GB1103492A - Improvements in or relating to the manufacture of fiber optical light-conducting devices - Google Patents

Abstract

A method of making fibre optical devices, e.g. a light-conducting face-plate, having spaced light receiving and emitting opposite end faces of large surface area formed from a number of multi-channelled light conducting structures of a polygonal cross-section composed of a multiplicity of glass clad glass light conducting fibres fused together in side-by-side prearranged geometrical relationship, each multi-channelled structure being equal in length to the distance between the opposite faces of said plate, comprises bundling said multi-channelled structures together in side-by-side relation with each other in such manner that the spacing therebetween is substantially no greater than the distance between their respective fibre elements, heating the bundle to fusion temperature and applying a radially inwardly directed compressing force substantially uniformly over substantially the entire length of the bundle to hermetically seal respective components of the assembly to each other and to render the resulting plate structure as a whole substantially impervious to air and gases. A number of fibres 20 (Fig. 3, not shown), having a glass cladding of lower refractive index than the fibres, are placed in an hexagonal channel in a mould not wetted by fused glass. The mould is heated in an electrical furnace to fuse the fibres to form a multichanelled structure 32. One end of this structure is then sealed in a member 52 (Fig.5 not shown) said member being held in a vertically movable clamp and being connected to a vacuum source. An annular heating element 60 is fixed around the now lower end of the structure 32. The structure is heated to softening point and simultaneously drawn downwards to form an elongated fibre structure 66 which is then divided up into light conducting elements 26 of the length desired for the face-plate. A plurality of these members 26, which are still hexagonal, are then placed in a glass ring member 68, the depth 70 (Fig. 7, not shown) of which represents the thickness of the face-plate. A steel band 78 (Fig. 9, not shown) is placed around the ring 68 and one end of the band is fixed to a stationary part 86 of a member 72, and the other end fixed to a rod 97 which is caused to move away from said fixed end by a compression spring 98. The assembly is heated to fusion temperature in a furnace the action of the band radially compressing the glass structure to cause the elements to hermetically seal to each other and to the ring to form a face-plate. The compressive force of the band 78 can be adjusted by controlling the compression of the spring 98. In an alternative method the members 26 are placed into a desirably shaped cavity between two blocks 136, 138 (Fig. 12, not shown) which can slide over a mica covered base 144 in a channel 134 in a member 130, the blocks being urged together by a spring 148.