GB1506967A - Resilient optical fibre cable - Google Patents

Abstract

1506967 Extrusion sheathing of optical fibres INTERNATIONAL STANDARD ELECTRIC CORP 20 Jan 1976 [29 Jan 1975] 02140/76 Heading B5A [Also in Division G2] A cable comprising a convoluted optical fibre 18 (e.g. of glass or silica) loosely contained in a flexible tubing 16 (e.g. of polyimide, polyamide, fluorocarbon, polyethylene, polypropylene, thermo-plastic or cross-linked polyester) is made by (a) extruding a given length of tubing 16 at a temperature above the crystalline melt point of the material; (b) feeding a smaller diameter, longer length optical fibre 18 to fit loosely within the tube; (c) longitudinally stretching the tube 16 to provide an axial strained orientation to the material (in Fig. 2, this is done by pulling capstan 24 while the tube and fibre pass through heater 20 and sizing die 22); (d) shrinking the tube 16 on to the fibre 18 to reduce the tube length and contract the fibre (in Fig. 3 this is done by driving capstan 36 slower than capstan 34 while the tub and fibre pass through heater 32) and (e) cooling the tube (e.g. at 37) to retain a given elastic orientation while permitting movement of the fibre within the tube. In a variation (Fig. 4) extruder 38 provides an oversized tube and the hot extruded tubing is then longitudinally stretched as it is drawn by the capstan 24 through the cooling chamber 40. This provides an axially oriented strain locked into the material without the added heating step of Fig. 2. A sizing die may be included in the cooling chamber 40. The tube is reheated, relaxed and shrunk as in Fig. 3.