OCDMA Code

In this paper, performance analysis of conventional spectral amplitude coding (CSAC) with hybrid (HSAC) for OCDMA system is investigated in local area network (LAN) environment. The CSAC is built based on arithmetic sequence with simple algebraic ways. The HSAC technique is used in which spectral amplitude coding (SAC) combined with wavelength division multiplexing (WDM) to effectively reduce multiple access interference (MAI) and mitigate the influence of phase induced intensity noise (PIIN) arising in photodetecting process. The main idea is to construct the code sequences in SAC domain then repeat it diagonally in the wavelength domain as groups which maintains the same cardinality of a given code weight. Results show that HSAC outperforms CSAC when the number of active users is high due to its better correlation properties. It has been shown that the HSAC can suppress intensity noise effectively and improve the bandwidth utilization significantly up to 4.2 nm.

This paper investigates the performance of vector combinatorial (VC) code for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a newly proposed subtract exclusive OR detection (SED) technique. VC code is constructed using Euclidean vector and algebraic ways. One of the important properties of this code is that the maximum cross correlation is one, which means that multiuser interference (MUI) and phase induced intensity noise (PIIN) are reduced. The weight for the VC code can be any positive integer number. The system performance was evaluated by comparing the theoretical studies using related equations and simulation results taken from the commercial optical systems, "VPI TM TransmissionMaker 7.1". Significant improvement in system performances has been observed when the proposed SED technique employing VC code was applied compared to other codes that utilize conventional balance detection techniques for spectral amplitude coding.

A hybrid subcarrier multiplexing (SCM) technique incorporating spectral amplitude coding and optical code division multiple access (SAC-OCDMA) technologies is investigated using both numerical and simulation methods. The hybrid SCM/SAC-OCDMA system combines the two above schemes in such a way that it is robust to multiple access interference and reveals much enhanced channel data rate. We improve the overall performance of the hybrid SCM/SAC-OCDMA system based on spectral amplitude coding to suppress a number of impairments and improve its sensitivity at a bit error rate of 10-9. As a result, the system suggested by us, which is based on a dynamic cyclic shift code, shows better performance when compared with the standard SAC-OCDMA systems employing the conventional code.

A hybrid subcarrier multiplexing (SCM) technique incorporating spectral amplitude coding and optical code division multiple access (SAC-OCDMA) technologies is investigated using both numerical and simulation methods. The hybrid SCM/SAC-OCDMA system combines the two above schemes in such a way that it is robust to multiple access interference and reveals much enhanced channel data rate. We improve the overall performance of the hybrid SCM/SAC-OCDMA system based on spectral amplitude coding to suppress a number of impairments and improve its sensitivity at a bit error rate of 10-9. As a result, the system suggested by us, which is based on a dynamic cyclic shift code, shows better performance when compared with the standard SAC-OCDMA systems employing the conventional code.

In this paper, two lower and upper bounds for the bit error rate of codes with fixed cross correlation in spectral-amplitude-coding optical code-division multiple access systems are offered. In this study, we consider only the phase-induced intensity noise and neglect other noises such as shot and thermal noises, in the performance analysis. Also, it is assumed that users are synchronous. This bound is obtained using combinatorics approach and utilizing simple inequalities. In numerical results, the comparison between the upper bound, lower bound, and simulation results for MQC, MFH, BIBD, and Hadamard codes is presented, and the tightness of the bounds is evaluated.

A novel family of codes for modified spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) is introduced. The proposed codes exist for more processing gains than the previously reported codes do. In the network using these codes, the number of users can be extended without any essential changes in the previous transmitters. In this study, we propose a construction method for these codes and compare their performance with previously reported codes.

This paper discusses the use of lattice cryptography and chaotic maps to encrypt OCDMA-coded optical flows. Unlike existing approaches, which have mainly focused on optical components such as phase masks and delay lines, our cryptosystem encompasses a secure code construction process. In fact, assuming that a pair of bases (a public basis and a private basis) is associated to every user, the OCDMA code-words are projected on a public basis before being sent so that only the user possessing the corresponding private basis can decrypt the keyword. We show that the projection of a codeword on the public basis of the receiver and the addition of a chaotic error enhances the confidentiality performance of the code. This distribution of this error is generated using a chaotic map. In this work, we study the impact of the parameters of this chaotic map on the robustness of the proposed cryptosystem.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5549040