Integrated optics achromatic splitter and an MxN coupler incorporating such a splitter

An achromatic integrated optics splitter with two inputs, for the transmission of an optical signal entering one input to two outputs, with a predetermined ratio of the signal powers at these two outputs, comprising a symmetrical X-junction of two identical rectilinear waveguides, single mode at the utilization wavelength, and defining at their intersection a half-angle (.alpha.), characterized in that two flat outer regions (9,10), perpendicular to the axis of the splitter, partially define the boundary of the intersection of the waveguides, these flat outer regions (9,10), cutting off the regions of the two vertices of half-angle (.alpha.) of the intersection, the half-angle (.alpha.) being greater than an angular value which is a function of the dimensions of the fundamental mode transmitted by the waveguides, the half-angle being selected to establish the predetermined power ratio.