Signal self-restoration characteristic and bit error rate performance of terrestrial cascaded erbium doped fibre amplifier systems

A normalised gain formula of perturbed erbium doped fibre amplifier (EDFA) is derived. For terrestrial systems where EDFAs work under low saturation, it is shown that optical power can regain 90% of its original 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 perturbation starts the more degradation in BER. Less saturated EDFAs would result in worse BER under the same perturbation