Fig. 1. Intensity distribution of the 4×1 fiber signal combiner with the 100/120/360 μm fiber output. (a) Intensity distribution; (b) intensity distribution in X direction; (c) intensity distribution in Y direction

Fig. 2. Intensity distribution of the 4×1 signal combiner with the twisted output fiber. (a) Schematic of the fiber twist; (b) twist angle is 100°; (c) twist angle is 720°

Fig. 3. Intensity distribution of the 4×1 signal combiner with the 200/220/360 μm fiber output. (a)Intensity distribution; (b) intensity distribution in X direction; (c) intensity distribution in Y direction

Fig. 4. Manufacturing process of the flat-top beam output signal combiner. (a) Tapering of the cone area; (b) cut off the cone area; (c) splicing between the tapered fiber bundle and 200/220/360 μm fiber; (d) tapering of the 200/220/360 μm fiber; (e)twist of the 100/120/360 μm fiber; (f) the finished product; (g) cross section of the tapered fiber bundle

Fig. 5. Intensity distribution of the flat-top beam output fiber signal combiner. (a) 2D distribution; (b) X direction distribution; (c) Y direction distribution; (d) 3D distribution

Fig. 6. Experimental results at different planes. (a) Beam radius as a function of the Z axis, the insets show the 2D intensity distribution of the beam at different planes; (b) σ as a function of Z; (c) Ω as a function of Z