Fiber-optic code division multiple access : multi-class optical orthogonal codes, optical power control, and polarization encoding
No Thumbnail Available
URL
Journal Title
Journal ISSN
Volume Title
Doctoral thesis (article-based)
Checking the digitized thesis and permission for publishing
Instructions for the author
Instructions for the author
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
2007-04-26
Major/Subject
Mcode
Degree programme
Language
en
Pages
64, [60]
Series
Technical report / Helsinki University of Technology, Communications Laboratory. T, 56
Abstract
Ever since the mid- 1980s when the single-mode fiber-optic media were believed to become the main highways of future telecommunications networks for transporting high-volume high-quality multipurpose information, the need for all-optical multi-access networking became important. An all-optical multi-access network is a collection of multiple nodes where the interconnection among various nodes is via single- or multi-mode fiber optics and for which they perform all their essential signal processing requirements such as switching, add-drop, multiplexing/demultiplexing and amplification in the optical domain. Optical CDMA networking is one possible technique that allows multiple users in local area networks to access the same fiber channel asynchronously with no delay or scheduling. Optical CDMA networks are not without their own problems. Search for codes suitable to the optical domain is one of the important topics addressed in the literature on optical CDMA. Existing codes developed in the late 80's are limited to single class traffic or can support multiclass traffic but with restrictions on code lengths and weights. Also the number of generated codes is severely limited due to orthogonality issues. In this thesis, we pay particular attention to propose new codes that can support multiclass traffic with arbitrary code weights and lengths. Therefore, data sources with varying traffic demands can be accommodated by optical CDMA networks using the proposed codes. We also present a simple generation technique for the proposed multiclass codes and analyze their performance. The number of users supported by the proposed multiclass codes will be limited since it is an extension of existing code designs with such limitation. We then propose the use of polarization dimension in order to double the number of supported users. On the other hand, incoherent optical CDMA systems are considered as positive systems meaning that only unipolar codes can be considered for such systems. Therefore, multiple access interference will be quite high in optical CDMA due to the nature of incoherent power detection. Reducing the effect of the interference on the performance of optical CDMA is an important topic. We propose the use of power control to decrease the effects of interference in optical star networks in which users' fiber lengths and data rates are not equal. We consider the case of optically amplified network with amplifier noise as the main source. We then elaborate by considering the nonlinearity in the photodetection process and propose the use of an iterative algorithm to find the solution of the non-linear optical power control problem. Finally, we propose an optical CDMA system based on polarization encoding. Since the encoding is performed in the spatial domain, therefore, positive and negative levels can be realized. This approach leads to increasing the number of supported users of optical CDMA by the use of known codes, such as Gold and Hadamard codes, with enhanced performance.Description
Keywords
optical CDMA, optical orthogonal codes, optical power control, polarization shift keying
Other note
Parts
- Naser Tarhuni, Timo Korhonen, Edward Mutafungwa, and Mohammed Elmusrati, Multiclass Optical Orthogonal Codes for Multiservice Optical CDMA Networks, Journal of Lightwave Technology, Vol. 24, Issue 2, Feb. 2006, Pages: 694-704. [article1.pdf] © 2006 IEEE. By permission.
- Naser Tarhuni, M. Elmusrati, and T. Korhonen, Polarized Optical Orthogonal Code for Optical Code Division Multiple Access Systems, Progress in Electromagnetics Research PIER, 65, Pages: 125-136, 2006. [article2.pdf] © 2006 EMW Publishing. By permission.
- Naser G. Tarhuni, Timo O. Korhonen, Mohammed Elmusrati, and Edward Mutafungwa, Power Control of Optical CDMA Star Networks, Optics Communications, Vol. 259, Issue 2, March 2006, Pages: 655-664. [article3.pdf] © 2006 Elsevier Science. By permission.
- Naser Tarhuni, M. Elmusrati, and T. Korhonen, Multi-Class Optical-CDMA Network Using Optical Power Control, Progress in Electromagnetics Research PIER, 64, Pages: 279-292, 2006. [article4.pdf] © 2006 EMW Publishing. By permission.
- Naser Tarhuni, M. Elmusrati, and T. Korhonen, Nonlinear Power Control for Asynchronous Fiber-Optic CDMA Networks, Proceedings of the 2006 IEEE International Conference on Communications, ICC 2006, Volume 6, Pages: 2782-2786, June 2006. [article5.pdf] © 2006 IEEE. By permission.
- Naser Tarhuni, Timo O. Korhonen, and Mohammed Elmusrati, State-of-Polarization Encoding for Optical Code-Division Multiple-Access Networks, Journal of Electromagnetic Waves and Applications JEMWA, Volume 21, Number 10, Pages: 1313-1321, 2007, scheduled for publication. [article6.pdf] © 2007 Brill Academic Publishers. By permission.