| The purpose of the 200 km circumference limit is to bound propagation delay.
For copper links, you count them as the length of fiber that has the same
signal propagation delay. As it turns out, the propagation speed of signals
over coax is somewhat faster than over fiber (10-15% faster). So if you treat
coax as equivalent to fiber, you're actually a bit conservative.
The individual link limit is a completely different issue: the consideration
there is signal quality, not delay, so there you do see a big difference
between fiber (2 km, or 40 km for single mode) vs. 100 m for copper.
paul
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| Correct. The 200 km limit is for propagation delay, for which copper counts
equal (or actually somewhat less, but you might ignore that) as fiber.
The per-station distance (2 km or 100 m or 40 km) is for signal integrity;
that one DOES change drastically depending on medium.
paul
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