Double pass L-band EDFA with an improved gain coefficient

A new double pass long wavelength hand erbium-doped fibre amplifier (L-band EDFA) with an improved gain is demonstrated by unpumping of the first 5 m of the EDF. The wasted conventional band (C-band) backward amplified spontaneous emission (ASE) was used as a secondary pump source for the unpumped EDF. Our experimental results have shown that, compared to a conventional double pass amplifier, the gain coefficient can be improved considerably from 0.24 dB/mW to 0.40 dB/mW. The new amplifier uses only 67% of the pump power to achieve a gain value equal to that for the conventional amplifier. The maximum gain enhancement of 22.5 dB was observed at a signal wavelength of 1568 nm of while signal and pump powers were fixed at -30 dBm and 62 mW, respectively.