Siti Barirah Ahmad Anas

Performance analysis of a variable-weight OCDMA system under the impact of fiber impairments

The impact of Chromatic Dispersion (CD) and Non-Linear Effects (NLE) including Self-Phase Modulation (SPM) and Four-Wave Mixing (FWM), on the performance of a Variable-Weight Optical Code Division Multiple Access (VW-OCDMA) system at 1.25 Gbps is analyzed by simulation. The results show that CD is the most dominant effect, which increases the users bit error rate (BER) especially for the users with higher weights. In order to investigate the performance of system in service differentiation for users with different weights, Dispersion Compensating Fiber (DCF) is used to mitigate the effect of CD caused by Single Mode Fiber (SMF). The results show that users with higher weights have better performance as expected and impact of NLE is negligible for distance up to 150 km, considering low launched power.

Throughput analysis of an enhanced CSMA/CD based single channel fast ethernet optical LAN

This paper presents throughput improvement of CSMA/CD based LAN by reducing collisions and eliminating packet loss. In this enhanced CSMA/CD, each user has a finite buffer capacity that helps to reduce collisions and Ethernet capture effect. At the same time, to eliminate packet loss, a new special-jamming signal is used. Networks throughput based on the proposed CSMA/CD is evaluated against several design parameters i.e. number of nodes, bus length and offered load. The results show significant performance improvement. Throughput against number of nodes is increased more than 40% whereas percentage of collisions is reduced to 3% compared to conventional CSMA/CD

Simultaneous vibration and humidity measurement using a hybrid WDM/OCDMA sensor network

In this paper a hybrid Wavelength Division Multiplexing (WDM) and Optical Code Division Multiple Access (OCDMA) sensor network is proposed to detect vibration and humidity simultaneously. Evaluation of the results for the proposed system is demonstrated using simulation setup. OCDMA is used for detection of vibration levels while WDM is for sensing humidity changes. Fiber Bragg gratings (FBGs) is used in both systems. In OCDMA FBGs were used as filter to form the OCDMA code and sensors to senses the vibration. In WDM FBGs were used as sensor alone to sense the humidity.

Fiber non-linear effects in multiple-wavelengths optical CDMA systems

Abstract Multi-wavelength Optical Code Division Multiple Access (OCDMA) systems suffer from fiber impairments including non-linear effects (NLE), especially when the number of wavelengths and input power level increase. In this paper, a review of NLE, including self-phase modulation, cross-phase modulation, four wave mixing (FWM), stimulated Brillouin scattering and stimulated Raman scattering on the system performance of OCDMA systems is presented. As some of the non-linearities may have correlated effects on the performance of the system, the relations between these effects are also investigated. Bit error rate results reveal that the most important unwanted effect was caused by FWM.

Variable weight Khazani-Syed code using hybrid fixed-dynamic technique for optical code division multiple access system

Abstract. Future Internet consists of a wide spectrum of applications with different bit rates and quality of service (QoS) requirements. Prioritizing the services is essential to ensure that the delivery of information is at its best. Existing technologies have demonstrated how service differentiation techniques can be implemented in optical networks using data link and network layer operations. However, a physical layer approach can further improve system performance at a prescribed received signal quality by applying control at the bit level. This paper proposes a coding algorithm to support optical domain service differentiation using spectral amplitude coding techniques within an optical code division multiple access (OCDMA) scenario. A particular user or service has a varying weight applied to obtain the desired signal quality. The properties of the new code are compared with other OCDMA codes proposed for service differentiation. In addition, a mathematical model is developed for performance evaluation of the proposed code using two different detection techniques, namely direct decoding and complementary subtraction.

Proposal of multi-service (MS) code to differentiate quality of services for OCDMA systems

The emergence of a broad range of network-driven applications (e.g. multimedia, online gaming) rises the demand for network environments with ability to provide multiservice capabilities with diverse Quality of Service (QoS) requirements. In this paper, a new code family of novel spreading sequences, called Multi-Service (MS) code has been constructed in order to support multiple services in OCDMA system. The performance of the proposed code is demonstrated using mathematical analysis. Different numbers of basic users are used to support triple-play services (audio, data and video) with different QoS requirements. Results indicate that the technique can clearly provide a relative QoS differentiation. Lower value of basic users can support larger number of subscribers as well as delivering better performance in terms of acceptable BER of 10-9 at fixed code weight.

OCDMA multi service with zero cross correlation code in free space optics

In this paper a variable weight code for Optical Code Division Multiple Access (OCDMA) is proposed to provide differentiated services in optical network. We call it multi service zero cross correlation (MS-ZCC) where it has zero-cross correlation. Using simulation, the performance of this code is compared with the conventional variable weight (VW)-ZCC code in free space optic (FSO) environment. The newly proposed code MS-ZCC shows an improvement of 300 meters link distance for weight 2 and 8, compared to VW-ZCC.

Effects of fiber dispersion on the performance of optical CDMA systems

Abstract In recent years, Optical Code Division Multiple Access (OCDMA) system had received great attentions due to its potential to support applications with various data rates and Quality of Service requirements in physical layer. Since the main part of any fiber-based transmission system is the optical fiber itself, OCDMA also suffers from fiber impairments especially dispersion. In this paper, a review of fiber dispersion effects on system performance of different coding techniques is presented, focusing on single mode fiber. The different coding techniques include direct-sequence, spectral amplitude encoding and wavelength hopping/time spreading. In addition, the basic dispersion compensation approaches, which have been proposed in the literature, for these particular coding schemes are also discussed.

Experimental realization of multi-service RoF system using OCS-PolMux techniques

Optical Carrier Suppression has been proven as an efficient way of generating high frequency optical carrier for Radio over Fiber (RoF) systems. However, previous studies show that OCS with the combination of RF and optical components can only transmit a single service in RoF system. This paper shows that two different services can be transmitted using a single wavelength through RoF system with the use of Polarization Multiplexing (PolMux) method. The combination of these two techniques enables multiservice RoF such as LTE and WiFi services to be transmitted simultaneously to the customers.

Investigation of circulation noise effect on SAC-OCDMA system with ring topology

In this paper, we investigate the performance of an OCDMA system with ring topology where number of the spans can be more than one. Effect of circulation noise is evaluated beside of shot noise and thermal noise. Through analytical approach, it is shown that higher amount of amplifier gain, produces higher amount of circulation noise. Also by increasing the number of nodes, the strength of the circulation noise is reduced and the ratio of this reduction is more for lower amplifier gain. For example, with increasing number of the nodes from 3 to 8, the amount of log variance of circulation noise increases only 1 unit (-13 to -14) for amplifier gain 20 dBm, while this value is 4 units (from -15 to -19) if gain is 10 dBm.