Fiber optic coupler and method for making same

A method for forming a fiber optic coupler comprising:

• providing at least two optical fibers each having a core with a cladding material disposed thereabout;
• in a limited length coupling region of each fiber, removing the cladding material to fully expose said core in a manner whereby the cladding material immediately adjacent the exposed core increases in thickness in smooth transition;
• removing, in the limited length coupling region, a portion of the core in a manner whereby the outer diameter of said core decreases in smooth transition from immediately adjacent the cladding material, said step including removing at least 4% of the outer diameter of the core of at least one of said fibers in said coupling regions arranging the fibers along side each other in crossed relationship with a constant azimuthal angle;
• and
• joining the exposed ores of said optical fibers in the limited length region by coalescing whereby light transmitted through said fibers is coupled in the coalesced region.

A method for formation of a a star coupler comprising

• providing a plurality of optical fibers each having a core with a cladding material disposed thereabout;
• in a limited length region of each fiber, removing the cladding material to expose said core in a manner whereby the cladding material immediately adjacent the exposed core increases in thickness in smooth transition;
• joining the exposed cores of said optical fibers in the limited length region by coalescing whereby light transmitted through said fibers is coupled in the coalesced region;
• and
• in said limited length coupling region, necking down the fibers abruptly in a manner to cause light transmitted therethrough to be randomized.

A method for forming a multimode fiber optic coupler comprising:

• providing at least two optical fibers each having a core with a cladding material disposed thereabout;
• drawing said core and cladding material of at least one said fiber into a biconical taper;
• thereafter, in a limited length region of each fiber, removing the cladding material to substantially expose said core in a manner whereby the cladding material immediately adjacent the substantially exposed core increases in thickness in smooth transition;
• arranging the substantially exposed cores of said fibers to extend generally lengthwise and substantially symmetrically along the sides of each other in crossed relationship;
• joining the substantially exposed cores of said optical fibers in the limited length region by coalescing whereby light transmitted through said fibers is coupled effectively int he coalesced region.

The method of forming an optical coupler comprising:

• a. mounting a first fiber in a first fixture in a manner to at least minimize torsional rotation of the first fiber and thus ensure said first fiber is in neutral condition,
• b. arranging a second fiber to lie in intimate cross contact with said first fiber in a coupling region, said second fiber so arranged in a manner to at least minimize torsional rotation of the second fiber and thus ensure said second fiber is in neutral condition;
• and
• c. with said fibers taut, applying heat to said coupling region to fuse said fibers.

A fiber optic coupler comprising:

• at least two optical fibers each having a core with a cladding material disposed thereabout, said fibers in a limited length coupling region having the cladding material removed and the core exposed, the thickness of the cladding material increasing in smooth transition from immediately adjacent the exposed core;
• said fibers crossing one another in a manner so as to maintain a constant azimuthal angle within each fiber;
• and
• said fibers joined in said coupling region by coalescing.