GAIN MONITORING OF ERBIUM-DOPED FIBER AMPLIFIERS BY DETECTING SPONTANEOUS EMISSION

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