1：Experimental Design and Method Selection:

The device is fabricated by fusion splicing of a section of no-core fiber (NCF) with multi-mode fiber (MMF) and single-mode fiber (SMF) at its two ends. The open end of MMF is etched to create an arc shaped cavity, with a microsphere glued at its bottom.

2：Sample Selection and Data Sources:

The bariom titanate glass microsphere (Cospheric Inc, BTGMS-4.21) has the RI of 1.9 (at 1550nm), with the diameter ranging from 22 to 27 μm.

3：21) has the RI of 9 (at 1550nm), with the diameter ranging from 22 to 27 μm. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Fusion splicer (Fujikura 80s), hydrofluoric (HF) acid, UV adhesive (Norland, NOA68), non-polarized broad-band light source (BBS), optical spectrum analyzer (OSA) (YOKOGAWA 6390).

4：0). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Fusion splicing of a short section of NCF with a MMF and a SMF at its two ends, etching the MMF with open end into HF acid, coating a thin layer of UV adhesive to the bottom of the cavity, adjusting the position of the microsphere until the WGM spectrum appears before using UV light to illuminate the adhesive to solidify the structure.

5：Data Analysis Methods:

The reflection spectrum of the WGM resonator sample is recorded and analyzed to determine the Q-factor and other parameters.