Beam quality improvement of high-power fiber signal combiner based on output fiber tapering post-processing

High-power fiber signal combiners are key components in power-combining systems, but the combining process inevitably degrades beam quality. This paper proposes a post-processing technique that introduces an additional tapered structure on the output fiber to improve beam quality. A 4 × 1 double-cone combiner using 20/250 μm input fibers and a 50/400 μm output fiber delivered 11.67 kW with efficiency exceeding 96% and M² = 2.95. After post-processing the output fiber, the beam quality was improved to M² = 2.70 with only a 0.5% reduction in efficiency. This work provides a flexible approach for high-brightness fiber laser systems.