Abstract: A device, utilized for the separation or combination of two signals of different wavelengths, of the type in which the waveguides comprise straight interaction segments (1.sub.1, 2.sub.1 ; 1.sub.in, 2.sub.in) parallel and close to one another and to curved approach segments with inflection points (1.sub.2, 2.sub.2, 1.sub.3, 2.sub.3 ; 1.sub.2n, 2.sub.2n, 1.sub.3n, 2.sub.3n), connected to the ends of the straight segments, and, for certain ones, to inputs/outputs (4,5,6) of the device. In accordance with the invention, the approach segments situated on at least the same side of the straight segments are free of any inflection point, the coupling of the straight segments being optionally modified to compensate for the variation of the coupling between the waveguides along said approach segments due to the omission of the inflection points.

Abstract: Efficient conversion between the LP.sub.01 and the LP.sub.11 modes in a two-mode optical fiber is realized in a fiber grating fabricated by forming a series of longitudinally-spaced cuts in the fiber cladding, and then annealing the fiber in the region of the cuts. The latter step uses the surface tension of the molten glass to transform the corrugation on the cladding into a sinusoidal deformation of the fiber core.