1：Experimental Design and Method Selection:

The experiment used a conventional drawing tower setup with an added UV radiation source from an excimer laser passing through a phase mask to inscribe FBGs during the optical fiber drawing process. The diameter of the optical fiber was varied by controlling the drawing speed to create a tapered fiber with an adiabatic transition.

2：Sample Selection and Data Sources:

A tapered optical fiber preform with germanium-silicate co-doping, boron photosensitive core, and isotropic structure was used. The drawn sample length was 60 m, with a core diameter of 6 μm for the 125 μm diameter section and a cutoff wavelength of 1350 nm.

3：List of Experimental Equipment and Materials:

Equipment included a drawing tower, excimer laser (248 nm wavelength, 4 mJ/mm2 energy density, 10 ns pulse duration), phase mask (period 1070 nm), optical frequency domain reflectometry device (Luna 4600), optical spectrum analyzer (Yokogawa AQ6370D), superluminescent fiber light source, halogen lamp, Ericsson FSU 975 splicer, and Thorlabs BP-109 beam profiler. Materials included the tapered optical fiber preform.

4：Experimental Procedures and Operational Workflow:

The tapered fiber was drawn with FBGs inscribed during the process. The fiber diameter varied between 125 and 229 μm. Measurements were conducted using OFDR and OSA techniques to analyze reflection spectra, optical loss, and mode propagation. S2 and M2 methods were used to study modal coupling and beam quality.

5：Data Analysis Methods:

Data were analyzed using OFDR for longitudinal profiling, OSA for spectral analysis, and techniques like inverse Fourier transformation for modal delay calculations. Statistical analysis included measuring reflection levels, spectral widths, and M2 parameters.