Ultimate spectral efficiency of information transmission of fibre amplifiers in WDM systems

Abstract

Numerical modelling of ultimate spectral efficiency of information transmission in wavelength-division multiplexing (WDM) systems is carried out for the case when the noise of optical fibre amplifiers determines the system capacity. The number-state model is used for finding spectral efficiency of communication lines with erbium-doped (EDFA) and chromiumdoped fibre amplifiers (CDFA). The results obtained show that spectral efficiency of CDFA exceeds that of EDFA throughout the conventional band and approaches the "quantum limit" in a window of transparency of advanced fibres in the high pump power limit. The ultimate capacity of communication systems with CDFA is estimated to be about 300 Tbit/s.