Partial gain-clamping in two-stage double-pass L-band EDFA using a ring resonator

A highly efficient and low noise gain-clamped long-wavelength-band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using a ring laser in double-pass system. The broadband fiber Bragg grating (FBG) operating at L-band region is used to retro-pass the test signal into the system for enhanced gain. A short length of forward pumped EDF is incorporated in front of the double-pass amplifier to achieve a low noise figure. The gain clamping is achieved by routing the backward ASE into the feedback loop to create ring laser. The gain is clamped at 26.8 dB from -40 to -16 dBm with a gain variation of less than 0.1 dB and a noise figure of less than 5.3 dB.