Gain monitoring of erbium-doped fiber amplifiers by detecting spontaneous emission

Gain monitoring by detecting the spontaneous emission (SE) emitted by 0.98- mu m laser diode (LD) pumped erbium-doped fiber amplifiers was investigated using three erbium-doped fibers (EDF's) with different absorption coefficients at 1.55 mu m ( alpha ). Unfavorable 0.98- mu m scattered light was observed and removed by an optical filter. The minimum gain accuracy was less than +or-0.21 dB for EDF-b ( alpha =1.5 dB/m) with launched pump powers (P/sub p/) from 10 to 30 mW. The minimum gain reproducibility over a 9-h period was +or- 0.015 dB for EDF-a ( alpha =3.3 dB/m) at P/sub p/=20 mW.<
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