Design of Ultimate Gain-Flattened O-, E-, and S+ C+ L Ultrabroadband Fiber Amplifiers Using a New Fiber Raman Gain Medium

By solving the inverse amplifier design problem, gain-flattened O (~17.5 THz), E (~15.1 THz), and S+ C+ L (~20.9 THz) ultrabroadband fiber Raman amplifiers (FRA) are designed using a new TeO₂-BaO-SrO-Nb₂O₅-P₂O₅-WO₃ (TBSNWP) tellurite fiber. When increasing the numbers of pump wavelengths from two to eight, the gain profiles become flatter, and the effective bandwidth becomes larger. Relative gain flatness of ~1% could be achieved over bandwidths of up to 15.1 THz (corresponds to E-band) without any gain equalization devices. When narrowing the gain bandwidth from the S+ C+ L-band (20.9 THz) to the E-band (15.1 THz), the relative gain flatness is reduced from 4.51% to 4.12%. The effects of the shape of the Raman gain spectra on the relative gain flatness and the effective bandwidth are also investigated using the TBSNWP glass with one broad Raman shift peak (full width at half maximum ~11 THz) and TeO₂-Bi₂O₃-ZnO-Na₂O (TBZN) glass with twin peaks. The simulation results show that the relative gain flatness and the effective bandwidth of TBSNWP FRA are better and larger than those of TBZN FRA, respectively. Our results suggest that the TBSNWP glasses are promising candidates for broadband FRA in photonic systems.