In order to solve the problems of signal attenuation and capacity limitation in optical fiber transmission, PbS doped ring core fiber is prepared by improved chemical vapor deposition(MCVD), and a reverse pump light amplification experimental device is built to realize broadband amplification in C band, which provides the possibility for the realization of less mode fiber amplifier by using PbS doped fiber. The experimental results show that the switching gain of sample fiber in C-band increases with the increase of pump power, the switching gain decreases with the increase of signal power. When the pump power is 750 mW and the signal power is 0.003 nW, the switching gain of the sample fiber in C-band is about 8 dB.