Linewidth rebroadening in DFB lasers due to bias dependent dispersion of feedback

It is shown that a linewidth rebroadening in some lasers, observed at relatively low power levels, can be explained as a result of a wavelength and power dependence of the distributed reflections. This type of linewidth rebroadening can occur in lasers where the loss increases with frequency in the vicinity of the emission frequency and in which the loss increases with bias level.