Research on pump light transmission efficiency and energy distribution in (8 + 1)×1 high-power pump and signal...

We report a fabrication method for the (8 + 1)×1 pump and signal combiner (PSC) and investigate its pump light transmission characteristics. It employs three specifications of fibers: the pump fiber is 220/242 µm and NA = 0.22; the signal fiber is 25/250 µm and NA = 0.065/0.46; the double-clad fiber (DCF) is 20/400 µm, and NA = 0.065/0.46. Based on the arrangement characteristics of the pump fibers and signal fiber, as well as the principle of brightness conservation, the optimal preparation parameters for the (8 + 1)×1 PSC are determined. In order to optimize the performance of the PSCs with different numbers of pump ports, the transmission efficiencies of pump light and pump light divergence angles are calculated for pump port numbers of 6, 7, 8, 9, 10, and 11, respectively. The results indicate that the maximum number of pump ports it can support is 8. Experimental results show that the transmission efficiencies of pump light and signal light are 98.20% and 96.66%, respectively. The measured beam quality of the (8 + 1)×1 PSC is M² = 1.19, and the beam quality degradation is ΔM² = 0.10. The total pump power is 5.736 kW, which is limited by the pump powers of the laser diodes (LDs). Compared to the (6 + 1)×1 PSC fabricated using the same method, the pump power increased by 1.604 kW. When the pump powers of both are approximately 4 kW, the temperature of the DCF coating layer in (8 + 1)×1 PSC is 17.8 ℃ higher than that in the (6 + 1)×1 PSC. The divergence angle of pump light combined by the (8 + 1)×1 PSC is 1.007 rad, and the experimental results are in good agreement with the simulation results.