# Patent

## Title
Universal remote radio unit fiber optic cable assembly

## Abstract

A fiber optic cable has a cable core that includes at least one optical fiber coupled to a fiber optic connector. A cable adapter sleeve is axially mounted on the cable core to surround the cable core, the cable adapter sleeve including a body portion that has a first outer diameter, a collar that has a second outer diameter that is greater than the first outer diameter, and a stop that has a third outer diameter that is greater than the first outer diameter.

## Background
BACKGROUND
1. Field of the Invention
This invention relates to fiber optic and hybrid electro-optical cable assemblies. More particularly, the invention relates to cable assemblies adaptable to a variety of different remote radio unit conductor entry dimensional specifications.
2. Description of Related Art
The wireless communications industry is changing from traditional signal delivery from ground based transceivers delivering/receiving the RF signal to/from the antenna atop the radio tower via bulky/heavy/high material cost semi-rigid metal RF coaxial cable to optical signal delivery to a tower top mounted transceiver known as a remote radio unit (RRU) or remote radio head (RRH) with implementation of fiber to the antenna (FTTA) cabling.
As this area of the market is evolving quickly, many original equipment manufacturers (OEM) are providing different RRU/RRH with different termination requirements, requiring different fiber optic cable assemblies with different cable outer diameter (OD) and breakout lengths. For example, even where the RRU/RRH are from the same OEM, the required cable assemblies may have different requirements.
One requirement may be for a shorter breakout length wherein the connectorized breakout is captive and connectorized inside a small cavity of the RRU enclosure, for example, via a rubber gland that seals only against 5 mm OD cable. Alternatively, the OD may be, for example, 6 or 7 mm and the connector connectorized with another connector that is on an outside plate of the RRU. This larger diameter OD receiving connector may also seal against the OD of the larger diameter cable.
Factory terminated hybrid cable assemblies are known. Furcation tubes may be applied to fibers and or fiber bundles stripped back from the cable end to protect the optical fibers from damage between the cable and the optical fiber termination. Optical fiber furcation tubes may consist of an inner polymer tube surrounded by a para-aramid synthetic fiber sheath, or a para-aramid synthetic fiber sheath alone.
Therefore, an object of the invention is to provide an optical and/or electro-optical cable solutions that overcome deficiencies in the prior art.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
FIG. 1 is a schematic isometric view of an exemplary cable assembly.
FIG. 2 is a schematic isometric view of an exemplary cable adapter sleeve.
FIG. 3 is a schematic cut-away side view of the cable adapter sleeve of FIG. 2 installed upon a cable core with an armor tube.
FIG. 4 is a schematic isometric view of an alternative cable adapter sleeve.
FIG. 5 is a schematic cut-away side view of the cable adapter sleeve of FIG. 5 installed upon a cable core with an armor tube.
FIG. 6 is a schematic isometric view of an RRU gasket.
FIG. 7 is a schematic cut-away side view of the RRU gasket of FIG. 6, seated upon the cable adapter and cable core of FIG. 5.
FIG. 8 is a schematic side view of a cable end corresponding to FIG. 7.
FIG. 9 is a schematic isometric view of an alternative RRU gasket.
FIG. 10 is a schematic partial cut-away side view of the gasket of FIG. 9 seated upon a cable adapter and cable core.



DETAILED DESCRIPTION
The inventor has recognized that it is time consuming, hazardous and expensive to install new cable assemblies on a tall radio tower. A single user may utilize different types of RRU/RRH. To avoid duplication of incompatible assemblies and simplify sourcing for the user, a single solution that can be used with multiple types of RRU/RRH has been devised. Thereby, should the rapidly evolving RRU/RRH technology adopt one or the other interconnection/sealing interfaces as a standard and/or the user select the alternative RRU/RRH in the future, the RRU/RRH may be easily exchanged in the future without also requiring exchange of the entire cable assembly.
These cable assemblies may include adapter sleeves which include a plurality of differently dimensioned outer diameter surfaces and other features, to allow the same cable assembly to be used with a variety of different RRU/RRHs, despite the differences in connection mechanisms on these various different RRU/RRHs.
A fiber optic cable 100, for example as shown in FIG. 1, includes a pair of cable cores 110 that each include a first and a second optical fiber 112. A first fiber optic connector 120 and a second fiber optic connector 130 are provided at respective ends of each of the cable cores 110. A portion of each cable core 110 are protected by a protective armor tube 140. It is the respective armor tubes 140 that are sealed against by the environmental seals of the RRU/RRHs.
The first and second optical fibers 112 may be single mode optical fibers, multi-mode optical fibers, etc. The first and second optical fibers 112 may be 900 micron buffered or 250 micron buffered optical fibers. The cable core 110 may be a loose tube cable, a ribbon cable or any other appropriate core configuration. In other words, the cable core 110 may be any suitable fiber optic cable core and, as discussed herein, may also include other elements such as one or more metal electrical conductors. In the exemplary embodiment demonstrated by FIG. 1, the first and second optical fibers 112 comprise buffered single mode optical fibers that run adjacent to each other in the cable core 110. Alternatively, the fibers may be single fiber strands. At the first end of the cable 100, the first and second optical fibers 112 split apart from each other at a first optical connector 120 provided as a duplex LC connector. In the depicted embodiment, each buffered optical fiber 112 may have an outer diameter of about 0.9 mm, although other sized optical fibers may be used. One of the optical fibers 112 may be used to carry signals that are to be transmitted from the antenna associated with the RRU/RRH while the other of the optical fibers 112 may be used to carry signals that are received at the antenna to the remainder of the base station equipment.
The first and second fiber optic connectors 120, 130 may each comprise any appropriate fiber optic connector including, for example, an LC, SC, or MPO connector.
In the depicted embodiment, the first and second fiber optic connectors 120, 130 are each implemented as a duplex LC connectors.
The protective armor tube 140 may comprise, for example, a polyethylene tube having an outer diameter of, for example, between about 6 mm and about 12 mm. In some embodiments, the outer diameter of the protective armor tube 140 may be sized to be received within a cable clamp that is provided on at least one of the RRU/RRHs with which the cable 100 is to be used. As will be discussed in further detail below, some RRU/RRHs such as, for example, a RRU-S01 manufactured by Ericsson Inc., Plano Tex., may have a gland that covers the fiber optic connector port on the RRU/RRH. This gland may provide an environmental sealing function (e.g., to reduce or prevent water or moisture ingress into the connector port area and/or into the RRU/RRH) and may also provide a strain relief function to prevent the cable 100 or the connector port on the RRU from being damaged if a pulling force is applied to the cable 100. The above referenced gland on the RRU may have a clamp that is designed to receive a certain diameter cable in order to provide the strain relief functionality. Thus, the protective armor tube 140 may have a diameter (e.g., about 6 mm to about 12 mm) that is designed to fit within the strain relief clamp on the gland of the RRU. The protective armor tube 140 may also provide enhanced protection to the optical fibers 112, 114 in the section of the cable 100 that is at the top of the tower where the RRU may be located, which is a portion of the cable 100 that may be more susceptible to being damaged.
A cable adapter sleeve 150, for example as shown in FIG. 2, is provided positioned axially on the cable 100. The cable adapter sleeve 100 may serve multiple functions including, for example, providing a different outer diameter in the region of the cable 100 adjacent the connector 120 that may be used to mate the cable 100 with additional types of RRU/RRHs. The cable adapter sleeve 150 may also perform a strain relief function. As shown best in FIG. 2, the cable adapter sleeve 150 includes a body portion 152, a collar 154 and a stop 156. The cable core 110 extends through all three of the body portion 152, the collar 154 and the stop 156. The collar 154 extends from the rear end of the body portion 152. The collar 154 may be formed integrally with the body portion 152 or as a separate piece that is attached to the body portion 152. As best shown in FIG. 3, the collar 154 is fitted over one end of the protective armor tube 140. The stop 156 extends from the other (front) end of the body portion 152. The stop 156 may also be formed integrally with the body portion 152 or as a separate piece that is attached to the body portion 152. The first and second optical fibers 112 extend all of the way through the stop 156 for insertion into the respective boots of the dual-boot duplex LC connector 120. The cable adapter sleeve 150 may comprise, for example, a polymer sleeve, a metal sleeve or a combination thereof.
The cable adapter sleeve 150 may be formed as a unitary single-piece adapter sleeve. The cable adapter sleeve 150 may be formed, for example, by injection molding, machining or any other appropriate manufacturing process, including in situ overmolding molding of materials such as TPE or silicon, around the cable core and an end of the protective armor tube 140. The cable adapter sleeve 150 may be generally cylindrical, with several separate portions of different circular cross-section diameters. The central body portion 152 may have a relatively small cross-sectional outer diameter, for example, of about 5 mm. The collar 154 may have a larger cross-sectional outer diameter, which in the depicted embodiment is about 12 mm, which allows the collar 154 to fit over the end of the protective armor tube 140 which has an outer diameter of about 10 mm. The stop 156 is a “two step” stop that has two different cross-sectional outer diameters: namely, a cross-sectional outer diameter of about 11 mm for the larger step 158 and a cross-sectional outer diameter of about 5 mm for the smaller step 159. Some RRU/RRHs include a rubber gasket that covers and protects the fiber optic connector port on the RRU/RRH, and thus it is necessary to insert the end of the cable 100 that includes fiber optic connector 120 through this rubber gasket to be received within the fiber optic connector port on the RRU/RRH. The increased cross-sectional outer diameters of the stop 156 may engage a back surface of the rubber gasket in order to function as a strain relief mechanism that resists axial forces that may otherwise pull the fiber optic connector 120 out of the mating fiber optic connector port on these RRU/RRHs.
The body portion 152 of cable adapter sleeve 150 is a tubular body that has a central passageway 153 that the first and second optical fibers 112 extend through. The collar 154 likewise has a tubular shape, but the central passageway 155 of the collar 154 may have a significantly larger internal diameter that may be sized, for example, to receive an end of the protective armor tube 140. An adhesive may be coated onto the outside of the protective armor tube and/or onto the interior surface of the passageway 155 in order to bond the protective armor tube 140 within the passageway 155 of the collar 154. The collar 154 may also include an aperture 160 that may receive a protrusion that is included on the gaskets that are included on some RRU/RRHs. By inserting this protrusion into the aperture 160, an improved seal and/or improved strain relief may be provided. The stop 156 may have an internal passageway 157 that is, for example, the same diameter as the internal passageway 153 of the body portion 152.
The outer diameter of the collar 154 may, in some embodiments, be sized to fit within a clamp for one or more different types of RRU/RRHs. For example, an RRU that is manufactured by Alcatel-Lucent, Murray Hill, N.J., has a clamp that is sized to receive a cable having an outer diameter of about 12 mm. The increased outer diameter of the collar 154 may be sized to fit within the clamp on the Alcatel-Lucent RRU so that the cable 100 may be properly connected to the Alcatel-Lucent RRU with full sealing and strain relief protection.
The outer diameter of the body portion 152 may, in some embodiments, be sized to fit a gasket or other aperture that provides access to the connector port on other types of RRU/RRHs. For example, the RRU-S11 and RRU-S12 RRU that are manufactured by Ericsson each include a gasket that is sized to receive a cable having an outer diameter of about 5 mm. The stop 156 may be passed through this gasket and may contact a back side of the gasket (i.e., the side of the gasket facing the RRU). The increased outer diameter of the stop 156 may be sufficiently large that it may be difficult to pull the collar through the gasket, and hence the stop 156 may perform a strain relief function for the cable 100 when the fiber optic connector 120 of cable 100 is received within a fiber optical connector port on either of the Ericsson RRU-S11 or RRU-S12 RRUs. The body portion 152 may have an outer diameter that allows the gasket to properly perform its sealing function.
As best shown in FIG. 3, a first annular groove 162 of the stop 156, open to the body portion 152, may be provided as a seat of an end of the gasket, for retaining the gasket immediately prior to mating with the RRU/RRH. In further embodiments, for example as shown in FIGS. 4 and 5, a second annular groove 164 of the collar 154, open to the body portion 152, may be applied, for improved gasket retention. The first and/or second annular grooves 162, 164 may be provided as a straight or tapered bore. Thereby, a gasket 166, for example as shown in FIG. 6, may be applied and retained by the first and second annular grooves 162, 164 as shown for example in FIGS. 7 and 8.
Alternatively, as shown in FIGS. 9 and 10, the collar 154 may also be provided with a gasket seat 168 at a cable end, provided with a diameter greater than the body portion 152 but less than the collar 154. Thereby a gasket 166 dimensioned to seat against the gasket seat 168 has a shoulder provided by the collar 154, operative again as a stop shoulder, preventing axial movement of the cable adapter sleeve 150 and thus the attached armor tube 140 out of the RRU/RRH when tension is applied from the cable end.
In the depicted embodiment, the axial cross-sections through the body portion 152, collar 154 and stop 156 are all substantially circular cross-sections, which facilitates inserting these portions of the cable adapter sleeve 150 within different clamps, gaskets and the like on commercially available RRU/RRHs so that proper sealing and strain relief may be provided when the cable 100 is connected to various of these RRU/RRHs. It will be appreciated, however, that other cross-sectional diameters may alternatively be used, particularly if appropriate for the clamp and gasket designs (and/or the designs of other features) on these RRU/RRHs.
Thus, as discussed above, it will be appreciated that the cable adapter sleeve 150 includes multiple sections having different cross-sectional outer diameters that may be received within different sized clamps, gaskets and the like on RRU/RRHs in order to facilitate using the cable 100 with a variety of different RRU/RRHs. The cable adapter sleeve 150 may be located adjacent the fiber optic connector 120 so that it will properly mate with the different sealing, clamping and/or strain relief components on the various RRU/RRHs. For example, in some embodiments, the front portion of the cable adapter sleeve (i.e., the portion of the cable adapter sleeve 150 that includes the stop 156) may be in the range of about 140 mm to about 200 mm from the front of the fiber optic connector (which is the forward most part of cable 100). The body portion 152 may need to have a minimum length so that the body portion 152 will properly fit through the aperture in the gaskets provided on various RRU/RRHs.
Returning to FIG. 1, one skilled in the art will appreciate that the cable adapter sleeves 150 may be applied to a single fiber conductor cable or to multiple armor tubes 140 of a multi-conductor cable which may include a plurality of optical cable cores 110 to be separately terminated. The multi-conductor cable may further include electrical conductors 170, the electrical conductors 170 provided with a shielded furcation tube 172 and a shield layer to multi-conductor cable shield interconnection at a transition housing 174 where the cable cores 110 are also broken out into their respective armor tubes 140. Shielded furcation tubes 172 and interconnections between the shield layer 176 of the shielded furcation tube 172 and the shield 178 of the multi-conductor cable are disclosed in detail in commonly owned U.S. patent application Ser. No. 13/791,248, “Shielded Electrical Conductor Furcation Assembly”, filed 8 Mar. 2013 by Nahid Islam, hereby incorporated by reference in its entirety. The number of optical and/or electrical conductors present in the may be selected as desired, according to the intended installation.
While the cables and cable adapter sleeves according to embodiments of the present invention have primarily been discussed above with respect to their use on RRU/RRHs, it will be appreciated that there may be other applications such as enclosure units and the like in which the fiber optic cables and cable adapter sleeves according to embodiments of the present invention may be used in order to provide universal cables that may be used with multiple of such units that have different cable clamping, sealing and strain relief designs.
One skilled in the art will appreciate that the application of the cable adapter sleeve enables a single cable assembly to be used with a wide range of RRU/RRH equipment, enabling simplified cable assembly manufacture, inventory, procurement and/or field exchange of equipment.










Table of Parts
















100
cable


110
cable core


112
optical fiber


120
first optical connector


130
second optical connector


140
armor tube


150
cable adapter sleeve


152
body portion


154
collar


155
passageway


156
stop


157
internal passageway


158
larger step


159
smaller step


160
aperture


162
first annular groove


164
second annular groove


166
gasket


168
gasket seat


170
electrical conductor


172
shielded furcation tube


174
transition housing


176
shield layer


178
shield









Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.

## Claims

1. A fiber optic cable mateable with a plurality of remote radio unit configurations, comprising:
a cable core that includes at least one optical fiber;
a fiber optic connector that receives the at least one optical fiber;
a monolithic cable adapter sleeve that is axially mounted on the cable core to surround the cable core, the cable adapter sleeve including a body portion that has a first outer diameter, a collar that has a second outer diameter that is greater than the first outer diameter, and a stop that has a third outer diameter that is greater than the first outer diameter; and
an armor tube surrounding the cable core has a fourth outer diameter that is greater than the first outer diameter but less than the second outer diameter, the protective armor tube coupled to an internal passageway of the collar.

2. The fiber optic cable of claim 1, further including a first annular grove provided in the stop, the first annular groove open to the body portion.

3. The fiber optic cable of claim 1, further including a second annular groove provided in the collar, the second annular groove open to the body portion.

4. The fiber optic cable of claim 1, wherein the stop, the body portion and the collar have circular cross-sections.

5. The fiber optic cable of claim 1, wherein the collar includes an aperture extending between an outer diameter of the collar and a passageway of the collar.

6. The fiber optic cable of claim 1, wherein the collar has a gasket seat at a cable end that has a fourth outer diameter which is greater than the first outer diameter and less than the second outer diameter.

7. The fiber optic cable of claim 1, wherein a fourth outer diameter of the protective armor tube is configured to be received within a clamp of a first remote radio unit.

8. The fiber optic cable of claim 1, wherein the first outer diameter of the body portion of the cable adapter sleeve is sized to sealingly fit within a gasket on a second remote radio unit.

9. The fiber optic cable of claim 1, wherein the second outer diameter of the collar of the cable adapter sleeve is configured to be received within a clamping structure of a third remote radio unit.

10. The fiber optic cable of claim 1, the fiber optic cable further includes at least one electrical conductor.

11. The fiber optic cable of claim 1, wherein a front of the fiber optic connector is positioned between about 140 mm and about 200 mm from a front of the collar of the cable adapter sleeve.

12. A method for manufacturing a fiber optic cable mateable with a plurality of remote radio unit configurations, comprising:
providing a cable core that includes at least one optical fiber;
coupling a fiber optic connector that to the at least one optical fiber;
mounting a monolithic cable adapter sleeve axially on the cable core to surround the cable core, the cable adapter sleeve including a body portion that has a first outer diameter, a collar that has a second outer diameter that is greater than the first outer diameter, and a stop that has a third outer diameter that is greater than the first outer diameter; and
coupling an armor tube to an internal passageway of the collar, the armor tube provided with a fourth outer diameter that is greater than the first outer diameter but less than the second outer diameter.

13. The method of claim 12, wherein the cable adapter sleeve is mounted by overmolding the cable adapter sleeve upon an outer diameter of the cable core.

14. The method of claim 12, wherein the cable adapter sleeve is mounted by passing the cable core through a passageway of the cable adapter sleeve and gluing the cable adapter sleeve at a desired axial position onto an outer diameter of the cable core.

15. The method of claim 12, wherein the cable adapter sleeve is mounted such that a front of the fiber optic connector is positioned between about 140 mm and about 200 mm from a front of the collar of the cable adapter sleeve.

16. The method of claim 12, further including at least one electrical conductor in the cable.

17. The method of claim 16, wherein the at least one electrical conductor is provided with a shielded furcation tube with a metallic shield layer.

18. The method of claim 17, wherein the metallic shield layer is coupled to a shield of the cable.