Research on high beam quality 3 × 1 double-cone fiber signal combiner at 9 kW level

The fiber signal combiner with high output power and high beam quality is an urgent problem to be solved. In this paper, the structure of the double-cone (both the input fibers and the output fiber are tapered) is proposed to improve the beam quality of the fiber signal combiner, and it is verified by simulation and experiment, with the output fiber of 50 µm core tapered to 35 µm as an example. The prepared 3 × 1 double-cone fiber signal combiner reaches the output power of 8.64 kW, and the beam quality is measured as M²= 2.91. Compared with the M²= 3.41 of the fiber signal combiner with non-tapered output fiber, the M² of the double-cone fiber signal combiner is reduced by 14.7%.