In this paper, an approach has been proposed to design an (OADM) made in silica- on silicon waveguide by combining Bragg gratings (BGs) and 2x2 3dB multimode interference couplers (3dB MMI coupler) in a Mach-Zehnder interferometer. This design technique shows an interesting result to obtain low insertion loss, low return loss, insensitive to polarization, high thermal stability, large optical bandwidth and low crosstalk.