Influence of temperature and dynamic gain tilt on the choice of probe wavelength for gain control within erbium doped fibre amplifiers

Gain control using an out of band probe wavelength is attractive. Temperature variations introduce lower gain ripples for blue end probes rather than red end. Dynamic gain tilt analysis also favours blue end control. The gain spectrum of erbium fibre is temperature dependent. This is becoming more important as fibre amplifier users require greater bandwidths for WDM transmission. Consideration as to how this affects the choice of probe wavelength for out-of band, probe laser gain control techniques has been given here and control at the blue end of the spectrum consistently allows smaller gain ripples as the temperature varies. A dynamic gain tilt analysis also suggests that errors in gain control will have a smaller ripple increase if blue-end probe wavelengths are used rather than red-end ones