Patent ID: 7099546

Claim:
A method of manufacturing a graded index plastic optical fiber wherein the index varies continuously between the center and periphery of the fiber, from at least one polymer P and at least one reactive diluent D1, to allow the refractive index of said fiber to vary, said method comprising the steps of: preparing two compositions with different refractive indices, the difference in refractive index between the two compositions being at least 5×10 −3 , each comprising at least the polymer P, one of the compositions, termed the first composition, also comprising at least the reactive diluent D1, a radical polymerization initiator being present in at least one of the compositions; active mixing of the two compositions to obtain a continuous variation in the refractive index of the optical fiber; spinning the mixture; curing the mixture to produce a cured optical fiber with a refractive index gradient, said method being characterized in that said polymer P is a terpolymer comprising at least three repeating units P1, P2 and P3 with the following general formulae: in which: X 1 , X 2 and X 3 , which may be identical or different, are taken from the group of atoms H, F, Cl and Br; R 1 is a H, F, Cl or Br atom or a carbonaceous group containing 1 to 10 partially or completely fluorinated carbon atoms; Y 1 and Y 2 , which may be identical or different, are taken either from the group of atoms comprising H, F, Cl and Br, or from the family of carbonaceous groups containing 1 to 10 carbon atoms; Y 3 is a carbonyl group or a divalent carbonaceous group; Z 1 , Z 2 and Z 3 , which may be identical or different, are hydrogen or fluorine atoms, or carbonaceous groups containing 1 to 10 carbon atoms; n equals 0 or 1; A is an ester function or an oxygen or sulfur atom; R 2 is taken from the group comprising divalent hydrocarbon groups containing 2 to 8 carbon atoms and partially halogenated divalent carbonaceous groups containing 2 to 8 carbon atoms; B x is an unsaturated reactive function; i, j and k correspond to a repeat number of units; the quantity of P3 units in the terpolymer being in the range 2 mole % to 40 mole %, preferably in the range 10% to 20%, and the mole ratio of the P1/P2 units being in the range 0.5 to 5.5, preferably in the range 1 to 2, said terpolymer being transparent, amorphous in nature and having a glass transition temperature (Tg) of more than 25° C.