SIGNAL SELF-RESTORATION CHARACTERISTIC AND BIT ERROR RATE PERFORMANCEOF TERRESTRIAL CASCADED ERBIUM-DOPED FIBER AMPLIFIER SYSTEMS

A normalised gain formula of perturbed erbium doped fibre amplifier (E DFA) is derived. For terrestrial systems where EDFAs work under low sa turation, it is shown that optical power can regain 90% of its origina l value within three stages when the system suffers a 3 dB dip of EDFA output power. On the other hand, the corresponding system BER will be deteriorated by more than two orders of magnitude and the later the p erturbation starts the more degradation in BER. Less saturated EDFAs w ould result in worse BER under the same perturbation.