Reduction of second- and third-order harmonic distortion by nonlinear absorption in gain-coupled DFB lasers

The analog modulation distortion due to nonlinear gain compression has been found to be reduced significantly in the gain-coupled (GC) DFB laser of absorptive grating type. It is because the gain compression is compensated by the loss compression in the grating. In order to investigate whether this effect really exists or not, we here analyzed second and third harmonic distortions (2HD and 3HD) in GC DFB LDs of absorptive grating type numerically, taking the dynamic nature of the absorptive grating into consideration.