Flat-gain optical amplification within 70 nm wavelength band using 199 cm long hybrid erbium fibers

A flat-gain amplification covering a wideband wavelength window was accomplished by using dual-stage erbium doped fiber amplifier (EDFA). The amplifier was constructed by combining two different active fibers; Bismuth erbium doped fiber (Bi-EDF) and Hafnium-bismuth erbium doped fiber (HB-EDF) that provide amplification in C- and L-band region, respectively. It employed only 199 cm of the total active fibers in double-pass parallel configuration. The 1480 nm pump powers were fixed at 90 and 170 mW for first and second stages, respectively. At input signal power of -30 dBm, the gain of the amplifier varied from 13 to 27 dB within a wavelength region from 1535 to 1590 nm. At input signal power of -10 dB, a flat gain of about 14 dB was realized with gain fluctuation less than 1 dB over 70 nm wavelengths from 1535 to 1605 nm. On the other hand, the corresponding noise figures were maintained below 13 dB over wideband region for both input signal powers.