Search

The combination of 1D zero cross correlation (ZCC) and 1D Multi Diagonal (MD) results a new two dimensional hybrid called 2D ZCC/MD code for spectral/spatial OCDMA system. The proposed code aims to enhance the functional qualities of Optical Code Division Multiple Access (OCDMA) and to overcome the limitations of one dimensional codes. In this paper, 2D ZCC/MD is evaluated at data rate; 622Mbps. A comparison of the proposed 2D ZCC/MD code to 1D Random Diagonal (RD) and 1D Modified Double Weight (MDW) highlight that 2D ZCC/MD can support a large number of active users even at the higher user bit rate. Furthermore, in term of effective power 2D ZCC/MD can achieve lower effective power.

Explosive growth of bandwidth demand together with advance in latest communication services and emerging applications have inspired interest in optical code division multiple access (OCDMA). The work focuses on analysis and demonstration of two-dimensional (2-D) modified double weight (MDW) OCDMA wavelength-time. The 2-D MDW uses balance-detection for mitigating multiple access interference. The property of cross-correlation results in optimum phase induces intensity noise suppression (PIIN). The proposed code achieves high scalability; below 10-9 BER error floor the code cardinality reaches 254 simultaneous numbers of users which is double the 2-D PDC performance. The lowest effective power (Psr) for minimum optical transmission requirement for smallest number of users is achieved at-17.5dBm. The 2-D MDW OCDMA simulation model is developed to validate the realization of the code for BER and distance performance. The 2-D MDW OCDMA code successfully suppresses PIIN and mitigating MAI which result in high cardinality, reduce Psr and improved distance.

A new two-dimensional (2-D) optical code division multiple access (OCDMA) scheme to increase the achievable system capacity is proposed. The code exhibits good cross-correlation property time and wavelength shift. Performances are analyzed on code size and correlation properties affecting two important system parameters, bit error rate (BER) as a function of cardinality generated and optical power transmission requirement. The proposed system can effectively suppress phase-induced intensity noise (PIIN) and has multi-access interference (MAI) cancellation property. Results in a good agreement indicate that 2-D modified double weight (MDW) offers 163.7% and 336.2% larger cardinality compare to 2-D perfect difference code (PDC) and 2-D modified quadratic congruence (MQC) code. By increasing spatial code (N) and keeps similar code length system performance can be further optimized. 2-D MDW (M = 45, N = 18) accommodates 252.2% and 18.3% cardinality increment and low effective transmitted power (Psr) at −17.9 dBm, compare to 2-D MDW (M = 247, N = 3) and (M = 84, N = 9) at 10−9 BER error floor. The architecture of the spectral/spatial MDW OCDMA system with property of MAI cancellation is presented.

In this paper, we show details of zero cross correlation (ZCC) code development and investigate performance by measuring bit-error-rates compared to other optical code division multiple access (OCDMA) codes using Avalanche photodiode (APD) and PIN photodetector. We present a configuration to determine how optical OCDMA systems can be applied with PIN and APD photodetector. Analysis of Avalanche photodiode gain optimization is discussed in ZCC code system. We also present analytical and numerical theoretical results for data transmission of spectrally encoded incoherent OCDMA signal and how signal-noise is being affected by using these two photodetectors.

This paper investigates the performance of hybrid scheme of subcarrier multiplexed spectral-amplitude-coding optical code division multiple access (SCM SAC-OCDMA) system based on AND Subtraction detection. In this system, Recursive Combinatorial (RC) code is used where it is a new code structure in SAC-OCDMA. The effects of noise such as phase-induced intensity (PIIN) noise, thermal noise and intermodulation distortion (IMD) are taken into consideration in order to analyze the system. The theoretical values are being compared based on some parameters. AND detection can discard the effects of multi access interference (MAI). As a result, the system performance are improved based on AND detection technique.

This paper analyses the spectral efficiency of hybrid subcarrier multiplexed (SCM) Optical Code Division Multiple Access (OCDMA) and conventional OCDMA based on AND Subtraction technique. We compared the spectral efficiency of SCM and the conventional OCDMA with respect the number of weights and number of users. Results indicate that the SCM OCDMA is more efficient compared to conventional OCDMA.

A detailed of code construction for an Optical Code Division Multiple Access (OCDMA) system with flexible cross correlation is presented to reduce the effect of interference thus optimizing the code length. In this paper, the proposed code called Flexible Cross Correlation (FCC) code. The FCC code can be constructed using a simple tridiagonal matrix compared to other OCDMA codes such as MDW and DCS codes thus the FCC code possesses various advantages including easy code construction and less complexity of encoder/decoder design. As a result, OCDMA system performance significantly improved by using FCC code with flexible cross correlation instead of fixed cross correlation such as MDW, MFH and DCS codes.

In this paper, we have proposed a high performance network design, which is based on mixed optical Code Division Multiple Access (CDMA) system using Zero Cross Correlation (ZCC) code and multiband Orthogonal Frequency Division Multiplexing (OFDM) called catenated OFDM. In addition, we also investigate the related changing parameters such as; effective power, number of user, number of band, code length and code weight. Then we theoretically analyzed the system performance comprehensively while considering up to five OFDM bands. The feasibility of the proposed system architecture is verified via the numerical analysis. The research results demonstrated that our developed modulation solution can significantly enhanced the total number of user; improving up to 80% for five catenated bands compared to traditional optical CDMA system, with the code length equals to 80, transmitted at 622 Mbps. It is also demonstrated that the BER performance strongly depends on number of weight, especially with less number of users. As the number of weight increases, the BER performance is better.

This paper proposes an integration of optical Code Division Multiple Access (OCDMA) with new catenated Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme. This effective combination based on Zero Cross Correlation (ZCC) code can enhanced the system capacity and increased spectral efficiency by fully utilizing the available electrical bandwidth. We investigate the performance of the proposed system for various number of user, number of weight and effective power. The performance assessment is carried out by means of the signal to noise ratio (SNR) and bit error rate (BER) for up to five catenated OFDM bands transmitted simultaneously through optical link at 622 Mbps. More specifically, mathematical expressions for SNR and BER performance are derived. The corresponding numerical results are presented and compared with traditional OCDMA-ZCC system to verified the feasibility of the proposed system. The results show that with OCDMA/catenated-OFDM based on ZCC code provides 86% more number of permissible user for SNR of 15 dB. In addition, this integration provides higher receiver sensitivity; an approximately –22.5 dBm for 20 number of user with 8 number of weight. It is also found that, to accommodate more user, the system requires higher effective power at the receiver.

In this paper, we demonstrate a novel architecture of variable weight Zero Cross Correlation code in the family of Spectral Amplitude Coding(SAC) Optical Code Division Multiple Access (OCDMA) to be utilized in the triple play services of OCDMA applications based on the end users demand and requirements. This is achieved by adapting multiple weights of Zero Cross Correlation (ZCC) code onto one system to accommodate different Quality of Service (QoS) requirements. The results are characterized by bit error rate (BER) and eye pattern simulated using OptiSystem software. Results proved a successful transmission of this scheme over 20km distance thus offering flexibility of independent QoS. It is also revealed that the performance is always better for users with larger number of code weight compared to those assigned with smaller code weight.

In this paper, an improvement of achievable system capacity Avalanche photodiode (APD) performance of spatial/spectral modified double weight (MDW) code for cardinality, bit error rates (BER) and noise interference is analyzed. The results in very good agreement indicate that 61% cardinality improvements compare to 2-D MDW code with PIN. The effective transmitted power (P sr ) for 2-D MDW-APD (M=135, N=3) improves by 8.5dBm at 10−9 error floor. At low gain BER value is mitigated through suppressing PIIN. Apparently, performance of the proposed system improves substantially with APD.

The wavelength-time modified double weight (MDW) optical division multiple access (OCDMA) scheme to reduce multiple access interference (MAI) and compensate bit error rate (BER) and phase-induced intensity noise (PIIN) in incoherent OCDMA systems is proposed. The analysis permits thorough understanding of PIIN, shot and thermal noises effect on 2-Dimensional (2-D) MDW OCDMA system performance. PIIN is the dominant noise factor in the OCDMA time-spreading scheme. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN is maximally suppressed by the proposed code through minimizing property of cross-correlation in comparison to the 2-D PDC and 2-D MQC OCDMA code.

A new family of spectral/spatial spectral amplitude-coding (SAC) optical code division multiple access (OCDMA) scheme using Modified Double Weight (MDW) code is developed. The new codes are derived from Modified Double Weight codes with good cross correlation. This proposed system can suppress the phase-induced intensity noise (PIIN) by using multiuser interference (MUI) cancellation property. The proposed 2-D OCDMA MDW can offer a much larger capacity compare to the 1-D OCDMA MDW Code.

In this paper, the implementation of subcarrier multiplexing technique in spectral amplitude coding (SAC) optical code division multiple access (OCDMA) network using Zero Cross Correlation code is developed and investigated. Theoretical analysis is done to determine the signal-to-noise ratio of such network and analysis of the performances in term of bit error rates are presented. Simulations are done using Optisys software version 6.0. Motivation to this research is driven to take advantage of both the low implementation cost of the SCM technology which uses the existing RF/microwave devices; and the attractive SAC which reduce the Multiple Access Interference (MAI) in OCDMA system. The use of ZCC code can eradicate phase induced intensity noise (PUN) which will contribute to better BER. For typical error rate of optical communication system of 10e-9, it has been observed fro theoretical results that the new hybrid SCM/OCDMA system provide better spectral efficiency and accommodate more users simultaneously with less code length and thus lower cost of implementations than the traditional OCDMA network utilizing the ZCC code. Thus this system could be one promising solution to the symmetric high capacity access network with high spectral efficiency, cost effective, good flexibility and enhanced security, which makes an attractive candidate for next generation broadband access network

A new detection scheme, namely AND subtraction technique is proposed and presented in this paper. The theory is being elaborated and experimental results have been done by comparing Double-Weight (DW) code against the existing code, Hadamard. In this paper we have proved that AND subtraction technique gives better Bit Error Rates (BER) performance than Complementary subtraction technique against the received power level. The overall system cost and complexity can be reduced by using less number of filters in this technique. At the same time, the performance of the OCDMA system is improved significantly because with less number of filters in the decoder, the total power loss can be reduced and this can be clearly seen in the result.

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.