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To: Frank A. Coluccio who wrote (9982)	12/30/2000 1:49:40 AM
From: Wallof Confusion	Read Replies (1) \| Respond to of 12823

You can tell I'm bored when I start replying to questions outside my area of expertise. But I guess this is not an answer, just another question poorly worded. I believe the velocity of an electron in a conductor is a function of the potential energy applied and the resistance to it's movement. So it will vary. However, I'm a little unsure if this is an appropriate measure since this might apply to electron drift as opposed to the rate of a signal transmission.( I've heard the analogy of a conductor to a full hose of water. The instant the pressure is applied (voltage), flow is noticed at the other end (signal). On the other hand, I always assumed light transmission in a fiber cable was at the speed of light (in glass/quartz??). Now I recall recently hearing about a technology that enables the signal transmitted by the light "flow", might be able to be pushed ahead of the light, thus a signal actually could be transmitted faster than the speed of light. Does this ring a bell with anyone? I suppose instantaneous is still faster than "above the speed of light". Now consider throughput?? That's different. Take it easy, Ger

To: Frank A. Coluccio who wrote (9982)	12/30/2000 2:58:07 AM
From: elmatador	Read Replies (1) \| Respond to of 12823

Isn't there a difference between speed and rate of transmission? Fiber allows higher bit rates, hence is faster than coax copper.

To: Frank A. Coluccio who wrote (9982)	12/31/2000 1:19:17 AM
From: Bernard Levy	Read Replies (1) \| Respond to of 12823

Hi Frank: Using the copper cable model in Chen's DSL book, I get that electrons travel at 210,000 km/sec over standard copper cables (the speed of light is 300,000 km/sec). This speed does not change much over 22 gauge, 24 gauge or 26 gauge copper. My guess is that the speeds of propagation of pulses over copper or fiber are comparable. Of course, the main difference is that copper has much more attenuation particularly at large frequencies, and thus a lower capacity. Best regards, Bernard Levy

To: Frank A. Coluccio who wrote (9982)	1/2/2001 1:04:36 PM
From: Darren DeNunzio	Read Replies (1) \| Respond to of 12823

Signal Propagation: Is copper faster than fiber? Network World Fusion Focus on High Speed LANs By John Curtis Network World, 01/11/99 As new technologies further define high performance networking, engineers and network administrators alike are taking a fresh look at cabling to further enhance overall network performance. Today's cables carry data signals at more than 50% of the speed of light in a vacuum, but there are measurable speed differences among cable types. Do such differences have a significant impact in overall network performance? Should they be considered when choosing between fiber and copper cable? Let's take a closer look. Today's leading fiber cables from vendors such as Corning, AT&T Network Cable Systems and Spectran Specialty, propagate signals along the cable at approximately two thirds the speed of light in a vacuum. (In technical jargon, they have an index of refraction, denoted by the Greek letter Eta, of approximately 1.5.) Today's Category 5 copper cables, by contrast, actually propagate signals faster than fiber -- approximately 72% of the speed of light in a vacuum (or 10% faster than fiber). To determine the real impact of this difference on network traffic, we need to do a little math. If we compare the time required to send data across 100 meters of fiber vs. copper cable, the copper transmission will arrive less than one tenth of one microsecond sooner - virtually undetectable by even the best network analyzers. Even if we were to stretch the distance to 20 kilometers, well beyond what's allowed for Category 5 copper, the difference in cable speeds still amounts to less than one microsecond. All of this means that, from the perspective of overall network performance, the propagation delays of fiber and copper cable are effectively identical. Clearly, issues such as cost and bandwidth remain key factors in choosing between the two technologies, but customers can comfortably ignore propagation delay as a performance metric in overall network performance.