Fig. 1. Schematic configuration of the PD measurement.

Fig. 2. (Color online) Average inversion and standard deviation of the inversion versus pump power for a core-pumped Yb3+/Al3+ co-doped silica fiber.

Fig. 3. (Color online) Dynamic equilibrium of PD and PB. PD>PB means PD is stronger than PB: (a) the powers at 633 nm are 0.01 and 1.7 mW; A–G indicate the experimental process, (b) the power at 633 nm is 1.7 mW.

Fig. 4. (Color online) Induced loss at 633 nm: (a) with different 974 nm pump powers, (b) PB with different wavelengths.

Fig. 5. (Color online) Induced loss at 633 nm with different powers at 633 nm, the power at 974 nm is 250 mW.

Fig. 6. (Color online) Relation between 633 nm laser power and saturated loss, time constant. Insert: a linear fit of the saturated loss.

Fig. 7. 2D-HYSCORE spectrum of the Yb3+/Al3+ co-doped silica fiber preform.