Ultra-broadband optical amplifiers based on bismuth-doped heterogeneous-core fibers

We report on the development of a cladding-pumped ultra-broadband optical amplifier for a spectral region of 1260-1480 nm using a Bi-doped fiber (BDF) with heterogeneous core formed by combination of P₂O₅- and GeO₂-containing glass layers. This BDF design ensures a favorable local environment for the effective formation process of BACs associated with P and Si atoms. The BDF amplifier (BDFA) pumped into the cladding by multi-mode laser diodes at 793 and 808 nm is characterized by a peak gain of ≈24 dB, a minimum noise figure of ≈6 dB, and a bandwidth of ≈160 nm at a gain level of 20 dB. The effect of the parameters of the fiber design on the output characteristics of BDFA was analyzed by numerical simulation. The calculated data were in good agreement with the experimental ones, which allowed us to outline possible ways to improve the BDFA.