LAMINATION OF OPTICAL FIBER FLEXFOILS

An optical fiber flexfoil (1) comprises optical fibers adhesively bonded between two flexible foils (3, 7) laminated to each other. A surface of a base flexible plastic sheet (3) is coated with a pressure sensitive adhesive (5) and optical fibers are bonded to the sheet by the adhesive (5). A top foil (7) having a similar coating (9) is placed on top of the base foil (3) contacting the optical fibers, air located between the foils is removed and the foils are pressed against each other using a rubber bag formed of two superposed rubber sheets (11, 13) to bond the foils to each other only by means of the adhesive coatings (5, 9). The adhesive is selected to have a low glass transition temperature such as below -50 ~C and to exhibit visco-elastic characteristics in the temperature range within which the flexfoil is to be used. The lamination of the foils is made at temperatures at the upper limit of the operational range using only moderate pressures. This gives low mechanical stresses on the fibers in the pressing operation. The fibers are not entirely rigidly fixed to the foils allowing them to move a little when bending the flexfoil, so that rather sharp bends of the flexfoil (1) can be made. Also, microbends formed in the lamination process can relax and thus be eliminated what produces a low attenuation in the optical fibers.