Silica-based erbium-doped fiber amplifier exhibits 70-nm bandwidth
To increase the transmission capacity of wavelength-division multiplexing, the gain spectrum of erbium-doped fiber amplifiers (EDFAs) must be broadened from the current standard of approximately 32 nm. Previously, an amplification band of 80 nm has been obtained with erbium-doped tellurite fiber. Now, researchers at NTT Optoelectronics Laboratories (Tokai, Japan) have realized the first silica-based EDFA with a bandwidth of 70 nm, a signal gain exceeding 20 dB, and a noise figure less than 5 dB. A 1530-1600-nm bandwidth was achieved with a hybrid configuration of a 980-nm-pumped first amplification unit and a 1480-nm-pumped second amplification unit. The maximum bandwidth with the lowest noise was achieved by adjusting the length of the silica-based erbium-doped fiber in the first unit to 10 m and the length in the second unit to 65 m. The noise characteristics were strongly dependent on the length of fiber in the first unit, although the gain spectrum did not change.