In this paper we analyse the effects of the spatial hole burning (SHB) in the steady-state performance of DFB lasers, using the transfer matrix method (TMM) to solve the mode equations that describe the system, combined with the carrier and photon rate equations. The non-uniform photon and carrier distributions in the above-threshold regime are seen to induce strong alterations in the effective refractive index profile along the laser cavity, that are responsible for significant modifications in the laser emission properties.