Method of providing recessed optical fiber ends for use in connector structures

• US 4,148,554 A
• Filed: 08/05/1977
• Issued: 04/10/1979
• Est. Priority Date: 08/05/1977
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Cronk, Bryon J., Magnusson, John M.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lee, John D.
• Application Number:
  US05/822,268
• Time in Patent Office: 613 Days
• Field of Search: 350/96.15, 350/96.17, 350/96.18, 350/96.20, 350/96.21, 350/178, 350/320, 51/5 C, 51/209 DL, 51/281 R, 51/284, 51/284 E, 51/323, 29/90 R, 65/61
• US Class Current: 385/85
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02B 6/3847 with means preventing fibre end damage, e.g. recessed fibre surfaces
• CPC Class Codes: G02B 6/3863 fabricated by using polishing techniques grinding of the fibre ends B24B19/226
• CPC Class Codes: G02B 6/3889 using encapsulation for protection, e.g. adhesive, molding or casting resin
• CPC Class Codes: G02B 6/4203 Optical features

Abstract

A connector structure for separably connecting optical fibers includes a pair of precision sleeves, each of which is adapted to surround one of the fibers such that the ends thereof are in axial alignment. A housing fitted around the sleeves maintains that alignment. After each fiber is fitted into a matching sleeve such that end portions thereof protrude through the sleeve, the fiber is permanently anchored therein to prevent relative motion and the end of the sleeve and fiber combination is ground substantially flat and perpendicular to the fiber axis. The end of the combination is then polished under a predetermined set of conditions selected to be consistent with predetermined wear characteristics of the sleeve and fiber in which the fiber is less wear resistant than the sleeve. During the polishing operation the fiber end becomes convex and recessed within the sleeve. A pair of fibers may thus be optically coupled by butting together the ends of two sleeves within an outer housing. The recess in the fiber end precludes scratching or chipping of the fiber due to contact with other members.

Claims

1. A connector adapted for providing an optical coupling between an optical fiber and an associated optical element, said connector comprising

a housing member having an opening extending between a rear portion and a front portion through which an optical fiber may be inserted to have an end of the fiber protruding beyond the end of the front portion, said front portion surrounding the opening and exhibiting a rate of wear adjacent the opening which is less than that of a protruding fiber end when both are polished under a predetermined set of polishing conditions,

means for permanently anchoring the fiber centered within the opening in the housing member and in said protruding position to prevent relative motion therebetween, and whereupon after the fiber is permanently anchored within the housing member, the front portion of the housing member and protruding fiber end may be ground to provide substantially planar ends which are perpendicular to the axis of the fiber and subsequently polished under said predetermined set of conditions to cause the fiber end to be polished smooth and slightly recessed within the front portion of the housing member as a result of differences in the rates of material removal, and wherein the

housing member further comprises means for maintaining the recessed fiber end axially aligned with, and the planar front portion abutting a support for an associated optical element and for enclosing the interface therebetween to prevent foreign elements from contacting the fiber end, thereby minimizing optical losses, while the recessed fiber end in the housing member results in a small gap between the fiber end and the associated optical element and thereby prevents degradation in optical efficiency as may otherwise result from chipping or scratching of the fiber end due to contact with other members during repeated connections or disconnections or when connected and in use.

2. A connector according to claim 1 adapted for providing an optical coupling between a pair of optical fibers, comprising a mating pair of said housing members, each being adapted to receive and anchor therein an end of one of said pair of fibers, wherein a front portion of each member and protruding fiber end are ground to provide substantially planar ends which are substantially perpendicular to their respective axes, wherein at least one of the respective fiber ends are polished smooth and slightly recessed within the front portion of its associated housing member as a result of differences in the respective rates of removal under predetermined polishing conditions, and wherein the mating housing members are adapted to receive and enclose both fibers such that the substantially planar front portions of both housing members are maintained axially butted together.

3. A connector according to claim 1, wherein the protruding end of a fiber within a housing member is ground and polished such that said substantially planar end is slightly convex, the axial portion thereof being closest to the plane of the end portion but still recessed therebelow.

4. A connector according to claim 3, wherein the axial portion of the fiber is recessed less than 3 mils (75 μ

m) below the plane of the end portion of the housing member.

5. A connector according to claim 3, wherein the slightly convex fiber end has a radius of curvature of not less than the diameter of the fiber.

6. A connector according to claim 1, wherein said front portion of the housing member comprises a metal composition and is adapted for use with an optical fiber having a core of a non-metallic material.

7. A connector according to claim 6, wherein the optical fiber further comprises a cladding around the core, the rate of removal of the cladding under said predetermined set of polishing conditions being greater than that of the core.

8. A connector according to claim 1, comprising at least two resilient mating housing members, one of which is secured to a said recessed fiber and one of which is secured to a said associated optical element, which resilient members are adapted to be force fitted together to maintain said axial alignment.

9. A connector according to claim 1, wherein said housing member comprises at least one tubular sleeve anchored within the housing and having a circular opening extending therethrough, said sleeve thus providing the opening in the housing which is adapted to receive and anchor a said optical fiber inserted therethrough, and exhibiting a rate of wear less than that of the fiber under said predetermined set of polishing conditions such that upon such polishing an end of a fiber becomes recessed within the end of the sleeve.

10. A connector according to claim 9, wherein the housing member further includes a second tubular sleeve anchored within the housing and having a circular opening extending therethrough of substantially the same diameter as the outer diameter of the first sleeve, and into at least a portion of which the first sleeve having the recessed fiber end therein may be inserted and into the opposite end of which another sleeve of the same outer diameter as the first sleeve and having another fiber anchored therein may be inserted such that the smaller sleeves become butted together and axially aligned.

11. A connector according to claim 1, adapted for providing an optical coupling between a said optical fiber and another optical element, including a said housing member adapted to receive and anchor therein an end of a said optical fiber, wherein a front portion of said member and a fiber end protruding therethrough may be ground to provide substantially planar ends which are substantially perpendicular to the fiber axis and subsequently polished under said predetermined set of polishing conditions to provide a smooth and recessed fiber end, and further including a mating housing member having a front portion adapted to provide a substantially planar end which may be butted against the planar front portion of the other housing member and which encloses and positions a said associated optical element therein such that said fiber recessed in the front portion of the first recited housing member is optically coupled to the associated optical element when both housing members are mated together such that the respective front portions are butted together.

12. A connector according to claim 11, wherein said first recited housing member comprises at least one tubular sleeve anchored within the housing, said sleeve having a circular opening extending therethrough, thus providing the opening in the housing which is adapted to receive and anchor a said optical fiber therethrough, and exhibiting a rate of wear less than that of the fiber under said predetermined set of polishing conditions such that upon such polishing, an end of a fiber becomes recessed within the end of the sleeve.

13. A connector according to claim 12, wherein the first recited housing member further includes a second tubular sleeve anchored within the housing and having a circular opening extending therethrough of substantially the same diameter as the outer diameter of the first sleeve, and into at least a portion of which the first sleeve having the recessed fiber end therein may be inserted and into the opposite end of which another sleeve of the same outer diameter as the first sleeve and having another fiber anchored therein may be inserted such that the smaller sleeves become butted together and axially aligned, and wherein said mating housing member includes said another sleeve of the same outer diameter as the first sleeve of the first recited member, said another sleeve having therewithin an optical fiber coupled to said associated optical element such that when both housing members are mated together the respective sleeves enclosing the fibers are butted together to optically couple the fibers and optical element.

14. A method for optically coupling an optical fiber to an associated optical element comprising

(a) providing a housing member having an opening of a predetermined diameter extending between a front portion and a rear portion for receiving an optical fiber, which front portion surrounds the opening and is characterized by a rate of wear less than that of the fiber when both are polished under a predetermined set of conditions,

(b) inserting a said fiber into the rear portion of the opening such that an end of the fiber protrudes beyond said front portion,

(c) permanently anchoring together the associated fiber and housing member in said protruded position to prevent relative movement,

(d) grinding the protruding end of the fiber and front portion of the housing member to provide substantially co-planar ends on the front portion and on the fiber which are perpendicular to the axis, and

(e) polishing the co-planar ends of the fiber and front portion under a said predetermined set of polishing conditions to cause the fiber end to be polished smooth and slightly recessed within the front portion of the housing member as a result of a difference in material removal rates under said predetermined conditions,

such that when the front portion is butted-up against a support for an associated optical element and the axis of the recessed fiber is optically aligned with the element, the recess results in a small gap along the axis and thereby prevents degradations in optical efficiency as may otherwise result from chipping or scratching of the fiber end or other members due to mutual contact during repeated connections and disconnections or when connected and in use.

15. A method according to claim 14, further comprising

(f) providing a mating housing member having a substantially planar front portion surrounding an opening therethrough, mating means for cooperatively coupling with the first recited housing member for maintaining the respective front portions butted-up against each other with the respective openings therethrough axially aligned and for enclosing the front portions to prevent foreign impurities from contacting the fiber end, and a cavity therein for receiving and anchoring a said associated optical element such that the element is optically coupled to the opening through the front portion,

(g) assembling a said associated element within said housing, and

(h) mating the respective housing members to complete the optical coupling.

16. A method according to claim 14, wherein said polishing includes providing a resilient and partially conformable surface and a polishing compound, polishing the exposed fiber and front portion of the housing member against the surface such that the more wear resistant front portion is less affected while the resilient member conforms into the less wear resistant fiber and results in preferential removal thereof.

17. A method according to claim 14, comprising polishing the ends of the fiber and front portion of the housing member under said predetermined polishing conditions including an appropriate polishing duration and pressure to provide a slightly convex fiber end, the axial portion thereof being closest to the plane of the end portion but still recessed therebelow.

18. A method according to claim 17, wherein the resilient polishing surface comprises a poromeric material.

19. A method according to claim 18, wherein the poromeric material is impregnated with a polishing compound of Al₂ O₃ or gamma Fe₂ O₃.

20. A method according to claim 14, comprising

providing as a component of said housing member a tubular sleeve member having a circular cross-sectional opening extending therethrough, and a periphery adapted to mate with the remainder of the housing to be anchored therein, said sleeve thus providing the opening in the housing into which is inserted and permanently anchored the optical fiber and the front portion of which is characterized by the rate of wear less than that of the fiber,

grinding and polishing a fiber permanently anchored within the sleeve member to cause the fiber end to be recessed therewithin, and

mounting the thus prepared fiber-sleeve combination within the remainder of the housing member.

21. A method according to claim 20, comprising preparing a combination of a plastic fiber and steel sleeve member by first grinding the fiber flush with the sleeve utilizing 600 mesh SiC and subsequently undercutting the fiber by polishing the combination on a poromeric lap impregnated with 0.3 μ

m Al₂ O₃ polishing compound.

22. A method according to claim 20, comprising preparing a combination of a plastic clad silica fiber and steel sleeve member by first grinding the fiber flush with the sleeve utilizing 600 mesh SiC and subsequently undercutting the fiber end by polishing the combination on a poromeric lap impregnated with 1.0 μ

m Fe₂ O₃ rouge.

23. A connector providing an optical coupling between an optical fiber and an associated optical element, said connector structure comprising

(a) at least one tubular sleeve having a circular cross-sectional opening axially extending therethrough, said opening having a diameter slightly greater than the outside diameter of an optical fiber to be inserted therethrough, said sleeve exhibiting a rate of wear less than that of the fiber when polished under a predetermined set of conditions and having an end portion surrounding said opening through which a said optical fiber inserted through the sleeve may protrude,

(b) at least one optical fiber inserted through a said sleeve in said protruding position,

(c) means for permanently anchoring the fiber centered within the sleeve in said protruding position to prevent relative motion therebetween, and whereupon after the fiber is permanently anchored within the sleeve to provide a sleeve-fiber combination, the end portion of the sleeve and protruding fiber of the combination is ground to provide a substantially planar end on the sleeve and fiber combination which is perpendicular to the axis, after which the planar end is polished under said predetermined polishing conditions to cause the fiber end to be polished smooth and slightly recessed within the end portion of the sleeve as a result of differences in the rates of material removal, and

(d) housing means for enclosing the sleeve-fiber combination and for maintaining the substantially planar end of the sleeve axially butted-up against a said associated optical element to prevent dirt and other impurities from contacting the fiber end thereby minimizing optical losses, while the recess of the fiber end within the sleeve results in a small gap between the fiber end and the associated optical element and thereby prevents degradation in optical efficiency as may otherwise result from chipping or scratching of the fiber end due to contact with other members during repeated connections and separations.

24. A connector adapted for providing an optical coupling between an optical fiber and an associated optical element, said connector comprising

a housing member having an optical fiber permanently anchored and extending between a rear portion and a front portion of the housing and protruding beyond the end of the front portion, said front portion exhibiting a rate of wear adjacent the fiber end which is less than that of the fiber end when both are polished under a predetermined set of polishing conditions, whereupon the front portion of the housing member and protruding fiber end may be ground to provide substantially planar ends which are pependicular to the axis of the fiber and subsequently polished under said predetermined set of conditions to cause the fiber end to be polished smooth and slightly recessed within the front portion of the housing member as a result of differences in the rates of material removal, and wherein the

housing member further comprises means for maintaining the recessed fiber end axially aligned with, and the planar front portion abutting a support for an associated optical element and for enclosing the interface therebetween to prevent foreign elements from contacting the fiber end, thereby minimizing optical losses, while the recess of the fiber end results in a small gap between the fiber end and the associated optical element and thereby prevents degradation in optical efficiency as may otherwise result from chipping or scratching of the fiber end due to contact with other members during repeated connections or disconnections when connected and in use.