High power ring spot adjustable fiber combiner based on (6 + 3) × 1 structure.

• For the first time, an all-fiber (6 + 3) structure was proposed for the fabrication of a ring spot signal combiner, and samples were successfully fabricated. • The samples produced showed a significant improvement in transmission efficiency compared to the cascaded 3 × 1 − (6 + 1) × 1 structure. • For the first time in the test method proposed return light test, and the sample test successfully passed. Aiming at the problem that the ring beam mode adjustable signal combiner with a single center port structure limits the output power of the laser beam in the inner ring of the laser. A new all-fiber structure (6 + 3) × 1 signal combiner is designed, which can independently carry more than 3 kW of power at each input port, and the output fiber is a ring-shaped dual-core fiber. The tapered fiber bundle adopts the (6 + 3) × 1 structure, where the three input ports in the center form a tapered fiber bundle to transmit the laser beam to the inner core of the output fiber, and the remaining six ports in the outer ring transmit the beam to the outer core of the output fiber, and the beams of the inner and outer cores can be transmitted independently, which effectively increases the output power of the center port. Combiner using (6 + 3) × 1 structure of the fiber transmission efficiency of more than 98 %, the center of the M2 is 5.32, can withstand the role of the return light. The structure of the output beam energy is more uniform, can effectively prevent sputtering, so that it can be applied to ultra-precision welding and other fields. At the same time, the structure also provides a feasible new solution to increase the center M2 of the beam splitter. [ABSTRACT FROM AUTHOR]