Abstract: An optical device for wavelength interleaving or dissociation includes a device for coupling a luminous flux generated by a source in an input fiber, a circulator linked to the input fiber and to an output fiber forming a first output gate of the optical device, and a polarisation beam splitter receiving the luminous flux coming out of the circulator and separating it into two components. A device is provided for transferring the luminous flux from one output to the other, a birefringent medium is interposed on the optical path and a fiber forms a second output of the optical device.