Influence of bidirectional pumping in high-power EDFA on single-channel, multichannel and pulsed signal amplification

A detailed analysis in terms of computational and experimental results of a high power erbium doped fibre amplifier using the bidirectional pumping scheme is presented. The differences between the signal evolution are discussed for unidirectionally and bidirectionally pumped amplifier for a single channel CW input. A comparison is made between the theoretically predicted gain and the experimental results for bidirectional pumping. The numerical analysis is further extended to multiwavelength propagation in the forward and bidirectional pumping schemes. In the case of a pulsed input, enhanced nonlinearity of the doped fibre and the differences in gain evolution between the different pumping schemes result in drastic changes in the pulse quality during its propagation through the amplifier fibre. The modifications of a Gaussian pulse in the time and spectral domains due to propagation through the doped fibre are analysed qualitatively to emphasise the advantages of bidirectional pumping for high power amplification.