Optical communications is an alternative to the microwave solution for high data rate interorbit (IOL) or intersatellite link (ISL), typically 500 Mbit/s. The optical system, using laser diode technology, only requires small size antennae, provided that multiplexing or power combining techniques are used. This paper presents a Wavelength Division Multiplexing/Demultiplexing System involving orthogonal polarizations for adjacent channels. This solution is preferred to the power combining technique to satisfy some specific system and interfaces constraints and to avoid a very accurate control of laser wavelength. The proposed design complies with system constraints like redundancy, minimum back-light on the laser junction, interchannel interferences, depolarization in the optical system, compacity, ... Its simplicity -the required components are only λ/4 plates, filters under normal incidence and polarizer beamsplitters- is attractive and the concept, descri-bed here for 4 wavelengths in the 0.817-0.84311μ range, can be applied to an unlimited number of wavelengths. The computed performances in transmission and isolation taking into account all parasitic reflections are given. A breadboard model is currently under development at MATRA to be tested in 1987. Preliminary results of sub-assemblies tests are presented.