Method of making plastic optical fibers

Claim 1

A method of making plastic optical fibers comprising the steps of pre-forming a rod-like core member of plastic, pre-forming a sheath member of plastic having a longitudinal internal passage shaped like but normally being smaller than the cross-section of said core member at room temperature, said core and sheath members being pre-formed to substantially the same length, said core member having an index of refraction greater than the index of refraction of said sheath member, placing said sheath member and said core member in a vacuum chamber of a Boule forming unit, operating heating units of said Boule forming unit to apply heat to said sheath member placed therein to raise and maintain the temperature of said sheath member above room temperature to enlarge the internal passage thereof such that said core member can be inserted into the internal passage of said sheath member, maintaining said core member at approximately room temperature in said Boule forming unit prior to insertion into said sheath member, thereafter inserting said core member into said internal passage of said sheath member, the internal passage of said sheath member being at said raised temperature at least slightly greater than and being at room temperature less than the external diameter of said core member at room temperature so that the sheath member will shrink onto said core member when said assembly is allowed to return to room temperature, allowing said assembled core member and sheath member to return toward room temperature in said vacuum chamber so that said sheath member will shrink tightly onto said core member homogeneously throughout the length thereof and form a Boule, and drawing said Boule to an increased length to form an optical fiber.

Claim 2

A method of making plastic optical fibers comprising the steps of pre-forming a rod-like core member of plastic, pre-forming a sheath member of plastic having a longitudinal internal passage shaped like but normally being smaller than the cross-section of said core member at room temperature, said core and sheath members being pre-formed to substantially the same length, said core member having an index of refraction greater than the index of refraction of said sheath member, placing said sheath member and said core member in a vacuum chamber of a Boule forming unit, operating heating units of said Boule forming unit to apply heat to said sheath member placed therein to raise and maintain the temperature of said sheath member above room temperature to enlarge the internal passage thereof such that said core member can be inserted into the internal passage of said sheath member, maintaining said core member at approximately room temperature in said Boule forming unit prior to insertion into said sheath member, thereafter inserting said core member into said internal passage of said sheath member, the internal passage of said sheath member being at said raised temperature at least slightly greater than and being at room temperature less than the external diameter of said core member at room temperature so that the sheath member will shrink onto said core member when said assembly is allowed to return to room temperature, allowing said assembled core member and sheath member to return toward room temperature in said vacuum chamber so that said sheath member will shrink tightly onto said core member homogeneously throughout the length thereof and form a Boule, and drawing said Boule to an increased length to form an optical fiber.

Claim 6

A method of making plastic optical fibers comprising the steps of pre-forming a rod-like core member of plastic, forming a sheath member of plastic having a longitudinal internal passage shaped like but normally being smaller than the cross-section of said core member at room temperature, said core member being made of plastic having an index of refraction greater than the index of refraction of said sheath member, assembling said sheath member and said core member together in a vacuum chamber of a Boule forming unit with the axes thereof extending vertically under a temperature condition greater than room temperature, operating heating units of said Boule forming unit to apply heat to said sheath member therein so that said sheath member is at a temperature greater than said core member during said assembling thereof together, the dimensions of said core member and said sheath member being such that said assembly thereof can be achieved at said raised temperature and said sheath member would normally have an internal diameter at room temperature less than the external diameter of said core member at room temperature so that said sheath member will shrink onto said core member when said assembly is allowed to return to room temperature, allowing said assembled core member and sheath member to return toward room temperature in said vacuum chamber so that said sheath member will shrink tightly onto said core member homogeneously throughout the length thereof and form a Boule, and drawing said Boule to an increased length to form an optical fiber.

Claim 7

A method of making plastic optical fibers comprising the steps of pre-forming a rod-like core member of plastic, forming a sheath member of plastic having a longitudinal internal passage shaped like but normally being smaller than the cross-section of said core member at room temperature, said core member being made of plastic having an index of refraction greater than the index of refraction of said sheath member, assembling said sheath member and said core member together in a vacuum chamber of a Boule forming unit with the axes thereof extending vertically under a temperature condition greater than room temperature, operating heating units of said Boule forming unit to apply heat to said sheath member therein so that said sheath member is at a temperature greater than said core member during said assembling thereof together, the dimensions of said core member and said sheath member being such that said assembly thereof can be achieved at said raised temperature and said sheath member would normally have an internal diameter at room temperature less than the external diameter of said core member at room temperature so that said sheath member will shrink onto said core member when said assembly is allowed to return to room temperature, allowing said assembled core member and sheath member to return toward room temperature in said vacuum chamber so that said sheath member will shrink tightly onto said core member homogeneously throughout the length thereof and form a Boule, and drawing said Boule to an increased length to form an optical fiber.