Experimental and theoretical studies of gain of erbium-doped fiber amplifiers with pump excited-state absorption and signal upconversion losses under co- and contradirectional pumping

This paper reports the results of an experimental study and numerical modelling of the gain characteristics of Erbium doped fiber amplifiers in the presence of pump excited state absorption losses and upconversion losses. The results reveal the differences in the gain characteristics for co and contradirectional pumping when these losses occur simultaneously in the amplifier.