Method of enlarging end of capillary tube bore

• US 5,152,816 A
• Filed: 10/16/1989
• Issued: 10/06/1992
• Est. Priority Date: 10/16/1989
• Status: Expired due to Term

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Berkey, George E.
• Primary Examiner(s): Jones, W. Gary
• Assistant Examiner(s): BURNS, TODD
• Application Number:
  US07/422,236
• Time in Patent Office: 1,086 Days
• Field of Search: 65/31, 65/3.15, 65/108, 65/109, 65/DIG. 9, 65/DIG. 16, 156/646, 156/663, 156/654
• US Class Current: 65/429
• CPC Class Codes: C03C 15/00 Surface treatment of glass, not in the form of fibres or filaments, by etching etching or surface-brightening compositions, in general C09K13/00
• CPC Class Codes: G02B 6/2835 formed or shaped by thermal treatment, e.g. couplers
• CPC Class Codes: G02B 6/3644 the coupling means being through-holes or wall apertures
• CPC Class Codes: G02B 6/3692 with surface micromachining involving etching, e.g. wet or dry etching steps surface micromachining involving subtractive techniques B81C1/00055
• CPC Class Codes: G02B 6/3803 Adjustment or alignment devices for alignment prior to splicing
• CPC Class Codes: G02B 6/3837 forwarding or threading methods of light guides into apertures of ferrule centering means
• CPC Class Codes: Y10S 65/09 Tube

Abstract

A method of forming a tapered aperture at the end of a capillary tube bore. A gaseous etchant such as a fluorine-containing compound flows through the bore and emanates from the first end of the tube. That tube end is heated to create a longitudinal temperature gradient. The gaseous etchant reacts with the tube and enlarges that portion of the bore at the first end. The resultant tapered aperture has a surface smoothness and shape that greatly facilitates the insertion of optical fibers during the fabrication of optical energy transfer devices.

Claims

1. A method of forming an enlarged tapered aperture in the bore of a capillary tube having a first end, a midregion and an end region between said first end and said midregion, said method comprising the steps of

flowing through said bore a gaseous etchant the reactivity of which is proportional to temperature, said gaseous etchant flowing through said midregion prior to reaching said end region, and

heating said end region to create a longitudinal temperature gradient therein, a portion of said tube in the vicinity of said first end being subjected to a maximum temperature, the temperature of said tube about the longitudinal axis thereof at any longitudinal position being substantially uniform, the steps of flowing and heating continuing for a sufficient length of time to permit said gaseous etchant to react with and etch that portion of said end region contacted by said etchant, thereby enlarging only that portion of said bore within said end region and forming a tapered aperture in said end region, a gradual transition existing between that portion of said bore within said midregion and the enlarged portion of said bore within said end region.

2. A method in accordance with claim 1 wherein the step of heating comprises rotating said tube about the longitudinal axis thereof.

3. A method in accordance with claim 1 wherein the step of heating comprises directing heat axially toward said first end of said tube.

4. A method in accordance with claim 1 wherein the step of heating comprises maintaining said tube stationary and directing heat axially toward said first end of said tube.

5. A method in accordance with claim 1 wherein the step of heating comprises heating said end region to a temperature that is sufficiently high that said gaseous etchant fractionates as it flows therethrough, the temperature of said midregion being below the fractionation temperature of said gaseous etchant.

6. A method in accordance with claim 5 wherein said maximum temperature occurs at said first end of said tube.

7. A method in accordance with claim 5 wherein said maximum temperature occurs within said end region at an axial position remote from said first end of said tube.

8. A method in accordance with claim 5 wherein said maximum temperature is such that the greatest enlargement of said tapered aperture occurs at said first end of said tube.

9. A method in accordance with claim 5 wherein said maximum temperature is such that the greatest enlargement of said tapered aperture occurs within said end region at an axial position remote from said first end of said tube.

10. A method in accordance with claim 1 wherein the step of flowing a gaseous etchant comprises flowing a gaseous compound which fractionates at a fractionation temperature to release an active constituent which reacts with the tube material.

11. A method in accordance with claim 10 wherein the step of flowing comprises flowing a fluorine-containing gaseous etchant that does not fractionate at the ambient temperature of the unheated portion of said tube, said gaseous etchant fractionating and releasing fluorine radicals at temperatures to which it is subjected within the heated region of said tube.

12. A method of forming a tapered aperture at an end of a capillary tube bore comprising the steps of

providing a tube comprising first and second ends, a midregion and first and second end regions extending from said midregion to said first and second ends, respectively,

flowing through said bore a gaseous etchant having a fractionation temperature, said gaseous etchant flowing from said midregion to at least said first end of said tube and emanating from said first end, the reactivity of said etchant being proportional to temperature, and

heating said first end region to create a longitudinal temperature gradient therein, a portion of said tube in the vicinity of said first end being subjected to a maximum temperature, the temperature of said tube about the longitudinal axis thereof at any longitudinal position being substantially uniform, the portion of said gaseous etchant flowing through said first end region being subjected to a temperature at least as high as said fractionation temperature, and the portion of said gaseous etchant flowing through said midregion not being heated to said fractionation temperature, the steps of flowing and heating being continued for a sufficient length of time to permit said gaseous etchant to react with and etch that portion of said end region contacted by said etchant, thereby enlarging that portion of said bore within said first end region such that a gradual transition exists between that portion of said bore within said midregion and the enlarged portion of said bore within said end region.