Fig. 1. (a) Calculated results of effective index differences with different fiber parameters. (b) Measured fiber dimension profile of the tapered multimode fiber.

Fig. 2. Geometric and refractive descriptions of the tapered fiber: (a) geometric dimensions at both ends; (b) measured refractive index profile.

Fig. 3. (a) Experimental setup for high-power delivery. (b) Relationship between the input and output power, and the total transmission efficiency.

Fig. 4. (a) Recorded spectra at different output powers. (b) Beam quality M² factors of the input and output laser.

Fig. 5. The evolutions of (a) signal and (b) Stokes power versus the injected Raman noise, and (c) the corresponding signal-to-SRS ratios in uniform fibers or the tapered fiber.

Fig. 6. Evolution of signal-to-SRS ratios as a function of the injected Raman noise in the tapered multimode fiber with laser power levels of 1000, 2000 and 3000 W.

Fig. 7. Spatially and spectrally resolved imaging results for the whole delivery path.

Fig. 8. Relationships between the initial Raman noise and the output properties with different fiber lengths and an injected signal power of 1000 W: (a) output signal power; (b) output Stokes power; (c) output signal-to-Stokes ratio.

Fig. 9. Relationships between the initial Raman noise and the output properties with different fiber lengths and an injected signal power of 2000 W: (a) output signal power; (b) output Stokes power; (c) output signal-to-Stokes ratio.

Fig. 10. Relationships between the initial Raman noise and the output properties with different fiber lengths and an injected signal power of 3000 W: (a) output signal power; (b) output Stokes power; (c) output signal-to-Stokes ratio.