Improvement of optical feedback immunity by usingadetuned gain-coupled DFB laser

Abstract
The Letter presents a comparison of the feedback sensitivity in a detuned gain-coupled (GC) DFB laser able to operate also in a Fabry-Perot (FP) mode. The comparison leads to a very accurate measurement of the reduction of the linewidth enhancement factor. A novel expression is proposed and a value close to 2.0 is found for the wavelength detuning around 28 nm.