmetric error correcting capability of the code. Our neighbor difference approach refers to the partition of different solutions into sub-classes, given in the correlation matrix form. It takes into account both direct and recursive combinatorial code construction methods, and the resulting characteristics are evaluated accordingly. A performance analysis based on the OCDMA channel is given, and a comparison with other difference family solutions is performed.

Investigation of Jervol water types properties effects on underwater optical wireless OCDMA system performances for different modulation techniques

In this paper, an analytical evaluation of the direct detection OCDMA system is presented in an underwater wireless optical channel. Performances were evaluated by varying the main simulation parameters (range, transmitted power, number of users, and inclination angle) considering different modulation techniques for different water types (categorized according to Jerlov classification). It is found that the BER performance of this system significantly depends on the water type and the receiver’s position and that QAM modulation provides the best performance for the proposed system. The work is supplemented by a simulation implementation using. the results thus obtained agree with those of the theoretical calculations.

Performance of EDW and MDW codes in spectral amplitude coded OCDMA system with SPD

Performance of EDW and MDW codes in spectral amplitude coded OCDMA system with SPD

Halton-Chaos and ALPSO power allocation methods for passive optical CDMA networks

The allocation of minimum power with guarantee of minimum rate in passive optical network optical code division multiple access (PON-OCDMA) networks is analyzed considering heuristic optimization methods such as Particle Swarm Optimization (PSO) and four variants. The base of the power-rate adaptive PON-OCDMA is the multi-length 2-D wavelength-hopping/time-spreading code called multiple-length extended wavelength-hopping prime code (MLEWHPC) to support the services of different media in accordance with the bit-rate and quality of service (QoS). The Halton-Chaos-β-PSO (HC-PSO) algorithm is proposed for solving the optimal power and rate allocation in order to maximize the EE of the optical system, subject to QoS restrictions based on the signal-to-interference plus-noise ratio (SINR) in each class of optical user and minimum required power. The proposed HC-PSO and the analytical–iterative–heuristic approach based on the augmented Lagrangian and PSO (ALPSO) method demonstrate promising performance-complexity trade-off, specially for high dimensionality OCDMA systems. The proposed hybrid analytical-evolutionary resource allocation method is corroborated by numerical simulation results, considering the tuning of heuristic evolutionary input parameters, which have demonstrated to improve the EE of the optical system when the power-rate allocation procedure is deployed dynamically in real time applications.

Security enhancement of 2-D DIM codes using 4 × 1 NOR logic based on FISO

Security enhancement and bandwidth increase are requirements of ultrafast future optical code division networks that also minimise the latency at nodes without distressing the traffic performance. In OCDMA systems, eavesdropper tries to breach the optical code, and encoded/encrypted data in order to get correct code word of legitimate user. For security enhancement, an ultra high speed 4 \(\times\) 100 Gbps two dimensional Diagonal identity matrix (2D-DIM) code and four input single output (FISO) all optical logic gate with private key encryption is proposed and its performance in terms of security is analyzed. Expressions for synchronous and asynchronous transmissions are derived for proposed work and it is perceived that asynchronous transmission has better security. Further performance/security analysis is carried out for different scenarios such as with/without FISO, with 1D-DIM/2D-DIM codes, using 4 \(\times\) 1 AND gate/NOR gate in terms of correct code detection rate (CCDR), max. eye amplitude, Received Q factor, Signal to noise ratio at different launched power levels for legitimate user and eavesdropper. Eavesdropper attacked the proposed system but due to FISO layering, private key encryption, and 2D-DIM codes, cannot get acceptable level of CCDR. To the best of author’s knowledge, proposed system is ultra high speed with enhanced security and no reported studies have investigated security enhancement at this much ultra high speed.

Performance analysis of 2D WH/TS OCDMA system through atmospheric turbulence channel

Performance analysis of 2D WH/TS OCDMA system through atmospheric turbulence channel

Lotka-Volterra distributed power control model for OCDMA systems

Dynamic continuous Lotka-Volterra model is used to build two new distributed power control algorithms (DPCA) for optical code division multiple access systems (OCDMA) communication systems, namely DPCA-LV and DPCA-LV* algorithms. The DPCAs features are described, while comparative performance analyses are carried out involving both proposed LV-based DPCAs, the classical Sigmoid DPCA (by Uykan and Uykan), and the Matrix inversion method (MIM) by Tarhuni, including the convergence speed, the normalized mean square error (NMSE), the average consumption of energy per user and complexity measured by the floating-point operations (flops). Under conditions of estimated errors, the proposed DPCA-LV* exhibits minor discrepancy regarding the ideal power vector solution and better convergence, considering both fixed and adaptive factor convergence regarding the DPCA-LV, the conventional Sigmoid DPCA, and MIM approach. The superiority of the DPCA-LV* in terms of performance-complexity tradeoff is more remarkable under high dimension optical networks.

Simulative Comprehensive Analysis of 2D Algebraically Constructed Codes for Optical CDMA

In this manuscript, comprehensive analysis of distinct optical codes belonging to family of algebraically constructed codes has been demonstrated. Many optical codes belonging to algebraically constructed family such as Extended Reed-solomon codes (E-RS), Multi-level prime codes (MPC), Extended-multi level prime codes (E-MPC), and Variable-weight quadratic congruence codes (VWQCC), Bipolar/Unipolar codes are taken into consideration. The performance characteristics of these codes are examined through Hard-error limiting probability (HEP) equations. Investigations revealed that Bipolar/Unipolar code is the one algebraically developed code that has outperformed all the codes considered here even in the presence of Multi-user interference effect. It has been observed that this optical 2D Bipolar/Unipolar code shows minimum BER value with increasing user count. Hence Bipolar/Unipolar code is robust to multiple user interference affected OCDMA systems.

Experimental Study of Multiband Acousto-Optic Filtering by Decoding of Spectrally Encoded Signals in Noncoherent OCDMA Systems

The possibility of using acousto-optic multiband filters for construction of code division multiple-access communication networks has been experimentally proved. Correlation interference has been studied for a set of bands with a spectrum close to sin(x)/x function which are used for encoding/decoding. For the case of several transmitters, a special technology was developed and realized that made it possible to perform studies on a transmission line based on two filters. The key component of this technology lies in emulating the sum signal from two to five transmitters on the first filter. The measured signal-to-interference ratio was more than 11 dB and decreased by less than 3 dB due to correlation interference from the network neighborhood and the emulation error of the sum signal.

A novel 2D polarization-spatial encoding approach for OCDMA system based on multi-core fiber

OCDMA plays an important role in optical fiber communication, this technique provides multiple attractive features such as the choices of exploiting several encoding approaches (Time, wavelength, ……). In this paper, we propose a novel encoding approach using the multi-cores fiber to generate the code words, this technique helps to avoid the complexity of encoding and decoding methods, limits the nonlinearity effects by sharing the signal power between cores, and promotes MCFs to enhance the system security. The proposed solution exploits ZCC code to check the efficiency of this method due of its properties such as the null cross correlation. Herein, the polarization provides a solution for compounding bitrate and the number of users. Also this approach moves OCDMA from the access network, to be adopted for long haul distance and high data rate.

4D encoding scheme for OCDMA system based on multi-diagonal code

This study represents four dimensions (polarization/spectral/temporal/spatial) encoding scheme for the multi-diagonal (MD) code implementation in an incoherent system, using a direct detection technique. In the proposed scheme, the spectral/temporal/spatial encoding is incorporated with polarization encoding as a fourth-dimension signature of MD code. The coder and decoder are based on polarization beam splitters, fiber bragg gratings, delay lines and star couplers. Spectral/temporal/spatial MD code is employed as the signature allocated to an individual horizontal or vertical state of polarization. The results indicate that the proposed scheme can be used for the high-speed transmission. Also, its performance capacity overpasses the existing codes. Hence, the proposed system enhances 1.5, 2, 2.16, 2.63 and 5.7 times the number of users of the systems based on three dimensional dynamic cyclic/ multi-diagonal (3D-DCS/MD), three-dimensional multi-diagonal (3D-MD), three dimensional perfect difference/multi-diagonal (3D-PD/MD), three dimensional perfect difference (3D-PD) and two dimensional multi-diagonal (2D-MD) systems, respectively.

Techno-economic analysis of two dimensional optical code division multiple access systems

This paper undertakes the ancillary topic of relation between the transmission capacity of two dimensional optical code division multiple (2D-OCDMA) systems and its economic aspects. A new code called 2D double weight zero cross-correlation (2D-DZCC) is developed and implemented in both spectral-spatial and spectral-temporal 2D-OCDMA systems for a comprehensive techno-economic analysis. In order to determine the most efficient network architecture in terms of system capacity and cost, both models are evaluated for allowed bandwidth in terms of data, and reach. The technological analysis is followed by investigation of capital expenditure (CAPEX) for both architectures in terms of the cost incurred on network components between the transmitter and receiver modules. Evaluation of both models demonstrates that spectral-temporal OCDMA system tends to provide relatively same transmission capacity with $$\approx 70 \%$$ reduced cost of implementation in comparison with the spectral-spatial system. Consequently, making spectral-spatial systems most suitable for the deployment of passive optical network (PON) at the low cost access domain.

An efficient 2D encoding/decoding technique for optical communication system based on permutation vectors theory

One dimensional encoding in optical communications has limitations in terms of the number of supported users and large bandwidth consumption. This study presents a new algorithm to generate two-dimensional (2D) encoding utilizing permutation vectors (PV) theory for incoherent multiple access network to suppress multiple access interference (MAI) and system complexity. The proposed code design approach is based on spectral/spatial techniques for code generation. All possible combinations of PV code-sets are obtained by utilizing all permutations of the vectors with the repetition of each vector weight (W) times. Furthermore, the 2D-PV code-set is constructed by combining two code sequences of the 1D-PV code. Furthermore, the transmitter–receiver architecture of the 2D-PV spectral/spatial (S/S) code based OCDMA system is presented. The Gaussian approximation is used to analyze the performance of the proposed OCDMA system with 2D- PV code by considering various noise sources (shot, thermal, and PIIN). Results indicate that the 2D-PV code provides increased cardinality by eliminating phase induced intensity noise (PIIN) effects with a minimum likelihood of interference between multiple user data. Simulation implementations validate the proposed system performance for an agreeable bit error rate (BER) of 10–9

Research on the system performance of SAC-FBGs codec scheme

The theory of codec based on non-coherent frequency domain codec (FBGs) and non-coherent spectral domain codec (SAC-FBGs) of light-brain grating is theoretically analyzed and its transmission performance is verified. The codec scheme with better performance is compared. An optical quadrature cyclic shift code with a code length N of 13, code weight ω of 4, and self-correlation λ of 1 is used to implement codec schemes using FBGs codec and SAC-FBGs codec, respectively. Based on multiple access interference, signal to interference ratio (SIR) and bit error rate (BER) are discussed separately. From experimental results, it can be concluded that under the condition that the optical orthogonal codes are identical and the number of concurrent users is the same, the signal to interference ratio of the OCDMA system obtained by using the SAC-FBGs coding and decoding scheme is higher than that of the OCDMA system obtained by using the FBGs coding and decoding scheme. The SIR has increased by nearly two orders of magnitude, and the multiple-site interference BER has decreased by 20 or even 100 orders of magnitude. The experiment verifies that the transmission performance of the same optical orthogonal code using the SAC-FBGs coding and decoding scheme is obviously higher than that of the system transmission performance using the FBGs coding and decoding scheme.

Evaluation Performance of Two-Dimensional Multi-Diagonal Code Using Polarization and Wavelength of OCDMA System

In this paper, a new encoder/decoder technique has employed two orthogonal polarization states (vertical and horizontal) of a two-dimensional optical code, which combined polarization and wavelength scheme (p/w). This technique employed in order to increase the number of users in the FTTH network. In addition, Optical Fiber Systems (OFS) and Free Space Optics (FSO) scenarios were utilized with different Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) codes. The FTTH network based on incoherent SAC-OCDMA is tested by using the One and Two Dimensional Multi-Diagonal (1D-MD, 2D-MD) codes and 1D and 2D Zero Cross Correlation (ZCC) codes. The results show that the number of the total supported homes for the 2D codes is doubled as a comparison with 1D codes. As well as, the simulation results show the performance of MD code is better presented than ZCC in both OFS and FSO scenarios

Optical Code Construction Based on Enhanced Quantum Logic Gate (EQLG) Technique for Spectral Amplitude Coding Optical CDMA Systems

Spectral Amplitude Coding Optical Code Division Multiple Access (SAC–OCDMA) is an auspicious advancement in an asynchronous environments. In this paper, we have presented an effective Enhanced Quantum Logic Gate (EQLG) code for SAC–OCDMA to improve the code construction, cross-correlation and minimize the noises. The EQLG code contains unitary matrices with minimum overlaps in code spectral wavelengths of various clients. This drops the Multiple Access Interference (MAI) and furthermore EQLG code, provides high data-rate transmission in networks. The development of the proposed EQLG code is depicted in following strides as; at first build a matrix utilizing the estimation of the weight value and the number of subscribers. Based upon that, the number of rows and columns are located in the matrix. Second, each diagonal sequences are computed by using the QLG method. The execution of the recommended EQLG code will be analysed with existing SAC–OCDMA systems in response to Bit Error Rate (BER). The simulations of encoding with 10–60 users with 622 Mb/s data transmission at a BER of 10−9 have been successfully achieved.

Design of Multiservice Code (MS) in Spectral/Temporal/Spatial Domain for OCDMA System

AbstractThis paper explores the design of multiservice code (MS) in spectral, time spreading and wavelength domains (3-Dimensional). The proposed 3D code is designed in such a manner that follows the ideal in phase unit cross correlation in spectral, time spreading and wavelength domains. The proposed encoder generates the MS code effectively in 3D domain and decoder suppresses the multi-user interferences successfully. Performance analyses are carried out by considering the all noises such as phase induce intensity noise(PIIN), shot noise and thermal noise. The analysis of 3D-MS code for variable code length is also performed for measurement of variation in bit error rate against the received power and number of active users in the design. The observed performances are also compared with existing codes such as 2D-MDW, 3D-PDC and 1D-MS code and the proposed code shows the better performance. The analysis of bit error rate of proposed code is carried out against the number of users at 0.622Gbits/s data rate and 0 dBm received power and comparison is also formed with the existing code such as 3D PD(M=21, N=3, P=3), 2DMDW(M=63, P=3), PDC(M=57, P=3) and 1D MS Code. It is noted that 3D MS code shows the better performance than the existing methods. Analysis is also evaluated for variable weight and variable length codes in order to observe the variation in bit error rate with variation in received power and number of simultaneous users.

Performance Evaluation of Correlation Properties of Quasi Orthogonal Prime Codes for Optical CDMA Communication

AbstractOptical code division multiple access (OCDMA) is one of the promising technologies to be implemented using all-optical networks. The performance of OCDMA system is largely dependent on the particular codes used for encoding. A proper choice of code family as well as code dimension is of prime importance due to various transmitter and receiver design considerations. This paper mainly aims at evaluation of desirable characteristics of various spreading codes based on the prime sequences. An extensive effort has been done in this paper to evaluate the correlation characteristics of various types of one-dimensional (1-D), 2-D and 3-D prime codes for OCDMA communication system. The detailed mathematical modelling has also been explained. It is observed that an addition in coding dimension leads to significant improvement in the code characteristics.

OCDM systems with PSK and QAM codes

A multiport encoder/decoder can simultaneously generate multiple PSK optical codes, and it has been effectively used in asynchronous, spectrally efficient access networks. To increase the system flexibility, as well as the number of simultaneous IoT signals, we introduce novel multi-level QAM orthogonal optical codes that are generated by the multiport encoder/decoder using optical phase modulators. The QPSK modulator simultaneously operates for data modulation and orthogonal code generation. The code orthogonality is improved, compared to conventional PSK codes, and we analyze the performance of 16-code × 10 GSymbol/s, OOK-, DPSK- and DQPSK-modulated OCDM systems, using conventional PSK and the proposed QAM codes.