Towards higher scalability of hybrid optical CDMA network

A novel approach for improving the number of simultaneous users in a hybrid OCDMAOTDMA network is proposed and analysed. OCDMA system is based on two-dimensional wavelength-hopping time-spreading codes with multi-wavelengths picosecond carriers. The scalability increase was achieved by adding a third dimension to separate OCDMA user groups within OTDMA time slots by assigning them into different wavelength bands. We have shown this will scale-up the system capacity proportionally to the number of assigned wavelength bands. A self-clocking all-optical time gate was then demonstrated as an effective means for suppressing the growing detrimental multi access interference noise resulted from this capacity increase

A NOVEL CONSTRUCTION OF VECTOR COMBINATORIAL (VC) CODE FAMILIES AND DETECTION SCHEME FOR SAC OCDMA SYSTEMS

There has been growing interests in using optical code division multiple access (OCDMA) systems for the next generation high-speed optical fiber networks. The advantage of spectral amplitude coding (SAC-OCDMA) over conventional OCDMA systems is that, when using appropriate detection technique, the multiple access interference (MAI) can totally be canceled. The motivation of this research is to develop new code families to enhance the overall performance of optical OCDMA systems. Four aspects are tackled in this research. Firstly, a comprehensive discussion takes place on all important aspects of existing codes from advantages and disadvantages point of view. Two algorithms are proposed to construct several code families namely Vector Combinatorial (VC). Secondly, a new detection technique based on exclusive-OR (XOR) logic is developed and compared to the reported detection techniques. Thirdly, a software simulation for SAC OCDMA system with the VC families using a commercial optical system, Virtual Photonic Instrument, “VPITM TransmissionMaker 7.1” is conducted. Finally, an extensive investigation to study and characterize the VC-OCDMA in local area network (LAN) is conducted. For the performance analysis, the effects of phase-induced intensity noise (PIIN), shot noise, and thermal noise are considered simultaneously. The performances of the system compared to reported systems were characterized by referring to the signal to noise ratio (SNR), the bit error rate (BER) and the effective power (Psr). Numerical results show that, an acceptable BER of 10−9 was achieved by the VC codes with 120 active users while a much better performance can be achieved when the effective received power Psr > -26 dBm. In particular, the BER can be significantly improved when the VC optimal channel spacing width is carefully selected; best performance occurs at a spacing bandwidth between 0.8 and 1 nm. The simulation results indicate that VC code has a superior performance compared to other reported codes for the same transmission quality. It is also found that for a transmitted power at 0 dBm, the BER specified by eye diagrams patterns are 10-14 and 10-5 for VC and Modified Quadratic Congruence (MQC) codes respectively

Indoor infrared wireless PPM systems

Optical wireless communication systems offer several advantages over their radio frequency counter parts. For example, cost, wavelength re-usability and a large unregulated bandwidth are among the advantages. The limitations of this technique include the optical power safety issue, multipath dispersion and interference from ambient light and background radiation. In this project, pulse position modulation is used for receiver sensitivity improvement, and code division multiple access is exploited to provide multiple access facilities. The limitations of an optical wireless system are studied and methods for performance improvement are suggested

A NOVEL CONSTRUCTION OF VECTOR COMBINATORIAL (VC) CODE FAMILIES AND DETECTION SCHEME FOR SAC OCDMA SYSTEMS

There has been growing interests in using optical code division multiple access (OCDMA) systems for the next generation high-speed optical fiber networks. The advantage of spectral amplitude coding (SAC-OCDMA) over conventional OCDMA systems is that, when using appropriate detection technique, the multiple access interference (MAI) can totally be canceled. The motivation of this research is to develop new code families to enhance the overall performance of optical OCDMA systems. Four aspects are tackled in this research. Firstly, a comprehensive discussion takes place on all important aspects of existing codes from advantages and disadvantages point of view. Two algorithms are proposed to construct several code families namely Vector Combinatorial (VC). Secondly, a new detection technique based on exclusive-OR (XOR) logic is developed and compared to the reported detection techniques. Thirdly, a software simulation for SAC OCDMA system with the VC families using a commercial optical system, Virtual Photonic Instrument, “VPITM TransmissionMaker 7.1” is conducted. Finally, an extensive investigation to study and characterize the VC-OCDMA in local area network (LAN) is conducted. For the performance analysis, the effects of phase-induced intensity noise (PIIN), shot noise, and thermal noise are considered simultaneously. The performances of the system compared to reported systems were characterized by referring to the signal to noise ratio (SNR), the bit error rate (BER) and the effective power (Psr). Numerical results show that, an acceptable BER of 10−9 was achieved by the VC codes with 120 active users while a much better performance can be achieved when the effective received power Psr > -26 dBm. In particular, the BER can be significantly improved when the VC optimal channel spacing width is carefully selected; best performance occurs at a spacing bandwidth between 0.8 and 1 nm. The simulation results indicate that VC code has a superior performance compared to other reported codes for the same transmission quality. It is also found that for a transmitted power at 0 dBm, the BER specified by eye diagrams patterns are 10-14 and 10-5 for VC and Modified Quadratic Congruence (MQC) codes respectively

Two-dimensional permutation vectors’ (PV) code for optical code division multiple access systems

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