Electronic Communication Systems 2nd Edition by Roy Blake

Exercise 6

An optical communications link is to be built using fiber rated for 5000 MHz-km. The light source is a laser diode producing 0.25 mW. The fiber has losses of 0.4 dB/km and is available in 2 km lengths. It can be spliced with a loss of 0.2 dB per splice, and there will be a 5 dB loss in the connectors throughout the system. The receiver used has a sensitivity of -30 dBm. The source rise time is 2 ns, and the receiver rise time is 4 ns.
(a) Prepare a loss budget for a Unk 20 krn long, and calculate the system margin in dB.
(b) What would be the maximum bandwidth that could be used with the system in (a)