Dual-stage gain-clamped erbium-doped fiber amplifier with fiber Bragg grating

We demonstrate a dual‐stage gain‐clamped erbiumdoped fiber amplifier. The first‐stage amplifier consists of a short length of erbium‐doped fiber to produce low noise figures. The second‐stage is constructed from a counter‐propagating ringlaser, in which the signals and the lasing wavelength propagate in the opposite direction. The lasing wavelength is selected via a reflective‐type of fiber Bragg grating. The gain‐clamping mechanism can be adjusted by either changing the fiber Bragg grating reflectivity or center wavelength. The noise figure penalty is about 1.5 dB for the gain‐clamping value from 11 dB to 20.5 dB. (© 2008 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)