Among many types of side-pumping combiner, which have been reported recently, a fused tapered method, which is based on direct fusion of one or several tapered pump fibers to the surface of a signal fiber, seems to be a potential method because of its high coupling efficiency and the capability of handling high pump power up to kW-class. However, the fused depth is seldom taken into consideration in the numerical analysis, which is not in agreement with the real situation. We present the numerical and experimental investigation about the influence of fused depth on the performance of the side-pumping combiners for all-fiber lasers and amplifiers. The experimental results agree well with the theoretical analysis. The fused depth shows great importance and should be paid much attention when designing and developing a side-pumping combiner by the fused tapered method. We develop a fused tapered side-pumping combiner, which is successfully applied in a backward pumped fiber amplifier with a 1080 nm output power of 1.458 kW. Our results may also offer detailed suggestion and instruction of fabricating side-pumping combiner for high-power fiber laser applications.
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