Fig. 1. Refractive index profile of Bi-doped fiber preform with cross-sectional image of BPSF shown in inset

Fig. 2. Absorption spectrum of BPSF

Fig. 3. Experimental setup for unsaturated loss measurement

Fig. 4. Fiber loss versus 1240 nm pump power

Fig. 5. Experimental setup for gain measurement of Bi-doped fiber

Fig. 6. Measurement results. (a) ASE spectrum under 1240 nm pump; (b) output spectrum when fiber length is 140 m with input spectrum shown in inset

Fig. 7. Measured results of BPSF amplification performance