Effect of endogenous pumping on amplification bandwidth broadening in bismuth-doped fiber amplifiers

The previous papers of the research group have already found that the excitation of a 1310 nm endogenous pump by signal feedback combined with a single fiber Bragg grating (FBG) under the condition of 1240 nm pumping can significantly enhance the gain effect of bismuth-doped fiber amplifiers (BDFA) at long wavelengths. In order to further clarify the effect of the endogenous pump generation mode and the different feedback mechanisms on the broadening effect, we have used a tunable dual grating combined with a controllable pump/signal feedback amplifier structure, and compare in detail the broadening characteristics under the different conditions mentioned above. The experimental results show that any form of endogenous pumping can result in amplification bandwidth expansion, but there is a difference in the behavior of the broadening due to the dual grating line cavity versus the grating-signal reflector line cavity, as well as in the degree to which the broadening is affected by the pump feedback. The effective utilization of this property can provide positive assistance in enhancing the gain-bandwidth performance of BDFA as well as in improving the transmission capacity of communication systems.