Effect of transverse distribution profile of thulium on the performance of thulium-doped fibre amplifiers

We study numerical models for different transverse thulium distribution profiles (TTDPs) characterising the fibres used in thulium-doped fibre amplifiers (TDFAs).Our models consider the overlap factor and the absorption/emission dynamics.Basing on the radial TTDP function of the form n T (r) = n T,max exp[-( r- / )  ], we show that the TDFA gain increases with increasing  parameter and decreases as the  parameter increases from 1 up to 3 µm, due to the overlap factor which affects the absorption and emission dynamics of the TDFA.The overlap factor increases with increasing  and decreases with increasing  value.Finally, the noise figure increases as  does so, due to suppression of the amplified spontaneous emission.