The invention relates to the coupling of light to and from an optical waveguide, such as an optical fiber. Light of a specific wavelength is deflected out from the fiber, or into the fiber, in a substantially transverse direction with respect to the propagation direction of light in the waveguide, by a deflector 16 arranged in the fiber core 10. Wavelength selectivity of the deflector 16 is provided by a Bragg grating means located in the fiber core 10. The deflected light is collimated, or converged towards a focus, by an interface 15 between a cladding 11, having one index of refraction, and an outer medium 12, having another index of refraction. The ratio between the radius of the cladding 11 and the radius of the core 10 made sufficiently small for the collimating, or converging, effect to appear.