Electronic Communication Systems 2nd Edition by Roy Blake

Exercise 39

A fiber system uses single mode fiber with a loss of 0.15 dB/km and dispersion of 0.7 ps/km. The laser diode sources used with this system have a power output of 4 mW and a rise and fall time of 50 ps. The receivers have a rise and fall time of 30 ps and require a power level of -30 dBm to operate. The system operates with a data rate of 2.5 Gb/s using an NRZ code. Allow 10 dB for losses other than those of the cable.
(a) What is the maximum distance over which this system can operate without either a repeator an amplifier
(b) Determine whether the maximum distance for a single link in this system is determined by dispersion or by loss.
(c) Suppose that you needed to communicate over a distance of 300 km with this system. Would you suggest using an optical amplifier or a repeater Why