Abstract: An optical switching device comprises an optical waveguide formed from two light-transmitting materials having an interface between them, and in which the refractive index of one of the materials can be altered by an external influence; the other has a light path directed at the interface at an angle such that by varying the refractive index of the first material the light can either pass through the material or be reflected at the interface. By utilizing a plurality of such interfaces in sequence the light may be selectively switched along several different paths.

Abstract: Integrated optical waveguides, for example planar waveguides with stripes of guiding material formed integrally on a substrate, are manufactured by depositing the doped glass guiding material by plasma chemical vapor deposition. Several substrates can be arranged in a suitably shaped apparatus so that deposition can take place on all of them at once.

Abstract: In the manufacture of a glass optical fibre preform by forming a coating of oxide material on the interior surface of a substrate tube, in particular a coating of silica and one or more dopant oxides on a vitreous silica tube, by causing a reaction to take place between oxygen and the vapor or vapors of one or more compounds such as halides, the reactant vapors are introduced into a perforated tube supported coaxially within the heated substrate tube and pass through the perforations into the annular space between the perforated and substrate tubes, while oxygen, and optionally an additional carrier gas, is passed either into the perforated tube or directly into said space. The coating-forming reaction is caused to take place in said space by generating energy in the space, in the form of a plasma, or a laser beam, and/or heat, and/or gas combustion, whereby the coating is formed simultaneously on the whole heated length of the substrate tube.