All-optical gain switching of erbium-doped fibre amplifiers

The gain switching characteristics of erbium-doped fibre amplifiers with signal wavelengths in the 1525 nm to 1550 nm range are examined. Short duration, high energy pulses at wavelengths within the signal bandwidth are used to rapidly switch the amplifier gain at the signal wavelength. Experimental results indicate that the switching time is governed by the pulse duration and pulse energy for switching pulses generated by a Q-switched erbium-doped fibre laser. Switch off times on the order of 10 ns were observed. This is many orders of magnitude lower than the fluorescence lifetime of erbium ions in a glass host--which limits the switching speed of amplifiers controlled by pump power modulation alone.;The dynamic range of switching, defined here as the difference in the amplifier gain before and after switching, is determined by the amplifier gain and the peak power of the short duration switching pulse.