Three-stage Gain-clamped L-band EDFA with Low Noise-figure Base on Ring Lasing

We demonstrated a three-stage gain-clamped L-band erbium-doped fiber amplifier (EDFA) with a low noise figure. The first stage was used as the preamplifier to improve the noise figure performance of the EDFA. The gain clamping was achieved by forming a ring laser base on the second and third stages by combining two C/L-band wavelength-division multiplexers (WDMs). As a result, the gain was clamped at 21.75 dB with a gain variation of less than 0.22 dB from an input signal power of −34 dBm to −10 dBm at 1580 nm. The noise figure was between 4.4 dB to 5.5 dB in the wavelength ranging from 1570 to 1610nm.