Performance analysis of a 2-D time-wavelength OCDMA wavelength-aware receiver with beat noise

The effect of beat noise on two-dimensional time-wavelength optical code-division multiple-access systems utilising wavelength-aware receivers is examined. A derivation of a general formula for the bit error probability taking into consideration multiple access interference (MAI) and other noise sources is given. In addition, a comparison between the system performance of such a receiver and the traditional configuration is presented. Studies to date that have focused only on the MAI limited case showed that the wavelength-aware configuration yields a better performance when compared to the traditional receiver. When beat noise is considered, the numerical results reveal that the performance of wavelength-aware receiver is very sensitive to beat noise and is not superior over the traditional receiver

Error Probability Bound Considering Beat Noise in 2-D OCDMA Systems

Considering a 2-Dimensional Optical Code Division Multiple Access (2-D OCDMA) system using spreading codes in both time and wavelength domains, we study in this paper the impact on the performance of one of the most predominant performance limitation which is beat noise due to the photo detection. The beat noise impact is correlated with the wellknown OCDMA limitation named Multiple Access Interference (MAI). Our contribution is to assess, through a theoretical analysis, an error probability bound of a system working in incoherent or partially coherent optical regime. Thanks to the theoretical error probability expression we have developed, the specifications and requirements needed to neglect beat noise effect in a 2-D OCDMA system with a conventional receiver are easily obtained. For a targeted Bit Error Rate (BER), and a given number of active users, one can determine from our results, the 2-D code family parameters, the available data rate and the optical source characteristics, required to be free of beat noise impact

Effect of variations in environmental temperature on 2D-WH/TS OCDMA code performance

Extensive research has been carried out on the performance investigation of two-dimensional wavelength hopping/time spreading optical code division multiple access (OCDMA) codes, which are based on picosecond multiwavelength pulses under the influence of temperature variations resulting from changing environmental conditions. Equations have been derived to theoretically evaluate the extent to which such temperature changes will degrade the overall OCDMA system performance. To mitigate these negative effects on the OCDMA system, several steps have been introduced to improve the code robustness. System design improvements have then been investigated. We also found they would help to improve the spectral efficiency

Investigation on optical code division multiplex access (OCDMA)

After successful application of CDMA techniques in wireless communications, optical CDMA has been considered as a candidate for future access networks. We will focus on passive optical networks (PONs) in particular. This work pursues three main goals: First, due to the depth and extension of the topic, offer a comprehensive overview. Several classes of optical codes are reviewed and different technologies for implementing codes are described and compared. Second, provide some guidelines in order to facilitate the design of OCDMA-based PONs. Since OCDMA allows flexible network design, different approaches can be considered. Finally, outline a possible solution, discussing and analyzing key issues as optical coding and encoding/decoding hardware. System performance or network architecture are also studied

Efficient large-scale multiplexing of fiber Bragg grating and fiber Fabry-Perot sensors for structural health monitoring applications

Fiber Bragg gratings have been demonstrated as a versatile sensor for structural health monitoring. We present an efficient and cost effective multiplexing method for fiber Bragg grating and fiber Fabry-Perot sensors based on a broadband mode-locked fiber laser source and interferometric interrogation. The broadband, pulsed laser source permits time and wavelength division multiplexing to be employed to achieve very high sensor counts. Interferometric interrogation also permits high strain resolutions over large frequency ranges to be achieved. The proposed system has the capability to interrogate several hundred fiber Bragg gratings or fiber Fabry-Perot sensors on a single fiber, whilst achieving sub-microstrain resolution over bandwidths greater than 100 kHz. Strain resolutions of 30n epsilon/Hz(1/2) and 2 n epsilon/Hz(1/2) are demonstrated with the fiber Bragg grating and fiber Fabry-Perot sensor respectively. The fiber Fabry-Perot sensor provides an increase in the strain resolution over the fiber Bragg grating sensor of greater than a factor of 10. The fiber Bragg gratings are low reflectivity and could be fabricated during the fiber draw process providing a cost effective method for array fabrication. This system would find applications in several health monitoring applications where large sensor counts are necessary, in particular acoustic emission

Overlapped CDMA system in optical packet networks : resource allocation and performance evalutation

Dans cette thèse, la performance du système CDMA à chevauchement optique (OVCDMA) au niveau de la couche de contrôle d'accès au support (MAC) et l'allocation des ressources au niveau de la couche physique (PRY) sont étudiées. Notre but est d'apporter des améliorations pour des applications à débits multiples en répondant aux exigences de délai minimum tout en garantissant la qualité de service (QoS). Nous proposons de combiner les couches PRY et MAC par une nouvelle approche d'optimisation de performance qui consolide l'efficacité potentielle des réseaux optiques. Pour atteindre notre objectif, nous réalisons plusieurs étapes d'analyse. Tout d 'abord, nous suggérons le protocole S-ALOHA/OV-CDMA optique pour sa simplicité de contrôler les transmissions optiques au niveau de la couche liaison. Le débit du réseau, la latence de transmission et la stabilité du protocole sont ensuite évalués. L'évaluation prend en considération les caractéristiques physiques du système OY-CDMA, représentées par la probabilité de paquets bien reçus. Le système classique à traitement variable du gain (YPG) du CDMA, ciblé pour les applications à débits multiples, et le protocole MAC ±round-robin¿ récepteur/émetteur (R31), initialement proposé pour les réseaux par paquets en CDMA optique sont également pris en compte. L'objectif est d ' évaluer comparativement la performance du S-ALOHA/OY-CDMA en termes de l'immunité contre l'interférence d'accès lTIultiple (MAI) et les variations des charges du trafic. Les résultats montrent que les performances peuvent varier en ce qui concerne le choix du taux de transmission et la puissance de transmission optique au niveau de la couche PRY. Ainsi, nous proposons un schéma de répartition optimale des ressources pour allouer des taux de transmission à chevauchement optique et de puissance optique de transmission dans le système OY-CDMA comme des ressources devant être optimalement et équitablement réparties entre les utilisateurs qui sont regroupés dans des classes de différentes qualités de service. La condition d'optimalité est basée sur la maximisation de la capacité par utilisateur de la couche PHY. De ce fait, un choix optimal des ressources physiques est maintenant possible, mais il n'est pas équitable entre les classes. Par conséquent, pour améliorer la performance de la couche liaison tout en éliminant le problème d'absence d'équité, nous proposons comme une approche unifiée un schéma équitable et optimal pour l'allocation des ressources fondé sur la qualité de service pour des multiplexages temporels des réseaux par paquets en CDMA à chevauchement optique. Enfin, nous combinons cette dernière approche avec le protocole MAC dans un problème d'optimisation d'allocation équitable des ressources à contrainte de délai afin de mieux améliorer le débit du réseau et le délai au niveau de la couche liaison avec allocation équitable et optimale des ressources au niveau de la couche PHY

Coherence-Multiplexed Optical RF Feeder Networks

An optical RF feeding system for wireless access is proposed, in which the radio access points are distinguished by means of coherence multiplexing (CM). CM is a rather unknown and potentially inexpensive optical code division multiple access technique, which is particularly suitable for relatively short-range applications with moderate transmission bandwidth requirements. Subcarrier multiplexing (SCM) can possibly be used on top of CM, either as single-channel or multichannel SCM. The performances of the resulting distribution networks are analyzed, incorporating the effect of chromatic dispersion, optical beat noise, shot noise, thermal noise, and—in the case of multichannel SCM—intermodulation distortion. The results of the IEEE 802.11b standard for wireless LAN.\u