The invention is a spectrally selective optical coupler with a new geometry and a new principle of action. An optical coupler according to the invention comprises an optical fiber and an external lightguide. In the fiber there is provided a deflector that is operative to deflect light of a predetermined wavelength into a propagating mode of said lightguide. The outcoupled light is transferred to a region remote from the outcoupling portion of the fiber. The invention can be used to couple light from a first to a second optical fiber.