In this paper we propose a new technique for optical wavelength demultiplexing (DEMUX) relaying on two phenomena: Goos-Haenchen (GH) shift and continuous refraction at a graded-index medium interface. IN the first case, two light beams are totally reflected at a plane interface separating two dielectric lossless media. The reflected beams suffer different lateral shifts (GH shifts) which depend on the wavelength; thus accomplishing the required spatial beam separation. In the second case, the two light beams have different “turning points” inside the graded index medium; hence the “back-refracted” beams are spatially separated. In this paper, we optimized the conditions of operation of such demultiplexing technique. This makes possible the integration of such technique in “planer integrated–optics” structures which can be used reliably in optical fiber communication networks.