An optical multiplexer device (D) is dedicated to inserting/dropping optical resources into or from an optical transmission line comprising incoming and outgoing optical fibers (F1, F2). The device (D) comprises: i) first coupler means (C1) having an inlet and an outlet connected respectively to the incoming optical fiber (F1) and to the outgoing optical fiber (F2), and an inlet/outlet (1) coupled to the inlet and the outlet; ii) both-way multiplexer/demultiplexer means (2) defining at least two internal channels (3) each connected to a primary inlet/outlet (ES1) coupled to the inlet/outlet (1) and comprising at least two secondary inlets/outlets (ES2) each connected to an internal channel (3); and iii) at least two send and/or receive modules (R, T) each coupled to a secondary inlet/outlet (ES2) by both-way light guide means (4′) fitted with optical processor means (5, 6) capable, on order, of taking up at least a reflection state reflecting an optical resource to the secondary inlet/outlet (ES2) that delivered it and a transmission state enabling an optical resource to be transferred between a send and/or receive module (R, T) and the associated secondary inlet/outlet (ES2), the optical power that is transmitted or reflected optionally being adjustable.