L-band gain clamped erbium-doped fiber amplifier incorporating a C/L-band WDM coupler

Gain clamping in a long-wavelength-band erbium-doped fiber amplifier (L-band EDFA) using a C/L-band WDM coupler is demonstrated. The gain for the amplifier is clamped at 15.5 dB with a gain variation of less than 0.2 dB from input signal power ranging from -40 to -14 dBm with almost negligible noise-figure penalty. However, the flatness of the gain spectrum is slightly degraded due to the nonoptimisation of the EDF length. The advantage of this configuration is that the oscillating light does not appear at the output port of the amplifier