04 Try it yourself Interactive

Pick a medium, set the run, count the regenerators

The same four media and the same 20 dB budget as section 02. Choose a medium and a run length, then step through the calculation one line at a time: the attenuation coefficient, the total loss over the run, how far a single segment reaches, and finally how many regenerators the run needs. The four counters are computed from the figures on screen, so every number is arithmetic you can redo on paper.

The loss coefficients are approximate and deliberately labelled as such. Real cable comes with a frequency-dependent insertion loss curve from its manufacturer, and real fibre is specified per wavelength window. These are honest order-of-magnitude figures for the conditions named beside each one, chosen because the conclusions they produce match reality: 20 dB on Cat 6 lands on exactly the 100 m that structured cabling standards allow, and 20 dB on single-mode fibre lands on the 100 km that submarine amplifier spacing is actually built to. Connector and splice losses are left out so that only one variable moves. Nothing plays on its own: Next, Back and Reset, or the arrow keys.

Cat 6 UTP, twisted pair
about 200 dB per km at 100 MHz
A regenerator sits at every join between segments, so the answer is always one fewer than the number of segments. Watch that the reach per segment never changes when you change the length: it is a property of the medium alone.
Press Next to begin. Each press works one line of the calculation.


      

        
Run length–

        
Total loss–

        
Reach per segment–

        
Regenerators–

      


      

      

        
        
        
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