Fiber optic receptacle and plug assembly including alignment sleeve insert

A fiber optic receptacle and plug assembly includes a fiber optic receptacle adapted to be mounted within a connector port of a network connection terminal and a fiber optic plug mounted upon an end of a fiber optic cable, wherein the fiber optic receptacle and the fiber optic plug comprise complimentary alignment and keying features that allow the fiber optic receptacle to receive only a fiber optic plug of like ferrule configuration. The fiber optic receptacle includes an alignment sleeve insert operable for receiving and optically connecting at least one receptacle ferrule and at least one opposing plug ferrule. The receptacle is suitable for use in enclosures requiring a minimal receptacle penetration depth, wherein the fiber optic receptacle comprises a shoulder that is secured against an inner wall of the enclosure to provide strain relief against cable-pulling forces of up to about 600 lbs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to assemblies for interconnecting optical fibers, and more specifically, to fiber optic receptacle and plug assemblies including an alignment sleeve insert with alignment and keying features for interconnecting optical fibers within a fiber optic communications network.

2. Technical Background

Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result, fiber optic communications networks include a number of interconnection points at which optical fibers are interconnected with other optical fibers. Fiber optic networks also include a number of connection terminals, examples of which include, but are not limited to, network access point (NAP) enclosures, aerial closures, below grade closures, pedestals, optical network terminals (ONTs) and network interface devices (NIDs). In certain instances the connection terminals include connector ports, typically opening through an external wall of the terminal, that are used to establish optical connections between optical fibers terminated from the distribution cable and respective optical fibers of one or more pre-connectorized drop cables, extended distribution cables, tether cables or branch cables, collectively referred to herein as “drop cables.” The connection terminals are used to provide communications services to a subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH) and “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.”

Conventional connector ports opening through an external wall of a connection terminal typically include a receptacle for receiving a connectorized optical fiber, such as a pigtail, optically connected within the connection terminal to an optical fiber of the distribution cable, for example in a splice tray or splice protector. At present, these receptacles are relatively large in size because the connection terminal in which they are located does not limit the size of the receptacle. Furthermore, existing receptacles include a two-piece receptacle housing defining an interior cavity that houses a biased alignment sleeve for receiving and aligning the mating ferrules. As previously mentioned, one of the mating ferrules is mounted upon the end of an optical fiber that is optically connected to an optical fiber of the distribution cable within the connection terminal. The other mating ferrule is mounted upon the end of an optical fiber of a drop cable that extends into the receptacle from outside the connection terminal. The alignment sleeve of the receptacle assists in gross alignment of the ferrules, and ferrule guide pins or other alignment means assist in more precise alignment of the opposing end faces of the ferrules.

In particular, a fiber optic plug mounted upon the end of a fiber optic drop cable is received within the receptacle through the external wall of the connection terminal. Typically, the plug includes a generally cylindrical plug body and a fiber optic connector including a plug ferrule disposed within the cylindrical plug body. The end of the cylindrical plug body is open, or is provided with one or more openings covered by a removable cap, so that the ferrule is accessible. The plug ferrule is mounted upon one or more optical fibers of the fiber optic drop cable such that mating the plug with the receptacle aligns the optical fibers of the drop cable with respective optical fibers terminated from the distribution cable within the connection terminal. In the process of mating the plug with the receptacle, the plug ferrule is inserted into one end of the alignment sleeve housed within the receptacle. As a result of the construction of a conventional fiber optic plug, the alignment sleeve is minimally received within the open end of the plug body as the plug ferrule is inserted into the alignment sleeve.

Several different types of conventional fiber optic connectors have been developed, examples of which include, but are not limited to, SC, ST, LC, DC, MTP, MT-RJ and SC-DC connectors. The size and shape of each of these conventional connectors are somewhat different. Correspondingly, the size and shape of the alignment sleeve, the receptacle and the plug are somewhat different. As a result, in conventional practice different fiber optic receptacles and plugs are utilized in conjunction with the different types of fiber optic connectors. In this regard, the fiber optic receptacles generally define different sized internal cavities corresponding to the sizes of the alignment sleeve and, in turn, according to a ferrule of the fiber optic connector to be inserted within the alignment sleeve.

In addition to requiring the use of different fiber optic receptacles and plugs based upon the specific type of optical connector, conventional receptacle and plug assemblies are relatively large in size. More compact and organized assemblies are needed for high-density installations. Current smaller sized assemblies, however, are not able to satisfy the high tensile loads required for FTTx installations, including for example the 600 lbs. drop cable pull test requirement. Exposure to adverse environmental conditions is also a significant concern since current network plans suggest that receptacles may remain unoccupied (without a mated plug) for an extended period of time due to initial service (also referred to as “take rates”) being less than total capacity. Based on tensile load requirements and the need for prolonged environmental protection, it would be desirable to provide a fiber optic receptacle and corresponding fiber optic plug suitable for foolproof mounting in a connection terminal or similar enclosure defining an external wall through which optical fibers are interconnected. As yet however, there is an unresolved need for a compact, yet sufficiently robust fiber optic receptacle that is configured to receive only a fiber optic plug having the same type of optical fiber connector. There is a further unresolved need for a fiber optic receptacle adapted to accommodate an alignment sleeve insert with alignment and keying features that correspond to complimentary alignment and keying features provided on a fiber optic plug of like ferrule configuration.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides various embodiments of fiber optic receptacle and plug assemblies adapted to receive like ferrule configurations. Thus, the present invention provides fiber optic receptacle and plug assemblies designed to readily mate any like number of optical fibers via the use of a connector port disposed within a wall of an enclosure. The present invention further provides smaller sized (i.e., low volume) fiber optic receptacles designed to be secured within connector ports or similar structures of an enclosure, while providing strain relief against drop cable-pulling forces of up to about 600 lbs.

In another aspect, the present invention provides a fiber optic receptacle and plug assembly comprising a fiber optic receptacle adapted to be mounted within a connector port of a network connection terminal and a corresponding fiber optic plug mounted upon an end of a fiber optic cable. The fiber optic receptacle and the fiber optic plug comprise complimentary alignment and keying features that allow the fiber optic receptacle to receive only a fiber optic plug of like ferrule configuration. The fiber optic plug engages a corresponding receptacle within a connector port disposed within a wall of a network connection terminal or other enclosure. The alignment and keying features of the fiber optic receptacle and plug assembly allow non-centric positions of at least one ferrule and radial alignment of the ferrule. The fiber optic receptacle defines an interior cavity for receiving and housing an alignment sleeve insert that includes an alignment sleeve holder defining one or more openings for receiving an alignment sleeve. The alignment sleeve insert is relatively shallow, thus minimizing the depth of the receptacle. The receptacle defines a keying and alignment feature within its interior cavity that is received within a keying and alignment slot defined by the alignment sleeve holder. The keying and alignment feature defined by the receptacle also corresponds to a plug insert of a corresponding fiber optic plug. The receptacle further comprises a shoulder that is secured against a wall of the connection terminal in order to provide strain relief. In an alternative embodiment, the alignment sleeve insert is a molded feature of the receptacle.

In yet another embodiment, the present invention provides a fiber optic receptacle and plug assembly comprising a fiber optic receptacle adapted to be mounted within a connector port of a connection terminal. The receptacle comprises a housing defining an interior cavity opening through opposed first and second ends, wherein the interior cavity is operable for receiving an alignment sleeve insert and a corresponding fiber optic plug through the first end. Any of a variety of pre-assembled back ends may be received through the second end of the receptacle housing such that at least one receptacle ferrule is received within the interior cavity and ultimately received within at least one alignment sleeve of the alignment sleeve holder. In one embodiment, the pre-assembled back end may be secured within the receptacle housing by a ferrule retainer disposed proximate the second end. The assembly further comprises a fiber optic plug including an inner housing, an outer housing, a coupling nut, at least one plug ferrule and a plug insert defining a keying slot and a clearance opening to allow the alignment sleeve holder to be received within the fiber optic plug during connection. The receptacle, alignment sleeve holder, plug housing and plug insert each define alignment and keying features based on ferrule configuration, thus providing a fiber optic receptacle and plug assembly that allows the receptacle to receive only a plug of like ferrule configuration and only in a preferred mating orientation. The receptacle and/or plug may further comprise biasing members that operably engage the ferrules to urge the opposing ferrules towards one another during mating.

It is to be understood that both the foregoing general description and the following detailed description present exemplary 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 into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the detailed description, serve to explain the principles and operations thereof. Additionally, the drawings and descriptions are meant to be illustrative and not limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. Although specific, fiber optic receptacle and plug assemblies for interconnecting optical fibers are shown throughout the figures, it should be understood that the receptacle and plug assemblies described and shown herein may be modified in certain respects, while still including an alignment sleeve insert with alignment and keying features in accordance with the intended scope of the present invention.

In the various embodiments described below, the present invention comprises fiber optic receptacle and plug assemblies for interconnecting optical fibers within an optical communications network. The receptacle portion of each assembly is designed such that it may be mounted in a wall of an enclosure or similar structure defining an external wall through which one or more optical fibers are routed. A rigid shoulder of the fiber optic receptacle is positioned within the enclosure and abuts against the external wall, thus providing superior retention for external pulling forces as compared to conventional assemblies that utilize a threaded nut on the inside of the wall for securing the receptacle. In the exemplary embodiments shown and described herein, the fiber optic plug portion is mounted upon the end of a fiber optic cable comprising one or more optical fibers to be optically connected to corresponding optical fibers routed to the receptacle portion of the assembly. As used herein, the fiber optic cable of the plug is referred to as the “drop cable” and is intended to include all types of fiber optic cables such as, but not limited to a distribution cable, a branch cable, an extended distribution cable, a tether cable, a flat dielectric drop cable, a figure-eight drop cable and an armored drop cable. Furthermore, the particular components of the fiber optic receptacle and plug assemblies described herein may be modified as necessary to accommodate different types of fiber optic cables.

In the exemplary embodiments shown, the drop cable comprises a cable jacket, and a strength component and an optical transmission component disposed within the cable jacket. In one embodiment, the strength component comprises two glass-reinforced plastic (GRP) strength components and the optical transmission component comprises an optical waveguide disposed within a central buffer tube. The drop cable may also comprise strength members that provide additional tensile strength. As used herein, the term “strength component” refers to a strength element having anti-buckling strength, while the term “strength member” refers to a strength element lacking anti-buckling strength. Furthermore, the term “tensile element” refers generically to either a strength component or a strength member. Strength members allow a fiber optic cable to have a smaller cross-sectional footprint due to the fact that they allow the strength components to have smaller diameters since they will not provide all of the tensile strength to the cable. In other words, both the strength components and the strength members carry the tensile load, while only the strength components provide anti-buckling strength. Moreover, by using strength members, the cable remains relatively flexible and is easier to handle. It is understood that other cable types may be used in conjunction with the present invention. Moreover, various optical connectors and/or ferrules may be used with different fiber optic cables according to the concepts of the present invention, thereby resulting in numerous fiber optic cable and connector/ferrule combinations. The drop cable is preferably designed to provide stable performance over a wide range of temperatures and to be compatible with any telecommunications grade optical fiber. As used herein, the term “optical fiber” is intended to include all types of single mode and multi-mode light waveguides, including one or more bare optical fibers, coated optical fibers, loose-tube optical fibers, tight-buffered optical fibers, ribbonized optical fibers or any other expedient no known or hereinafter devised for transmitting light signals.

The fiber optic receptacle and plug assemblies of the present invention provide a sealed environment that prevents moisture and contamination from reaching the end faces of the opposing ferrules. In all embodiments, O-rings or flat elastomeric gaskets provide static seals. The position of the seals combined with relief features provided on the receptacle and plug minimize vacuum build-up while uncoupling the plug from the receptacle and pressure build-up while mating the plug with the receptacle. Generally speaking, most of the components of the receptacle and plug assembly are formed from a suitable polymer. Preferably, the polymer is a UV stabilized polymer such as ULTEM 2210 available from GE Plastics. However, other suitable high strength materials, including composite materials and metals may also be used. For example, stainless steel or any other suitable metal may be used for various components to provide an even more robust receptacle and plug assembly.

Referring now toFIGS. 1-2, a fiber optic receptacle and plug assembly according to one embodiment of the present invention is shown.FIG. 1is a perspective view of a dual-fiber version of a fiber optic receptacle and plug assembly shown disengaged and partially disassembled.FIG. 2is a perspective view of the end faces of the fiber optic receptacle and corresponding plug ofFIG. 1illustrating alignment and keying features for ensuring that the opposing ferrules are mated in a desired orientation. The assembly includes a fiber optic receptacle20and a corresponding fiber optic plug22. Although not shown for purposes of clarity, the receptacle20is typically mounted within an opening, referred to herein as a “connector port,” located in a wall of an enclosure, such as a connection terminal in a fiber optic communications network. In a particularly advantageous embodiment, the receptacle20is mounted within a connector port located in an external wall of a connection terminal. As such, the receptacle20is operable for connecting optical fibers routed to the connector port from outside the connection terminal with optical fibers routed to the connector port from within the connection terminal. It should be understood, however, that the fiber optic receptacle20may be mounted to other enclosures and structures, including an internal wall of a re-enterable connection terminal. Each connector port is operable for receiving at least one receptacle20having at least one connectorized optical fiber routed to the receptacle from the inside of the connection terminal, and a plug22having at least one connectorized optical fiber of a drop cable24routed to the receptacle from the outside of the connection terminal. The plug22is mounted upon the end portion of the drop cable24and is adapted to mate with the corresponding receptacle20. The plug22and the receptacle20are further operable for aligning and maintaining the opposing optical fibers in physical contact. A single connector port may interconnect one optical fiber or more than one optical fiber, either by accommodating a multi-fiber ferrule or by accommodating multiple single-fiber ferrules within a receptacle configured to receive a corresponding plug. A single connector port may also be adapted to accommodate more than one receptacle20that is likewise configured to receive more than one plug22.

Still referring toFIGS. 1-2, the receptacle20and the corresponding plug22are shown disengaged and with the respective protective dust cap and pulling cap removed. To secure the plug22and receptacle20together, a threaded coupling nut26engages the threaded end of the receptacle20. The coupling nut26of the plug22is operable for securing the plug22to the receptacle20upon threaded engagement, and may also be used to secure a protective pulling cap to the plug22during installation of the drop cable24. As with the plug22of the assembly, the receptacle20may also be covered and sealed with a threaded dust cap that engages the threaded end of the receptacle and is removed immediately prior to inserting the plug22into the receptacle20. At the end of the receptacle20opposite the threads, a protective boot (not shown) may be used to protect the receptacle20, and in some embodiments may also provide sealing. The use of a protective sealing boot allows the assembly to be installed in a breathable or re-enterable enclosure and may become obsolete in the event the receptacle20is otherwise reliably sealed from adverse environmental conditions.

The fiber optic receptacle20includes a receptacle housing38operable for mounting through the wall of the connection terminal. The housing38retains a ferrule assembly39, such as a pre-assembled back-end ferrule assembly, and is at least partly responsible for aligning the ferrule assembly39of the receptacle and the ferrule assembly of the corresponding fiber optic plug22so that the receptacle and the plug can be engaged in only one desired orientation, as will be described in more detail below. This feature is particularly advantageous for installations including Angled Physical Contact (APC) type ferrules where minimal angular offset is required, as well as installations including multiple single-fiber ferrules. The receptacle housing38defines an interior cavity40opening through a first end42and an opposed second end44. Typically, the opening through the first end42is relatively large so as to receive the corresponding fiber optic plug22. Conversely, the opening through the second end44is typically smaller, and in one advantageous embodiment, is sized to be only slightly larger than the ferrule assembly39. The relatively large opening of the first end42permits cleaning, for example the ferrule end face, with a cotton swab or special cleaning tool. This is advantageous since receptacles, in contrast to fiber optic plugs, may be exposed to adverse environmental conditions while not being used for a prolonged period of time during which the end face of the ferrule may become contaminated with dust dirt, oil, etc. Such an embodiment allows for easy cleaning and improved access without requiring disassembly.

Although the fiber optic receptacle20may include a variety of fiber optic connectors including SC, LC, MTRJ, MTP, SC-DC, and the like, the receptacle20of the embodiment shown and described herein includes dual SC connectors by way of example, and not of limitation. An alignment sleeve insert41, including an alignment sleeve holder43and alignment sleeves45, is received within the interior cavity40of the receptacle housing38through the first end42. As shown inFIGS. 1-2, the alignment sleeve insert41is a component of the receptacle20. In the alternative exemplary embodiments shown inFIGS. 3-16, the alignment sleeve insert41is a component of the plug22and is inserted into the interior cavity40of the receptacle20upon engagement of the plug22with the receptacle. The alignment sleeve holder43defines a relatively flat, disc-shaped portion47for seating against an inner wall of the housing38, and a protruding portion49defining openings51for receiving the alignment sleeves45. The flat portion47further defines a slot53that operates as a clearance to receive a molded alignment feature and key108of the receptacle20. Thus, only an alignment sleeve holder43having a key slot53complimentary to the key108formed within the housing38may be properly inserted into the interior cavity40.

As described above, the plug22engages the receptacle20to optically connect the optical fibers routed to the plug22and the receptacle20. The protruding portion49of the alignment sleeve holder43defines alignment sleeve openings51corresponding to the number and type of mating ferrules. In the embodiment shown, two alignment sleeve openings51are formed to accept two alignment sleeves45used to mate a pair (dual) single-fiber SC ferrules, thus providing a “duplex” optical connector. The alignment sleeve insert41is positioned and retained within the interior cavity40of the receptacle20. A plug outer housing68retains a plug insert55that defines a clearance opening57for receiving the protruding portion49of the alignment sleeve holder43. The plug insert55defines a further opening59that aligns with a feature provided on the plug outer housing68, both of which define a clearance for receiving the key108of the receptacle housing38to properly align the plug22with the receptacle20. Thus, the key slot53of the alignment sleeve holder43, the opening59of the plug insert55, and the feature of the plug outer housing68are all aligned in such a manner that they collectively pass over the key108of the housing38upon insertion of the plug22into the receptacle20. The plug outer housing68may also define at least one opening104along its length for receiving a detent feature106defined by the plug insert55. As shown, detent features106and openings104may be provided on each side, and may be of a different size and/or shape in order to properly align the plug insert55within the plug outer housing68, and thereby properly align the opening59of the plug insert55with the outer housing68.

To form an optical connection, the plug22is inserted into the receptacle20. As previously mentioned, the receptacle20may only receive a plug22of like ferrule configuration. The receptacle20defines the key108which may have any desired shape and is preferably molded into the housing38of the receptacle20. Receptacles having specific key shapes may be created for each type and/or number of ferrules. In an alternative embodiment, an insert having a specific key shape may be inserted into the receptacle housing38to accommodate a specific plug, thus allowing a generic receptacle housing to be used for different connector types. Upon engagement, the key108ensures that the receptacle20will accept only a plug22having a like ferrule configuration, while also properly aligning the plug22within the receptacle20. Because the alignment and keying features extend to about the end of the plug22(i.e., beyond the ferrule), a plug22having a ferrule configuration different than the receptacle20may not be inserted into the receptacle20, thereby eliminating potential damage to the ferrules.

The receptacle housing38is cylindrically shaped and defines an outwardly depending shoulder portion48positioned medially between the first end42and the second end44. During installation through an external wall of a connection terminal, the first end42of the receptacle housing38is inserted through the wall from the inside of the connection terminal until the radial surface of the shoulder portion48facing the first end42abuts the inner surface of the wall. By securing the receptacle20within the opening through the external wall of the connection terminal using shoulder portion48, as opposed to a threaded nut for example, the relatively low profile receptacle20provides strain relief against cable-pulling forces of up to about 600 lbs. Preferably, a seal is provided between the shoulder portion48of receptacle housing38and the wall using an O-ring, an elastomeric ring, a multi-point seal50(as shown) or like sealing means.

The ferrule assembly39includes a ferrule retainer56for retaining the ferrule assembly39within the receptacle housing38. The ferrule retainer56and the receptacle housing38can be connected in various manners, but, in one advantageous embodiment, the ferrule retainer56includes hooks58that are received by detent features60formed on the receptacle housing38. The ferrule retainer56can be removed from the receptacle housing38in order to access the ferrules, such as for cleaning, repair, replacement or the like. The design of the ferrule retainer56allows for easy removal without a special tool. Once the ferrule assembly39has been cleaned, repaired or replaced as necessary, the ferrule retainer56can be connected once again to the receptacle housing38. The hooks58may be of differing sizes on each side of the retainer59and may be received within different sized features60in order to orient the ferrule assembly39within the receptacle housing39in a desired manner (e.g., polarization). The ferrule retainer56may also define different sized ears61that are received by different sized detent features60, such the slots shown herein, within the interior of the receptacle housing38adjacent the second end44.

The ferrule assembly39may also include one or more bias members disposed within for operably engaging and urging the ferrules46toward the first end42of the receptacle housing38. Typically, the bias members consist of one or more springs. Thus, each receptacle ferrule46is spring-loaded and thereby permitted to float axially within the interior cavity40, thus absorbing compressive forces between the receptacle ferrules46and the opposing plug ferrules70(FIG. 2).

Referring toFIG. 3, the receptacle20and the corresponding plug22are shown disengaged and with the respective protective dust cap34and pulling cap28removed. A threaded coupling nut26of the plug22operable for securing the plug22to the receptacle20following engagement may also be used to secure the protective pulling cap28on the plug assembly during shipment and deployment prior to installation on the receptacle20. The pulling cap28defines a threaded portion29at its rearward end and a pulling loop30at its forward end. The pulling cap28provides protection of the optical connector32of the plug22during shipping, deployment and until engagement with the receptacle20. The pulling cap28may be secured to the drop cable24using a tether33so that the pulling cap28may be reused if the plug22is disengaged from the receptacle20at a later time. In preferred embodiments, the pulling loop30should be able to withstand cable-pulling forces up to about 600 lbs. The pulling loop30and the pulling cap28have a generally rounded forward end to facilitate deployment through conduits and ducts, or over sheave wheels and pulleys. As with the plug22of the assembly, the receptacle20may also be covered and sealed with a threaded dust cap34that is removed prior to inserting the plug22within the receptacle20. The dust cap34may also be secured to the receptacle20using a like tether33. At the end of the receptacle20opposite the threaded end, a protective boot36provides protection for the receptacle20, and in some embodiments may also provide sealing. The boot36allows the assembly to be installed in a breathable enclosure and may become obsolete in the event the receptacle20is otherwise reliably sealed from the adverse environment.

Referring toFIG. 4, the fiber optic plug22is shown mounted upon the end portion of the fiber optic drop cable24and mated with the corresponding fiber optic receptacle20. To secure the plug22and receptacle20together, the coupling nut26engages the threaded end of the receptacle20. The manner in which the receptacle20and plug22assembly is secured within the connector port through the external wall of the connection terminal is described in further detail below in conjunction with other embodiments.

Referring toFIG. 5, another embodiment of a fiber optic receptacle20includes a receptacle housing38operable for mounting to the wall of a connection terminal. The housing38holds a ferrule assembly and aligns both the ferrule assembly and the fiber optic plug22so that they can engage in only one preferred orientation. This feature is advantageous for installations including Angled Physical Contact (APC) type ferrules where only minimal angular offset is tolerable, as well as multi-fiber ferrules that often are not centric. The receptacle housing38defines an interior cavity40opening through opposed ends, a first end42and a second end44. Typically, the opening through the first end42is relatively large so as to receive the corresponding fiber optic plug22. Conversely, the opening through the second end44is typically smaller and, in one advantageous embodiment, is sized to be only slightly larger than the receptacle ferrule46, such that the ferrule46can be inserted through the opening. The relatively large opening of the first end42allows cleaning with a cotton swab or special cleaning tool.

Although the fiber optic receptacle20may include a variety of fiber optic connectors including SC, LC, MTRJ, MTP, SC-DC, and the like, the receptacle20of the particular embodiment is shown to include a single SC connector by way of example, and not of limitation. Although not included in this particular embodiment, the fiber optic receptacle20may include an alignment sleeve disposed within the interior cavity40defined by the receptacle housing38. In the embodiments shown throughoutFIGS. 3-16, the alignment sleeve is a component of the plug22and is inserted into the interior cavity40of the receptacle20upon insertion of the plug22. In this regard, the plug ferrule of the fiber optic plug22is inserted into one end of the alignment sleeve, while the receptacle ferrule46that is mounted upon the ends of optical fibers routed from within the connection terminal is inserted through the opening defined by the second end44of the receptacle20and into the opposite end of the alignment sleeve.

As shown, the receptacle housing38is cylindrically shaped and defines a shoulder portion48positioned medially between the first end42and the second end44. During installation through an external wall of a connection terminal, the first end42of the receptacle housing38is inserted through the wall from the inside of the connection terminal until the radial surface of the shoulder portion48facing the first end42abuts the inner surface of the wall. By securing the receptacle20within the opening through the external wall of the connection terminal using shoulder portion48, as opposed to a threaded nut for example, the relatively low profile receptacle20provides strain relief against cable-pulling forces of up to about 600 lbs. Preferably, a seal is provided between the shoulder portion48of receptacle housing38and the wall using an O-ring, an elastomeric ring, a multi-point seal50(as shown) or like sealing means. The receptacle housing38defines a notch52between the shoulder portion48and the threaded end for receiving the multi-point seal50. The notch52may further receive a crescent ring54for retaining the multi-point seal50in place and securing the receptacle20within the connector port defined by the opening in the wall of the connection terminal. The coupling nut26of the plug22is used to further secure the receptacle20within the connector port when the plug22is mated with the receptacle20.

The fiber optic receptacle20also includes a ferrule retainer56for retaining the receptacle ferrule46within the interior cavity40of the receptacle housing38. The ferrule retainer56and the receptacle housing38can be connected in various manners without departing from the intended scope of the preset invention. In one advantageous embodiment, the ferrule retainer56includes hooks58that are received by detent features60protruding outwardly from the receptacle housing38. The ferrule retainer56can be removed from the receptacle housing38in order to access the receptacle ferrule46, such as for cleaning, repair, replacement or the like. The design of the ferrule retainer56allows for easy removal without a special tool. Once the receptacle ferrule46has been cleaned, repaired or replaced as necessary, the ferrule retainer56can be connected once again to the receptacle housing38.

The fiber optic receptacle20of the exemplary embodiment also includes a bias member disposed within the receptacle housing38. The bias member is positioned between and operably engages the ferrule retainer56and the receptacle ferrule46to urge the receptacle ferrule46toward the first end42of the receptacle housing38. As shown herein, the bias member consists of one or more linear coil springs62. Thus, the receptacle ferrule46is spring-loaded and is allowed to float axially within the interior cavity40, thus absorbing compressive forces between the receptacle ferrule46and the opposing plug ferrule70. A flexible boot36protects the components of the receptacle20positioned on the inside of the wall of the connection terminal. The protective boot36further defines an opening64for receiving optical fibers and/or a fiber optic cable (not shown) from the inside of the connection terminal.

FIG. 6is a cross-section of the assembled receptacle assembly20ofFIG. 5taken along line6-6with like parts indicated by like reference numbers. An O-ring66may be used to provide a seal between the dust cap34and the receptacle housing38. As is shown inFIG. 6, the multi-point seal50is retained within the groove52of the receptacle housing38and provides sealing points between the receptacle housing38and the wall of the connection terminal. The wall is positioned between the shoulder portion48of the receptacle housing38and the crescent ring54. In one embodiment, the crescent ring54secures the receptacle20in place. In an alternative embodiment, the dust cap34or the coupling nut26of the fiber optic plug22is used to secure the receptacle20in place.

Referring toFIG. 7, the fiber optic plug22further includes a plug ferrule70, an inner housing72with a crimp, an alignment sleeve74, an outer housing68and a coupling nut26. There may also be a plug boot (not shown) made of a flexible (silicone, rubber or other like) material secured over a portion of the outer housing68and a portion of the drop cable24in order to seal the exposed portion of the drop cable24while generally inhibiting kinking and providing bending strain relief to the cable24near the end of the plug22. The strength components78of the cable24are terminated and a crimp band80is secured around the strength components78. The crimp band80is preferably made from brass, but other suitable deformable materials may be used. The strength members (not shown) are cut flush with the stripped back jacket76, thereby exposing the strength components78and optical component82adjacent the end of the drop cable24. The crimp band80thereby provides strain relief for the cable24. The inner housing72is assembled by first crimping the crimp band80onto the strength components of the cable24. The outer housing68is then slid over the inner housing72. The outer housing68is positioned onto the cable24before the inner housing72.

The plug ferrule70is at least partially disposed within the inner housing72and extends lengthwise. The plug ferrule70may therefore be mounted within the inner housing72such that the front face of the plug ferrule70extends somewhat beyond the forward end of the inner housing72. As with the corresponding fiber optic receptacle20, the fiber optic plug22may include a variety of fiber optic connectors including SC, LC, MTRJ, MTP, SC-DC, and the like. The plug22of the exemplary embodiment is shown to include a single SC connector because a receptacle20can only receive a plug of like ferrule configuration. In this embodiment, the alignment sleeve74is positioned at least partially within the inner housing72and defines a lengthwise passageway for receiving the plug ferrule70and the opposing receptacle ferrule46when the plug22is mated with the receptacle20.

The outer housing68has a generally cylindrical shape with a forward first end84and a rearward second end86. The outer housing68generally protects the inner housing72and in preferred embodiments also aligns and keys engagement of the plug22with the mating receptacle20. Moreover, the inner housing68includes a through passageway between the first and second ends84and86. The passageway of the inner housing72includes a keying feature so that the inner housing72is inhibited from rotating once the plug22is assembled. The first end84of the outer housing68includes a key slot88(FIG. 7andFIG. 9) for aligning the plug22with the receptacle20, and consequently, the inner housing72relative to the receptacle20. The plug22and the corresponding receptacle20are shaped to permit mating in only one orientation. In preferred embodiments, this orientation may be marked on the receptacle20and on the plug22using alignment indicia so that a less skilled field technician can readily mate the plug22with the receptacle20. Any suitable indicia may be used. After alignment, the field technician engages the internal threads of the coupling nut26with the external threads of the receptacle20to secure the plug22to the receptacle20.

The outer housing68of the plug22may further define a shoulder90that provides a mechanical stop for both a conventional elastomeric O-ring92and the coupling nut26. The O-ring92provides a weatherproof seal when the coupling nut26engages the threaded portion of the receptacle20. The coupling nut26has a passageway sized so that it fits over the second end86of the outer housing68and easily rotates about the outer housing68. In other words, the coupling nut26cannot move in the direction of the receptacle20beyond the shoulder90, but is able to rotate with respect to the outer housing68.FIG. 8is a cross-section of the assembled plug22ofFIG. 7taken along line8-8with like parts indicated by like reference numbers.

FIG. 9is an end view of the receptacle20and plug22ofFIG. 3further illustrating the alignment and keying features of the assembly. As described above, the plug22engages the receptacle20to optically connect the optical fibers of the corresponding plug ferrule70and receptacle ferrule46. The receptacle20and the alignment sleeve74define ferrule openings100corresponding to the number and type of mating ferrules. In the embodiment shown throughoutFIGS. 3-9, one ferrule opening100is used to mate single-fiber SC ferrules, thus providing a “simplex” optical connector. The alignment sleeve74is retained and positioned within the outer housing68of the plug22such that the key slot102of the alignment sleeve74is aligned with the key slot88defined by the plug outer housing68. In a preferred embodiment, the plug outer housing68defines a pair of openings104along its length adjacent first end84for receiving features106defined by the alignment sleeve74. The features106are received by the openings104in order to properly align the alignment sleeve74within the plug outer housing68, thus properly aligning the key slot102of the alignment sleeve74with the key slot88of the outer housing68.

To perform an optical connection, the plug22is inserted into the receptacle20. The receptacle20may only receive a plug22of like ferrule configuration. The receptacle20defines a key108that is received within the key slot88of the plug housing68and the key slot102of the alignment sleeve74. As shown, the key108is a “T-shaped” structure, preferably molded into the receptacle20. Receptacles having specific key shapes may be created for each type and/or number of ferrules. In an alternative embodiment, an insert having a specific key shape may be inserted into the receptacle housing38to accommodate a specific connector, thus allowing a generic receptacle housing to be used for different connector types. Upon connection, the key108accepts only a plug22of like ferrule configuration, while also properly aligning the plug22within the receptacle20. Because the alignment and keying features extend to about the end of the plug22, a plug22having a ferrule configuration different than the receptacle20may not be inserted into the receptacle20, thereby eliminating potential damage to the ferrules. Alignment orientation is especially important in mating APC ferrules. The end face of an APC ferrule is disposed at a non-orthogonal angle, and generally at an angle of between about 6 and about 11 degrees relative to a plane normal to the longitudinal axis defined by the ferrule. Typically, the end face of an APC ferrule is disposed at about an 8-degree angle relative to the plane that extends normal to the longitudinal axis defined by the ferrule. In order to properly interconnect the optical fibers of a pair of opposing APC ferrules, the ferrules must be positioned such that the angled end faces are complimentary to one another, that is, the forwardmost portion of the end face of one ferrule is opposite the rearward most portion of the end face of the other ferrule. In order to facilitate the alignment of the ferrules in this complimentary fashion, the key108is disposed in a predetermined orientation relative to the end face of the ferrule.

Referring toFIG. 10, a dual-fiber version of a fiber optic receptacle20and plug22assembly is shown disengaged and with the protective dust cap34and pulling cap28of the receptacle and plug, respectively, removed. In this embodiment, the drop cable comprising two optical waveguides is not shown for purposes of clarity. The plug22is aligned with and engages only a receptacle20of like optical connector and ferrule configuration. The plug22shown allows a single receptacle20of a connection terminal to accommodate more than one optical fiber of the drop cable for optical connection with more than one optical fiber terminated from a distribution cable within the connection terminal. At the same time, the drop cable associated with the plug22is strain relieved at the connector port to withstand a drop cable-pulling force of up to about 600 lbs.

The receptacle20and the corresponding plug22are shown disengaged and with the respective dust cap34and pulling cap28removed. A threaded coupling nut26of the plug22is operable for securing the pulling cap28during shipping and deployment and for securing the plug22to the receptacle20following engagement when mating the plug22to the receptacle20. A flexible boot36allows the assembly to be installed in a breathable enclosure and may become obsolete in the event that the receptacle20is otherwise reliably sealed within the connection terminal from adverse environmental conditions. As in the previous embodiment, the plug outer housing68has a generally cylindrical shape and includes alignment and keying features for mating the plug22with the receptacle20. In particular, the outer housing68defines an alignment and keying feature on plug22. As shown herein and previously described, the alignment and keying feature is in the form of a lengthwise key slot94. The key slot94has a specific shape so that the plug22and receptacle20mate in only one orientation. In preferred embodiments, the orientation may be marked on both the outer housing68and the receptacle housing38so that a less skilled field technician can readily mate the plug22with the receptacle20by aligning an alignment indicia on the outer housing68with a complimentary alignment indicia disposed on the receptacle housing38. Thereafter, the field technician engages the internal threads of the coupling nut26with the external threads on the receptacle housing38to secure the plug assembly22to the receptacle20.

Referring toFIG. 11, the fiber optic plug22may be mounted upon any suitable fiber optic drop cable including more than one optical fiber since the optical connector shown includes more than one ferrule, such as a pair of LC ferrules. To secure the plug22to the receptacle20, the coupling nut26engages the threaded end of the receptacle20. The plug22may be secured in the field without special tools, equipment or training. Additionally, the physical connection may be easily connected or disconnected, thereby mating or un-mating the plug22with the receptacle20, by engaging or disengaging the threads of the coupling nut26with the threads of the receptacle20. Thus, the receptacle20and plug22assembly of the present invention allows the deployment of multiple optical fibers through a connector port provided in an external wall of a conventional network connection terminal in an easy, fast and economical manner.

Referring toFIG. 12, as in the embodiment described above, the fiber optic receptacle20includes a receptacle housing38operable for mounting to the wall, while holding a ferrule and aligning the ferrule with the fiber optic plug22so that they can engage in only a preferred orientation. The receptacle housing38defines an interior cavity40opening through opposed ends, a first end42and a second end44. The openings through the second end44are typically smaller and, in one advantageous embodiment, are sized to be only slightly larger than the receptacle ferrules46, such that the receptacle ferrules46can be inserted through the opening. Although the fiber optic receptacle20may include a variety of fiber optic connectors including SC, LC, MTRJ, MTP, SC-DC, and the like, the receptacle20of the particular embodiment is shown to include a pair of LC connectors by way of example, and not of limitation. As in the previous embodiment, the alignment sleeve74is a component of the plug22and is inserted into the interior cavity40of the receptacle20upon insertion of the plug22through first end42of receptacle20.

The receptacle housing38in the embodiment shown is cylindrically shaped and defines a shoulder portion48positioned medially between the first end42and the second end44. Upon installation of the receptacle20within a connector port through an external wall of a connection terminal, the first end42of the receptacle housing38is inserted through the wall from the inside of the connection terminal until the surface of the shoulder portion48facing the first end42comes into contact with the inner surface of the wall. A seal may be provided between the receptacle housing38and the wall using an O-ring, multi-point seal50(as shown) or like sealing means. The receptacle20also includes a ferrule retainer56operable for retaining the receptacle ferrules46within the interior cavity40of the receptacle housing38. The ferrule retainer56defines clips or hooks58that grip detent features60defined by the receptacle housing38. The ferrule retainer56can be removed from the receptacle housing38to access the receptacle ferrules46, such as for cleaning, repair, replacement or the like.

The fiber optic receptacle20of this exemplary embodiment also includes bias members disposed within the receptacle housing38. The bias members operably engage the receptacle ferrules46and the ferrule retainer56to urge the receptacle ferrules46toward the first end42of the receptacle housing38. As shown herein, the bias members consist of one or more linear coil springs62. Thus, the receptacle ferrules46are spring-loaded and thereby allowed to float axially within the interior cavity40, thus absorbing compressive forces between the receptacle ferrules46and the opposing plug ferrules70. It should be understood, however, that the fiber optic receptacle20can include other types of bias members, in addition to or instead of one or more springs62. The ferrule holder56may also include one or more posts (not shown) extending in a lengthwise direction such that a spring can be mounted upon each respective post. In such case, each spring62would be longer than its respective post, even in the compressed state. As such, the posts serve to position the springs62that, in turn, contact the receptacle ferrules46.FIG. 13is a cross-section of the assembled plug22ofFIG. 12taken along line13-13with like parts indicated by like reference numbers. An elastomeric O-ring seal66may be disposed between the dust cap34and the receptacle housing38. The fiber optic receptacle20is adapted to receive a corresponding fiber optic plug22such that plug ferrules70of the fiber optic plug22are aligned with and inserted into the first end42of the receptacle housing38.

Referring toFIG. 14, the corresponding plug22for the receptacle20shown inFIGS. 12-13generally includes a plug inner housing72, plug ferrules70, an alignment sleeve74, outer housing68and coupling nut26. There may also be a plug boot (not shown) made of a flexible material (e.g., silicone, rubber or the like) secured over a portion of the outer housing68and a portion of the drop cable (not shown) to seal and provide bending strain relief to the cable near the plug22. The crimp band80is secured around the strength components (not shown) of the cable and provides strain relief for the cable. The plug ferrules70are partially disposed within the inner housing72and extend lengthwise. To match the corresponding receptacle20, the fiber optic plug22may include a variety of fiber optic connectors including SC, LC, MTRJ, MTP, SC-DC, and the like. The plug22of this exemplary embodiment is shown to include a pair of LC connectors which are smaller than SC connectors, thus allowing the diameter of the assembly to remain the same as the exemplary embodiment utilizing SC connectors previously described. The plug ferrules70are received within a lengthwise passageway defined by the alignment sleeve74for mating the plug ferrules70and the receptacle ferrules46. The receptacle ferrules46are inserted into the open, forward end of the alignment sleeve74. Thus, the alignment sleeve74serves to align the plug ferrules70positioned within the alignment sleeve74with the receptacle ferrules46received within the opposite end of the alignment sleeve74when the plug22is inserted into the receptacle20. As such, the optical fibers upon which the respective ferrules are mounted are correspondingly aligned and optically interconnected.

The outer housing68generally protects the inner housing72and in preferred embodiments also aligns and keys mating of the plug22with the receptacle20. Moreover, the inner housing72includes a through passageway that is keyed so that the inner housing72is inhibited from rotating when the plug22is assembled. The outer housing68includes a key slot88defined by the outer housing68for aligning the plug22with the receptacle20. The plug22and the corresponding receptacle20are shaped to permit mating in only one orientation. After alignment, the field technician engages the internal threads of the coupling nut26with the external threads of the receptacle20to secure the plug22to the receptacle20.

The outer housing68may further define a shoulder90that provides a mechanical stop for both an O-ring92and the coupling nut26. The O-ring92provides a weatherproof seal between the plug22and the receptacle20. The coupling nut26has a passageway sized so that it fits over the end of the outer housing68and easily rotates about the outer housing68.FIG. 15is a cross-section of the assembled plug22ofFIG. 14taken along line15-15with like parts indicated by like reference numbers.

FIG. 16is an end view of the receptacle20and plug22ofFIG. 10further illustrating the alignment and keying features of the assembly. The receptacle20and the alignment sleeve74define ferrule openings100corresponding to the number and type of receptacle ferrules46and plug ferrules70, respectively. In the embodiment shown throughoutFIGS. 10-15, pairs of ferrule openings100are used to mate the opposing pairs of LC receptacle ferrules46and LC plug ferrules70, respectively, thus providing a “duplex” optical connector. The alignment sleeve74is retained and positioned within the outer housing68of the plug22such that the key slot102of the alignment sleeve74is aligned with the key slot88defined by the plug outer housing68. In a preferred embodiment, the plug outer housing68defines a pair of openings104along its length for receiving detent features106defined by the alignment sleeve74. The features106are received by the openings104in order to properly align the alignment sleeve74within the plug outer housing68, thus properly aligning the key slot102of the alignment sleeve74with the key slot88of the outer housing68. While the key slot102of the alignment sleeve74is preferably specific for each connector type, the key slot88of the outer housing68may be generic for all connector types, thus permitting the use of a common plug outer housing68for all connector types.

To perform an optical connection, the plug22is inserted into the receptacle20. The receptacle20is configured to receive only a plug22of like ferrule configuration. The receptacle20defines a key108that is received within the key slot88of the plug housing68and the key slot102of the alignment sleeve74. As shown, the key108is an “I-shaped” structure, preferably molded into the receptacle20. Receptacles having specific keying shapes may be created for each type and/or number of ferrules. In an alternative embodiment, an insert having a specific key shape may be inserted into the receptacle housing38to accommodate a specific connector, thus allowing a generic receptacle housing to be used for different connector types. Upon connection, the key108accepts only a plug22of like ferrule configuration, while also properly aligning the plug22within the receptacle20. Because the alignment and keying features extend to about the end of the plug22, a plug22having a ferrule configuration different than the receptacle20may not be inserted into the receptacle20, thereby eliminating potential damage to the receptacle ferrules46and the plug ferrules70.

In alternative embodiments, the threads of the coupling nut26and the receptacle housing38may be replaced with a bayonet or push-pull style mechanism to secure the plug22within the receptacle20. Alternatively, a spring clip or similar device may be added to engage the plug22and the receptacle20to secure them together. Sealing may be removed or relaxed based upon the extent of the adverse environmental conditions to which the assembly is exposed. The plug boot may be pre-manufactured and assembled onto the plug inner housing72and the drop cable24, or may be overmolded using a technology available from Corning Cable Systems LLC of Hickory, N.C. Further, heat shrinkable tubing may be used to fulfill the same purpose as the boot when aesthetics are less important and bend characteristics less stringent. As previously demonstrated in the embodiment illustrated inFIGS. 1-2, the alignment sleeve74may be integrated into the receptacle20while maintaining the same assembly technique and allowing for easy removal and cleaning.

Designs for several types of ferrules (including multi-fiber) can be derived from the base design shown and described herein. Multi-fiber ferrule designs driven by the available space and requirements are possible, such as MTP, MTRJ, DC, multiple 1.25 mm, multiple 2.5 mm, etc. Additional strain relief may be added to the receptacle20if needed. Crimping solutions may differ depending on the drop cable type and requirements. If the drop cable does not include the dual GRP dielectric strength members as shown in the first embodiment, the methods of coupling the strength member to the plug body may include glue or other means of fastening, such as clamps.

The embodiments described above provide advantages over conventional fiber optic receptacle and plug assemblies. For example, the small size of the exemplary embodiments described herein allows for about a 38 mm diameter package for FTTx distribution cables and allows the receptacles to be mounted in connection terminals or other enclosures requiring very little penetration depth of the receptacle into the terminal or enclosure. The alignment and keying features of these assemblies makes them fully APC capable, and the unique fit prevents assembly errors during production and installation. An overmolded boot eliminates the need for heat shrinkable tubing and also improves the sealing integrity of the assembly under adverse environmental conditions in which a pre-formed boot may disengage from the plug22.

The foregoing is a description of various embodiments of the invention that are given here by way of example only. Although fiber optic receptacle and plug assemblies have been described with reference to preferred embodiments and examples thereof, other embodiments and examples may perform similar functions or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the appended claims.