Thermally expanded core fiber fabrication method and optical...

Optical waveguides – With splice – Fusion splicing

Reexamination Certificate

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Details

C385S049000, C385S050000, C385S095000

Reexamination Certificate

active

06244757

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber fabrication method, and more particularly, to a fabrication method of a thermally extended core (TEC) fiber by which a core of an optical fiber is expanded using diffusion generated when optical fibers having different outer diameters are arc-fusion-spliced, and an optical fiber coupling method.
2. Description of the Related Art
Optical elements having optical fibers as their input/output ports use a TEC fiber so as to be coupled effectively when light received from the section of the optical fiber in an input port pass through functional elements to then be output to an output port. In an exemplary TEC fiber fabrication method of the contemporary art, a TEC fiber is fabricated such that a flame is applied in close proximity to an optical fiber whose core is to be expanded, using a torch which generates a high temperature heat and then the optical fiber is thermally treated at a high temperature lower than the fusion point. Then, the thermally treated fiber is post-treated to fabricate the TEC fiber. However, according to this method, much fabrication time and cost are required. Also, a problem may arise in the repeatability of the step of thermally expanding a core to a constant size.
Since the diameter of a fiber core is very small, i.e., about 10 &mgr;m, in order to couple two fibers, cores of the two fibers to be coupled must be precisely aligned. Even if the coupled cores are only slightly misaligned, the fiber coupling efficiency decreases considerably. Also, when an optical fiber and an optical element are coupled, the coupling efficiency decreases if the size of a waveguide is small and the shapes of waveguides are not the same.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method of fabricating a TEC fiber.
It is a further object to provide a TEC fiber fabrication method which allows fabrication more quickly and at lower cost.
It is a yet further object of the present invention to provide a TEC fiber fabrication method which eliminates problems in variability of the TEC core size.
It is another object of the present invention to provide an improved optical fiber coupling method.
It is another object of the present invention to provide a method for coupling two optical fibers having different clad diameters.
To achieve these objects, the present invention provides a method for fabricating a TEC fiber using two optical fibers having different outer diameters for enhancing the coupling efficiency of an optical signal. Accordingly, there is provided a method for fabricating a thermally expanded core (TEC) fiber including the steps of arc-fusion splicing two optical fibers having different clad outer diameters, and cutting a boundary surface between the optical fiber having the smaller clad outer diameter and the optical fiber having the larger clad outer diameter of the two optical fibers to obtain the thermally expanded core (TEC) fiber. Preferably, the method may further include the step of polishing the cut face of the optical fiber having the smaller clad outer diameter of the two cut optical fibers.
To achieve the above objects, there is also provided a method for coupling two optical fibers having different clad outer diameters including the steps of aligning the two optical fibers having different clad outer diameters, and coupling the optical fibers by arc-fusion splicing the aligned optical fibers by using an arc fusion splicer.


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