Method of making polarization retaining fiber

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• shrinking said tube onto said core preform, thereby forming a solid preform having longitudinal apertures in said cladding glass on opposite sides of said core,
• fusing said core preform to said tube at the interface therebetween, thereby forming a consolidated assembly having longitudinal apertures that are parallel to said core,
• enlarging the cross-sectional area of the apertures of said consolidate assembly,
• inserting into each of the enlarged apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the following steps performed in the order in which they are set forth:

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• shrinking said tube onto said core preform, thereby forming a solid preform having longitudinal apertures in said cladding glass on opposite sides of said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass,
• evacuating the space between said stress rods and the surface of said cladding glass that forms said apertures,
• heating said draw blank to fuse each of said stress rods to the surface of the aperture into which it has been inserted, and thereafter
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the following steps performed in the order in which they are set forth:

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed side of said core,
• shrinking said tube onto said core preform,
• fusing said core preform to said tube at the interface therebetween, thereby forming a consolidated assembly having longitudinal apertures that are parallel to said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• heating the assembly formed by inserting said core preform into said tube, and applying a differential pressure across said tube whereby the pressure on the outer tube surface exceeds that on the inner tube surface, whereby said tube shrinks onto and fuses to said core preform to form a consolidated assembly having longitudinal apertures that are parallel to said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• depositing a coating of glass particles on the outer surface of said tube to form a coated assembly,
• heating said coated assembly to consolidate said particles, the consolidation of said particles exerting a force radially inwardly on said tube, said tube shrinking onto and fusing to said core preform, thereby forming a solid preform having longitudinal apertures in said cladding glass on opposite sides of said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,

• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• shrinking said tube onto said core preform, thereby forming a solid preform having longitudinal apertures in said cladding glass on opposite sides of said core,
• inserting into each aperture a stress rod of glass having a coefficient of expansion different from that of said cladding glass, said stress rods being shorter than said apertures,
• inserting into each aperture at each end of a stress rod a length of glass plug,
• attaching said plugs to said draw blank to prevent said stress rods from melting and flowing from said apertures during the step of drawing, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• shrinking said tube onto said core preform, thereby forming a solid preform having longitudinal apertures in said cladding glass on opposite sides of said core,
• providing a pair of stress rods of glass having a coefficient of expansion different from that of said cladding glass,
• forming a composite rod by attaching to each end of each of said stress rods a glass plug, the thermal coefficient of expansion of which is intermediate that of said cladding glass and said stress rod,
• inserting one of said composite rods into each of said apertures, the length of each stress rod being such that a portion of each of said plugs is within its corresponding apertures,
• attaching said plugs to said draw blank to prevent said stress rods from melting and flowing from said apertures during the subsequent step of drawing, and
• drawing the resultant draw blank to form an optical fiber.

A method of making polarization retaining single-mode optical fiber comprising the steps of

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• depositing a coating of glass particles on the outer surface of said tube to form a coated assembly,
• heating said coated assembly to consolidate said particles, the consolidation of said particles exerting a force radially inwardly on said tube, causing said heated tube to shrink onto and fuse to said core preform, thereby forming a consolidated assembly having longitudinal apertures in said cladding glass that are parallel to said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the following steps performed in the order in which they are set forth:

• forming longitudinal grooves on diametrically opposed sides of a cylindrically-shaped core preform having a glass core surrounded by cladding glass, said grooves extending into said cladding glass and being spaced from said core,
• inserting said core preform into a glass tube to form an assembly having longitudinal apertures in said cladding glass on diametrically opposed sides of said core,
• shrinking said tube onto said core preform,
• fusing the interface between said core preform and said tube, thereby forming a consolidated assembly having longitudinal apertures in said cladding glass that are parallel to said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, and
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• providing a preform having a glass core surrounded by cladding glass, a pair of longitudinal apertures in said cladding glass on opposite sides of said core, said apertures being spaced from said core,
• inserting into each of said apertures a stress rod of glass having a coefficient of expansion different from that of said cladding glass, thereby forming a draw blank,
• evacuating the space between said stress rods and the surface of said cladding glass that forms said apertures,
• fusing each of said stress rods to the surface of the aperture into which it has been inserted, and thereafter
• drawing the resultant draw blank to form an optical fiber.

A method of making a polarization retaining single-mode optical fiber comprising the steps of

• providing a cylindrically-shaped core preform having a glass core surrounded by cladding glass and longitudinal grooves extending into said cladding glass on diametrically opposed sides said core, said grooves being spaced from said core,
• providing a glass tube,
• providing a pair of glass stress rods having a coefficient of expansion different from that of said cladding glass,
• forming an assembly in which said tube surrounds said core preform, said grooves and the inner surface of said tube coacting to form longitudinal apertures in which said stress rods are disposed, and
• drawing the resultant draw blank to form an optical fiber.