The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Design and Performance Analysis of Pure and Hybrid WDM Optical Networks

Edward Mutafungwa

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 9th of July, 2004, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-7175-3)   [1005 KB]
Dissertation is also available in print (ISBN 951-22-7174-5)

Abstract

In optical networking, information-bearing electrical signals are transported by up-converting the signals into the optical domain and then transmitting them over high-capacity low-loss optical fiber links. Furthermore, optical switching nodes with a large throughput can be used to alleviate the contention for fibers, route the optical signals and avoid failed fiber links. This guarantees a robust always-on service for entities transporting their signals via the optical network. Based on those merits, optical networking technologies are now being increasingly adapted in most operational medium and long range networks. Of the existing technologies, wavelength-division multiplexing (WDM) transmission is ubiquitous due to its ability to multiply the capacity of the installed fiber base and to enhance the flexibility of provisioning of the fiber capacity by utilizing the wavelength degree of freedom in an intelligent optical layer.

This thesis focuses on flexibility improvement techniques that enable dynamic provision of bandwidth available in optical networks within acceptable cost bounds. The aforementioned nodes for optical connection provisioning are studied in detail. From the study, novel node architectures are proposed with improved scalability for handling more connections and reduced signal impairment for increased transmission range. The thesis proposes techniques for incorporating dependability enhancement during initial node design stage and the gradual node scaling after deployment by optimizing the allocation of redundant modules. Analytical comparison based on example dependability-enhanced nodes indicate significant improvements compared to corresponding nodes without redundancy.

Hybrid WDM networks utilize an extra optical degree of freedom in addition to signal wavelength. The virtues of hybrid WDM as an optical layer grooming method are investigated. To that end, the thesis pays particular attention to hybrid OCDM (optical code-division multiplexing) / WDM transmission. The connection acceptance improvement due to OCDM/WDM transmission is analysed and the possible limitations of various light-path schemes are noted. The potential application of hybrid WDM for radio-over-fiber systems is explored for an urban-wide hierarchical metropolitan network. In that case, the more complex hybrid WDM scheme showed significant improvement in utilization of optical resources compared to conventional WDM implementation. Semi-hybrid WDM is proposed as a compromise solution between pure and hybrid WDM implementations. Furthermore, a 60 GHz radio-over-fiber OCDM/WDM system is proposed and guidelines are presented for possible performance improvement.

This thesis consists of an overview and of the following 8 publications:

  1. Mutafungwa E., 2001. Circulating loop simulations for transmission performance comparison of various node architectures. Journal of Optics A: Pure and Applied Optics 3, number 4, pages 255-261. © 2001 Institute of Physics Publishing Ltd. By permission.
  2. Mutafungwa E., 2001. Optical hop number limits imposed by various 2 × 2 cross-connect node designs. Optics Express 9, number 8, pages 400-410. © 2001 Optical Society of America (OSA). By permission.
  3. Mutafungwa E., 2001. An improved all-fiber cross-connect node for future optical transport networks. Optical Fiber Technology 7, number 3, pages 236-253. © 2001 Elsevier Science. By permission.
  4. Mutafungwa E. and Kazaura K., 2001. A modified optical add-drop multiplexer with improved transmission performance. Presented at the 7th Asia-Pacific Conference on Communications (APCC2001), Tokyo, Japan, 17-20 September 2001, and published in IEICE Transactions on Communications, volume E84-B, number 11, appendix pages 546-549. © 2001 Institute of Electronics, Information and Communication Engineers (IEICE). By permission.
  5. Mutafungwa E., 2002. GORA: an algorithm for designing optical cross-connect nodes with improved dependability. Computer Communications 25, number 16, pages 1454-1464. © 2002 Elsevier Science. By permission.
  6. Mutafungwa E. and Halme S. J., 2002. Analysis of the blocking performance of hybrid OCDM-WDM transport networks. Microwave and Optical Technology Letters 34, number 1, pages 61-68.
  7. Mutafungwa E., Halme S. J., Kazaura K., Wakahara T. and Matsumoto M., 2003. Strategies for resource provisioning in optical networks supporting broadband wireless access networks. Journal of Optical Networking 2, number 3, pages 55-68. © 2003 Optical Society of America (OSA). By permission.
  8. Mutafungwa E., Halme S. J., Kazaura K., Matsumoto M. and Wakahara T., 2003. Millimeter-wave over fiber systems using hybrid OCDM/WDM transmission. International Journal of Infrared and Millimeter Waves 24, number 7, pages 1113-1126. © 2003 Kluwer Academic Publishers. By permission.

Keywords: optical networking, optical layer, wavelength-division multiplexing, optical cross-connects, optical add-drop multiplexers, transmission performance, hybrid WDM, optical code-division multiplexing, radio-over-fiber

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© 2004 Helsinki University of Technology

Last update 2011-05-26