Quantitative analysis of energy transfer processes in Thulium–Bismuth germanate co-doped fiber amplifier

Energy transfer processes in Thulium–Bismuth co-doped germanate fiber amplifier at 1800 nm region have been studied quantitatively in this work. Energy transfer models are utilized in order to investigate the effect of dopants concentration on energy transfer parameters. A series of non-linear rate equations were derived using the energy transfer parameters and solved by means of a semi-analytical method. A general model of optical fiber amplifier in conjunction with rate equations is employed to simulate Thulium and Bismuth ions population distribution along the fiber. Thulium and Bismuth concentrations are noted as critical factors that control the output power and saturation length. The optimum values of Thulium and Bismuth concentration which result in maximum gain at 1800 nm are 0.5 wt.% and 2 wt.% respectively.

► A quantitative study on energy transfer processes in Tm–Bi germanate is presented.
► A general model for Tm–Bi fiber amplifier is suggested based on the rate equations.
► Dopants’ distribution along fiber verifies the estimated energy transfer processes.
► The effect of dopants’ concentration on the gain is studied through a 3D simulation.