High-bismuth-content phospho-silicate fiber for optical amplification

We report a fiber fabrication process combining modified chemical vapor deposition and solution doping, which maximizes material retention to produce bismuth-doped fibers with high doping content. With a detectable amount of Bi at the 0.1 wt.% level, fabricated fibers exhibit low levels of background and unsaturable loss. Moreover, a flat and broad absorption profile is obtained and is attributed to a balanced level of phosphorus and silica-related bismuth active centers (BACs). Our photoluminescence results suggest excitation-dependent emission spectra, including broad luminescence under 808 and 980 nm pump wavelengths. The BPFs present a flat gain spectrum, free from OH-related absorption, reaching 34 dB peak gain with 100 nm bandwidth (>20 dB) and a noise figure (NF) in the range of 3.7 - 5.7 dB over the E- and S-band.