Using　transmissive-writing　and　orthogonal-readout　scheme,　a　dual-channel　wavelength　division　multiplexer　on　the　bases　of　two　volume　holographic　gratings　is　demonstrated　for　the　first　time.　The　two　gratings　locate　in　different　areas　of　a　piece　of　doubly　doped　LiNbO3　photorefractive　crystal,　so　that　each　grating　can　reach　the　maximal　diffraction　efficiency　of　the　crystal.　The　gratings　are　recorded　in　the　crystal　by　using　green　laser.　During　the　readout,　the　input　infrared　light　is　incident　on　a　surface　of　the　material　perpendicularly,　and　the　light　beam　diffracted　by　one　of　the　two　channels　emerge　from　a　surface　adjacent　the　input　one.　The　two　diffracted　beams　both　propagate　normally　to　the　output　surface.　This　makes　it　easier　to　couple　the　communication　light　beams　into　and　out　of　the　device.　The　filter　works　at　the　third　window　of　optical　communication　with　a　channel　space　of　0.72　nm.　©　2009　SPIE.