Characterization and assessment of multiple bismuth active centres in Bi/Er doped fiber

Bismuth/Erbium doped fiber (BEDF), with multiple emission bands over O, E, S, C and L bands is being developed as a broadband optical active media. Since bismuth active centers (BACs) are generated by the unshielded outer shell electrons of bismuth, various energy level structures can be formed depend on the host glass composition. This feature will lead to a complex spectral emission profiles consisting multiple BACs and their individual contributions. In this paper, we introduce a method to identify multiple BACs, by measuring fluorescence lifetime (FLT) and emission spectrum. We identified different types of bismuth active centers including BAC-Si, BAC-Al, BAC-P and BAC-Ge in our BEDFs. With this method, we are able to characterize BACs in BEDFs and this will enable us to assess fiber composition and dopant concentration for further improvement in gain, bandwidth and flatness of the ultra-broadband spectrum in BEDFs.