S. A. Aljunid

A new family of optical code sequences for spectral-amplitude-coding optical CDMA systems

A new code structure for spectral-amplitude-coding optical code-division multiple-access system based on double-weight (DW) code families is proposed. The DW code has a fixed weight of two. By using a mapping technique, codes that have a larger number of weights can be developed. Modified double-weight (MDW) code is a DW code family variation that has variable weights of greater than two. The newly proposed code possesses ideal cross-correlation properties and exists for every natural number n. Based on theoretical analysis and simulation, MDW code is shown here to provide a much better performance compared to Hadamard and modified frequency-hopping codes.

Spectral amplitude coding OCDMA using and subtraction technique

An optical decoding technique is proposed for a spectral-amplitude-coding-optical code division multiple access, namely, the AND subtraction technique. The theory is being elaborated and experimental results have been done by comparing a double-weight code against the existing code, Hadamard. We have proved that the and subtraction technique gives better bit error rate performance than the conventional complementary subtraction technique against the received power level.

Improved BER based on intensity noise alleviation using developed detection technique for incoherent SAC-OCDMA systems

The major drawback of incoherent spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems is their inherent intensity noise originating due to the incoherency of the broadband light sources. In this paper, we propose a developed detection technique named the modified-AND subtraction detection for incoherent SAC-OCDMA systems. This detection technique is based upon decreasing the received signal strength during the decoding process by dividing the spectrum of the utilized code sequence. The proposed technique is capable of mitigating the intensity noise effect, as well as suppressing the multiple-access interference impact. Based on modified quadratic congruence (MQC) code, the analytical results reveal that the modified-AND detection offer best bit-error rate (BER) performance and enables MQC code to support higher transmission rate up to 1.25 Gb/s compared to conventional AND detection. Furthermore, we ascertained that the proposed technique enhances the system performance using a simulation experiment.

Improving spectral efficiency of SAC-OCDMA systems by SPD scheme

This letter presents a single photodiode detection (SPD) as an effective technique for eradicating both multiple-access interference (MAI) and phase-induced intensity noise (PIIN) in spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. Mathematical analysis and simulation experiments are used to investigate the spectral efficiency (SE) of SAC-OCDMA systems utilizing different detection techniques. Results show that the SPD technique significantly enhances the SE compared to AND as well as modified-AND subtraction detections.

Development of modified double-weight code and its implementation in multi-rate transmissions

This paper presents a new code structure and its ability in supporting multiple transmission rates in point to point spectral amplitude coding-optical code division multiple access (SAC-OCDMA) links. The double-weight (DW) code family that has a basic fixed weight of 2 was proposed. Modified double weight (MDW) code is a DW code family variation that has variable weight of greater than two. The ability of MDW codes to support simultaneous transmissions at different bit rates is shown through simulated results of the bit error rate (BER) and the eye patterns. Four MDW encoded channels were used at the bit rates of 2.5 Gbps and 10 Gbps. MDW code shown here significantly performs better than Hadamard and modified frequency hopping (MFH) codes.

Performance comparison of different detection techniques in long-haul fiber SAC-OCDMA systems

Progress in fiber optic technology have made long-haul communications systems reach distance that were once unheard of. This distance is made possible by using modulation techniques that do not require a complex link design which best applied in spectral-amplitude coding optical code-division multiple access (SAC-OCDMA) system. In this paper, we investigate the use of different detection schemes namely the modified-AND subtraction detection as well as AND subtraction detection for SAC-OCDMA systems. We simulate the system performance of the mentioned detection approaches using OptiSystem7.0 software. The entire effects of fiber nonlinearities, dispersion and attenuation were considered in the simulation of SAC-OCDMA systems. Based on modified double weight (MDW) codes, the simulation results revealed that the modified-AND subtraction detection improves SAC-OCDMA system performance significantly compared to the conventional AND subtraction detection. Moreover, for the same quality of service (QoS) for bit-error rate (BER) of 10-20 and data rate of 622 Mbps, modified-AND subtraction detection allows longer transmission distance of 30 % in the fiber length as compared to AND detection.

Enhanced performance of new family Modified Double Weight codes spectral amplitude coding optical CDMA system network

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.

Mitigation of multiple access interference using two-dimensional modified double weight codes for optical code division multiple access systems

We proposed newly two-dimensional (2- D ) spectral amplitude coding optical code division multiple access (OCDMA) scheme using modified double weight (MDW) code capable of suppressing phase-induced intensity noise (PIIN). The architecture of the spectral/spatial MDW OCDMA system with the property of multi-access interference cancellation is presented. The proposed code exhibits good cross-correlation property. At the optimized data transmission rate of 0.745 Gbps, 2-D MDW, M = 63, N = 3, reaches maximum cardinality of 200% increases compared to 2- D perfect difference code, M = 57, N = 3. The performance is severely deteriorated if the data rate further increases above 0.745 Gbps. The proposed code meets the optical transmission requirements at 10−9 bit error rate error floor, with lowest effective transmitted power ( P sr), −17.5  dBm, in comparison to the others through minimizing interference noise that result in PIIN suppression. The proposed system reaches optimum requirements performance in terms of cardinality, data transmission rate, and low effective transmitted power.

Analytical comparison of various SAC-OCDMA detection techniques

This paper presents the performances comparison of the Modified Double Weight (MDW), Enhanced Double Weight (EDW) and Zero Cross Correlation (ZCC) codes using different detections technique, which are complementary subtraction, AND subtraction and spectral direct detection (SDD). The MDW and EDW codes are the modification of the double weight (DW) code, which has the variable code weight that greater than DW code. The MDW code has an even code weight which is greater than two while the EDW code has the odd code weight which is greater than three. The ZCC code is a code that is built using the concept of “non-overlapping of bit 1” in a codeword among users who can suppress phase induced intensity noise (PUN) and also prevent the interference between users. Theoretically, for all mentioned SAC-OCDMA, SDD shows a better performance than complementary subtraction and AND subtraction through the analysis of the eye diagram, bit error rate (BER) and signal to noise ratio (SNR).

Design configuration of encoder and decoder modules for modified double weight (MDW) code spectral amplitude coding (SAC) optical code division multiple access (OCDMA) based on fiber Bragg gratings

In this work, we are proposing the serial and parallel configurations of encoder and decoder modules to encode and decode a new developed spectral amplitude coding (SAC) known as modified double weight (MDW) code for optical code division multiple access (OCDMA) system. This coding scheme is designed in a way to decrease the number of FBGs used in the encoder and decoder modules and to maintain the cross-correlation parameter to 1.