Demonstration of a bismuth-doped fiber amplifier operating in the S-band with 42 dB gain

High-fluorescence bismuth-doped fiber (BDF) in the S-band (1460-1530 nm) has been fabricated by using the modified chemical vapor deposition (MCVD)-solution doping technique. The unsaturated loss (UL) and fluorescence properties of BDF are investigated to develop high-performance bismuth-doped fiber amplifiers (BDFA) operating in the S-band. Both single-pass and double-pass structures are employed to investigate the performance of the BDFA. The experimental results demonstrate that: the unsaturated absorption of this BDF is only 0.08 dB/m, which is 14% of the total small-signal absorption measured; The BDFA achieves net gain amplification for the full S-band in both structures. Under single-pass structure, the BDFA achieves an average gain of 39.8 dB in the range of 1440-1470 nm with a pump power of 1 W and an input power of -30 dBm, with a maximum gain of 41.7 dB and an NF of 5.4 dB at 1450 nm; Under double-pass structure, the BDFA achieves an average gain of 37.6 dB in the S-band range of 1460-1500 nm, where the highest gain of 42.8 dB and an NF of 7.4 dB is achieved at 1470 nm; For the S-band edge 1530 nm, the BDFA also achieves a gain of 11.8 dB. We believe that this BDF has great potential as a high-performance S-band amplifier and laser.