WO2014031556A1

WO2014031556A1 - Ferrule holder having increased adhesive region

Info

Publication number: WO2014031556A1
Application number: PCT/US2013/055640
Authority: WO
Inventors: JR. Robert Elvin BARNETTE; John Wayne BEATTY; II Robert Bruce ELKINS; Robert Max SANETICK; Hieu Vinh Tran
Original assignee: Corning Cable Systems Llc
Priority date: 2012-08-22
Filing date: 2013-08-20
Publication date: 2014-02-27

Abstract

A ferrule holder includes first (92), second (96), and third (98) bores in fluid communication with each other but having different bore widths. The third bore is defined between first and second bores. A transition area (100) between the second and third bore defines a stop configured and sized to prevent at least a portion of a section of optical fiber (82) from entering the third bore. This allows the section of optical fiber that does enter the third bore to be surrounded by adhesive (90) before entering a ferrule received in the first bore of the ferrule holder. The first bore has at least one groove (102) disposed on a bore surface to vent the adhesive during curing and thereby prevent the formation of voids around the section of optical fiber in the third bore.

Description

FERRULE HOLDER HAVING INCREASED ADHESIVE REGION CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S.

Provisional Application Serial No. 61/692,073 filed on August 22, 2012, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

[0002] The disclosure relates generally to fiber optic connectors and more particularly to a ferrule holder that advantageously positions an optical fiber in relation to a ferrule and adhesive within the ferrule holder. Related components, cable assemblies, and methods are also disclosed.

[0003] In a system that uses fiber optic cables, there are typically many locations where the cables connect to equipment or other fiber optic cables. Fiber optic connectors are provided on the ends of the cables to allow the transfer of light at these connection points. A fiber optic connector typically includes a ferrule with one or more bores that receive optical fiber(s) from the cable. The ferrule is held by a ferrule holder and serves to align the optical fiber(s) from the cable with optical fiber(s) or waveguides in a mating component (e.g., another connector or equipment).

[0004] The process of terminating individual optical fibers from a cable is referred to as "connectorization." Connectorization is an important step in the installation of fiber optic systems, whether done in a factory or the field. This is partly due to the number of potential sources for damage during the connectorization process. For example, one or more layers of material are typically stripped from the glass portion of the optical fiber so that only the glass portion (i.e., core and cladding) is inserted into the ferrule of the connector. In many instances this includes stripping a 900 micron-diameter buffer layer in a first step, and then stripping a 250 micron-diameter acrylic coating in a second step so that only a 125 micron- diameter glass portion remains. Stripping tools have been developed to reduce the likelihood of damaging the glass portion during these steps, but the potential remains nonetheless, especially in the region where a stripping tool begins to remove the buffer layer and/or outer coating.

[0005] Even if an optical fiber is properly stripped and prepared for insertion into the bore ("micro -hole") of a ferrule, the insertion itself can be challenging and has the potential to introduce flaws in the glass portion. For example, the ferrule bore typically includes a cone- shaped lead-in to facilitate directing the glass portion into the bore. An adhesive such as epoxy is first injected into the bore from the back end of the ferrule holder, thereby filling the bore, lead-in, and any space within the ferrule holder between the rear end of the ferrule and the injection needle. The injection needle is then removed, and the optical fiber is inserted through the adhesive and into the bore of the ferrule. Shear forces between the fiber and the adhesive may cause the fiber to buckle within the lead-in of the ferrule bore and perhaps even make contact with the edge of the ferrule.

[0006] An optical fiber that sustains damage from either or both of the above-described scenarios may still withstand failure in most conditions, especially if the glass portion is properly supported by adhesive within the ferrule. However, sometimes air or other gas can get trapped within the adhesive and cause voids. These voids may even end up around the damaged region of the glass portion and increase the potential for a fiber break. This is particularly true for cables used in an outside plant environment (i.e., outdoor cables or indoor/outdoor cables), which may be exposed to a variety of environmental and mechanical extremes.

[0007] These aspects can be better understood with reference to Fig. 3, which shows a portion of a conventional fiber optic connector 10 in an assembled state. A ferrule 12 is received in a ferrule holder 14, and an optical fiber 16 is secured in a ferrule bore 18 by adhesive 20. As can be seen, a buffer layer 22 and outer coating 24 have been stripped from the optical fiber 16 so that only a glass portion 26 (core and cladding) are inserted into the ferrule bore 18. The adhesive may surround portions of the outer coating 24 and buffer layer 22 as well.

[0008] An air void or bubble 30 may form in the adhesive when the adhesive is injected and/or when the adhesive injection needle (not shown) is withdrawn. Even if the air void 30 is formed in a region of the adhesive remote from where the optical fiber 16 is inserted, the air void 30 may migrate toward the optical fiber 16 during or after the insertion. This may ultimately result in the air void 30 contacting or surrounding a region of the glass portion 26 that is prone to damage. As can be seen, the damaged regions mentioned in both of the above-describe scenarios may be the same. That is, where the outer coating 24 is stripped from the optical fiber 16 may be the same place where the fiber has increased potential to buckle and contact an edge of the ferrule 12 during insertion into the ferrule bore 18. The presence of an air void creates a non-uniform distribution of the adhesive 20 around this damage-prone region in the lead-in 32 of the ferrule bore 18, which in turn can lead to increased loads/stresses on the damage-prone region during thermal expansions and the like. The loads/stresses may result in the optical fiber 16 breaking in this region. Therefore, a need exists to address the above-mentioned challenges.

SUMMARY

[0009] One embodiment of the disclosure relates to a ferrule holder for a fiber optic connector. The ferrule holder includes a ferrule body that is generally tubular and has a first end and a second end. An axis extends from the first end to the second end of the ferrule body. The ferrule holder also includes a first end portion that defines a first bore having a first bore width, a second end portion opposite the first end portion, and a through passage disposed between the first end portion and the second end portion. The first bore is configured to receive at least a portion of a ferrule and has at least one groove disposed on a bore surface. The second end portion defines a second bore having a second bore width and configured to receive at least a section of an optical fiber. The through passage defines a third bore between the first and second bores, with the third bore being configured and sized to allow a glass portion of the section of the optical fiber to pass from the second end portion to the first end portion. The first bore, second bore and third bore are in fluid communication with each other. The ferrule holder also includes a transition area between the second bore and the third bore. The transition area defines a stop configured and sized to prevent at least a portion of the section of the optical fiber from entering the third bore, which has a width that is smaller than the second bore.

[0010] This arrangement allows the section of optical fiber that does enter the third bore to be surrounded by adhesive before entering the ferrule received in the first bore. An increased length of fiber can be encapsulated by the adhesive within the ferrule holder compared to conventional designs. Additionally, the at least one groove disposed on the bore surface of the first bore is configured to vent the adhesive during curing and thereby prevent the formation of voids around the increased length of encapsulated fiber.

[0011] Another embodiment of this disclosure relates to a cable assembly for a fiber optic connector. In addition to a ferrule holder like that described above, the cable assembly includes a fiber optic cable having at least one optical fiber and a ferrule having a mating end and an insertion end. The insertion end of the ferrule is received in the first end portion of the ferrule holder. [0012] Related methods are also disclosed. For example, one method involves inserting a ferrule into a first end of a ferrule holder. The ferrule holder has a first bore, a second bore, a third bore at least partially defining a through passage, at least one groove disposed on a first bore surface, and at least one stop disposed between the second bore and the third bore. An adhesive delivery devices is introduced into the second end of the ferrule holder and pressed against the at least one stop. Adhesive is then delivered into the ferrule holder. The method also involves determining when the adhesive flows out of a ferrule bore disposed in the ferrule, inserting a portion of a fiber optic cable into the second end of the ferrule holder, at least partially abutting a buffer layer against the at least one stop thereby preventing the buffer layer from entering the third bore, and inserting a portion of the fiber optic cable into the ferrule.

[0013] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.

[0014] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims.

[0015] The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a perspective view of one embodiment of a fiber optic connector.

[0017] Fig. 2 is an exploded plan view of the fiber optic connector shown in Fig. 1.

[0018] Fig. 3 is a cross-sectional view of a portion of a fiber optic cable assembly having a fiber optic connector with a conventional arrangement.

[0019] Fig. 4 is a cross-sectional view of a portion of a fiber optic cable assembly having a fiber optic connector according to one embodiment of the present disclosure.

[0020] Fig. 5 is a cross-sectional view of a ferrule holder used in the fiber optic connector of Fig. 4.

[0021] Fig. 6 is schematic view of a portion of the ferrule holder of Fig. 5. [0022] Figs. 7A-7E are cross-sectional views sequentially illustrating a method of terminating an optical fiber with the fiber optic connector of Fig. 4.

DETAILED DESCRIPTION

[0023] Various embodiments will be further clarified by the following examples. To this end, Figs. 1 and 2 illustrate one example of a fiber optic connector 50 ("connector") for a cable assembly (the cable is not shown). Although the connector 50 is shown in the form of a SC-type angled physical contact (APC) connector, the description below relates to details that may apply to other types of fiber optic connectors. This includes ST, LC, FC, and MU-style connectors with or without angled end faces, for example.

[0024] In general, the connector 50 includes a ferrule 52 having a mating end 54 and an insertion end 56, a ferrule holder 58 having opposed first and second end portions 60, 62, and an inner housing 64. The insertion end 56 of the ferrule 52 is received in the first end portion 60 of the ferrule holder 58 while the mating end 54 remains outside the ferrule holder 58. The second end portion 62 of the ferrule holder 58 is received in the inner housing 64. A spring 66 may be disposed around the second end portion 62 and configured to interact with walls of the inner housing to bias the ferrule holder 58 (and ferrule 52). Additionally, a lead- in tube 68 may extend from a rear end 70 of the inner housing 64 to within the second end portion 62 of the ferrule holder 58 to help guide the insertion of an optical fiber (not shown in Figs. 1 and 2) into the ferrule 52. An outer shroud 72 is positioned over the assembled ferrule 52, ferrule holder 58, and inner housing 64, with the overall configuration being such that the mating end 54 of the ferrule 52 presents an end face 74 configured to contact a mating component (not shown).

[0025] In a manner not shown herein, a fiber optic cable providing the optical fiber also includes one or more layers of material (e.g., strength layer of aramid yarn) that may be crimped onto the rear end 70 of the inner housing 64. A crimp band may be provided for this purpose. Additionally, a strain-relieving boot may be placed over the crimped region and extend rearwardly to cover a portion of the fiber optic cable. Variations of these aspects will be appreciated by persons skilled in the design of fiber optic cable assemblies. Again, the embodiment shown in Figs. 1 and 2 is merely an example of a fiber optic connector to which the details described below may apply. The general overview has been provided simply to facilitate discussion and put the details in context. [0026] With this in mind, Fig. 4 illustrates the ferrule 52, ferrule holder 58, and inner housing 64 in further detail. An optical fiber 82 has been inserted into the ferrule 52 from the second end portion 62 of the ferrule holder 58. Specifically, the optical fiber 82 is part of a fiber optic cable 80 having a buffer layer 84 that surrounds the optical fiber 82. A portion of the buffer layer 84 has been stripped from the optical fiber 82, which includes a glass portion 86 ("glass fiber") in the form of a core and cladding and an outer coating 88 ("acrylic layer"). A portion of the outer coating 88 has also been stripped off so that only the glass portion 86 is inserted into the ferrule 52. The insertion process will be described in detail further below.

[0027] The optical fiber 82 is secured within the ferrule 52 and ferrule holder 58 by adhesive 90, which may be an epoxy. Particular features on the ferrule holder 58 help ensure that the optical fiber 82 is sufficiently encapsulated by the adhesive 90 within the ferrule holder 58 so as to reduce the chances of the optical fiber 82 breaking during thermal expansions and other stress-inducing conditions. These features include geometry of the ferrule holder 58 that separates the damage-prone areas discussed in the background section (with reference to Fig. 3) and/or features on the ferrule holder 58 that help reduce or eliminate the formation of air voids or bubbles in the adhesive 90.

[0028] To this end, and with additional reference to Figs. 5 and 6, the first end portion 60 of the ferrule holder 58 defines a first bore 92 having a first bore width (Wi) for receiving the ferrule 52. A slight interference fit may be provided. The first end portion 60 is also shaped so that a gap (g) is maintained between the insertion end 56 of the ferrule 52 and an inner wall 94 of the ferrule holder 58 that represents an end of the first bore 92. The second end portion 62 of the ferrule holder 58 defines a second bore 96 having a second bore width (W₂). The ferrule holder 58 may also include a third bore 98 defined by a through passage between the first and second bores 92, 96, with the third bore 98 having a third bore width (W₃). As used herein, the term "bore width" refers to bore diameter when the associated bore is cylindrical. The third bore width is smaller than the second bore width so that the buffer layer 84 is prevented from entering the third bore 98. If desired, a transition area 100 may be provided between the second bore 96 and third bore 98 to serve as a hard stop for the buffer layer 84. The transition area 100 in the embodiment shown defines a chamfered step having an angle (a) relative to a longitudinal axis of the ferrule holder 58. In some embodiments, the chamfered step may be at an angle of from about 20 degrees to about 50 degrees. For example, angle a may be about 30 degrees. [0029] The first, second, and third bore widths have particular relationships with respect to each other and/or the ferrule width/diameter. The purpose of these relationships will soon be more apparent. The same applies to the length of the third bore 98 and the gap maintained between the insertion end 56 of the ferrule 52 and an inner wall 94 of the ferrule holder 58.

[0030] The ferrule holder 58 may also have a groove 102 formed in a bore surface 104 defined by the first end portion 60. In the particular embodiment shown, the groove 102 is an internal thread such that helical ridges 106 are formed around the first bore 92 (the ridges 106 have crests defined by the bore surface 104). Other groove designs are possible, however, as long as at least one groove extends in a circumferential direction so that ridges are formed completely or partially around the first bore 92. For example, in an alternative embodiment the ferrule holder 58 may include discrete grooves extending only in a circumferential direction or both in a circumferential and axial direction. One or more axial grooves may be provided to interconnect the discrete grooves so that at least a portion of the groove pattern in general extends from where the insertion end 56 of the ferrule 52 is located within the first bore 92 to an entrance 108 of the first bore 92. Other variations will be appreciated by persons skilled in the design of fiber optic connectors. The same applies to the manner in which the groove 102 is formed. That is, persons skilled in the design of fiber optic connectors will appreciate different ways of forming the groove 102, such as by machining or molding, based on the groove pattern, material of the ferrule holder 58, and other

considerations.

[0031] Figs. 7A-7E illustrate the process for securing the optical fiber 82 within the ferrule 52. This process terminates the cable 80 with the connector 50 to form a cable assembly. First, as shown in Fig. 7A, the ferrule 52 is inserted into the first bore 92 of the ferrule holder 58. An injection needle 110 (Fig. 7B) or other adhesive delivery device is then introduced into the second end portion 62 of the ferrule holder 58 via the second bore 96. Eventually the injection needle 1 10 is pressed against the transition area 100, which provides a hard stop by limiting further insertion. The chamfered or otherwise tapered shape of the transition area 100 helps align the injection needle 1 10 with the third bore 98 and thereby functions as a centering element for the injection needle 1 10. In the embodiment shown, the injection needle 1 10 has an inner diameter that corresponds to the third bore width. The interaction between the injection needle 1 10 and transition area 100 (i.e., the hard stop) is such that the end/inner diameter of the injection needle 100 is positioned at the entrance to the third bore 98. In essence, a continuous, constant-diameter pathway is established from the injection needle 1 10 to the third bore 98.

[0032] Fig. 7C illustrates how adhesive 90 (e.g., epoxy) is next delivered from the injection needle 1 10 into the ferrule holder 58. The adhesive 90 supplied by the injection needle 1 10 flows through the third bore 98 and into the first bore 92 to fill the gap between the insertion end 56 of the ferrule 52 and inner wall 94 of the first bore 92. Eventually the adhesive 90 is also forced into a ferrule bore 112 ("micro-hole"). Although the groove 102 in the bore surface 104 of the ferrule holder 58 may extend from the gap to the end face of the ferrule holder 58 and thereby provide another path for the adhesive 90, the size and length of the groove 102 is designed to make such a path more resistant to flow than the ferrule bore 112. Accordingly, the adhesive 90 fills the ferrule bore 112 before the adhesive 90— or at least before any significant amount of the adhesive 90— enters the groove 102 and flows around the ferrule 52.

[0033] Eventually the injection needle 1 10 is removed from the ferrule holder 58, as shown in Fig. 7D. The hard stop provided by the transition area 100 and matching diameters of the injection needle 1 10 and third bore 98 help prevent the injection needle 110 from being pulled back through any adhesive. This, in turn, helps prevent the formation of air voids within the adhesive 90 because no adhesive is pulled away from the walls of the ferrule holder 58 by the injection needle 110 (e.g., through surface tension or otherwise) upon withdrawing the injection needle 110.

[0034] Finally, as shown in Fig. 7E, the optical fiber 82 is inserted into the second end portion 62 of the ferrule holder 58. This occurs after the optical fiber 82 has been prepared for insertion by stripping a portion of the buffer layer 84 and a portion of the outer coating 88, leaving the glass portion 86 exposed. The glass portion 86, which may be 125 microns in diameter, extends through the adhesive 90 and into the ferrule bore 112 as the optical fiber 82 is inserted. The insertion continues until the buffer layer 84 remaining on the optical fiber 82 contacts a hard stop provided by the the transition area 100. At this point the glass portion 86 extends through the ferrule bore 112 and beyond (or at least to) the mating end 54. The adhesive 90 is then allowed to cure before performing any remaining steps commonly performed to terminate an optical fiber, such as polishing the end of the glass portion 86.

[0035] Referring back to Fig. 4, the optical fiber 82 is better encapsulated/surrounded by the adhesive 90 compared to conventional designs (e.g., Fig. 3) in the sense that a section of the glass portion 86 is covered by the adhesive 90 behind the ferrule 52. The presence of the third bore 98 in general and the third bore width being smaller than the diameter of the buffer layer 84 results in the buffer layer 84 being spaced from the insertion end 56 of the ferrule 52 by a first distance (Di). The first distance is long enough such that the outer coating 88 of the optical fiber 82 is also spaced from the insertion end 56 of the ferrule 52. In other words, the region of the optical fiber 82 where the outer coating 88 has been stripped away to expose the bare glass portion 86 is also spaced from the ferrule 52 by a distance (e.g., a second distance D₂). This second distance is long enough such that the exposed section of the glass portion 86 begins in the third bore 98, leaving more of the glass portion 86 exposed behind the ferrule 12. Therefore, the adhesive 90 surrounds an increased length of the glass portion 86 within the ferrule holder 58 compared to conventional designs, which helps secure the optical fiber 82. The bond length of the optical fiber 82 is longer, which effectively increases the overall pull strength of the cable assembly. Additionally, the damage-prone region of the optical fiber 82 from stripping the buffer layer 84 and/or outer coating 88 (i.e., where the exposed glass portion 86 begins, as explained above) is now separated from the damage-prone region from insertion (i.e., the region in or near a lead-in 1 16 of the ferrule bore 1 12, as explained above). This helps reduce the likelihood of a fiber break due to stresses in that there is no region of the optical fiber likely to have increased damage.

[0036] The first distance Di may be greater than about 1.5 mm in some embodiments to effectively provide the above-mentioned benefits. For example, the first distance Di may be about 2 mm in some embodiments. And although a gap (g) is shown in the figures between the ferrule 52 and ferrule holder 58, in alternative embodiments there may not be any such gap-

[0037] The first, second, and third bore widths may have particular relationships with respect to each other to provide the above-mentioned benefits. For example, in some embodiments the second bore width may be from about 55% to about 60% of the first bore width. The third bore width may be: a) from about 20% to about 30% of the first bore width, b) from about 22% to about 26% of the first bore width, or c) about 24% of the first bore width. The relationships may alternatively be expressed as ratios involving the first bore width. For example, the ratio of the first bore width to the second bore width may be: a) from about 1.6 to about 1.9, or b) about 1.8. The ratio of the first bore width to the third bore width may be: a) from about 3.9 to about 4.3, or b) 4.1. The ratio of the second bore width to the third bore width may be: a) from about 1.9 to about 2.4, or b) about 2.3. [0038] In terms of more specific embodiments, the first bore width may be: a) from about 2.4 mm to about 2.5 mm, or b) about 2.47 mm. The second bore width may be about 1.37 mm. And the third bore width may be: a) from about 0.13 mm to about 0.85 mm, b) from about 0.5 mm to about 0.7 mm, or c) from about 0.6 mm to about 0.65 mm.

[0039] Again, the adhesive 90 surrounds/encapsulates an increased length of the glass portion 86 within the ferrule holder 58 compared to conventional designs. The encapsulation is able to help prevent fiber breaks because the groove 102 reduces or eliminates the formation of air voids and the presence of debris in the adhesive 90, thereby allowing the adhesive to distribute stresses imparted by environmental conditions or the like more evenly. More specifically, the groove 102 in the ferrule holder 58 serves as a vent while the adhesive 90 cures. Air or gas that may be present in the adhesive 90 is able to move into the groove 102 and ultimately vent to the surrounding. Thus, although air voids or gas bubbles may be less likely to form in the adhesive 90 due to the features above (e.g., the injection needle ID matching the third bore width), the potential for some air or gas to be present in the adhesive 90 nevertheless remains. The air or gas may be present in the adhesive 90 even before the adhesive 90 is supplied by the injection needle 110, for example. There may also be debris present in the ferrule holder 58 prior to supplying the adhesive 90. Rather than becoming trapped in the adhesive 90, the debris can migrate into the groove 102 and possibly even out from the adhesive 90 while the adhesive 90 cures. Thus, the groove 102 serves as a vent for air, gas, and/or debris.

[0040] In one embodiment, the groove 102 has a depth (d) (Fig. 6) relative to the bore surface 104 that is from about 0.8% to about 2.4% of the diameter of the ferrule 52 to provide the above-mentioned effects. Accordingly, for a 2.5 mm-diameter ferrule, the groove has a depth that is from about 20 microns (0.00079") to about 60 microns (0.0024"). One particular example is an embodiment where the groove 102 has a depth of about 40 microns (0.0016").

[0041] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosure. For example, although the embodiments described above are single-fiber connectors, it will be apparent that multi-fiber connectors (e.g., MTP connectors) may be provided with the same features. The bores in the ferrule holder may not necessarily be circular in such embodiments, but a groove may nevertheless be provided to result in the increased gripping and venting mentioned above. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A ferrule holder for a fiber optic connector, comprising:

a ferrule body, the ferrule body being generally tubular having a first end and a second end with an axis extending from the first end to the second end;

a first end portion, the first end portion defining a first bore having a first bore width, the first bore configured to receive at least a portion of a ferrule, the first bore having at least one groove disposed on a bore surface;

a second end portion, the second end portion opposite the first end portion and defining a second bore having a second bore width, the second bore configured to receive at least a section of an optical fiber;

a through passage disposed between the first end portion and the second end portion, the through passage defining a third bore between the first and second bores, the third bore configured and sized to allow a glass portion of the section of the optical fiber to pass from the second end portion to the first end portion, the first bore, second bore and third bore being in fluid communication with each other; and

a transition area between the second bore and the third bore, the transition area defining a stop configured and sized to prevent at least a portion of the section of the optical fiber from entering the third bore, the third bore having a width that is smaller than the second bore.

2. The ferrule holder of claim 1, the second bore width being from about 55% to about 60% of the first bore width.

3. The ferrule holder of claim 2, the third bore width being from about 20% to about 30% of the first bore width.

4. The ferrule holder of claim 3, the third bore width being from about 22% to about 26% of the first bore width.

5. The ferrule holder of claim 4, the third bore width being about 24% of the first bore width.

6. The ferrule holder of claim 1, the ratio of the first bore width to the second bore width being from about 1.6 to about 1.9.

7. The ferrule holder of claim 6, the ratio of the first bore width to the second bore width being about 1.8.

8. The ferrule holder of claim 6, the ratio of the first bore width to the third bore width being from about 3.9 to about 4.3.

9. The ferrule holder of claim 8, the ratio of the first bore width to the third bore width being about 4.1.

10. The ferrule holder of claim 6, the ratio of the second bore width to the third bore width being from about 1.9 to about 2.4.

1 1. The ferrule holder of claim 10, the ratio of the second bore to the third bore being about 2.3.

12. The ferrule holder of claim 1, the transition area defining a generally chamfered step.

13. The ferrule holder of claim 12, the chamfered step being at an angle relative to the longitudinal axis.

14. The ferrule holder of claim 13, the chamfered step being at an angle of from about 20 degrees to about 50 degrees.

15. The ferrule holder of 14, the chamfered step being at an angle of about 30 degrees.

16. The ferrule holder of claim 12, the chamfered step being a centering element for the optical fiber.

17. The ferrule holder of claim 12, the chamfered step being a centering element for an adhesive delivery device.

18. The ferrule holder of any of claims 1 -17, the at least one groove having a depth below the bore surface of from about 20 microns (μιη) to about 60 μιη.

19. The ferrule holder of claim 18, the at least one groove having a depth below the bore surface of from about 40 μιη.

20. The ferrule holder of claim 18, the first portion defining a ferrule receiving portion in communication with the first end, the ferrule receiving portion having a ferrule seat disposed at a distance from the first end, the ferrule seat being an annular surface generally transverse to the axis.

21. The ferrule holder of claim 20, the at least one groove extending along the bore surface from the first end to the ferrule seat.

22. The ferrule holder of claim 21 , the at least one groove being a threaded groove.

23. The ferrule holder of any of claims 1-17, the first bore width being from about 2.4 millimeters (mm) to about 2.5 mm.

24. The ferrule holder of claim 23, the first bore width being about 2.47 mm.

25. The ferrule holder of claim 24, the second bore width being about 1.37 mm.

26. The ferrule holder of claim 25, the third bore width being from about 0.13 mm to about 0.85 mm.

27. The ferrule holder of claim 26, the third bore width being from about 0.5 mm to about 0.7 mm.

28. The ferrule holder of claim 27, the third bore width being from about 0.6 mm to about 0.65 mm.

29. A cable assembly for a fiber optic connector, comprising:

a fiber optic cable having at least one optical fiber;

a ferrule holder, the ferrule holder including:

a first end portion, the first end portion defining a first bore having a first bore width, the first bore configured to receive at least a portion of a ferrule, the first bore having at least one groove disposed on a bore surface; a second end portion, the second end portion opposite the first end portion and defining a second bore having a second bore width, the second bore configured to receive at least a section of an optical fiber;

a through passage disposed between the first end portion and the second end portion, the through passage defining a third bore between the first and second bores, the third bore configured and sized to allow a glass portion of the section of the optical fiber to pass from the second end portion to the first end portion; and

a transition area between the second bore and the third bore, the transition area defining a stop configured and sized to prevent at least a portion of the section of the optical fiber from entering the third bore, the third bore having a width that is smaller than the second bore; and

a ferrule having a mating end and an insertion end, the first end portion of the ferrule holder receiving the insertion end.

30. The cable assembly of claim 29, the fiber optic cable comprising at least an optical fiber and a buffer layer, the optical fiber having a section of the buffer layer removed at an end, revealing a length of the optical fiber.

31. The cable assembly of claim 30, a portion of the buffer layer disposed in the second portion and least partially abutting the stop.

32. The cable assembly of any of claims 29-31, the optical fiber having a section of an acrylate layer removed, revealing a glass fiber.

33. The cable assembly of claim 32, a length of the acrylate layer and the glass fiber disposed in the third bore.

34. The cable assembly of claim 33, a length of the glass fiber disposed in the ferrule.

35. A cable assembly for a fiber optic connector, comprising:

a ferrule holder, the ferrule holder including:

a first end portion defining a first bore that is configured to receive at least a portion of a ferrule, the first end portion having an outside rim and a seat surface;

a second end portion defining a second bore that is configured to receive at least a portion of an optical fiber; a through passage defining a third bore between the first and second bores, the third bore configured and sized to allow a portion of the optical fiber to pass from the second end portion to the first end portion;

a step located between the second bore and the third bore, the step defining a stop configured and sized to prevent at least a portion of the optical fiber from entering the third bore, wherein the third bore has a width that is smaller than the second bore;

a ferrule having a mating end and an insertion end, the first end portion of the ferrule holder receiving the insertion end; and

a fiber optic cable having at least one optical fiber, a portion of the at least one optical fiber being a 125μιη glass fiber surrounded by an adhesive along a centroidal region of the third bore.

36. A method of assembling a cable assembly for a fiber optic connector, comprising the steps of:

inserting a ferrule into a first end of a ferrule holder, the ferrule holder having a first bore, a second bore and a third bore at least partially defining a through passage, and at least one groove disposed on a first bore surface and at least one stop disposed between the second bore and the third bore;

introducing an adhesive delivery device into the second end of the ferrule holder; pressing the adhesive delivery device against the at least one stop;

delivering an adhesive into the ferrule holder;

determining when the adhesive flows out of a ferrule bore disposed in the ferrule; inserting a portion of a fiber optic cable into the second end of the ferrule holder; at least partially abutting a buffer layer against the at least one stop, preventing the buffer layer from entering the third bore; and

inserting a portion of the fiber optic cable into the ferrule.

37. The method of claim 36, wherein delivering an adhesive into the ferrule holder includes injecting the adhesive into the ferrule holder while the adhesive delivery device is pressed against the stop, the adhesive being forced into an adhesive chamber defined by the ferrule holder and the ferrule.

38. The method of claims 36 or 37, further including the step of removing the adhesive delivery device from the ferrule holder.