Gain-clamped double-pass L-band erbium-doped fiber amplifier using a ring laser and fiber Bragg grating

A highly efficient gain-clamped tong-wavelength-band erbium-doped fiber amplifier (L-band EDFA) using a ring laser in a double-pass system is demonstrated. A broadband fiber Bragg grating (FBG) operating in the L-band region is used to retropass the test signal into the system to enhance the gain. The forward conventional-band (C-band) amplified spontaneous emission passes through the FBG and is routed to the input end of the amplifier via a C/L-band wavelength-selective coupler (WSC) so as to create a laser for gain clamping. The gain is clamped at 16.3 dB in the input power range from -40 to -8 dBm with a gain variation of less than +/-0.2 dB at a variable optical attenuator setting of 12 dB. However, the noise figure is relatively high in the proposed amplifier due to the incorporation of a C/L-band WSC and a FBG.