HK1150076B - Fiber optic distribution cables and structures therefor - Google Patents

Abstract

Fiber optic distribution cables and methods for manufacturing the same are disclosed. The fiber optic distribution cables present one or more optical fibers outward of the protective covering for distribution of the same toward the subscriber. In one fiber optic distribution cable, a length of distribution optical fiber that is removed from the distribution cable and presented outward of the protective covering is longer than the opening at access location. In another embodiment, a demarcation point is provided for inhibiting the movement (i.e., pistoning) of the distribution optical fiber into and out of the distribution cable. In still another embodiment, an indexing tube is provided for indexing a tether tube within the indexing tube for providing the distribution optical fiber with a suitable excess fiber length. Additionally, other embodiments may include a fiber optic distribution cable having a dry construction and/or a non-round cross-section.

Description

Optical fiber distribution cable and structure thereof

Technical Field

The present invention relates generally to an optical fiber distribution cable, a method of making the optical fiber distribution cable, and a tool and kit for use therewith. More particularly, the present invention relates to an optical fiber distribution cable for distributing optical fibers to subscribers, such as in fiber to the home or street applications (FTTx), a method of making the same, and a tool and kit.

Background

Communication networks are used to transmit various signals such as voice, video, data transmissions, and the like. Conventional communication networks utilize copper wire cables to transmit information and data. However, copper cables have disadvantages because they are large, heavy and reasonable cable diameters can only transmit relatively limited amounts of data. Optical cables therefore replace most copper cables in long haul communication network lines, providing greater bandwidth capacity for long haul lines. However, most communication networks still use copper cables on the subscriber side of the central office for distribution purposes and/or drop lines. In other words, users can only obtain a limited amount of available bandwidth due to the copper cables in the communication network. In other words, copper cables are a bottleneck that prevents users from fully utilizing the relatively high bandwidth capacity of long-haul line fibers.

As optical fibers are used deeper into communications networks, users will be able to obtain increased bandwidth. However, a definite obstacle to distributing optical fibers from fiber optic cables to subscribers is that they are difficult and expensive. For example, one conventional method of accessing optical fibers for distribution from a fiber optic cable requires a relatively long break in the cable jacket to access the appropriate length of optical fiber. Fig. 1 depicts a fiber optic cable 10 having a break B in the fiber optic housing having a break length BL. The breach length BL depends on the length OF the optical fiber OF required for the process used for the access procedure. For example, if a craftsman needs 30 centimeters OF distribution optical fiber OF for the access procedure, breach length BL has a slightly longer length, e.g., 35 centimeters, to provide 30 centimeters OF optical fiber OF outside the cable jacket. More particularly, the desired optical fiber is selected for distribution and cut near downstream OF breach B and then deployed out OF the cable near upstream OF breach B to provide the craftsman with the desired length OF optical fiber OF. One disadvantage of this approach is that the break length BL is relatively long and undermines the protection provided by the cable jacket. In other words, the breach B has to be closed and/or sealed in order to provide a suitable protection, which requires a relatively large protective layer, which is bulky, heavy and/or stiff. As a result, the distribution cable is too large and/or stiff at the distribution location, making it difficult, if not impossible, to place an effective path for cable distribution through a jacket, tube, or the like during installation.

Another conventional method of accessing optical fibers for distribution from a fiber optic cable requires splitting the cable jacket at two locations, as shown in fig. 2. FIG. 2 depicts fiber optic cable 10' having a first cable jacket breach B1 and a second (i.e., downstream) cable jacket breach B2 separated by an effective distance D. For example, the typical distance D between cable jacket splits B1 and B2 is about 30 centimeters. The desired optical fiber OF is then selected for distribution to the subscriber and cut at the location OF the second cable jacket breach B2. Next, the severed optical fiber OF is positioned at the first cable jacket breach B1 at the second cable jacket breach B2 location and then pulled toward the first cable jacket breach B1 until protruding therefrom, as shown. Simply stated, the optical fiber OF for distribution must be positioned twice (once in each OF the jacket breaches B1 and B2) and the length OF the optical fiber OF protruding from the first cable jacket breach B1 depends on the distance D between the cable jacket breaches B1 and B2. Typically, cable housing splits B1 and B2 are closed, such as by overmolding or with heat shrink tubing, to provide environmental protection. Thus, such conventional procedures for accessing and providing optical fibers for distribution are time consuming, may damage the optical fibers, and/or create relatively large protrusions after sealing a breach in the cable jacket.

Accordingly, a low cost solution for distribution cables with a smooth installation process is desired. Furthermore, the solution also needs to provide a relatively small footprint, flexible dispensing location, easy repair/repair, and/or versatility of connections. In addition, the reliability and robustness of the distribution cable assembly needs to withstand the harsh external environment. The present invention provides a reliable and low cost solution that enables a craft to smoothly distribute optical fibers from a fiber optic cable to a subscriber in a relatively small and flexible distribution location.

Disclosure of Invention

One aspect of the present disclosure is directed to a fiber optic distribution cable that guides optical fibers to a subscriber. The optical distribution cable includes a plurality of optical fibers and a distribution optical fiber within a protective layer. The distribution optical fiber is one of the plurality of optical fibers of the fiber optic distribution cable and is presented outwardly of the protective covering at an access location for distribution to a subscriber. The access location has a length AL and the distribution optical fiber removed from the fiber optic distribution cable has a distribution optical fiber length DOFL, wherein the distribution optical fiber length is about 5/4AL or greater.

Another aspect of the present invention relates to a fiber optic distribution cable that includes a plurality of optical fibers, a protective covering, distribution optical fibers, and a demarcation point. The distribution optical fiber is one of the plurality of optical fibers of the fiber optic distribution cable and the distribution optical fiber is presented outwardly at an access location of the protective covering. The demarcation point is disposed about a portion of the distribution optical fiber to inhibit movement of the distribution optical fiber. In other words, the demarcation point prevents the distribution optical fiber from pistoning into or out of the fiber optic distribution cable.

Yet another embodiment of the present invention is directed to a fiber optic distribution cable that includes a plurality of optical fibers, a protective covering, at least one distribution optical fiber, an indexing tube and a tether tube. The at least one distribution optical fiber is selected from one optical fiber of the fiber optic distribution cable and protrudes from the access location of the protective covering. The tether tube is disposed about a portion of the at least one distribution optical fiber to protect the at least one distribution optical fiber. Also, the tether tube is attached at a predetermined position relative to the indexing tube to obtain fiber lengths on the distribution fibers. In addition, other steps that may or may not require other components can be performed on the fiber optic distribution cable by the process. For example, a transition tube (transition tube) may be slid over the distribution optical fiber to protect the distribution optical fiber.

It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together with the description, serve to explain the principles and operations of the invention.

Drawings

Fig. 1 is a perspective view of a conventional method of opening a relatively large length of fiber optic cable to access a suitable length of optical fiber for fiber distribution.

Fig. 2 is a perspective view of another conventional method of opening two locations on a fiber optic cable to access a suitable length of optical fiber for fiber distribution.

Fig. 3 is a perspective view of a generic fiber optic distribution cable showing distribution optical fibers protruding from a first access location of the fiber optic distribution cable after the distribution optical fibers have been severed at a cutting location within the fiber optic distribution cable according to the present invention.

Fig. 3a-3g are cross-sectional views of preferred fiber optic distribution cables that are representative of the generic fiber optic distribution cable of fig. 3.

Fig. 4 is a flow chart of steps of a method for manufacturing the fiber optic distribution cable of fig. 3 according to the present invention.

Fig. 5 and 5a-5f are perspective views of an illustrative tool (explanatory tool) and variations thereof, respectively, for cleaving optical fibers within a fiber optic distribution cable according to the present invention.

Fig. 6a depicts the tool of fig. 5 with the cutting element looped around the plurality of distribution optical fibers prior to severing of the fiber optic distribution cable of fig. 3.

Fig. 6b depicts the tool of fig. 5 inserted into the fiber optic distribution cable of fig. 3 for severing the distribution optical fiber at a severing location within the fiber optic distribution cable.

Fig. 6c depicts an exploded view of the fiber optic distribution cable of fig. 3 and a kit of parts according to the present invention.

Fig. 6d is a cross-sectional view of the cap of fig. 6 c.

Fig. 6e is a perspective view of the fiber optic distribution cable of fig. 3 and the set of parts of fig. 6c assembled thereon in accordance with the present invention.

Fig. 6f depicts the assembly of fig. 6e after the cap has been protected with a suitable material.

Fig. 6g depicts the tool of fig. 5 positioned about a portion of a fiber optic ribbon to cleave the ribbon along the length of the ribbon prior to severing the distribution optical fibers at the severing location.

Fig. 6h is a perspective view of the fiber optic distribution cable of fig. 3 having an alternative cap configuration according to the present invention;

fig. 6i is another fiber optic distribution cable having a demarcation point disposed on a distribution optical fiber according to the present invention.

Fig. 7 is a side view of a fiber optic distribution cable assembly according to the present invention.

Fig. 8 is an exploded view of the fiber optic distribution cable assembly of fig. 7 according to the present invention.

Fig. 9 is a cross-sectional view of the fiber optic distribution cable assembly of fig. 7 along line 9-9.

Fig. 10 is another cross-sectional view of the fiber optic distribution cable assembly of fig. 7, taken along line 10-10, and fig. 10a is a partial view of the cross-sectional view of fig. 10.

Fig. 11 is another cross-sectional view of the fiber optic distribution cable assembly of fig. 7, taken along line 11-11.

Fig. 12-16 are perspective views showing portions of the distribution cable assembly of fig. 7 at various stages.

Fig. 17 is a perspective view of another fiber optic distribution cable including a ferrule according to the present invention.

Fig. 18 is a perspective view of the distribution cable of fig. 17 with a portion of the overmold removed for clarity.

Fig. 19 is a perspective view of a tether tube having a front connector plug attached thereto for plug-and-play connection in accordance with the present invention.

Fig. 19a is a perspective view of a ferrule attached to a distribution optical fiber according to the present invention.

Fig. 19b-19e are perspective views of an assembly for achieving latching and connectivity in accordance with the present invention.

Fig. 20 is a perspective view of an alternative seal portion according to the present invention.

Fig. 20a-20c are perspective views of alternative fiber optic distribution cables according to the present invention.

Fig. 21 is a side view of a fiber optic distribution cable having a safety pull out device according to the present invention.

Detailed Description

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Distribution cables and methods of making the same are disclosed in which one or more optical fibers of the cable are presented for distribution outside of a protective layer, such as a cable jacket. Additionally, methods of tooling useful for making distribution cables are also disclosed. In one embodiment, a relatively small opening is formed at the access location of the fiber optic cable to leave a relatively small access footprint on the fiber optic cable (i.e., a small portion of the protective covering and/or other cable components is removed). While forming a relatively small opening (e.g., cable jacket breach) at the access location, the present method advantageously provides a length of distribution optical fiber protruding from the access location that is longer than the opening at the access location. For example, if the opening in the cable jacket is about 2 centimeters, the distribution optical fiber is severed within the distribution cable and has a length of about 2.5 centimeters or more. In other words, while a relatively small opening or breach must be handled at each access location of the protective covering, the process has the appropriate distribution fiber length for distribution. Unlike conventional acquisition methods, the present embodiment of the invention does not require: (1) a plurality of cable breaches at a single access location; or (2) a relatively long cable split or opening approximately commensurate with the length of the distribution optical fiber. Thus, conventional access methods result in a stiff, bulky and relatively large dispensing footprint after reclosing and sealing the access location for protection. However, the access location for the fiber optic distribution cable of the present invention is relatively small and flexible in length and/or cross-sectional area, thereby overcoming the problems of conventional methods of accessing fiber optic cables to provide a suitable length of distribution optical fiber outward from the protective covering. However, some aspects of the invention may be practiced with more than one breach or other aspects of conventional approaches.

Fig. 3 is a perspective view of a generic distribution cable 30 (hereinafter distribution cable 30) according to the present invention. Distribution cable 30 depicts distribution optical fibers 32 protruding from a first access location 38a on a protective covering 38, such as a cable jacket. As described above, the first access location 38a has an access length AL that is the length of the opening or breach in the protective layer 38. Further, the distribution optical fiber 32 has a distribution optical fiber length DOFL that is about 5/4 times or more the access length AL, and more preferably about 3/2 times or more the access length AL. In other words, distribution optical fibers 32 are cut or severed at a cutting location CL within distribution cable 30. For example, if the access length AL (i.e., the opening or breach of the protective covering 38 at the first access location 38 a) is 5 centimeters, the distribution optical fiber 32 has a distribution optical fiber length DOFL of about 6 centimeters or greater, and more preferably, about 7.5 centimeters or greater. Simply stated, the distribution optical fiber length DOFL is greater than the access length AL of the first access location 38a because the distribution optical fiber is severed from within the fiber optic cable. The present invention thus provides the appropriate length of distribution optical fiber for the process with a relatively small opening or cleft in the protective covering, thereby allowing for a relatively small footprint for the selected distribution configuration. Of course, cable 30 may have any suitable number of distribution optical fibers 32 protruding from first access location 38 a. Likewise, fiber optic distribution cables can have any number of access locations disposed along the cable, if desired. Fiber optic distribution cables of the present invention may also be constructed using one or more different methods and/or components depending on the type of fiber optic cable selected and the type of connection desired.

Distribution cable 30 is generic in that it represents an optical cable that allows for the cutting of distribution optical fibers within a protective layer in accordance with the present invention. By way of example, FIGS. 3a-3g depict samples of cable configurations useful in accordance with the present invention. FIGS. 3a-3g depict, respectively: stranded loose tube optical cable (fig. 3 a); slotted core optical cables (fig. 3 b); single tube optical cable (fig. 3 c); flat ribbon cable (fig. 3 d); indoor optical cables (fig. 3 e); a cable having a plurality of tubes bundled together (fig. 3 f); fiber optic cable with bundle (fig. 3 g). Simply stated, distribution cable 30 can have any suitable construction. Furthermore, the present invention is also applicable to optical fibers of different cable types, such as multiple ribbons, loose optical fibers, buffered optical fibers, bundles of optical fibers, and the like.

Fig. 4 illustrates a flow chart 40 of a method of manufacturing a distribution cable utilizing the principles of the present invention. First, at step 41, a distribution cable, such as distribution cable 30, having a plurality of optical fibers (not visible) and a protective covering, such as a cable jacket, needs to be provided. Next, step 43, the making of an opening (opening or breach in protective covering) at a first access location of the distribution cable is performed to access one or more optical fibers within the distribution cable. More particularly, the protective layer is opened at the first access location to have an access length AL sufficient to practice the methods disclosed herein. One reason this method of the present invention is advantageous over previous dispensing methods is that only a relatively small opening is required at each access location. In addition, depending on the configuration of the distribution cable selected, other cable components or portions thereof may need to be cut, opened, and/or removed to access the desired optical fibers within the distribution cable. For example, a craftsman may have to remove or cut away water swellable tapes, armor, strength members, etc. to gain access to a plurality of optical fibers within a distribution cable. Thereafter, method 40 entails step 45 of selecting at least one of the plurality of optical fibers of the distribution cable as a distribution optical fiber.

The process then performs a step 47 of cutting (i.e., cleaving) the distribution optical fiber 32 at a cutting location within the distribution cable at a downstream location. As used herein, a cut location within a distribution cable refers to a location along the distribution cable where the protective covering is not split. As best shown in fig. 6a and 6b, this cutting step is performed by positioning or inserting a suitable cutting tool within the distribution cable, thereby allowing the tool to cut one or more distribution optical fibers at a cutting location within the distribution cable. Thereafter, a step 49 of guiding the distribution optical fiber through the opening at the first access location such that a portion of the distribution optical fiber is disposed outside of the protective covering is performed. Other optional steps are also possible after the distribution optical fibers are provided outside the protective layer. For example, the distribution cable can optionally include other steps and/or components such as providing a demarcation point, a transition tube, or a component suitable for optical connection.

The method of flow 40 can be used for both factory and field applications due to its simplicity, reliability and process success. For example, the method of process 40 requires only one access location opening at each distribution location and the distribution optical fiber length DOFL provided at the access location is greater than the length of the cable breach or opening. Other methods may include one or more optional steps such as providing other components and/or other steps. More particularly, the method may also comprise one or more steps, such as: providing a transition tube to guide the distribution optical fiber (fig. 6 c); providing a cap to close the first access position (fig. 6 c); providing a demarcation point for the distribution optical fiber (fig. 6 i); providing tether tubes for distribution of optical fibers (fig. 10); providing a plug for indexing the tube and/or tether tube (fig. 10 a); sealing the first access position (fig. 14); providing an indexing tube to create excess fiber length or ribbon length in one or more distribution fibers (fig. 15); and/or attaching ferrules, connector bodies, etc. (fig. 17 and 18). Additionally, a set of components disclosed herein can be used to implement the methods and/or construct the distribution cables of the present invention.

Fig. 5 depicts an illustrative tool 50 for cleaving one or more distribution optical fibers within a distribution cable in accordance with the present invention. The tool 50 has an elongated body 52 with a first end 54 having an opening 56 and a cutting element 58. Cutting element 58 flexibly fits within opening 56 and is movable through opening 56 when pulled to sever or cut one or more optical fibers at a cutting location within the distribution cable. More specifically, pulling cutting element 58 causes the optical fibers captured by cutting element 58 to bend away from their final bend radius in order to be severed or cut. As best shown in fig. 6a, the cutting element 58 is loose with respect to one or more distribution optical fibers and both ends 58a and 58b of the cutting element 58 are guided through the opening 56 and positioned toward the upwardly bent second end of the tool 50 to form a handle for use by an operator. Thereafter, tool 50 is slid into the distribution cable to the desired cutting location (i.e., the loop in the cutting element is proximate the cutting location), and then both ends 58a, 58b of cutting element 58 are pulled until one or more distribution optical fibers within the distribution cable are severed. Thus, the length of the distribution optical fiber length DOFL is greater than the length of the breach in the protective covering because the distribution optical fiber is severed within the distribution cable.

Cutting element 58 requires certain features to cut or sever one or more distribution optical fibers. For example, the cutting element 58 must have the necessary strength to sever the distribution optical fiber without breaking when pulled, and flexibility to loop into the at least one opening of the tensile body when pulled to move through the at least one opening. The severing element 58 can use any suitable structure, size, shape, and/or material to meet these requirements. Examples include structures such as one or more filaments, threads, rovings or yarns, and examples of shapes include circular, rectangular, and the like. In one embodiment, the severing element 58 is an aramid material such as Kevlar (Kevlar) having a denier of about 2450. However, the cutting element 58 may be formed from other suitable materials, for example, polymeric materials such as polyester or nylon, fishing line, metallic materials such as steel wire, cotton materials, and the like. For example, one embodiment utilizes, for example, a trademark of50 pounds of test fishing line.

Likewise, the elongated body 52 may be formed of any suitable material, such as metal or plastic, that allows for suitable sizing to fit within a selected distribution cable and also maintain some flexibility while having the necessary strength. As shown in fig. 5a, the elongated body 52 is formed from a metal strip having a tool height TH of about 2 millimeters or less and a tool width TW of about 8 millimeters or less, thereby achieving flexibility in one direction. As shown, the opening 56 is a generally rectangular shape that is about 5 millimeters long and about 2 millimeters wide, but the opening 56 can have other suitable sizes and/or shapes. Of course, the size and shape of the elongated body can be tailored to the spatial size and shape of the distribution cable, and thus the tool must fit within such a rectangle or circle. For example, a tool having an arcuate or rod shape may be better suited for sliding into a circular buffer tube. In addition, other variations of the tool 50 are also contemplated by the present invention.

Fig. 5b-5f depict variations of an illustrative tool according to the present invention. Fig. 5b depicts a portion of a tool 50b having a plurality of openings 56b near the first end. As shown, tool 50b has three openings 56b, so the position of cutting element 58 may vary across the width of tool 50 b. Fig. 5c depicts a portion of a tool 50c having an opening 56c that is non-circular and large to easily pass the end of the severing element therethrough and guide the severing element as it is pulled. Likewise, the opening of the tool need not be closed on itself. Fig. 5d and 5e depict a portion of tools 50d and 50e, respectively, in which openings 56d and 56e both communicate with the outer edge of the tool, thereby allowing cutting element 58 to be more easily inserted into the tool. Fig. 5f depicts a tool 50f having a handle 57f for pulling a movable portion 59f of the cutting element 58 to sever one or more distribution optical fibers. As shown, the two ends 58a and 58b of the cutting element 58 are wrapped around protrusions (not labeled) of the movable portion 59f of the handle 57f so that when the movable portion 59 is pulled in the direction indicated by the arrow, the two ends 58a and 58b of the cutting element 58 are actuated, thereby pulling the two ends 58a and 58b of the cutting element 58 to cut the distribution optical fiber. Of course, other tool variations can be used to pull, wind, guide and install, or otherwise modify the disclosed tool to sever the distribution optical fiber.

Fig. 6a and 6b illustrate the processing of distribution cable 30 of fig. 3 using tool 50. More particularly, fig. 6a illustrates distribution cable 30 after the opening is made at the first access location and one or more optical fibers are selected as the distribution optical fibers. As further shown, cutting element 58 of tool 50 is looped over a selected plurality of distribution optical fibers 32. In other words, the tool 50 and its cutting element 58 are positioned to cut the plurality of optical fibers captured by the loop of the cutting element 58. Further, both ends 58a and 58b of the severing element 58 are moved towards the second end 55 of the tool 50 and the severing element 58 is concealed (snugged-up) with respect to the distribution optical fiber 32. Thereafter, tool 50 is inserted within distribution cable 30 and slid to a downstream location (e.g., away from the head of the distribution cable). Fig. 6b illustrates insertion of tool 50 into distribution cable 30 to sever the plurality of distribution optical fibers at cutting location CL. Thereafter, ends 58a and 58b of cutting element 58 are pulled with sufficient force to sever distribution optical fiber 32 disposed between the loop of cutting element 58 and elongated body 52. After tool 50 is removed from within distribution cable 30, distribution optical fibers 32 severed within distribution cable 30 are routed through an opening at first access location 38a such that a portion of the distribution optical fibers are routed outside protective covering 38a, as shown in fig. 3. In this regard, the distribution cable of the present invention may also include other manufacturing steps and/or other components to manufacture other assemblies of the present invention, such as splicing the distribution optical fibers and/or attaching ferrules to the distribution optical fibers.

For example, fig. 6c shows distribution cable 30 of fig. 3 and a kit of parts 60 for closing first access location 38a and routing distribution optical fibers 32 to the exterior of protective covering 38. More particularly, kit of parts 60 includes a transition tube 62 that guides and protects distribution optical fibers 32 outside of protective covering 38 and a cap 64 that closes first access location 38a and shields other optical fibers within the distribution cable. In this embodiment, the transition tube allows limited movement of the distribution optical fiber into and out of the distribution cable (i.e., allows for pistoning) when it is bent. Generally, when the transition tube is utilized as a pass-through conduit, the transition tube allows the distribution optical fiber to have a pass-through configuration that allows limited movement thereof. In another embodiment, a demarcation point is provided with respect to the distribution optical fiber at or near the access location to generally prevent its plunger from entering or exiting the distribution cable. The use of a pass-through structure or demarcation point structure may depend on the distribution cable structure and/or cable characteristics, such as the degree of fiber coupling within the cable. In other words, some cable designs are better suited for free-running, while other cable configurations are better suited for the demarcation point. Furthermore, if the distribution optical fiber is typically material fixed, the transition tube may be used in the manner of a demarcation point, thereby creating a demarcation point.

As described above, cap 64 includes an opening 64a, such as a circle, rectangle, etc., sized to receive transition tube 62 therethrough. After distribution optical fibers 32 are routed through first access location 38a and out protective covering 38, transition tube 62 is slid over distribution optical fibers 32 and pushed into a portion of distribution cable 30, as shown in fig. 6 e. In other words, transition tube 62 protects and guides the distribution optical fibers because they transition from a position within the distribution cable to a position outside the distribution cable when some movement is allowed. The exposed end of transition tube 62 is then directed through opening 64a of cap 64 so that transition tube 62 extends therefrom, as shown in phantom in fig. 6 c. The transition tube 62 is formed of a suitable material that is flexible, but it may also be formed of a relatively rigid material. For example, the transition tube 62 is a PTFE tube (i.e., a PTFE tube)A tube) that is capable of withstanding the high temperatures applied. In another embodiment, the PTFE transition tube is chemically etched. Likewise, cap 64 is formed from a suitable material such as PTFE or other flexible material, although cap 64 may also be formed from a relatively rigid material. Furthermore, the cap for closing the access position can have other configurations. Fig. 6h shows a cap 64' that utilizes a notch (not labeled) as an opening to guide the transition tube and/or optical fiber outside of the protective layer. In other words, the distribution optical fiber and/or the transition tube pass through the notch of cap 64' and a portion of the access location. Of course, other kits of parts can include other components such as a tool for severing a distribution optical fiber, tether tubes, indexing tubes, shrink tubing, sealing components, plugs, and/or front connection taps that can include ferrules, receptacles, connector bodies, and the like. Likewise, other distribution cable assemblies of the present invention can include other components or steps described herein.

As shown in fig. 6e, the cap 64 is larger (i.e., longer) than the opening of the access location AL and is positioned so that a portion thereof protrudes from the underlying protective layer 38. In addition, cap 64 may be relatively thin and flexible so that it is easily tucked under protective covering 38 by the craft. For example, cap 64 is sized so that about 5 millimeters long of cap 64 at the end is disposed under protective layer 38 and cap 64 has a thickness of about 0.3 millimeters. After cap 64 is positioned, a step of securing cap 64 with material 66 may be performed, as shown in fig. 6 f. In the present embodiment, material 66 is a hot melt adhesive available from Loctite under the trade name Hysol83245-232, but any other suitable material or method may be used to secure the cap, such as glue, adhesive, silicone, sonic welding, etc., so long as the material used is compatible with the optical fibers, ribbons, protective coatings, and/or other components with which it may come into contact. In addition, cap 64 and/or material 66 may also function to prevent any optional sealing material, such as an over-molded sealing material, from entering the distribution cable. In addition, material 66 can be applied under cap 64.

Of course, cap 64 can have other suitable configurations and can vary depending on the distribution cable. For example, cap 64 can be shaped or cut to match the shape of the portion of protective covering 38 removed from the distribution cable. In other words, the cap has a length and a width that match the length and the width of the opening of the first access position, and has an inner and outer shape that matches the shape of the protective layer of the removed portion. Thus, the cap closes the first access position with a generally flat surface. By way of example, a generally circular distribution cable jacket would utilize a cap having similar inner and outer diameters as a cable jacket having the appropriate arc length, axial length, and width to match the access location opening. Fig. 6d shows a cross-sectional view of cap 64, with cap 64 shaped to close the access location of a generally round distribution cable, but other shapes, profiles, and/or lengths of caps are possible that can be tailored to fit other fiber optic cables and/or openings. Advantageously, cap 64 may be secured to first access location 38a using a suitable material or method, such as adhesive, glue, sonic welding, or the like.

As described above, the method of process 40 requires selecting at least one of the plurality of optical fibers of the distribution cable as the distribution optical fiber. Any configuration and/or type of optical fibers can be present within the distribution cable and the principles of the present invention can be used with different configurations and/or types of optical fibers. For example, the present invention is suitable for cables with bare optical fibers (e.g., the stranded loose tube cable of fig. 3a) and cables with one or more ribbons (e.g., the slotted core cable of fig. 3b, the single tube cable of fig. 3c, or the flat ribbon cable of fig. 3 d). Still other distribution cables may have buffered optical fibers (fig. 3e), fiber bundles, and the like. Distribution cables having buffered optical fibers may require more force to be applied to the cutting element to sever the buffer and optical fibers, but are also within the scope of the present invention. After selecting the optical fibers for distribution, the remaining portion of the distribution cable and the selected optical fibers may be separated at the access location using a cleaving tool (not shown), such as a thin metal or plastic sheet.

In cables utilizing ribbons, it may be desirable to select less than all of the optical fibers in the ribbon as distribution optical fibers. For example, four distribution fibers are required at the access location and each ribbon of the distribution cable has twelve fibers. As shown in fig. 6g, ribbon R has a cleft S formed by the process between the fourth and fifth fibers of ribbon R at a short distance near the access location. Thus, the desired optical fibers for distribution are separated to cleave the ribbon R along their axial length before they are severed. More particularly, FIG. 6 shows that the severing element 58 of the tool 50 is then looped around the four separate optical fibers of the cleaved ribbon R, and the tool 50 is positioned prior thereto. Thereafter, a breach S in the ribbon is propagated within the distribution cable along its axial length by the tool. In other words, as described above, before tool 50 is slid within the distribution cable to the cutting location CL, cutting element 58 splits the ribbon along its axial length by shearing the bonding material of the ribbon between the desired optical fibers as tool 50 is slid into position to the cutting location. Thereafter, one or more selected distribution optical fibers are cleaved using the tool as described above.

As noted above, the distribution optical fiber is typically secured against movement. Fig. 6i depicts a distribution cable 30 'having a demarcation point 80 for generally inhibiting movement of distribution optical fibers 32' at or near an access location. Generally, the demarcation point 80 secures the distribution optical fiber near the access location to inhibit movement of the distribution optical fiber to reduce undue stress on the distribution optical fiber when bent, thereby preserving optical performance. One method for providing demarcation point 80 is by applying or injecting a suitable material around distribution optical fiber 32' at the access location. For example, a demarcation material may be applied and/or injected into the distribution cable around the distribution optical fibers to inhibit movement of the distribution optical fibers. Any suitable material may be used as a demarcation point disposed about the distribution optical fiber, such as hot melt adhesive, silicone, and the like. However, the material used as a demarcation should be compatible with the optical fibers, ribbons, protective layers, and/or other components with which it may come into contact. Further, the demarcation point 80 may be used with or without the cap 64', and if a cap is used, the demarcation point 80 may be located either inward or outward of the cap. If the cap is omitted, the demarcation point 80 may also serve to prevent any optional sealing material, such as an over-molded sealing material, from entering the distribution cable.

Additionally, the principles of the present invention may be implemented without cutting distribution optical fibers from within the distribution cable. For example, fig. 6i depicts a typical distribution cable 30 'having first and second openings 38 a' and 38b 'in a protective layer 38'. In other words, the demarcation point 80 is applied in a conventional access method wherein the cable is opened at two locations 38a 'and 38 b' to obtain the desired length of distribution optical fiber. Additionally, one or more of the openings 38a ' and 38b ' may be closed by a suitable cap 64 ' as described. Likewise, the methods described below by directing the provision of excess fiber length to the distribution optical fiber may be performed without severing the distribution optical fiber from within the distribution cable.

Fig. 7 and 8 depict perspective and exploded views, respectively, of a particular illustrative fiber optic distribution cable assembly 100 (hereinafter cable assembly 100) according to the present invention. As best shown in fig. 8, distribution cable assembly 100 includes distribution cable 110, distribution optical fiber pigtail 115', cap 120 for accessing location AL, transition tube 130, tether tube 140, indexing tube 150, indexing tube plug 160, splice protector 170, heat shrink tube 180, and sealing portion 190. Fig. 9-11 are cross-sectional views of assembly 100 along lines 9-9, 10-10, and 11-11, respectively. Additionally, for purposes of clarity, fig. 10 and 10a only show the cavity of the distribution cable. The cable assembly 100 includes an indexing tube 150 so that a predetermined amount of Excess Ribbon Length (ERL) or Excess Fiber Length (EFL) can be loaded into the distribution optical fiber, as will be described below. Loading the ERL or EFL into the distribution optical fiber will dampen stresses on the distribution optical fiber during bending of the cable assembly. Additionally, cable assembly 100 is one example of many different distribution cables according to the present invention that may include fewer or more components, have different configurations, different component configurations, and the like.

Both distribution cable 110 and tether tube 140 depicted in fig. 9 have a generally non-round interface, such as a generally flat plate shape, thereby allowing for a relatively small overall cross-sectional size of assembly 100. In other words, flat plate portions of distribution cable 110 and tether tube 140 are generally aligned to allow for a small footprint as compared to using two round cables. For example, distribution cable assembly 100 and other similar assemblies can have a cross-sectional maximum dimension MD as shown in fig. 11, which is diagonal. The cross-sectional maximum dimension MD can vary depending on the size of the component being used, but in embodiments it is advantageous for the particular application of the tube that the cross-sectional maximum dimension be about 30 millimeters or less, more preferably about 28 millimeters or less, and most preferably about 25 millimeters or less, to allow the cable assembly to be pulled into the tube. Of course, other embodiments can have other larger or smaller cross-sectional maximum dimensions for a given application.

Distribution cable 110 is advantageous for several reasons, however, the use of other distribution cables is possible. First, distribution cable 110 and other similar distribution cables are advantageous because they have relatively high optical wave derivatives and relatively small cross-sectional footprints. For example, distribution cable 110 has four ribbons, each having twenty-four optical fibers for a total fiber count of ninety-six. With the ribbon having a twenty-four fiber count, distribution cable 110 has a primary cable dimension W of about 15 millimeters or less and a secondary cable dimension H of about 8 millimeters or less. Second, distribution cable 110 is readily accessed from one of the generally flat surfaces of the cable (e.g., the upper or lower surface) so that the process can access any optical fibers desired for distribution. Third, distribution cable 110 allows for quick and reliable access while inhibiting damage to the optical fibers or strength members during the access procedure. In other words, the craftsman can simply cut through the protective layer to slot into the cable cavity having the optical fibers therein. Also, in this embodiment, distribution cable 110 has a dry construction (i.e., the fiber optic cable does not include grease or gel that blocks water), and thus, the craft does not need to remove or dislodge the grease or gel from the optical fibers, ribbons, tools, etc.

Of course, the distribution cable according to a particular application of the present invention may have any suitable size, configuration, and/or fiber count. For example, other distribution cables can include other components and/or structures for waterproofing, such as grease, gel, extruded foam, silicone, or other suitable waterproofing components. In addition, suitable water-resistant structures may also be provided intermittently along the distribution cable. Likewise, other distribution cables can have other suitable cable components, such as armor, ripcords, or tubes. For example, another embodiment of a distribution cable may have a color tunable portion to position the cable in buried applications.

As shown in fig. 9, distribution cable 110 includes a plurality of optical fibers 112 and a protective covering 118. In the present embodiment, distribution cable 110 is a tubeless design having a cavity 111 for receiving a plurality of optical fibers 112, the plurality of optical fibers 112 configured as a plurality of ribbons 113 (shown in horizontal lines) arranged in an unstranded, stacked configuration. The distribution cable 110 also includes strength members 114 and water-swellable components 116. As described above, strength members 114 are disposed on opposite sides of cavity 111 and impart preferential bending characteristics to distribution cable 110. Strength members 114 provide tensile and/or flexural strength to the distribution cable and may be formed from any suitable material such as a dielectric, a conductor, a composite, and the like. By way of example, strength members 114 are circular glass reinforced plastic (grp) having a diameter of about 2.3 millimeters, which is smaller than the height of cavity 111. Of course, the strength members 114 can have shapes other than circular, for example, elliptical strength members.

The water-swellable component 116 is utilized as a dry structure for the distribution cable 110. The water-swellable components 116 can have any suitable form, e.g., waterproof yarns, filaments, tapes, and the like. In this case, distribution cable 110 utilizes two water-swellable components 116 configured as spun-yarn wound ribbons. As described above, a major (e.g., planar) surface (not labeled) of the water-swellable component 116 is generally aligned with a major (e.g., horizontal) surface (not labeled) of the cavity 111, thereby generally inhibiting corner fiber contact from occurring with ribbon stacks disposed in a round tube while allowing for a compact and efficient configuration. Further, the strips are generally aligned with a major surface (i.e., a horizontal surface) of the cavity 111 at the top and bottom and also generally aligned with the width (i.e., a major surface) of the water-swellable component 116, thereby forming a composite stack of strips/water-swellable components within the cavity 111. Thus, the rectangular (or square) ribbon stack is secured to a corresponding generally rectangular (or square) cavity and avoids the problems associated with placing the rectangular (or square) ribbon stack within a circular buffer tube (i.e., stress on the corner fibers of the ribbon stack in a circular buffer tube can cause the cable to have no optical performance requirements such as bending).

More particularly, water-swellable components 116 are disposed on the top and bottom of a ribbon stack (not labeled) and include a compressible layer 116a and a water-swellable layer 116 b. In other words, the water-swellable layer 116 is sandwiched between the multiple ribbons 113 of the non-stranded stack, thereby forming a cable core. Thus, the one or more strips 113, the major surfaces of the water-swellable components 116 and the major (horizontal) surfaces of the cavities 111 are generally aligned (i.e., generally parallel) to create a compact structure. Additionally, the water-swellable components 116 contact at least a portion of the respective top or bottom band. In other embodiments, one or more elongated strips may be wrapped around the optical fibers or disposed on one or more sides of the optical fibers. For example, compressible layer 116a is a layer such as open-cell polyurethane foam and water-swellable layer 116b is a water-swellable tape. However, other suitable materials can be used for the compressible layer and/or the water-swellable layer or portions thereof. As shown, the compressible layer 116a and the water-swellable layer 116b are attached together, however, they may be used as separate components. Generally, water-swellable components 116 are multi-functional in that they provide a degree of coupling for ribbons 113, inhibit the migration of water along cavity 111, cushion the ribbons/optical fibers, and enable the ribbons (or optical fibers) to move and separate in response to bending of distribution cable 110. In another embodiment, the distribution cable may use other cable components disposed within the cavity 111 for coupling, cushioning and/or waterproofing the optical fibers. For example, the distribution cable may use foam tapes or extruded foams that do not include water-resistant features.

As indicated above, the cavity 111 has a generally rectangular shape with a fixed orientation to accommodate the non-stranded ribbon stack, however, other shapes or configurations of cavities are possible, such as a generally square, circular, or oval shape. For example, the lumen may be rotated or twisted along its axial length in any suitable manner. The cavity can also be partially vibrated by a certain angle, e.g., the cavity can be rotated between a clockwise angle less than a full rotation and then rotated at a counterclockwise angle less than the full rotation. In addition, cavity 111 can be offset toward a planar surface of distribution cable 110, thereby allowing easy opening and access from one side.

Ribbons 113 used in distribution cable 110 can have any suitable design or ribbon count. Ribbon 113 can have a splittable configuration, for example, by utilizing one or more subunits or stress concentrations as are known in the art, thereby allowing the ribbon to be split into smaller groups of optical fibers. For example, the ribbon may utilize subunits, each subunit having four optical fibers; however, ribbons without subunits are also possible and subunits may have different fiber counts. The subunits allow for the predetermined splitting of the ribbon into predictable smaller fiber count units prior to splitting it along its length with tool 50. In one embodiment, each depicted ribbon 113 includes six four-fiber subunits, and a total of twenty-four fibers. Of course, other numbers of fibers per ribbon, numbers of ribbons, and/or other suitable subunit configurations are possible, such as two twelve fiber units, three eight fiber units, or six four fiber units, depending on the network configuration requirements. Examples of suitable optical fiber configurations include ribbons with or without subunits, reinforced ribbons with tight buffer layers, tight buffered or colored optical fibers, loose optical fibers in tubes, optical fibers in modules, or optical fibers arranged in bundles.

In addition, ribbons 113 of the present illustrative embodiment of distribution cable 110 have an Excess Ribbon Length (ERL) of about 0.5% or greater, such as in the range of about 0.6% to about 0.8%, to accommodate bending and/or coiling of distribution cable 110, although the amount of ERL used may vary depending on the particular cable design. The ERL of ribbon 113 is related to the ERL of the ribbon within the cable and is different from the ERL loaded in the distribution optical fiber using the indexing tube briefly described above. The minimum bend radius of distribution cable 110 is about 125 millimeters, which allows the fiber optic cable to be coiled in a relatively small diameter for slack storage. Of course, distribution cables having other suitable fiber/ribbon counts may have other ERL values and/or cable dimensions. For example, a cable similar to distribution cable 110 can have four ribbons with different fiber counts, such as: (1) twelve ribbons having a major cable dimension W of about 12 mm or less, for a total of forty-eight optical fibers; (2) thirty-six ribbons having a major cable dimension W of about 18 millimeters or less, totaling one hundred and forty-four optical fibers; (3) forty-eight ribbons having a major cable dimension W of about 21 millimeters or less for a total of two hundred and sixteen optical fibers.

In addition, the cavity 111 has a cavity height CH and a cavity width CW suitable for the desired configuration of the optical fiber, ribbon, etc. For example, each ribbon 113 has a height of about 0.3 millimeters and a total ribbon height of about 1.2 millimeters (4 times 0.3 millimeters), and the cavity height CH of the cavity 111 is about 5.5 millimeters. Cavity width CW is typically determined by the width of the ribbon (or fiber count) for which the cable is designed and will be about 7.5 millimeters for a twenty-four fiber ribbon. In the present embodiment, each water-swellable component 116 has an uncompressed height of about 1.8 millimeters, however, other suitable uncompressed heights are possible. If the cable includes a positive ERL (i.e., the ribbons are coiled within the cavity), the compression of the water-swellable component 116 in the cable is its local maximum compression and occurs where the ribbon or ribbon stack has the greatest displacement from the neutral axis.

For example, the illustrative embodiment has a total height for the uncompressed water-swellable components 116 and the bands 113 of about 4.8 millimeters, which is less than the cavity height CH of 5.5 millimeters. Thus, normal ribbon pullout forces are typically caused by a stack of crimped ribbons resulting in local maximum compression of the water-swellable component 116 due to ERL and/or friction. For example, when the overall uncompressed height of the dry insert is about 40% or more of the cavity height CH, proper coupling of the ribbon stack (or ribbon or optical fiber) may be achieved, for example, by utilizing two 1 millimeter water-swellable components 116 within a cavity having a cavity height CH of about 5 millimeters. Of course, other suitable ratios are possible as long as the optical properties can be preserved. In the illustrative embodiment, the combined compressed height of water-swellable components 116 (2 times 1.8 millimeters equals 3.6 millimeters) is about 65% of the cavity height CH (5.5 millimeters), which is greater than 50% of the cavity height CH. Of course, the chambers, bands and/or water-swellable components 116 may have other suitable dimensions, as long as the suitable performance is still provided. For example, thinner tapes and/or water-swellable components may be used. Although the depicted chamber 111 is rectangular, it may be difficult to manufacture the rectangular chamber shown, i.e., the extrusion process may produce a chamber having some irregular rectangular shape. Likewise, the cavities can have other suitable shapes besides generally rectangular, e.g., oval, circular, etc., which may generally alter the relative relationship (alignment) between the dry insert, the ribbon, and/or the cavity.

In general, positioning water-swellable components 116 on opposite sides of a ribbon stack (or individual ribbons or loose optical fibers) helps to influence and maintain a generally uniform ERL distribution along distribution cable 110 during different conditions, thereby helping to preserve optical performance. Furthermore, ribbon and cable coupling is beneficial for influencing a relatively consistent ERL distribution along the cable, for example during bending, which typically allows for small cable bend radii. Other factors such as the size of the cavity and/or the compression of the dry insert or inserts may also affect the ERL/EFL distribution along the cable.

Another optical performance aspect of distribution cables having a generally flat plate shape with a stack of non-stranded ribbons is the total amount of ERL required for suitable cable performance. The total amount of ERL for proper cable performance is typically dependent on the cable design, such as ribbon count. Generally, the minimum ERL for a cable having a single ribbon is determined by the allowable fiber strain level required at the rated cable load; however, the minimum ERL for multi-ribbon cables is typically affected by the bending performance. More particularly, when selecting the minimum ERL limit based on the cable design, the geometry and material (i.e., cross-sectional area and Young's modulus) of the strength members should be considered to calculate the desired level of fiber strain at the rated tensile load of the cable design. In addition, the amount of ERL required for bending generally increases as the number of ribbons in the stack increases because the outer ribbons in the ribbon stack are farther from the neutral axis of the cable. However, the upper end of ERL has a limit to suitable optical performance (i.e., too much ERL can degrade optical performance). In addition, distribution cables having relatively high ERL ratings, such as in the range of 0.6% to 1.5%, may be suitable for free-standing installations, such as NESC reloading, but the portion of the ERL for a particular design should have the required cable performance. On the other hand, a distribution cable similar to distribution cable 110 having loose optical fibers may have a low value of Excess Fiber Length (EFL), e.g., about 0.2% EFL, because all of the optical fibers are located near the neutral axis of the cable.

Turning now to cable assembly 100, fig. 12-16 depict perspective views of a portion of distribution cable 110 in different structural levels (i.e., subassemblies) for explaining a method of making cable assembly 100. Fig. 12 depicts distribution cable 110 after access location AL is fabricated in protective covering 118 and distribution optical fibers 115 are severed and routed within distribution cable 110 through an opening having a cap 120 at access location AL and a transition tube 130 is installed, thereby forming a subassembly 102 of cable assembly 100. Depending on the subassembly 102, different distribution cables may be constructed, such as the cable assembly 100 shown in fig. 7 and 8 and the cable assembly 200 shown in fig. 17 and 18. In addition, subassembly 102 or other subassembly structures are suitable for field use. Briefly, in the field, a craftsman provides the distribution optical fibers of subassembly 102 to the exterior of the distribution cable for use. If used in this manner, a tape or other cladding may be disposed about the distribution optical fibers and/or the access location to protect them until access is needed in the field.

The formation of subassembly 102 will be described below. First, protective covering 118 of distribution cable 110 about access location AL is roughened by a channeled structure and/or flame-burn procedure. The roughened protective layer 118 improves the adhesion of the sealing portion 190 to the protective layer and is more easily and safely achieved prior to opening the protective layer. Thereafter, an opening 118a is made in the protective layer 118 to access the location AL. Opening 118a may be any suitable length, and in this case, is about 25 millimeters long. Any suitable cable entry means may be used to open protective covering 118, such as a utility knife or the like. After opening protective covering 118, a portion of upper water-swellable component 116 of distribution cable 110 is exposed at access location AL. This exposed portion of water-swellable component 116 is removed, for example, cut with scissors, thereby allowing easy access to the optical fibers within distribution cable 110. Thereafter, the desired optical fibers for distribution are selected for cutting within the distribution cable and special tools such as parting tools may be used. In this example, less than all of the fibers in the top ribbon are selected for distribution, so the top ribbon includes a cleft S between fibers, as shown in fig. 6 f. In particular, four fibers of the top ribbon at access location AL are selected to become distribution fibers. Of course, the optical fibers of other ribbons in the stack may also be selected for distribution. Additionally, if the ribbon above the accessed ribbon has already been used, the used ribbon may be removed to access the desired optical fibers for distribution. The craftsman makes a break S in the top tape using a suitable tool and/or their fingers. Thereafter, the severing element 58 of the tool 50 is positioned around the break S, as shown in fig. 6 f. The slack in the cutting element 58 is then taken up and the tool 50 is slid into the cavity 111 of the distribution cable 110, thereby cleaving the ribbons between the optical fibers along their axial lengths as the tool 50 is moved into position. After tool 50 is positioned at cutting location CL within distribution cable 110, cutting element 58 is pulled with sufficient force to cut distribution optical fibers 115 within distribution cable 110.

In this case, tool 50 is inserted so as to cut distribution optical fiber 115 175 mm downstream of access location AL. Thus, the distribution fiber length DOFL is about 7 times greater than the acquisition length AL. After tool 50 is removed from distribution cable 110, distribution optical fibers 115 are pulled out of cavity 111 and emerge outside of protective covering 118. Next, a cap 120 (similar to cap 64) and a transition tube 130 (similar to transition tube 62) sized and shaped according to the distribution cable 110 having the access location AL are installed, similar to that shown in FIG. 6 e. More particularly, transition tube 130 has a length of about 65 millimeters and a generally rectangular shape to slide over the optical fibers cleaved from optical fiber ribbons 113, and cap 120 is generally flat and has a length slightly greater than access location AL so that a portion can fit within cavity 111 of distribution cable 110. Transition tube 130 is slid over distribution optical fiber 115 so that approximately 35 millimeters is disposed within cavity 111 of distribution cable 110. The exposed end of transition tube 130 is then directed through opening 120a of cap 120 and cap 120 is positioned so that a portion thereof is inserted into cavity 111 of distribution cable 110. Prior to this, cap 120 closes access location AL and transition tube 130 protects distribution optical fibers 115 as they are directed out of distribution cable 110. Thereafter, a material (not shown), such as a hot melt adhesive, is applied over the cap 120 and around the transition tube 130 to secure the cap 120 and transition tube 130 at the access location opening, similar to that shown in fig. 6 f.

Fig. 13 depicts a perspective view of another subassembly 104 of the cable assembly 100 for explaining the method of manufacture. More particularly, fig. 13 illustrates the subassembly 102 of fig. 12 after splicing the distribution optical fiber 115 having a distribution optical fiber pigtail 115' and protecting the splice location with a splice protector 170. For this embodiment and the access location of cable assembly 110, distribution fiber pigtails 115' are four fiber ribbons that are all fusion spliced with distribution fibers 115 cleaved from the top ribbon. In other words, the distribution optical fiber pigtail 115' is in optical communication with and becomes a part of the distribution optical fiber 115. In addition, this step increases the length of the distribution optical fiber based on the desired connection configuration, such as the length of the tether tube, or other configuration. Splice protector 170 is used to protect and secure the splice (not visible) and may be pushed onto distribution optical fiber pigtail 115' prior to splicing and then positioned over the splice after it is manufactured. Likewise, other components may also be slid over the distribution optical fiber pigtail 115' according to the configuration of this embodiment. Similar to subassembly 102, different distribution cables may be constructed from subassembly 104 or other similar subassemblies. Cable assembly 100 includes tether tube 140 having a stub end of the distribution optical fiber (the second end of distribution optical fiber pigtail 115') for optical connection, however, other configurations may be used. For example, the second end of the distribution optical fiber pigtail 115' can have one or more ferrules attached thereto and the ferrules can be part of a receptacle, plug, or the like for plug and play connections. By way of example, FIG. 19 depicts the second end of tether tube 140' having a distribution optical fiber attached to a ferrule that is part of a plug 195 as is well known in the art. Of course, the second end of tether tube 140 'can have any suitable configuration for connection, such as splice-ready fibers, connectors or receptacles with ferrules, multiports, etc., to provide flexibility for the craftsman's downstream connections. For example, fig. 19a depicts distribution optical fiber 115' attached to ferrule 196. The ferrule 196 is a multi-fiber ferrule, however, a single fiber ferrule may be attached to one or more distribution fibers. Figure 19b depicts multiport 198 having a plurality of receptacles 198a attached to the end of tether tube 140. Likewise, FIG. 19c depicts another multiport 199 having a plurality of receptacles 199a attached to the end of tether tube 140. Fig. 19d and 19e illustrate the use of tether tube branches for plug and play connection furcation legs. More particularly, fig. 19d shows an assembly 193 having a plurality of plugs 193a disposed on the ends of a plurality of furcation legs 193b, while fig. 19e shows an assembly 194 having a plurality of receptacles 194a disposed on the ends of a plurality of furcation legs 194 b. Of course, other types and/or configurations can be used for the optical connection, such as a single receptacle, etc. As explained below, cable assembly 100 has a splice disposed within the cavity of indexing tube 150, which will be explained below for protecting the splice and loading the ERL or EFL into the distribution optical fiber.

As best shown in fig. 10a, the splice indexing tube 150 is slid over a portion of the distribution optical fibers 115 and a portion of the transition tube 130. Thus, the splice protector 170 is disposed within the lumen 150a of the indexing tube 150 and the fiber stub 115' extends from the second end of the indexing tube 150. Further, the joint 170 can have an optional cushioning element (not shown) such as a foam board disposed therearound. For example, foam may be disposed around the fitting 170, e.g., the foam is folded over the fitting 170 before the indexing tube 150 is slid over the fitting 170. As further shown, the indexing tube insert 160 is then pushed into the downstream end of the indexing tube 150. The indexing tube 160 is used to prevent the sealing portion 190 from being injected into the indexing tube 150 during subsequent processing. The indexing tube plug 160 may be formed of any suitable material, such as foam, soft polymer, etc., and is sized to fit within the cavity of the indexing tube 150 along the transition tube 130 with a light friction fit. Indexing tube 150 may then be taped or otherwise secured to distribution cable 110 to fold it into place, if desired. In this embodiment, indexing tube 150 is a portion of distribution cable 110 having a cavity, as best shown in fig. 11. In other words, indexing tube 150 is the portion of distribution cable 110 from which band 113 and water-swellable components 116 are removed from cavity 111 (i.e., only protective layer 118 having strength members 114 is embedded therein). Of course, the use of other suitable indexing tubes having other sizes and/or shapes such as circular, square, etc. is also possible.

Fig. 14 depicts a perspective view of a subassembly 106 of the cable assembly 100 disposed within a module 192 shown in phantom before injecting a curable material to form the sealing portion 190. The subassembly 106 also includes the step of applying a material 106a, such as a hot melt adhesive, to seal and/or secure the components of the assembly together, for example, to fix the position of the transition tube 130. The application material 106a prevents the injection material from entering the indexing tube, gaining access to the opening of the site, and/or preventing moving parts during the overmolding process, thereby preserving optical performance. In addition, it facilitates faster heating of a portion of subassembly 106 prior to forming sealing portion 190 therearound to facilitate bonding of sealing portion 190 and subassembly 106. Thereafter, the subassembly 106 is placed into a mold 192 as shown in FIG. 14 and the sealing portion 190 is formed by injecting a sealing material under pressure into the mold. The sealing portion 190 provides external protection for the access location AL and can provide structural integrity. In the present embodiment, the sealing portion 190 is a 2-part material formed of an isocyanate resin obtained from Loctite and a polyhydroxy hardener. In the present embodiment, the sealing portion 190 has a generally uniform minimum wall thickness of about 3-5 millimeters, however, other dimensions are possible. Other methods and/or materials for making the sealing portion 190 are possible so long as they meet the requirements of the desired application. The sealing portion 190 may be formed by techniques or manufacturing methods other than injecting a curable material into the mold. For example, fig. 20 depicts a sealing portion 190' that is a preformed housing that mates with the sub-assembly 106 and is then heated (or otherwise reacted) to partially or fully melt and/or form the housing, thereby sealing the access site. More particularly, the sealing portions 190 'have hinge lines 192' to allow them to be folded about the subassembly 106. In other embodiments, the sealing portion 190' can be two or more separate portions. A sealing portion such as sealing portion 190' may be used with any suitable distribution cable. For example, fig. 20a-20c depict the use of an alternative sealing portion 190 "and distribution cable 110 ' and tether tube 140 ' having a circular cross-section to form cable assembly 100 '. In yet another embodiment, a stiffening tube (not shown) may be placed around the access location and then injected with a suitable material to seal the ends of the stiffening tube or the entire stiffening tube. The sealing portion 190 may also be formed using heat shrink tubing disposed around the access site if the application permits.

FIG. 15 depicts a perspective view of the subassembly 108 of the cable assembly 100 prior to indexing the tether tube 140 with respect to the indexing tube 150. More particularly, the indexing tether tube 140 enters the indexing tube 150 and can be loaded with a predetermined amount of ERL associated therewith into the distribution optical fiber 115 and/or the distribution optical fiber pigtail 115'. Thus, the ERL and EFL of the distribution optical fiber prevent forces from being applied to the distribution optical fiber that would result in reliability and/or optical loss. As best shown in fig. 10, lumen 150a of indexing tube 150 is sized so that tether tube 140 fits within indexing tube 150. Fig. 9 depicts tether tube 140 comprising a plurality of strength members 142 disposed on opposite sides of lumen 141 and housing a portion of distribution optical fiber 115' therein. Tether tube 140 has a generally flat plate shape, however, tether tubes of other sizes and/or shapes may be used in accordance with the principles of the present invention. Fig. 15 depicts tether tube 140 disposed within a portion of indexing tube 150 and tensioned to remove excess tape length indicated at M1. Thereafter, tether tube 140 is advanced (i.e., indexed) into indexing tube 150a predetermined distance D, represented by reference M2. In the present cable assembly, the distance D is about 5 millimeters, so about 5 millimeters of ERL is introduced into the distribution optical fiber, i.e., accumulated, generally within the indexing tube 150. Of course, other suitable distances D may be used to load the desired ERL or EFL. After indexing occurs, tether tube 140 needs to be secured in a position to maintain ERL or EFL. As shown in FIG. 7, a heat shrink tube 180 is applied over a portion of tether tube 140 and a portion of indexing tube 150 to maintain relative position, but other methods can be used to maintain relative position, such as overmolding or the like. Additionally, it should be understood that the method of indexing a first tube with a second tube to provide ERL or EFL may be used without the step of cutting the distribution optical fiber within the distribution cable. Of course, other variations of the cable assembly 100 are possible. For example, fig. 16 depicts cable assembly 100 having an optional cable tie 196 to secure distribution cable 110 and sealing portion 190 near the downstream end to prevent separation forces therebetween.

As noted above, the subassemblies of the present invention may be constructed in other cable assembly configurations. For example, fig. 17 and 18 depict a cable assembly 200 that includes a subassembly 102 having a distribution optical fiber pigtail 115' spliced thereto and protected by a splice protector 270. As best shown in fig. 18, the distribution optical fiber pigtail 115' protects a ferrule (not visible) attached thereto. In this embodiment, the ferrule is a multi-fiber ferrule. Further, the ferrule is part of the connector body 220, thereby providing plug and play optical connection in the access position instead of the end of the tether tube.

Of course, cable assemblies 100 and 200 are examples of multi-tube distribution cables made in accordance with the principles disclosed. As noted above, other assemblies can utilize other cable cross-sections or have fewer, more, and/or different components. For example, sealing portion 190 of distribution cable 100 can include segmented end 190a as shown in phantom line drawing in fig. 7. The segmented end 190a allows for some strain relief at the front end of the dispensing location. Additionally, the cable assembly of the present invention can include other components to assist in installation of the cable assembly into a conduit. For example, fig. 21 depicts a distribution cable 300 having a pull safety device 302 disposed at the front of the access location, as shown. More particularly, pulling the safety device 302 allows a craftsman to detect a blockage and/or compression in the conduit so that the craftsman does not damage the access location when attempting to pull the distribution cable through the blockage or compression in the conduit. In this embodiment, the safety pull is sized slightly larger than the sealing portion 190, thereby allowing the craftsman to feel the increased force and/or damage the pull safety device 302 before reaching the access location. Of course, the safety pull can have a size and/or shape similar or identical to the sealing portion. Thus, the craft is able to pull the distribution cable out of the conduit before damaging the distribution cable and repair and clean the conduit before attempting to reinstall the distribution cable. In another embodiment, the safety pull device may be shaped to facilitate twisting or alignment of the distribution cable to fit through a jam or compression.

Those skilled in the art will appreciate that various modifications and changes may be made without departing from the spirit and scope of the invention. For example, the principles described herein may be adapted for use with any suitable fiber optic cable design. Likewise, the fiber optic cable may include other suitable cable components such as ripcords or other components for optical connectivity. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (33)

1. A fiber optic distribution cable, comprising:

a fiber optic distribution cable having a plurality of optical fibers and a protective covering;

a distribution optical fiber that is one of the plurality of optical fibers of the fiber optic distribution cable, the distribution optical fiber being severed at a severing location within the fiber optic distribution cable and protruding from an access location of the protective covering, wherein the access location has a length AL, the distribution optical fiber removed from the fiber optic distribution cable having a distribution optical fiber length DOFL that is about 5/4 times or more the access length AL.

2. The fiber optic distribution cable of claim 1, having a non-circular cross-section.

3. The fiber optic distribution cable of claim 1, having a non-circular cross-section and further comprising a tether tube having a non-circular cross-section disposed about a portion of the distribution optical fiber for protecting the distribution optical fiber.

4. The fiber optic distribution cable of claim 1, having a cross-sectional maximum dimension of about 30 millimeters or less.

5. The fiber optic distribution cable of claim 1, further comprising a demarcation point disposed about the access location for the distribution optical fiber to inhibit movement of the distribution optical fiber.

6. The fiber optic distribution cable of claim 1, further comprising a transition tube for protecting a portion of the distribution optical fiber.

7. The fiber optic distribution cable of claim 1, further comprising a cap for closing the access location.

8. The fiber optic distribution cable of claim 1, further comprising a cap for closing the access location and a transition tube for protecting a portion of the distribution optical fiber.

9. The fiber optic distribution cable of claim 3, further comprising an indexing tube, wherein a portion of the tether tube is disposed within the indexing tube at a predetermined location relative to the indexing tube such that the tether tube loads the excess fiber length in the distribution optical fiber to allow the excess fiber length in the distribution optical fiber.

10. The fiber optic distribution cable of claim 9, further comprising a heat shrink tube disposed about a portion of the indexing tube, the heat shrink tube for maintaining a relative position between the indexing tube and the tether tube.

11. The fiber optic distribution cable of claim 1, further comprising a tether tube disposed about a portion of the distribution optical fiber for protecting the distribution optical fiber.

12. The fiber optic distribution cable of claim 1, further comprising a sealing portion disposed about the access location.

13. The fiber optic distribution cable of claim 1, wherein the distribution optical fiber is at least one optical fiber of a fiber optic ribbon.

14. The fiber optic distribution cable of claim 1, further comprising a ferrule attached to the distribution optical fiber for optical connection.

15. The fiber optic distribution cable of claim 1, further comprising a tether tube disposed about a portion of the distribution optical fiber for protecting the distribution optical fiber and a ferrule attached to the distribution optical fiber for optical connection.

16. The fiber optic distribution cable of claim 1, wherein the fiber optic distribution cable has a dry construction.

17. The fiber optic distribution cable of claim 1, further comprising a sealing portion disposed about the access location and an indexing tube through which the at least one distribution optical fiber is guided, the indexing tube having one end sealed by the sealing portion and another end extending beyond the sealing portion.

18. The fiber optic distribution cable of claim 1, comprising an unstranded stack of optical fiber ribbons.

19. The fiber optic distribution cable of claim 1, including an unstranded stack of fiber optic ribbons and a first water-swellable component disposed on a first side of the unstranded stack and a second water-swellable component disposed on a second side of the unstranded stack.

20. The fiber optic distribution cable of claim 1, further comprising a plurality of access locations.

21. A fiber optic distribution cable, comprising:

a fiber optic distribution cable having a plurality of optical fibers and a protective covering;

at least one distribution optical fiber selected from one of the optical fibers of the fiber optic distribution cable, the at least one distribution optical fiber extending from an access location of the protective covering, wherein the access location has a length AL, the distribution optical fiber having a distribution optical fiber length DOFL that is about 5/4 times or more the access length AL prior to splicing;

a sealing portion disposed around the access location;

an index tube through which the at least one distribution optical fiber is guided and in which an optical fiber connector is provided for protruding the at least one distribution optical fiber, and one end of which is sealed by the sealing portion and the other end of which protrudes from the sealing portion; and

a tether tube disposed about a portion of the at least one distribution optical fiber to protect the at least one distribution optical fiber, wherein the portion of the tether tube is disposed within the indexing tube at a predetermined location relative to the indexing tube such that the tether tube loads excess fiber length in the distribution optical fiber.

22. The fiber optic distribution cable of claim 21, further comprising a heat shrink tube disposed about a portion of the indexing tube, the heat shrink tube for maintaining a relative position between the indexing tube and the tether tube.

23. The fiber optic distribution cable of claim 21, having a non-circular cross-section.

24. The fiber optic distribution cable of claim 21, the fiber optic distribution cable having a non-circular cross-section and the tether tube having a non-circular cross-section.

25. The fiber optic distribution cable of claim 21, having a cross-sectional maximum dimension of about 30 millimeters or less.

26. The fiber optic distribution cable of claim 21, further comprising a cap for closing the access location.

27. The fiber optic distribution cable of claim 21, further comprising: a transition tube for guiding and protecting the distribution optical fibers outside of the protective covering, and a cap for closing the access location and shielding other optical fibers within the fiber optic distribution cable.

28. The fiber optic distribution cable of claim 21, wherein the distribution optical fiber is at least one optical fiber of a fiber optic ribbon.

29. The fiber optic distribution cable of claim 21, further comprising a ferrule attached to the distribution optical fiber for optical connection.

30. The fiber optic distribution cable of claim 21, wherein the fiber optic distribution cable has a dry construction.

31. The fiber optic distribution cable of claim 21, comprising an unstranded stack of optical fiber ribbons.

32. The fiber optic distribution cable of claim 21, comprising an untwisted stack of optical fiber ribbons and a first water-swellable component disposed on a first side of the untwisted stack and a second water-swellable component disposed on a second side of the untwisted stack.

33. The fiber optic distribution cable of claim 21, further comprising a plurality of access locations.