Ultra-Low-Loss Splicing of Silica and Crystal Fibers by Optimized Molten Zone Welding

This study demonstrates a practical solution for achieving ultra-low splicing loss between dissimilar silica fiber and Cr-doped crystalline core fibers (CDFs). We employ a novel molten zone fusion welding technique, which enables precise control over the molten zone volume, resulting in a practical minimum splice loss of 0.3 dB for silica single-mode fiber (SMF-28) of 125-µm core and CDFs of 125-µm core. Compared with mechanical splicing (0.5-1.0 dB) and laser welding (0.4-0.6 dB), our method achieves a 40% to 70% reduction in insertion loss, significantly enhancing optical transmission efficiency. The discharge power and process time are optimized using an empirical formula, ensuring the formation of a stable intermediate material at the splice interface while providing excellent mechanical strength. This innovative approach overcomes the limitations of conventional splicing methods, including high Fresnel losses, weak mechanical integrity, and limited thermal stability, making it particularly suitable for high-power fiber laser systems, optical communication, and precision sensing applications.