CONCEPTOS BÁSICOS.
TIPOLOGÍA DE VIVIENDA.
In this chapter we have discussed and analysed a few of the fundamental issues associated with photonic networks and AON architectures. In particular we have discussed the relative merits of the two types of optical network; namely, broadcast & select and selectively routed optical networks.
Although substantial device and systems work still remains it seems clear that photonic technology is rapid reaching a level of maturity where it may be applied within telecommunication networks not only as direct equivalents of the current electronic components but also in a manner to enhance the network’s functionality. Using wavelength as an additional dimension in (optical) networks has been shown to be feasible and may prove to be very profitable.
In summary, it seems clear to the author that one may apply the use o f photonic technology according to one o f several principles
• Transmission
• Back-plane or interconnects, e.g. switches etc.
• Closed local networks, self routing networks or ‘Super LANs’ • The Utopian ‘Optical Ether’
• A new type of network based around the available photonic technology and the strengths o f optics — with no direct (opto-)electronic equivalent
Optics is already the transmission technology o f choice for many communication systems. This is due to its low cost and high reliability. It has also been applied as interconnective back-planes both between electronic sub-systems and in reconfiguring systems such as telecommunication switches. Although the latter application has been shown to be feasible, it is the author’s opinion that it may not be making the best use o f optics’ strength. As also discussed in section 2. 1- “optics versus electronics” - due to the non-interaction o f optical signals (waves), photonic processing systems require at the very least electronic control. Consequently, so called ‘optical’ devices which rely on electronic control must be developed and used with caution as a comparable exclusively electronic device may ultimately be more versatile and/or cheaper.
Indeed it seems clear to the author that this in turn leads to the conclusion that optics is best put to use in transmission systems unless a new type o f network can be developed that makes use o f the advantages of photonic technology and minimises the functions that optics is not so good at, i.e. processing. Such a network would probably have no direct electronic equivalent.
I l l
The above statement are very closely related to a networks controllability which we (superficially) investigated in the final section of this chapter. It was shown that even if equivalent optical technology was available, how it should be controlled is a non-trivial issue.
In the remaining two chapters in this section, chapter 5 & 6 we discuss the potential and relative merits of optical network systems and architectures with reference to the access network and a hypothetical national transparent optical network, respectively. We do briefly outline the control functions necessary although we do not discuss any specific means of implementation. In part III of the thesis we propose a generic multi service broadband network management & control scheme. Although we analyse that in the broadest terms it certainly is also applicable to optical networks. Especially the analysis o f access or individual network resource control.
4.5 Bibliography
c.
A. Brackett, “On the Capacity of Multiwavelength Optical Star Packet Switches”, IEEE Lts. Magazine, pp. 33-37, May 1991M. Ajmone Marsan, Andrea Bianco, Emilio Leonardi, Fabio Neri, “Topologies for Wavelength-Routing All-Optical Networks”, IEEE/ACM Transactions on Networking, Vol. 1, No. 5, pp. 534-546, October 1993
4.6 References
[1]
c.
Brendan S. Traw, Jonathan M. Smith, “Striping Within the Network Subsystem”, IEEE Network, pp. 22-32, July/August 1995[2] M. S. Goodman, J L Gimlett, H. Kobrinski, M. P. Vecchi, R. M. Bulley, “The LAMDANET Multiwavelength Network; Architecture, Applications and Demonstrations”, IEEE J Selected Areas Commun., Vol. 8, pp. 995-1004, 1990 [3] H. Kobrinski, R. M. Bulley, M. S. Goodman, M. P. Vecchi, C. A. Brackett,
L. Curtis, J. L. Gimlett, “Demonstration o f High Capacity in the LAMBDANET Architecture: A Multiwavelength Optical Network”, Electron. Letts., Vol. 23, pp. 824-826, 1987
[4] P. A. Kirkby, Symfonet: Ultra-High Capacity Distributed Packet Switching Network for Telecoms and Multiprocessor Computer Applications”, Electron. Letts., Vol. 26, pp. 19-21, 1990
[5] N. R. Dono, P. E. Green, K. Liu, R. Ramaswami, F. Tong, “A Wavelength Division Multiple Access Network for Computer Communication”, IEEE J. Select. Areas Commun., Vol. 8, pp. 983-994, 1990
[6] Swie Tsing Tan, David H. C. Du, “Embedded Unidirectional Incomplete Hypercubes for Optical Networks”, IEEE Transactions on Commun., Vol. 41, No. 9, pp. 1284-1289, 1993
[7] P. Cochrane, R. Heckingbottom, D. Heatley, “The Hidden Benefits of Optical Transparency”, IEEE Commun. Mag., Vol. 32, No. 9, pp. 90-97, 1994
Chapter 5
This chapter is based upon a consultancy study undertaken for GPT LTD.,
“Potential for Wavelength Division Multiplexing in Local Broadband networks” in 1994 following a meeting between BT Labs, Siemens, GPT, GMMT & UCL, Wednesday 18th May 1994 at the Heathrow Excelsior hotel under the Optical Switching in Networks Collaboration. It later resulted in further collaboration between the Electronic and Electrical Engineering Department, UCL and GPT Ltd, under a EPSRC (CASE) PhD award.