This invention relates generally to assemblies for interconnecting or otherwise terminating optical fibers and, more particularly, to fiber optic plugs for mating with corresponding receptacles.
Optical fibers are used in an increasing number and variety of applications, such as a wide variety of telecommunications and data transmission applications. As a result, fiber optic networks must include an ever increasing number of enclosures in which one or more of the optical fibers are interconnected or otherwise terminated. For example, fiber optic networks, such as cable television (CATV) networks, may include a number of optical network units (ONUs) in which the optical signals propagating along the optical fibers are converted to respective electrical signals. In addition, telephone and CATV networks can include a number of network interface devices (NIDs); each NID is associated with a particular subscriber. Upon receiving the incoming optical signals, the NID splits and routes the signals to predetermined locations, such as to various telephone or CATV outlets. Like an ONU, the NID can also convert the incoming optical signals to electrical signals, if necessary. Fiber optic networks can also include a number of other closures, including splice closures, in which various ones of the optical fibers are spliced or optically connected. Regardless of the type, these enclosures provide protection, such as from moisture or other forms of environmental degradation, for the optical fibers and, more particularly, the point at which the optical fibers are spliced or are otherwise optically connected.
These enclosures, such as ONUs, NIDs, and other closures, typically include one or more receptacles in which the individual optical fibers of a fiber optic cable are connected to respective optical fibers within the enclosure. The optical fibers within the enclosure can then be interconnected or otherwise terminated as desired. Conventionally, receptacles have included a receptacle housing defining an internal cavity and an adapter sleeve disposed in a fixed position within the internal cavity defined by the receptacle housing. The adapter sleeve is designed to receive a pair of ferrules, each of which is mounted upon the end portions of a plurality of optical fibers. One of the ferrules is attached to the end of optical fibers extending from a cable, ribbon, or optical fiber device that extends into or is located in the interior of the enclosure to facilitate splicing or other interconnection or termination of the optical fibers. As described below, the other ferrule is mounted upon optical fibers extending from a cable, ribbon, or optical fiber device that extends outside or is located outside of the enclosure, such as the optical fibers of a fiber optic cable. The adapter sleeve assents in gross alignment of the ferrules, and ferrule guide pins or other alignment means assent in detailed alignment of the optical fibers mounted on the end faces of each ferrule.
In order to mate with the receptacle of a conventional enclosure, a fiber optic plug is mounted upon the end portion of a fiber optic cable. Typically, the plug includes a generally cylindrical plug body and a fiber optic connector including a plug ferrule disposed within the cylindrical plug body. In order to protect the plug ferrule, the cylindrical plug body may partially or completely surround the lateral sides of the fiber optic connector. While the end of the cylindrical plug body is open such that the ferrule is accessible, the end of the cylindrical plug body does extend slightly beyond the ferrule to provide further protection. The ferrule is mounted upon a plurality of optical fibers of the fiber optic cable such that mating of the plug and the receptacle will align or connect the optical fibers of the fiber optic cable with respective optical fibers within the enclosure.
In the process of mating the plug and the receptacle, the plug ferrule is inserted into one end of the adapter sleeve of the receptacle. The adapter sleeve therefore aligns the plug ferrule with a receptacle ferrule that is attached to the end portions of optical fibers from a cable, ribbon, or optical fiber device that extends into or is located in the interior of the enclosure. As a result of the construction of a conventional fiber optic plug, one end of the adapter sleeve is received within the open end of the plug body as the plug ferrule is inserted into the adapter sleeve. In addition, in order to retain the plug ferrule within the adapter sleeve, the fiber optic connector of the fiber optic plug and the adapter sleeve are designed to be mechanically coupled, such as by means of a pair of latches. While the latches effectively couple the plug ferrule and the adapter sleeve, the mechanical coupling of the fiber optic connector and the adapter sleeve disadvantageously limit float between the plug ferrule and the adapter sleeve.
Once the plug and the receptacle have been mated, the fiber optic cable may be subjected to forces that create torque upon the fiber optic connector including the plug ferrule. This torque will disadvantageously increase the attenuation of the optical signals transmitted via the optical fibers upon which the plug ferrule is mounted. Even worse, this torque may break the optical fiber. Traditionally, the fiber optic cables upon which the fiber optic plugs are mounted have been quite flexible such that the plug ferrule has been subjected to only minimal amounts of torque. More recently, however, fiber optic plugs are being installed upon fiber optic cables that are much stiffer, such as the armored fiber optic cables designed for outdoor applications. As a result of the increased stiffness of these fiber optic cables, forces upon the fiber optic cable are much more readily transmitted to the plug ferrule, thereby imposing increased torque upon the plug ferrule. As a result of the increased attenuation of the optical signals created by the torque, it would be advantageous for the fiber optic plug to at least partially isolate the plug ferrule and the optical fibers upon which the plug ferrule is mounted from those forces to which the fiber optic cable are subjected.
Prior to engagement with the receptacle, a fiber optic cable, including the end portion of the fiber optic cable upon which the plug is mounted, must oftentimes be installed, such as by pulling, along a predetermined cable path. In some instances, the fiber optic cable must extend through ducts or other small passageways that are not much larger than the fiber optic cable itself. Since the plug body must be sufficiently large to receive and surround one end of the adapter sleeve, the size of the plug body may limit the minimum size of the duct or other passageway through which the fiber optic cable is installed. This limitation on the minimum size of the duct is becoming increasingly disadvantageous as additional emphasis is now placed upon reducing the space required for installing a fiber optic cable, i.e., reducing the duct size, in view of the large number of fiber optic cables that are currently installed. To date, however, reductions in the size of the duct through which a fiber optic cable is pulled are limited, at least in part, by the size of the plug body mounted upon the end portion of the fiber optic cable.
In order to pull a fiber optic cable, a pulling grip is typically mounted to the leading end of the fiber optic cable including the fiber optic plug in those embodiments in which a fiber optic plug has been mounted upon the end portion of the fiber optic cable. The pulling grip is designed to securely engage the end of the fiber optic cable load coupled to the strength element of the cable and to provide a point of attachment for a rope, a cable or the like that is utilized to pull the fiber optic cable. Since the fiber optic cable must frequently be pulled along a predetermined cable path that twists and turns, pulling grips designs are adapted to swivel or rotate relative to the fiber optic cable to avoid imparting undesirable torque on the fiber optic cable as it is pulled along a path. Typically, a pulling grip that is adapted to swivel relative to the fiber optic cable includes a plurality of components that must be connected to the fiber optic cable. The components of this conventional pulling grip are connected to each other in a manner that permits the component to which the rope, cable, or the like is attached to rotate or swivel relative to the component directly attached to the fiber optic cable. Thus, while pulling grips that swivel relative to the fiber optic cable are available, it would be advantageous to provide a pulling grip that is adapted to swivel relative to the fiber optic cable that has a simpler construction in order to facilitate use of the pulling grip and to reduce the cost of the pulling grip.
An improved fiber optic plug is provided according to this invention. According to one embodiment of this invention, the fiber optic plug is designed to facilitate the pulling of the fiber optic plug and an associated fiber optic cable through relatively small passageways. In order to further facilitate the pulling of the fiber optic plug and associated fiber optic cable through a passageway, the fiber optic plug of includes a cap mounted upon and adapted to swivel relative to the remainder of the fiber optic plug thereby providing a mechanism for pulling the fiber optic cable and for permitting the fiber optic cable to swivel or rotate relative thereto while having fewer parts than conventional pulling grips. Further, the fiber optic plug isolates the fiber optic connector and, in turn, the plug ferrule, from torque otherwise created by forces to which the fiber optic cable is subjected.
According to an embodiment, the fiber optic plug includes a fiber optic connector having a connector housing and a plug ferrule at least partially disposed within the connector housing and capable of being mounted upon end portions of a plurality of optical fibers. The fiber optic plug also includes a plug body extending lengthwise between opposed first and second ends and defining a longitudinal axis. The plug body has a shroud proximate the first end. In one embodiment, the shroud defines at least one opening that extends lengthwise from at least a medial portion of the shroud to the first end of the plug body. In a preferred embodiment, the shroud defines a pair of openings on opposite sides that extend lengthwise from at least a medial portion of the shroud to the first end of the plug body. In other embodiments, the shroud does not include openings.
In embodiments in which the shroud is cylindrical and has a pair of openings, the first end of the shroud therefore includes a pair of arcuate shroud portions separated by the openings. Preferably, the openings defined by the shroud are aligned with one another. The fiber optic connector is disposed within the plug body in a fixed position with respect to the plug body relative to rotation about the longitudinal axis such that the openings defined by the shroud are also longitudinally aligned with the plug ferrule. In this regard, the plug ferrule typically defines a plurality of bores extending lengthwise in a reference plane. As such, the openings defined by the shroud are preferably centered about this reference plane.
According to an embodiment, a fiber optic assembly is also provided in which a fiber optic receptacle is designed to mate with a fiber optic plug. The fiber optic receptacle includes a fiber optic receptacle housing defining an internal cavity opening through opposed first and second ends. The fiber optic receptacle also includes an adapter sleeve disposed within the internal cavity defined by the receptacle housing. The adapter sleeve defines a lengthwise extending passage for receiving a portion of the plug ferrule of the fiber optic plug. In this regard, the plug ferrule is disposed within the plug body such that the plug ferrule is accessible within the shroud via the first end of the plug body, even though the shroud preferably extends somewhat beyond the plug ferrule. Further, the shroud and the adapter sleeve are sized such that portions of the adapter sleeve are disposed within the openings defined by the shroud once the plug ferrule of the fiber optic plug is inserted into the adapter sleeve. Thus, in this embodiment the shroud does not completely surround the adapter sleeve as provided by conventional fiber optic plugs. Accordingly, the shroud can be reduced in size relative to the shrouds of conventional fiber optic plugs, thereby decreasing the overall size of the fiber optic plug in this embodiment of this invention. Since the fiber optic plug sometimes limits the size of a duct or other passageway through which the fiber optic plug and the associated fiber optic cable are pulled, the fiber optic plug of this embodiment can advantageously be pulled through smaller ducts and other passageways than conventional fiber optic plugs.
According to another embodiment of this invention, a fiber optic plug is provided that includes a fiber optic connector having a connector housing and a plug ferrule at least partially disposed within the connector housing. The fiber optic plug also includes a crimp band. A first portion of the crimp band is adapted to operable engage the fiber optic connector and a second portion of the crimp band is adapted to engage the fiber optic cable. The fiber optic plug of this embodiment also includes a plug body defining a longitudinal axis. According to this embodiment, the crimp band and the plug body include respective engagement members that mate with one another in order to mechanically couple the crimp band and the plug body and in order to prevent relative rotation therebetween about the longitudinal axis. For example, the crimp band typically includes a key. Correspondingly, the plug body generally defines a lengthwise extending passageway and a keyway opening into the passageway. The crimp band can therefore be at least partially disposed within the passageway defined by the plug body such that the key engages the keyway. In this embodiment, both the key defined by the crimp body and the keyway defined by the plug body preferably extend in a longitudinal direction. Thus, longitudinal motion between the crimp band and the plug body is permitted while relative rotation between the crimp band and the plug body about the longitudinal axis is prevented. By preventing relative rotation between the crimp band and the plug body, any torque to which the fiber optic cable is subjected is transmitted to the plug body via the crimp band and, in turn, to the receptacle housing of the receptacle to which the fiber optic plug is connected. Thus, the fiber optic connector and, in particular, the plug ferrule are protected or isolated from any torque to which the fiber optic cable is subjected since the plug body to which the fiber optic connector is engaged via the engagement members of the crimp band and plug body will move very little, if at all, in response to torque on the fiber optic cable.
In an embodiment, the crimp band extends lengthwise between opposed first and second ends and the first and second portions of the crimp band are proximate the first and second ends, respectively. In embodiments in which the crimp band includes a key, the key may therefore be carried by a medial portion of the crimp band that is disposed between the first and second portions of the crimp band. Alternatively, the crimp band may include an enlarged portion that is disposed proximate the second portion of the crimp band that carries the key. Regardless of the configuration, the first and second portions of the crimp band are capable, however, of being compressed in order to secure the crimp band to the fiber optic connector and the fiber optic cable, respectively. Although the first and second ends are compressed, the key portion of the crimp band is only slightly deformed, if at all.
In an embodiment, the fiber optic connector includes a spring push attached to the connector housing. In this embodiment, the first end of the crimp band engages the spring push. More particularly, the spring push may include a crimp body designed to be engaged by the first portion of the crimp band. With respect to the engagement of the fiber optic cable by the crimp band, the fiber optic cable may further include a support tube disposed within the cable jacket of the fiber optic cable and surrounding the plurality of optical fibers. The support tube is aligned with the second portion of the crimp band such that the second portion of the crimp band crimps the cable jacket between the second portion of the crimp band and the support tube. Thus, the crimp band securely engages both the fiber optic cable and the fiber optic connector. Moreover, the respective engagement members of the crimp band and the plug body may mechanically couple the crimp band and the plug body and prevent relative rotation therebetween, thereby protecting the fiber optic connector and, in turn, the plug ferrule from the otherwise deleterious effects of torque imparted upon the fiber optic cable.
According to another embodiment, the fiber optic plug includes a plug body extending in a lengthwise direction between opposed first and second ends and defining a longitudinal axis therethrough. The fiber optic plug also includes a fiber optic connector having a connector housing and a plug ferrule at least partially disposed within the connector housing. The fiber optic connector is disposed within the plug body such that the plug ferrule is accessible via the first end of the plug body. The fiber optic plug also includes a cap mounted upon the plug body so as to cover at least the first end thereof. The cap is mounted upon the plug body such that travel of the cap in the lengthwise direction is limited while permitting the cap to rotate about the longitudinal axis relative to the plug body. Thus, the cap is adapted to swivel relative to the remainder of the plug body, while remaining connected to the plug body. The cap may therefore effectively serve as a pulling grip in order to pull the fiber optic plug and the fiber optic cable to which the fiber optic plug is connected through a passageway. In this regard, the cap may define an opening that may be engaged by a rope, a cable or the like to facilitate the pulling of the fiber optic plug and the fiber optic cable through the passageway. Not only does the cap protect the fiber optic connector while pulling the fiber optic plug and the fiber optic cable through the passageway, but the cap is relatively small and, in fact, need not be much larger than the plug body. Thus, the cap does not substantially limit the size of the passageway through which the fiber optic plug and the fiber optic cable may be pulled.
The plug body preferably includes a shaft and a collar disposed upon the shaft such that travel of the collar in the lengthwise direction is limited even though rotation of the collar about the longitudinal axis defined by the shaft is permitted. In one embodiment, the shaft includes a threaded portion and the collar includes an internally threaded portion. Thus, the collar may be mounted upon the shaft by threadably advancing the collar onto the shaft. The plug body also includes a shroud proximate the first end of the plug body and adjacent the shaft. The shroud is larger than the shaft such that travel in the collar is limited by the threaded portion of the shaft on one end and the shroud on the other end. The cap is adapted to be attached to the collar for movement therewith. Once the cap is removed, such as following the pulling of the fiber optic cable through a passageway and in preparation for mating the fiber optic plug with a corresponding receptacle, the collar is adapted to engage the fiber optic receptacle.
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