Investigation on gain-clamped characteristics of ring cavity L-band EDFA

A novel gain-clamped Long wavelength band erbium doped fiber amplifier (L-band EDFA) based on ring erbium-doped fiber laser cavity was demonstrated. By using a fiber Bragg grating (FBG) at the output end of the amplifier, a portion of forward conventional band (C-band) amplified spontaneous emission (ASE) was reflected back into the system, this new design provided a good gain clamping and decreased noise effectively. It used 1480nm laser diode (LD) to pump high Er3+-concentration erbium-doped fiber for higher efficiency and lower noise figure (NF). The gain was clamped at 17.5dB with a variation of 0.3 dB, from input signal power of -30dBm to -12dBm for a pump power of 180mW. By adjusting the intra-cavity loss, the gain reached 19.78dB with inputting small signal and NF below 5dB was obtained. At the longer wavelength (1614nm) of L-band 9.2dB gain was obtained.