Optimised bandwidth of optical filter in optical preamplifier

An optimisation scheme is proposed for the optical-filter bandwidth in an optical preamplifier for a given tolerance in the signal-wavelength and a given filter profile. The optimised bandwidth is 3.46 times the conceivable detuning for a Lorentzian-shaped filter profile. Preamplifiers with optimised bandwidth can operate with the lowest noise figure at maximum detuning.