WO2012103162A1

WO2012103162A1 - A fiber optic drop cable assembly

Info

Publication number: WO2012103162A1
Application number: PCT/US2012/022459
Authority: WO
Inventors: Roberto C ALEJOS VAZQUEZ; Alvin J MCDONALD; Hieu V Tran
Original assignee: Corning Cable Systems Llc
Priority date: 2011-01-25
Filing date: 2012-01-25
Publication date: 2012-08-02
Also published as: AU2011100108A4; CA2825482A1; CN103348274A; CA2825482C; CN103348274B

Abstract

A fiber optic drop cable assembly (10), including: a fiber optic cable (12) including one or more strength members (16) and one or more optic fibers (14) and a fiber optic connector (22) mounted to the one or more optic fibers (14). A demarcation section (26) is positioned behind the fiber optic connector (22) and is operable to separate the fiber optic connector (22) from strength member forces from the one or more strength members (16) of the fiber optic cable (12). The demarcation section (26) includes a protective tube (28) around the one or more optic fibers (14) and a fiber lock down arrangement (34,38) for inhibiting one or more optical fibers (14) from being pulled from the fiber optic connector (22) exerted via the fiber optic cable (12).

Description

A FIBER OPTIC DROP CABLE ASSEMBLY

Related Applications

This application claims the benefit of priority of Australian Patent Application Serial No. 201 1 100108 filed on January 25, 201 1 the content of which is relied upon and incorporated herein by reference in its entirety.

Field of the Invention

The present disclosure relates to connectorized drop cables, and more particularly to connectorized drop cables that may be readily interconnected with a mid-span access location of a fiber optic cable while including a demarcation point for isolating the connector from forces generated in the cable.

Background of the Invention

Within fiber optic networks, flat drop cables are often used to provide the end connection to one or more subscribers, such as at a home or office building.

Within these networks, it is desirable to deploy robust cable assemblies with connectorized flat drop cables to provide simple interconnections while reducing field installation labor, skill and cost.

A problem with robust cable assemblies is that they are expensive and there is a growing need to reduce costs. To do this, one approach is to reduce the amount of strain relief material in the cable, however, doing this can result in strain reaching the connector when the cable is loaded.

A solution is needed that keeps tension from reaching the connector while also being low cost.

It would therefore be desirable to provide a drop cable which alleviates or at least ameliorates the above problems.

It will be appreciated that a reference herein to any matter which is given as prior art is not to be taken as an admission that matter was known or that the information it contains was part of the common general knowledge as at the priority date of the claims forming part of this specification. Summary of the Invention

With this in mind, one aspect of the present disclosure provides a fiber optic drop cable assembly, including: a fiber optic cable including one or more strength members and one or more optic fibers; a fiber optic connector mounted to the one or more optic fibers; a demarcation section positioned behind the fiber optic connector operable to separate the fiber optic connector from strength member forces from the one or more strength members of the fiber optic cable, the demarcation section including:

a protective tube around the one or more optic fibers and a fiber lock down

arrangement for inhibiting one or more optical fibers from being pulled from the fiber optic connector.

In exemplary embodiments this arrangement may inhibit the optic fibers from being removed from the fiber optic connector in use. In a further embodiments, this arrangement may isolate the fiber optic cable's influence on the fiber optic connector, which can only withstand a limited amount of force.

In some embodiments, the fiber optic drop cable assembly may further include an overmold which covers the demarcation section and a portion of the fiber optic cable. Additionally, the overmold may protect the demarcation section.

In exemplary embodiments, the fiber optic drop cable assembly may further include one or more retaining bands that are included at one or more points along the demarcation section to secure the one or more strength members, or the one or more strength members and the protective tube in place. Such an embodiment may provide for improved strength in the demarcation section. Further, the strength members may be bonded into the overmold, providing further strength to the fiber optic cable assembly.

In some embodiments, the fiber lock down arrangement may include one or more of: an adhesive applied to the optic fibers and over the protective tube and the fiber optic cable or an adhesive lined retaining band applied over the protective tube. In these embodiments, the adhesive secures the optic fibers in place and prevents the fiber optic cable from affecting the connection to the fiber optic connector (in particular, the optic fibers are inhibited via the adhesive, from being removed from the fiber optic connector in use).

In exemplary embodiments, the fiber optic cable may include a protective outer jacket. The outer jacket may be made of any suitable environmental protecting material such as nylon. The overmold may extend over the outer jacket to prevent the ingress of water, for example.

The following description refers in more detail to the various features and steps of the present disclosure. To facilitate an understanding of the disclosure, reference is made in the description to the accompanying drawings where the disclosure is illustrated in various embodiments. It is to be understood however that the disclosure is not limited to the embodiments illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a fiber optic cable of the fiber optic drop cable assembly according to the disclosure;

FIG. 2a is a view of the fiber optic drop cable assembly showing a demarcation section;

FIG. 2b is a detailed view of a portion of the demarcation section shown in FIG.

2a;

FIG. 2c is a cross-section of the fiber optic drop cable assembly shown in FIG. 2b;

FIG. 3 is a view of a fiber optic drop cable assembly according to the

disclosure with an overmold applied;

FIG. 4 is a schematic drawing showing the steps involved in preparation of the cable drop assembly for connecting to a connector according to a first embodiment;

FIG. 5a to 5i shows the steps involved in preparing the cable of the disclosure for attachment to a fiber optic connector according to the first embodiment;

FIG. 6 is a schematic drawing of the steps in preparation of the fiber optic cable assembly for attachment to a connector according to a second embodiment;

FIGS. 7a to 7g show the steps involved in preparing the cable for attachment to a connector according to the second embodiment; and

FIG. 8 is a view showing the fiber optic drop cable assembly with an overmold applied.

Detailed Description of Embodiments of the Invention

For clarity, like reference numerals will be used where the parts are the same. Referring now to FIG. 1 , there is shown a cross-section of the fiber optic drop cable assembly 10 of the disclosure including the fiber optic cable 12 which includes optic fibers 14 within a cavity of the cable, and which are housed in a protective tube 28 over a demarcation section 26 (best shown in FIG. 2a). Fiber optic cable 12 may also optionally include water-locking binders 20 such as water-swellable tapes, yarns, or the like for inhibiting the migration of water along fiber optic cable 12. Fiber optic cable 12 also may include strength members 16 which run along side the cavity containing the optic fibers 14 and protective tube 28. Strength members 16 may be encased in a material 18 and may provide tensile strength and bending resistance for fiber optic cable 12. In exemplary embodiments, material 18 (i.e., the inner jacket) may be covered by an outer jacket 24. Outer jacket 24 may be an environmental protective cable jacket, for example, made of such a material as nylon, which is termite resistant. In some embodiments, outer jacket 24 may be omitted, depending on the requirements. As an example, material 18 could form an outer jacket as well as acting, for example, as a filler material. A fiber lockdown arrangement 34, 38 (see FIGS. 2a-2c and 7b-7g) of demarcation section 26 may lock down protective tube 28 and optic fibers 14 together with strength members 16, for example, to provide a strengthened portion of fiber optic cable 12 suitable for inhibiting forces from being transferred from the cable to a fiber optic connector 22 (see FIG. 2a). In exemplary embodiments, this arrangement may inhibit the optic fibers 14 from being removed, for example, pulled from the fiber optic connector in use.

In some embodiments, optic fibers 14 may be in the form of such ribbon designs as a twelve fiber ribbon, for example, but it will be appreciated that other fiber counts and/or types of fiber ribbon could be used as required. Likewise, optic fibers 14 could have a loose arrangement if desired.

Strength members 16 may be any suitable width, or diameter. In exemplary embodiments strength members 16 may have a width or diameter of 1 .25 mm and may be made, for example, of glass reinforced plastic for strength and may be coated, for example, in ethylene acrylic acid (EAA). Of course, strength members may be formed from other suitable materials and/or have other shapes/sizes as desired. Fig. 2a is a schematic diagram of the fiber optic drop cable assembly 10 having a fiber optic connector 22 connected at one end and showing demarcation section 26. The fiber optic drop cable assembly 10 includes a demarcation section 26 downstream from the fiber optic connector 22 to provide strength so that the cable is not strained and so that the optic fibers 14 are inhibited from being removed (i.e., pulled) from the fiber optic connector in use. Put another way, the demarcation section 26 overlaps and ties the end portions of strength members 16 of fiber optic cable 12 with the strength members of a furcation section that has its strength members attached to the connector. Consequently, there is a demarcation between fiber optic cable 12 and the connector.

Demarcation section 26 includes a first end 30a, a second end 30c and a mid point 30b. At first end 30a, one or more retaining bands 32a are applied to the one or more strength members 16 of fiber optic cable 12 and strength members 16 of a sheath section 18' at the overlap in order to secure the strength members 16 and retain them in place. Sheath section 18' may include a cable carcass (e.g., not having any optic fibers inside) similar to fiber optic cable 12, for example. At mid point 30b, one or more retaining bands 32b may also be applied to the one or more strength members 16 to secure strength members 16 of the fiber optic cable 12 with strength members 16 of sheath section 18' at the overlap and retain them in place. At second end 30c, retaining bands 32c may extend over the one or more strength members 16 to secure the strength members 16 in place and retain them in place. It will be appreciated that one or more of the retaining bands 32a, 32b, 32c may extend over all strength members 16 and protective tube 28 in order to retain the items in place and to provide additional strength, and further aligning strength members 16 about protective tube 28 for keeping protective tube 28, and optic fibers 14, substantially within a preferential bending region. More retaining bands 32 could be used, but it has been found that this provides adequate strength while at the same time keeping down cost.

FIG. 2b shows further detail of second end 30c where the material 18 has been stripped away on the top surface to allow for the fiber lockdown arrangement in the form of an adhesive 34 to be applied. The adhesive 34 envelops the strength member 16, the protective tube 28 (and the optic fibers 14 which are within the protective tube 28). The fiber lock down arrangement is provided to secure the optic fibers 14 in place and to prevent the fiber optic cable 12 from affecting the connection to the fiber optic connector 22 (in particular, the optic fibers 14 are inhibited from being removed from the fiber optic connector 22 in use). The steps required in order to provide this arrangement will be further described with reference to FIGS. 5 and 7. Although, this embodiment uses an adhesive for the fiber lockdown other suitable structures are possible according to the concepts disclosed herein.

FIG. 2c more clearly shows the cross-section of Fig. 2b taken along the line A - A and illustrates the outer jacket 24, material 18 and adhesive 34 which locks down the fibers and protective tube 28 (and optic fibers 14) together with strength members 16. This also provides the seal to prevent the overmold material leaking into the cable.

FIG. 3 shows a schematic diagram of overmold 36 which encloses

demarcation section 26 and also captures outer jacket 24. Overmold 36 is applied by bringing two cavities having symmetrical geometry together and then applying a fill material at low pressure to fill the cavity. In exemplary embodiments, the bonding of strength members 16 into overmold 36 provides further strength to fiber optic cable assembly 10. In such embodiments, overmold 36 also may protect the demarcation section 26 from such environmental factors as water and sunlight (UV protection). In some embodiments, overmold 36 may extend over outer jacket 24 to prevent, for example, the ingress of water and the like.

FIG. 4 is a schematic diagram illustrating the steps required in preparing fiber optic cable 12 for creation of demarcation section 26 of the fiber optic cable assembly 10. The outer jacket 24 on the fiber optic cable 12 is removed via a splitting tool or the like back to a point marked A. Next, the material 18 is also removed along side the fiber optic cable 12 back to mark B by using a cable splitting tool or the like. The material 18 is then peeled away (which will be described in more detail with reference to FIG. 5) and removed leaving only a stub of the material 18 exposed at the length of A minus B. Next, the stub in the material 18 is removed on one side of the cable back to mark A, leaving only the underside of the cable having material 18 extending to point B. This effectively leaves a window 18a on one side of the cable of material 18 in which an adhesive 34 can be placed. Next the strength members 16 are cut off at mark C and finally a protective tube 28 is inserted and slid over the optic fibers 14 to the start of mark D. The other half of the cut strength members 16 (not shown) are introduced at a later stage in a furcation arrangement with the strength members 16 to provide more strength to the demarcation section 26 (this will be described with reference to FIG. 5 and 7). A fiber lock down arrangement is then provided to secure the optic fibers 14 in place. This will be described in more detail with regard to FIGS. 5 and 7.

FIG. 5a shows the outer jacket 24 removed to mark A as shown in FIG. 4 and the material 18 has been split to mark B as shown in FIG. 4. In FIG. 5b, the material 18 has been removed and left at point B. Further, the top half of the material 18 has been removed leaving only the window 18a as can be seen in FIG. 5b.

In FIG. 5c the protective tube 28 is slid over the material 18 and then, as shown in FIG. 5d, a fiber lock down arrangement in the form of an adhesive 34 is applied. The protective tube 28 is not slid all the way along to the intersection of the window 18a and the outer jacket 24, but rather at a midpoint on the window 18a. This is to ensure that the adhesive is applied to both the optic fiber 14 and the protective tube 28 so that movement of the optic fiber 14, protective tube 28 and window 18a is inhibited. The adhesive 34 bonds the protective tube 28 and the optic fibers 14 to the fiber optic cable 12 via the window 18a together with the strength members 16. In exemplary embodiments, this arrangement isolates the fiber optic connector 22 from being influenced by fiber optic cable 12, for example, because the fiber optic connector 22 can only withstand a limited amount of force. Further, this arrangement inhibits the optic fibers 14 from impacting the mating of the endface of the connector 22. The endface of the connector 22 will lose physical contact if excessive force is applied to the optic fibers 14 (e.g., force which is more than the connector spring force, for example, two (2) pounds-force).

As shown in FIG. 5e, the strength members 16 of fiber optic cable 12 which were cut (see FIG. 4) are overlapped with the ends of strength members 16 of the furcation section such that the strength members 16 from both portions overlap each other. In FIG. 5e, there are two strength members 16 from each portion running alongside a portion of the demarcation section 26.

To provide addition strength to the demarcation section 26, and to keep the strength members 16 in place and in alignment with each other, retaining bands 32 are applied over each strength member 16 at a mid point 30b of the demarcation section 26. In exemplary embodiments, these retaining bands 32 are used to couple the strength members 16 in the correct location prior to applying the overmold 36 (shown in FIG. 5i). In addition, as shown in FIG. 5g, two additional retaining bands 32a, 32c are applied at first end 30a and second end 30c but also are applied around both the strength members 16 and the protective tube 28 (and the optic fibers 14) to provide additional strength and to generally align protective tube 28 centrally between strength members 16.

As shown in FIG. 5h, the retaining bands 32a, 32c are secured in place. The retaining bands 32a, 32c in this case are heat shrinks which may be secured in place by applying heat. It will be appreciated that any other type of retaining band may be used in order to place and secure the strength members 16 and/or the protective tube 28. For example, a metal crimp ring could be used since it may also increase the coupling force. In a further alternative, the retaining bands could be made out of injection moulded plastic parts which will provide adequate coupling force together with ease of installation.

FIGS. 5i shows the overmold 36 applied over the demarcation section 26 in order to secure and protect the demarcation section 26. Further, the overmold 36 provides additional strength to the demarcation section 26.

FIGS. 6-8 depict an alternative fiber optic cable assembly according to the concepts of the present disclosure, which is similar to the first embodiment. FIG. 6 is a schematic diagram showing the incisions made in the cable in order to prepare the demarcation section 26 and apply the overmold 36 such as described above.

FIG. 7a shows the material 18 being removed as described with reference to FIG. 6 back to point B.

FIG. 7b illustrates the outer jacket 24 removed as shown in at point D of FIG. 6 and includes the cut-off strength members 16, the optic fibers 14 and a fiber lock down arrangement in the form of an adhesive lined retaining band 38 which is applied over the optic fibers 14 and protecting tube 28. The adhesive lined retaining band 38 may be, in exemplary embodiments, in the form of an adhesive tube, but could take any other suitable form. For example, adhesive lined retaining band 38 can be replaced by using a plastic insert and then filling the insert with an adhesive to provide the coupling (fiber lock down) and then insert the coupling into the overmold material to provide fiber locking mechanism.

FIG. 7c shows the protective tube 28 being applied over the optic fibers 14, but underneath a portion of the adhesive lined retaining band 38.

In exemplary embodiments, the protective tube 28 over the optic fibers 14 acts to protect the optic fiber 14 and ensure that the overmold 36 bonds onto protective tube 28 in addition to preventing overmold material bonding over the optic fibers 14 and flowing into the optic fiber cable 12.

FIG. 7d shows adhesive tube 38 having heat applied to it and shrinking down and securing the protective tube 28 to the adhesive tube 38 in addition to retaining the optic fibers 14 in position.

FIG. 7e illustrates a retaining band 32a which is applied over the first end 30a of the demarcation section 26. The retaining band 32a covers both the outer jacket 24 together with the adhesive tube 38, strength members 16, protective tube 28 and optic fibers 14.

FIG. 7f shows a demarcation arrangement where the cable which was cut is applied so that the strength members 16 from fiber optic cable overlap the strength members of the furcation section along each side of the optical fibers like the first embodiment. In other words, the ends of the respective strength members from each portion overlap and are tied together. The retaining band 32a also encompasses the strength members 16. In addition to this, a retaining band 32b is applied at a mid point 30b between the first end 30a and second end 30c of the demarcation section 26. As noted above, with reference to FIG. 3, the purpose of the retaining band 32 is to hold the strength members 16 in place and to better secure the demarcation section 26 ready for the overmold 36 in order to provide strength.

FIG. 7g shows the retaining bands 32 in effect on the demarcation section 26.

In this case the retaining bands 32 are in the form of heat shrinks, but it will be appreciated that any suitable retaining band could be used. The retaining band 32a covers both the outer jacket 24 and the protective tube 28 together with all of the strength members 16 formed by the demarcation (i.e. four strength members). In exemplary embodiments, this arrangement seals the optic fiber cable from the overmold material.

FIG. 8 shows the overmold 36 applied over the demarcation section 26. In exemplary embodiments, the overmold 36 works with the strength members 16 in order to provide tensile coupling. The arrangement can withstand, for example, more than 100 pounds of force. The lock down of the optic fibers 14 via the fiber lock down arrangement also provides additional strength together with the overmold 36.

In exemplary embodiments, the overmold 36 also acts to protect the overall demarcation section 26 while at the same time being flexible and weather resistant. Although the exemplary embodiments of the disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various

modifications, additions and substitutions are possible without departing from the scope of the present disclosure. By way of example, the fiber lock down could be accomplished using other structures such as foam plugs; however, this method may not be as robust as the other methods described. Therefore, the present disclosure is not limited to the above-described embodiments but is defined by the following claims.

Claims

What is claimed is:

1 . A fiber optic drop cable assembly, including:

a fiber optic cable including one or more strength members and one or more optic fibers;

a fiber optic connector mounted to the one or more optic fibers;

a demarcation section positioned behind the fiber optic connector operable to separate the fiber optic connector from strength member forces from the one or more strength members of the fiber optic cable, the demarcation section including: a protective tube around the one or more optic fibers and a fiber lock down arrangement for inhibiting one or more optical fibers from being pulled from the fiber optic connector exerted via the fiber optic cable.

2. The fiber optic drop cable assembly of claim 1 , further including an overmold which covers the demarcation section and a portion of the fiber optic cable.

3. The fiber optic drop cable assembly of claim 2, wherein one or more retaining bands are included at one or more points along the demarcation section to secure the one or more strength members, or the one or more strength members and the protective tube in place.

4. The fiber optic drop cable assembly of any of claims 1 -3, wherein the fiber lock down arrangement includes one or more of: an adhesive applied to the protective tube and the fiber optic cable or an adhesive lined retaining band applied over the protective tube.

5. The fiber optic drop cable assembly of claim 1 , wherein the fiber optic cable includes a protective outer jacket or a fiber optic connector.

6. A method of making a fiber optic drop cable assembly, comprising the steps of: preparing a fiber optic cable for creation of a demarcation section, including: removing a first length of a protective outer jacket;

removing a second length of a cable material;

cutting strength elements to a third length; installing a buffer tube about a fiber optic ribbon;

installing a locking arrangement;

installing a sheath section;

securing at least one strength member of the fiber optic cable to at least one strength member of the sheath section;

securing the strength members to the buffer tube; and

overmolding the demarcation section.

7. The method of claim 6, including the step of leaving a section of the cable material protruding from the fiber optic cable.

8. The method of claim 7, including removing a top half of the section of the cable material.

9. The method of claims 6-8, the step of installing the locking arrangement including the step of applying an adhesive material to the cable material, the buffer tube and the fiber optic ribbon.

10. The method of claim 6, the step of installing the locking arrangement including installing an adhesive lined retaining band about the fiber optic ribbon and positioning the adhesive lined retaining band proximate to the fiber optic cable.

1 1 . The method of claim 10, the step of installing the locking arrangement including installing the buffer tube in a position within the adhesive lined retaining band and securing the adhesive lined retaining band to the buffer tube and the fiber optic ribbon.

12. The method of claim 6, the step of securing the strength members to the buffer tube including installing at least one retention band about the buffer tube and the strength members, the at least one retention band being selected from the group consisting of one of a heat shrink and a metal band.

13. The method of claim 6, the step of installing the sheath section including placing the fiber optic ribbon throughout the length of the sheath section.

14. The method of claim 6, including the step of installing a fiber optic connector to one of an end of the sheath section or and end of the fiber optic cable.

15. The method of any of claims 10-14, the step of overmolding the demarcation section including overmolding at least a portion of the fiber optic cable and at least a portion of the sheath section.