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To: Peter Church who wrote (7825)	5/26/2000 4:08:00 PM
From: The Ox	Respond to of 10309

The bandwidth demand/requirements associated with each node is increasing at a substantially higher rate than the rate at which nodes are being added to the network.

To: Peter Church who wrote (7825)	5/26/2000 9:23:00 PM
From: James Connolly	Read Replies (1) \| Respond to of 10309

Moore's law and the Telecosm...... Moore's law A doubling in processor power every 18 months. Therefore from 1990 to today (if you do the calculations) processor power has increased by a factor of 128 times, e.g. a 1 Ghz processor now is equivalent to a 8Mhz processor in 1990. Law of the Telecosm (Bandwidth) In 1990 a typical fiber backbone ran at around 45 megabits a second (45x10E6). Today with the latest fiber technology speeds close to Petabits (1x10E15) have been demonstrated in the lab. Therefore during the last 10 years bandwidth has increased by a maximum of 22 million i.e. (1x10E15)/(45x10E6)=22x10E6. Lets just say 1 million fold to be conservative. Therefore the ratio of Moore's law to the increase in bandwidth is about 8000 (1 million/128) taken over the last 10 year period. Now you could argue about some of the numbers but the point is that the increase in bandwidth over the last 10 years divided by the increase in processing power is a very large number, which ever way you look at it. Looking at it another way Bandwidth is increasing at about 4 times faster than Moore's law/per year. This increase in Bandwidth has been driven mainly by improvements in WDM (Wave Division Multiplexing) or DWDM (Dense Wave Division Multiplexing). The idea is quite simple. Just put a prism at the end of the fiber (or a piece of optics that does a similar job like a diffraction gating). You then send as many bit streams as you like down the fiber making sure that each bit stream is at a slightly different wavelength (or color). Once the combined bit streams reach the end of the fiber they are then split back into there individual bits streams in exactly that same way white light is split into the colors of the rainbow while going through a prism, i.e. each at a slightly different angle and detector. Therefore the bandwidth of a fiber is limited by how closely spaced (Dense) the different wavelengths of light are and hence by the resolving power of the optics used. The optics has to be able to distinguish one closely spaced wavelength from another. As time goes by the resolving power of the optics increases and hence the wavelength spacing decreases, with this the number of channels (and bandwidth) increases. Another factor which increases the bandwidth of fibers is the transparency window of fibers. Fibers are very transparent in the infra red region of the spectrum. However outside of the infra red region fibers absorb light quite strongly. When fibers absorb light strongly that particular wavelength becomes totally uneconomic. The number of repeater stations (booster stations) required over lets say a link from the US to Ireland becomes far too expensive to justify it's existence. The light signal decays far to quickly and it needs to be boosted far too often. Again as time passes by manufactures of fibers find ways to increase the "economic transparency window" of fibers by reducing the OH ion content (i.e. traces of water). As the transparency window increases in width so to do the number of wavelengths/channels/lambdas that can be packed into the available space. As you can see Moore's law is having a hard time keeping pace, after all modern fibers move at not just Internet speed but light speed. Regards JC.