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Optical code division multiple access (OCDMA) shows limitations in terms of the inefficient bandwidth utilization and low spectral density with one-dimensional (1D) codes. To overcome these limitations, a novel design is presented using a two dimensional (2D) spectral/spatial multiwavelength coding scheme. The proposed code is constructed using a 1D balanced incomplete block design (BIBD) technique. Theoretical and analytical results indicate that the proposed code provided improvement in the number of simultaneous users, code construction, and cross-correlation and minimized noise. Moreover, the bandwidth requirements can be minimized, and it can provide flexibility in addressing code sequences. Finally, results were compared with existing spectral-spatial 2D codes such as diagonal eigenvalue unity (DEU) and 2D diluted perfect difference (DPD). It was observed that the 2D-BIBD code fulfilled optical transmission needs with minimum effective source power (Psr = −27.5 dBm) when compared to 2D-DEU (−26.5 dBm) and 2D-DPD (−25.5 dBm) codes. Overall, our results suggested that the performance of BER for the proposed code was 72% and 22% higher than the existing 2D-DPD and 2D-DEU codes, respectively. [ABSTRACT FROM AUTHOR]

This paper presents design and implementation of a new two-dimensional fixed right shifting (2D-FRS) code in optical code-division multiple access (OCDMA) systems. The proposed code employs spatial domain in combination with spectral encoding to elevate orthogonality between the adjacent codes. In comparison with the existing 2D coding schemes, 2D-FRS not only reserves the multiple interference-cancellation property, but also provides better performance against the effects of shot, thermal and phase-induced intensity noise. Investigation of the proposed system using numerical and simulation approach shows that larger number of simultaneous users can be supported by 2D-FRS system in comparison with existing counterparts under given bit-error-rate (BER). This paper further examines the effect of dispersion on performance of 2D-FRS based OCDMA system due to the use of numerous fiber strands between the transmitter and receiver modules for spatial encoding operation. Investigation is made in terms of data rate, fiber span and channel spacing. Analysis using a highly recognized software called OPTISYSTEM verifies that the proposed system is able to support data rates of up to 32 × 1 Gbps without employing dispersion compensation fibers (DCFs). It is also shown that application of DCF can further negate MAI and support higher transmission capacity leading to a tradeoff between the limited dispersion effects and the MAI. If g = 0 ∩ h ≠ 0 and h = 0 ∩ g ≠ 0, hence R I (1)(g , h) and R I (2)(g , h) have nonzero value. This can be used to remove the effect caused by A g,h with g = 0 ∩ h ≠ 0 and g ≠ 0 ∩ h from R I (0)(g , h). Deducting Eqs. (7) and (8) from Eq. (6), Eq. (9) is attained as follows [ABSTRACT FROM AUTHOR]

Highlight • Development of a new 2D-FRS code. • Gaussian approximation is used to analyze performance analysis of 2D-FRS system. • Simulation validation of 2D-FRS numerical model. • Power saving feature at 2D-FRS receiver. • Accommodation of large number of active users with high bit rate. Abstract In this paper a new algorithm to generate two dimensional fixed right shifting (2D-FRS) code sequences is proposed, which is based on spectral/spatial incoherent OCDMA system. The proposed 2D-FRS algorithm is designed using 1D-FRS code with minimum cross correlation (MCC). The 2D-FRS codes enhance the system cardinality and offer elimination capability of MCC and its associated phase induced intensity noise (PIIN). Furthermore, the proposed algorithm allows multiple users with different code sequences to transmit data with minimum likelihood of interference. The architecture of transmitter-receiver structure of spectral/spatial 2D-FRS OCDMA system is presented. Gaussian approximation is used to analyze performance of the proposed 2D-FRS OCDMA system by investigating noise sources at photodiodes (PDs). It is shown that PD-1 and PD-3 have lower contribution in terms of noise power as compared to PD-0 and PD-2 due to division operation in MCC elimination process at the balanced detectors. Simulation results also validates the proposed system for an agreeable bit error rate (BER) of 10−9. It is observed that the 2-D FRS OCDMA system can support a higher number of users in deterministic and stochastic methods compared to the reported techniques such as Diagonal Eigenvalue Unity (DEU) and Two-Dimensional Diluted Perfect Difference codes (2D-DPD codes). The 2D-FRS cardinality surpassing the 2D-DPD and 2D-DEU by ≈71.21% and ≈9.09% respectively at the BER of 10−9. At 622 Mbits/s transmission data rate, the 2-D FRS meets the optical transmission requirements with lowest effective transmitted source power (P sr), −27.5 dBm in comparison to published codes. [ABSTRACT FROM AUTHOR]

• Development of new SSM families. • A configurable transmitter–receiver structure using S S M SSM code to support QoS. • High and Low QoS diversity are offered based on user choices. • Accommodation of large number of active users with high bit rate. This paper proposes a new coding scheme for spectral amplitude coding (SAC) family, known as Sigma Shift Matrix (SSM). Two techniques are proposed for the design of SSM coding scheme. The first technique combines the identity and upper shift matrices to form an SSM coding matrix named as SSM I. The second approach adapts the assembly of a single – entry, lower and upper shift matrices to compose another SSM matrix called SSM s. Combination of these matrices generates variable SSM code families, which can provide more flexibility in code weight selection and the number of users respectively. Furthermore, a modified SSM (MSSM) coding scheme is proposed through bitwise ANDing of SSM I and SSM S to further elevate performance of the proposed setup. The optimized structure of SSM coding scheme eliminates the influence of multiple access interference (MAI) and alleviate the effect of phase induced intensity noise (PIIN). Numerical results show that MSSM, SSM I and S S M S SSM S outperform the existing coding schemes in descending order and proves to be an efficient candidate for the implementation of high capacity next generation of optical communication networks. [ABSTRACT FROM AUTHOR]

In this paper, we present a new algorithm to generate two-dimensional (2D) permutation vectors' (PV) code for incoherent optical code division multiple access (OCDMA) system to suppress multiple access interference (MAI) and system complexity. The proposed code design approach is based on wavelength-hopping time-spreading (WHTS) technique for code generation. All possible combinations of PV code sets were attained by employing all permutations of the vectors with repetition of each vector weight (W) times. Further, 2D-PV code set was constructed by combining two code sequences of the 1D-PV code. The transmitter-receiver architecture of 2D-PV code-based WHTS OCDMA system is presented. Results indicated that the 2D-PV code provides increased cardinality by eliminating phase-induced intensity noise (PIIN) effects and multiple user data can be transmitted with minimum likelihood of interference. Simulation results validated the proposed system for an agreeable bit error rate (BER) of 10−9. [ABSTRACT FROM AUTHOR]