Experimental Study of Output Characteristics of Bi-Directional Pumping High Power Fiber Amplifier in Different Pumping Schemes

In this paper, we have constructed an all-fiberized bi-directional pumping fiber amplifier. The output time domain signals and limitations of copumping and counterpumping schemes were experimentally investigated. The power scaling of copumping and counterpumping scheme is restricted by stimulated Raman scattering (SRS) and transverse modal instability (TMI), respectively. The highest output power of 3.06 kW was achieved by using bi-directional pumping. Finally, we tested the relationship between SRS threshold and injected seed power.