Noise figure monitoring of a cascaded in-line erbium-doped fiber amplifier

The noise figure (NF) of a cascaded in-line erbium-doped fiber amplifier (EDFA) is monitored with an accuracy of +or-0.05 dB and a reproducibility of +or-0.03 dB. A simple approximated equation is proposed to derive the NF. The power of the amplified spontaneous emission (ASE) from the monitored EDFA is detected at 1.542 mu m after eliminating the wavelength components (1.5515 mu m) with a bandpass filter (BPF) having a large loss at 1.5515 mu m (80 dB). Another BPF having a large loss at 1.542 mu m (39.5 dB) is inserted after each EDFA to remove the propagating ASE at 1.542 mu m.<>