Bandwidth refers to the amount of data that can be carried from one point to another. Fibre bandwidth is given in MHz-km. A product of frequency and distance, bandwidth scales with distance: if you half the distance, you double the frequency. If you double the distance, you half the frequency. What does this mean in premises cabling? For a 100 metre run (as allowed for twisted pair cable), the bandwidth for 62.5/125 micron fibre is 1600 MHz at 850 nm and 5000 MHz at 1300 nm. For the 2-km spans allowed for most fibre networks, bandwidth is 80 MHz at 850 nm and 250 MHz at 1300 nm. With Singlemode fibres, the bandwidth for a 100 metre run is about 888 GHz.