Fig. 1. Schematic diagram of bi-directional mode-field matching of SMF and LMA fiber

Fig. 2. Schematic illustration of a thermally expanded core fiber

Fig. 3. Mode field characteristics of TEC fiber

Fig. 4. Schematic of the tapered LMA fiber

Fig. 5. Mode field characteristics of tapered LMA fiber

Fig. 6. Schematic of bi-directional transmission of SMF and LMA fiber

Fig. 7. Simulation results of bi-directional transmission of SMF and LMA fiber

Fig. 8. Schematic of core offset and angular misalignment

Fig. 9. Simulation results of core offset and angular misalignment

Fig. 10. Power loss and MFD of TEC fiber at different heating times

Fig. 11. Micrographs of the TEC fiber cross-section at different heating times

Fig. 12. Schematic drawing of MFA property measurement

Fig. 13. T_R=1 and T_R=2 of LMA1 fiber， the insertion loss of MFA1 at different heating times

Fig. 14. T_R=1 and T_R=2 of LMA2 fiber， the insertion loss of MFA2 at different heating times

Fig. 15. TheαB-F and M² of MFA1 and MFA2 at different αM