Method of making polarization preserving optical fiber

Claim 1

A method of forming a polarization preserving optical fiber having multiple light transmitting cores comprising providing a preform of glass having a first composition, forming on one end of said preform a flat surface that is substantially perpendicular to the axis thereof, forming in said preform a plurality of longitudinally-extending holes, fusing to said endface a thin-walled glass cylinder, providing a pair of rods of glass having a refractive index which is greater than that of said cladding glass, the diameters of said rods being less than that of said holes, enlarging the diameter at one end of each of said rods thereafter inserting one of said rods into each of said holes such that the enlarged end of each rod protrudes from the respective hole, wherein said rods are prevented from melting and sliding downwardly in said holes, affixing a vacuum connection to said cylinder and evacuating the space within said cylinder and the space between said rods and the adjacent walls of said holes, and drawing the resulting assembly to bond together said glass rods and said preform into an integral optical fiber.

Claim 2

A method of forming a polarization preserving optical fiber having multiple light transmitting cores comprising providing a preform of glass having a first composition, forming on one end of said preform a flat surface that is substantially perpendicular to the axis thereof, forming in said preform a plurality of longitudinally-extending holes, fusing to said endface a thin-walled glass cylinder, providing a pair of rods of glass having a refractive index which is greater than that of said cladding glass, the diameters of said rods being less than that of said holes, enlarging the diameter at one end of each of said rods thereafter inserting one of said rods into each of said holes such that the enlarged end of each rod protrudes from the respective hole, wherein said rods are prevented from melting and sliding downwardly in said holes, affixing a vacuum connection to said cylinder and evacuating the space within said cylinder and the space between said rods and the adjacent walls of said holes, and drawing the resulting assembly to bond together said glass rods and said preform into an integral optical fiber.

Claim 4

A method of forming a polarization preserving optical fiber comprising the steps of providing a cylindrical preform comprising a centrally disposed glass core surrounded by a layer of cladding glass having a first composition, said preform cladding glass having a refractive index lower than that of the core glass, forming in said cladding glass on diametrically opposed sides of said preform core a pair of longitudinally-extending holes, the axes of which are parallel to that of said core, providing a pair of glass rods having a thermal coefficient of expansion which differs from that of said preform cladding glass, the cross-sectional area of said rods being slightly smaller than that of said holes except at one end thereof where the rod cross-sectional area is greater than that of said holes, inserting one of said rods into each of said holes prior to drawing, the large diameter ends of said rods protruding above said preform, wherein said rods are prevented from melting and sliding downwardly in said holes, affixing a vacuum connection to that end of said preform from which the large diameter ends of said rods protrude, whereby the space between each rod and the adjacent walls of said holes is evacuated, and drawing the resulting assembly to bond together said glass rods and said preform into an integral optical fiber.

Claim 5

A method of forming a polarization preserving optical fiber comprising the steps of providing a cylindrical preform comprising a centrally disposed glass core surrounded by a layer of cladding glass having a first composition, said preform cladding glass having a refractive index lower than that of the core glass, forming in said cladding glass on diametrically opposed sides of said preform core a pair of longitudinally-extending holes, the axes of which are parallel to that of said core, providing a pair of glass rods having a thermal coefficient of expansion which differs from that of said preform cladding glass, the cross-sectional area of said rods being slightly smaller than that of said holes except at one end thereof where the rod cross-sectional area is greater than that of said holes, inserting one of said rods into each of said holes prior to drawing, the large diameter ends of said rods protruding above said preform, wherein said rods are prevented from melting and sliding downwardly in said holes, affixing a vacuum connection to that end of said preform from which the large diameter ends of said rods protrude, whereby the space between each rod and the adjacent walls of said holes is evacuated, and drawing the resulting assembly to bond together said glass rods and said preform into an integral optical fiber.