Fig. 1. Experimental diagram for measuring the loss of the same few-mode fiber fusion splicing

Fig. 2. Experimental diagram for measuring the loss of the different few mode fibers fusion splicing

Fig. 3. Experimental measurement system of mode purity based on off-axis digital holography. (a) Fiber configuration for the same type of few-mode fibers fusion splicing; (b) fiber configuration for the different types of few-mode fibers fusion splicing

Fig. 4. Refractive index distribution of the fiber used in the experiment

Fig. 5. Measurement results of mode purity before and after FMF1 fiber fusion splicing. (a) Before fusion splicing; (b) after fusion splicing with the optimal parameters; (c) influence of relative arc power on mode purity; (d) influence of arc time on mode purity, where the black dashed line represents the measured mode purity in (a)

Fig. 6. Comparison of fusion splicing results at two fusion modes. (a) Measured mode purity at automatic fusion mode; (b) comparison of fusion splicing results

Fig. 7. Measured mode purity before and after FMF1 and FMF2 fusion splicing. (a) Before fusion splicing; (b) after fusion splicing with the optimal parameters; (c) influence of relative arc power on mode purity; (d) influence of arc time on mode purity, where the black dashed line represents the measured mode purity in (a)

Fig. 8. Measured mode purity before and after FMF1 and FMF3 fusion splicing. (a) Before fusion splicing; (b) after fusion splicing with the optimal parameters; (c) influence of relative arc power on mode purity; (d) influence of arc time on mode purity, where the black dashed line represents the measured mode purity in (a)

Fig. 9. Measured mode purity before and after FMF2 and RCF fusion splicing. (a) Before fusion splicing; (b) after fusion splicing with the optimal parameters; (c) influence of relative arc power on mode purity; (d) influence of arc time on mode purity, where the black dashed line represents the measured mode purity in (a)