Wide flat amplification bandwidth utilizing partial double-pass hybrid fiber amplifier

In this paper, the experimental results of a wide flat amplification bandwidth utilizing a partial double-pass hybrid fiber amplifier are demonstrated. Double-pass Raman gain at long band (L-band) wavelength region and single-pass erbium gain at conventional band (C-band) wavelength region are achieved. To achieve these two bands, two different laser pump units with a wavelength of 1495 and 1480 nm were used for Raman and erbium amplifier, respectively. The total pump power used is 490 mW (450 mW for Raman amplifier and 40 mW for erbium amplifier). At small input signal power region (− 30 dBm), a wide flat amplification bandwidth of 85 nm from 1530 to 1615 nm is obtained with an average gain level of 35 dB. The same flat amplification bandwidth is achieved for large input signal power (−5 dBm) with an average gain level of 16 dB.