A point-to-point optical communications system operating at 1550 nm contains 3 Erbium Doped Fibre Amplifiers (EDFAs) which are equally spaced along the total transmission distance. The laser output power is -6 dBm and the receiver sensitivity is -31 dBm. The fibre has and a dispersion parameter of D = 17 ps/nm.km a loss coefficient of = 0.24 dB/km at 1550 nm. All system losses are due to fibre attenuation. The operator of the system has factored in a power margin of 7 dB.

(a) Considering that the gain of each amplifier is set at 14 dB, such that the minimum received power requirements are met for satisfactory performance. Calculate the link distance.

(b) Calculate the length of Dispersion Compensation Fibre (DCF) required to completely overcome the dispersion introduced by the first fibre span (i.e. from the transmitter to the first EDFA). The Group Velocity Dispersion of the DCF is 2 = +89.22 ps2 /km.