The impact of(1+1)×1 coupler pump arm numbers on the pump coupling efficiency was numerically studied.It is shown that pump coupling efficiency decreases with more pump arms built on the coupler,yet in a slightly decreasing manner.The coupling efficiencies of(1+1)×1 and(2+1)×1 couplers were studied and compared under the same tapered length and the same input mode field,it implies that large number of pump arms could have adverse impact on the total coupling efficiency.According to the simulation results,two side-pumped(1+1)×1 couplers were made and the two signal fibers were spliced to form a cascaded structure.A total output power of this cascaded-structured pump coupler was about 564 W,corresponding to a coupling efficiency as high as 93.6%.And,two side-pumped(2+1)×1 couplers were made respectively and the two signal fibers were spliced to form a cascaded structure.A total output power of this cascaded-structured pump coupler was about 1 120 W,corresponding to a coupling efficiency as high as 92.5%.The loss of (N+1)×1 cascaded structure coupler signal light were less than 0.4%.Achievied the kW class output power of pump light.