Analysis of thermal effects in high power Yb doped fiber amplifier by distributed pumping

We have introduced a theoretical modeling based on arbitrary pump mode, derived the analytic functions of distributed amplifier along the fiber, and constructed a steady state heat equations of Yb-doped double-clad fiber amplifiers with both quantum defect and propagation losses being considered. Thermal effects and output power characteristics of kilowatt all fiber master-oscillator power amplifier (MOPA) are investigated by distributed pumping. Proper designs for reducing the temperature at the end of the fiber are proposed, the effect of the pumping mode and fiber length on the output performance and the temperature of fiber amplifiers is discussed and proposed a method to alleviate the thermal effect and improve amplifier efficiency. At last we also analyzed the output power and temperature characteristics by changing the power of seed laser, the results show that with the increasing the power of seed laser, the output power and temperature increase.