Patent Description:
This disclosure relates generally to optical connectivity, and more particularly to fiber optic cable assemblies that include over-molded strain boots (i.e., strain-relief members).

Optical fibers are useful in a wide variety of applications, including the telecommunications industry for voice, video, and data transmissions. In a telecommunications system that uses optical fibers, there are typically many locations where fiber optic cables that carry the optical fibers connect to equipment or other fiber optic cables. To conveniently provide these connections, fiber optic connectors are often provided on the ends of fiber optic cables. The process of terminating individual optical fibers from a fiber optic cable is referred to as "connectorization. " Connectorization can be done in a factory, resulting in a "pre-connectorized" or "pre-terminated" fiber optic cable, or the field (e.g., using a "field-installable" fiber optic connector).

Regardless of where installation occurs, a fiber optic connector typically includes a ferrule with one or more bores that receive one or more optical fibers. The ferrule supports and positions the optical fiber(s) with respect to a housing of the fiber optic connector. Thus, when the housing of the fiber optic connector is mated with another connector (e.g., in an adapter), an optical fiber in the ferrule is positioned in a known, fixed location relative to the housing. This allows an optical connection to be established when the optical fiber is aligned with another optical fiber provided in the mating connector.

The housing or body components of a fiber optic connector are often relatively rigid so that the fiber optic connector can withstand a variety of forces during handling and use without affecting the optical connection that may be or has been established. Having rigid components, however, presents design challenges elsewhere. For example, fiber optic cables upon which fiber optic connectors are installed are typically much less rigid than connector bodies. The rapid transition from high stiffness to low stiffness may result in stress concentrations where the cable meets the connector body. Radial loads applied to the cable may then result in the cable bending (e.g., where the stresses are concentrated) beyond a minimum bend radius that must not be exceeded for the cable to function properly.

To address the above-mentioned challenges, a fiber optic connector typically includes a flexible, strain-relieving boot that snaps onto the connector body and extends rearwardly over a portion of the cable. The boot provides a transition in stiffness between the fiber optic connector and the cable. Although many different boot designs have been proposed to properly provide this transition, new solutions are still desired.

<CIT> discloses a strain relief boot and a fiber optic cable assembly. The strain relief boot has a first conduit made of at least a first material. The first conduit has a front segment and a rear segment. The rear segment includes at least one discontinuity to make the rear segment more flexible than the front segment. The rear segment also includes at least one projection extending outwardly from the rear segment at a location adjacent to the at least one discontinuity. The strain relief boot also has a second conduit made from at least a second material that is less rigid than the first material. The second conduit at least partially surrounds at least the rear segment of the first conduit and extends rearwardly of the first conduit.

Embodiments of fiber optic assemblies are provided in this disclosure. According to one embodiment, a fiber optic assembly comprises a fiber optic cable having at least one optical fiber, a cable jacket surrounding the at least one optical fiber, and aramid fibers between the cable jacket and the at least one optical fiber. The fiber optic cable assembly also includes a fiber optic connector installed on an end of the fiber optic cable. The fiber optic connector includes a connector body that has a back-end portion. The at least one optical fiber extends through the back-end portion of the connector body. The cable jacket includes a jacket end portion defining an end of the cable jacket that is spaced from the back-end portion of the connector body. At least some of the aramid fibers extend beyond the end of the cable jacket and over the back-end portion of the connector body. The fiber optic connector also includes a tube having a first portion positioned over the back-end portion of the connector body and a second portion positioned over the jacket end portion. At least some of the aramid fibers extend between the first portion of the tube and the back-end portion of the connector body. The fiber optic connector also includes a boot molded over the back-end portion of the connector body and the jacket end portion such that the boot is also molded over the tube. The tube is configured to prevent material of the boot from entering space between the end of the cable jacket and the back-end portion of the connector body.

According to one aspect or embodiment, the first portion of the tube is not deformed. There is no crimping of the tube, for example.

According to another aspect or embodiment, there is no heat shrink tube over the jacket end portion of the cable jacket or the tube.

According to another aspect or embodiment, the first portion of the tube is cylindrical. The second portion of the tube may also be cylindrical in some embodiments. And furthermore, the first portion of the tube may be larger than the second portion of the tube. For example, the first portion of the tube have a first outer diameter, and the second portion of the tube may have a second outer diameter that is less than the first outer diameter.

According to another aspect or embodiment, the boot conforms to the tube such that the boot contacts at least <NUM>% of an exterior of the tube.

According to another aspect or embodiment, at least some of the aramid fibers have respective end portions extending beyond the first portion of the tube and at least partially encapsulated by the material of the boot.

According to another aspect or embodiment the material of the boot comprises a polyamide thermoplastic material. The tube may comprise a different material, such as metal.

In some embodiments, the at least one optical fiber consists of a single optical fiber, the fiber optic connector further includes a ferrule that is biased relative to the connector body, and the single optical fiber is secured to ferrule. In other embodiments, the at least one optical fiber comprises first and second optical fibers, wherein: the fiber optic connector further comprises first and second connector sub-assemblies supported by the connector body; each of the first and second connector sub-assemblies includes a connector housing and a ferrule supported within the connector housing; the first optical fiber is secured to the ferrule of the first connector sub-assembly; and the second optical fiber is secured to the ferrule of the second connector sub-assembly.

Methods of forming a fiber optic cable assembly are also provided in this disclosure, wherein the fiber optic cable assembly is formed from a fiber optic cable that includes at least one optical fiber, a cable jacket surrounding the at least one optical fiber, and aramid fibers between the cable jacket and the at least one optical fiber. According to one embodiment, a method comprises: positioning a tube on the cable jacket; removing some of the cable jacket so that a length of the at least one optical fiber and at least some of the aramid fibers extend beyond an end of the cable jacket; positioning a connector body on the length of the at least one optical fiber, wherein the connector body includes a back-end portion through which the at least one optical fiber extends, and wherein the connector body is positioned on the length of the at least one optical fiber so that the back-end portion is spaced from the end of the cable jacket; moving the tube along the cable so that a first portion of the tube is positioned over the back-end portion of the connector body and a second portion of the tube is positioned over a jacket end portion that defines the end of the cable jacket, wherein the at least some of the aramid fibers extend between the first portion of the tube and the back-end portion of the connector body; and molding a boot over the back-end portion of the connector body and the jacket end portion of the cable jacket such that the boot is also molded over the tube. The tube prevents material of the boot from entering space between the end of the cable jacket and the back-end portion of the connector body.

According to a further aspect or embodiment, the method further comprises: placing the back-end portion of the connector body, the tube, and a portion of the fiber optic cable within a cavity of a mold; flowing the material of the boot into the cavity of the mold, wherein the material is kept at a temperature below <NUM> and at a pressure less than <NUM> kPa; solidifying the material to form the boot within the mold; and removing the portion of the fiber optic cable, the back-end portion of the connector body, and the boot from the mold.

Additional features and advantages will be set out in the detailed description which follows, and in part will be readily apparent to those skilled in the technical field of optical connectivity. It is to be understood that the foregoing general description, the following detailed description, and the accompanying drawings are merely exemplary and intended to provide an overview or framework to understand the nature and character of the claims.

The accompanying drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments. Features and attributes associated with any of the embodiments shown or described may be applied to other embodiments shown, described, or appreciated based on this disclosure.

Various embodiments will be further clarified by examples in the description below. In general, the description relates to fiber optic cable assemblies having over-molded connector boots. In other words, the description relates to fiber optic cables assembled with fiber optic connectors (thereby forming fiber optic cable assemblies), with some of the connectors having a boot molded over a region where the cable joins to another component of the connector. The connector may otherwise have a conventional design, like the examples shown in <FIG> and <FIG>. <FIG> illustrates a fiber optic connector <NUM> ("connector <NUM>") in the form of a simplex LC connector (e.g., according to IEC standard <NUM>-<NUM>:<NUM>), and <FIG> illustrates a fiber optic connector ("connector <NUM>") in the form of a duplex LC connector (e.g., also according to IEC <NUM>-<NUM>:<NUM>). The connectors <NUM>, <NUM> will first be described to provide context for the principles of this disclosure, which may be applied to these or other connector designs.

As shown in <FIG>, the connector <NUM> includes a ferrule <NUM> configured to support an optical fiber (not shown) extending in a generally longitudinal direction DL through a bore <NUM> of the ferrule <NUM>. An intermediate portion of the ferrule <NUM> extends through a cap <NUM> coupled to a connector body <NUM> (also referred to as a "connector sub-assembly body <NUM>," "connector housing <NUM>," or simply "housing <NUM>"). The ferrule <NUM> extends from a ferrule holder (not shown) that is retained within the connector body <NUM> by the cap <NUM>. A spring (not shown) biases the ferrule holder forward within the connector body <NUM> so that a front end <NUM> of the ferrule <NUM> projects forward beyond a front end <NUM> of the connector body <NUM>. The front end <NUM> of the ferrule <NUM> presents the optical fiber extending through the bore <NUM> for optical coupling with a mating component (e.g., another fiber optic connector).

The connector <NUM> further includes a latch arm <NUM> extending outwardly and rearwardly from (e.g., in a slanted direction relative to) a portion of the connector body <NUM>. In this regard, the latch arm <NUM> has a proximal end <NUM> coupled to the connector body <NUM> and a distal end <NUM> spaced from the connector body <NUM>, with the connector body <NUM> and the latch arm <NUM> being separated from one another and defining a space therebetween. An intermediate portion of the latch arm <NUM> includes cantilever latch tabs, which protrude laterally from the latch arm <NUM>. The distal end <NUM> of the latch arm <NUM> may be depressed toward the connector body <NUM> to disengage the connector <NUM> from another structure, such as an adapter or a dust cap (neither shown in <FIG>).

Normally a crimp ring or band <NUM>, a heat shrink tube <NUM>, and elastomeric boot <NUM> are provided with the connector <NUM>; they are installed at the time of installing other components of the connector <NUM> onto a cable (not shown in <FIG>). The crimp ring <NUM> is typically a metal component that is crimped (i.e., deformed) onto a back-end portion <NUM> of the connector body <NUM> to secure the cable to the connector <NUM>. Specifically, cables may include strength elements in the form of aramid yarns or fibers, and these aramid fibers may be extended over the rear portion <NUM> of the connector body <NUM>. Placing the crimp ring <NUM> over this cable-connector interface and performing the crimping secures the aramid fibers to the connector body <NUM>. The heat shrink tube <NUM> is then used to cover the interface between the crimp ring <NUM> and the portion of the cable from which the aramid fibers extend. Finally, the boot <NUM> is used to cover portions of both the connector <NUM> and cable to help limit bending at the cable-connector interface.

<FIG> is a perspective view of the duplex connector <NUM>, which includes as sub-assemblies two of the simplex connectors <NUM> according to <FIG>. For convenience, the term "connector sub-assemblies" (or "connector elements") will be used to refer to the connectors <NUM> when discussing these elements in connection with the connector <NUM>. Indeed, in alternative embodiments, duplex connectors may include connector elements that are not similar to simplex fiber optic connectors in all respects.

Still referring to <FIG>, proximal portions of the connector sub-assemblies <NUM> in the connector <NUM> are separated by a lateral gap <NUM>. Rear portions of each connector sub-assembly <NUM> are received within a shell <NUM> that surrounds a common connector body or internal housing <NUM> that supports each connector sub-assembly <NUM>. The shell <NUM> includes a front end <NUM> defining a generally rectangular opening that receives rear portions of the connector sub-assemblies <NUM>. The shell <NUM> also includes a rear end <NUM> having a narrowed width in comparison to the front end <NUM>. An outer boot <NUM> is arranged proximate to the rear end <NUM> of the shell <NUM>, and may be fitted over a portion of the connector body <NUM>. A trigger <NUM> extends outwardly and forwardly (e.g., in a slanted direction relative to) the shell <NUM> above a recess <NUM>, with a front end <NUM> of the trigger <NUM> extending over distal ends <NUM> of the latch arms <NUM> of the connector sub-assemblies <NUM>. In operation, a user may press the trigger <NUM> (e.g., at a finger receiving area <NUM>) in a direction toward the shell <NUM> to cause the distal ends <NUM> of the latch arms <NUM> to move toward the respective connector bodies <NUM>, thereby operating the latch arms <NUM> to permit disengagement of the connector sub-assemblies <NUM> from another structure, such as an adapter or a dust cap (neither shown in <FIG>).

Having described the connector <NUM> shown in <FIG> and the connector <NUM> shown in <FIG> for comparison purposes, fiber optic assemblies having over-molded connector boots will now be described. The fiber optic cable assemblies include a fiber optic connector with a connector body, such as the connector body <NUM> (e.g., when the fiber optic connector is a simplex connector) or the common connector body <NUM> (e.g., when the fiber optic connector is a duplex connector), but a different boot design than what is shown in <FIG> and <FIG>. For convenience, an example will be described using the connector body <NUM> and the new boot design. The example can be best understood from a description of how the cable assembly is formed.

Starting with <FIG>, a fiber optic cable ("cable <NUM>") includes one or more optical fibers (represented by line <NUM>), a cable jacket ("jacket <NUM>") surrounding the optical fiber(s) <NUM>, and aramid fibers <NUM> (i.e., yarns) between the jacket <NUM> and the optical fiber(s) <NUM>. <FIG> illustrates one end of the cable <NUM> after removing a portion of the jacket <NUM> to expose a length L of the optical fiber(s) <NUM> and aramid fibers <NUM>. In other words, the jacket <NUM> may have an initial end (not shown) covering the length L, but then be cut or otherwise removed to expose the previously-covered length L of the optical fiber(s) <NUM> and aramid fibers <NUM>. This results in the jacket <NUM> having a new end <NUM> ("end <NUM>"), which is what is shown in <FIG>.

<FIG> also illustrates a tube <NUM> positioned on an end portion <NUM> ("jacket end portion <NUM>") of the jacket <NUM> that defines the end <NUM>. The tube <NUM> may be placed on the cable <NUM> before or after cutting the jacket <NUM> to expose the optical fiber(s) <NUM> and aramid fibers <NUM>. In the embodiment shown, the tube <NUM> includes a cylindrical first portion <NUM> that defines a front end <NUM> of the tube <NUM>, a smaller cylindrical second portion <NUM> that defines a back end <NUM> of the tube <NUM>, and a transition region <NUM> between the first and second portions <NUM>, <NUM>. The first portion <NUM> has an inner diameter larger than an outer diameter of the jacket <NUM> such that a gap exists between an inner surface of the tube <NUM> in the first portion <NUM> and an outer surface <NUM> of the jacket <NUM>. The second portion <NUM> has an inner diameter that is slightly smaller than or approximately equal to the outer diameter of the jacket <NUM>. For example, there may be a slight interference between the second portion <NUM> of the tube <NUM> and the jacket <NUM>, with the inner surface of the tube <NUM> in the second portion <NUM> contacting the outer surface <NUM> of the jacket <NUM>. If there is slight interference, the forces are such that the tube <NUM> can still be easily moved (e.g., slid) along the jacket <NUM>. The tube <NUM> may be constructed from metal or another suitable material.

<FIG> illustrates the connector body <NUM> positioned on the end of the cable <NUM>. To do so, the connector body <NUM> is moved over the optical fiber(s) <NUM> (not shown in <FIG>) such that the optical fiber(s) <NUM> extend through at least a back-end portion <NUM> (<FIG>) of the connector body <NUM>. The aramid fibers <NUM> have been cut to a shorter length compared to <FIG> and positioned over the back-end portion <NUM> of the connector body <NUM>. The back-end portion <NUM> remains spaced from the end <NUM> of the jacket <NUM> so that the aramid fibers <NUM> can extend out of the jacket <NUM> and over the back-end portion <NUM>.

As shown in <FIG>, the tube <NUM> may then be moved along the cable <NUM> until the first portion <NUM> is positioned over the back-end portion <NUM> of the connector body <NUM>. This results in portions of the aramid fibers <NUM> extending between the first portion <NUM> of the tube <NUM> and the back-end portion <NUM> of the connector body <NUM>. Although the aramid fibers <NUM> are accommodated in such a manner, space between the first portion <NUM> of the tube <NUM> and the back-end portion <NUM> of the connector body <NUM> is minimal. For example, the first portion <NUM> of the tube <NUM> may have an inner diameter that is within <NUM>% of an outer diameter of the back-end portion <NUM>. Respective ends <NUM> of the aramid fibers <NUM> may remain outside of the tube <NUM> (i.e., uncovered).

Still referring to <FIG>, the second end portion <NUM> of the tube <NUM> does not move off the jacket end portion <NUM>. That is, at least some of the second portion <NUM> remains positioned over the jacket end portion <NUM>. Thus, the tube <NUM> covers the space between the back-end portion <NUM> of the connector body <NUM> and the end <NUM> of the jacket <NUM>.

<FIG> illustrate examples of respective first and second mold components <NUM>, <NUM>, and <FIG> illustrates the first and second mold components <NUM>, <NUM> assembled together to define a mold <NUM>. The cable <NUM> with the connector <NUM> partially assembled in the manner described above may be placed into a cavity <NUM> of the mold <NUM>. As can be appreciated from <FIG>, the back-end portion <NUM> of the connector body <NUM> may be received in the cavity <NUM>, and a remainder of the connector body <NUM> may remain outside the cavity <NUM> on one side of the mold <NUM>. The cable <NUM> (not shown in <FIG>) extends out of the cavity <NUM> on an opposite side of the mold <NUM>. Thus, the back-end portion <NUM> of the connector body <NUM>, the jacket end portion <NUM>, and the tube <NUM> that is positioned over the back-end portion <NUM> and jacket end portion <NUM> are positioned in the cavity <NUM>. Molding material may be introduced into the cavity <NUM> through an injection port <NUM> and injection channels <NUM> defined by the first and second mold components <NUM>, <NUM>. Additional details relating to the molding material and process will be described in further detail below.

Although the molding material may be flowable when being introduced into the cavity <NUM>, the tube <NUM> prevents the molding material from entering into the connector body <NUM> and jacket <NUM>. For example, this may be due to the close-fitting arrangement between: a) the first portion <NUM> of the tube <NUM> and the back-end portion <NUM> of the connector body <NUM>, and b) the second portion <NUM> of the tube <NUM> and the jacket end portion <NUM>. The ends <NUM> of the aramid fibers <NUM> that remained exposed (see <FIG>) may be at least partially encapsulated by the molding material.

Ultimately the molding material fully occupies the cavity <NUM> and is brought into a non-flowable state, such as by allowing to cool or by actively cooling. As shown in <FIG> and <NUM>, which illustrate the cable <NUM> removed from the mold, this results in the molding material forming a boot <NUM> that has the shape of the cavity <NUM>. The cable <NUM> together with the connector <NUM> (including the boot <NUM>) form a cable assembly <NUM>. The boot <NUM> conforms to the shape of the components it covers. Material of the boot <NUM>, for example, may be in contact with substantially all (e.g., at least <NUM>%) of an exterior of the tube <NUM> and adjacent portions of the connector body <NUM> and jacket <NUM>. Thus, unlike the boots <NUM>, <NUM> (<FIG>), the cable assembly <NUM> does not include a heat shrink tube (e.g., the heat shrink tube <NUM> in <FIG>) over the cable-connector interface. The material costs and processing steps associated with applying such heat shrink tubes (e.g., using ovens or other devices to apply heat) can be avoided.

The same can be said with respect to the crimp ring <NUM> (<FIG>). That is, the cable assembly <NUM> avoids the need to perform a crimping step; there is no need to deform the tube <NUM> or any other component onto the back-end portion <NUM> of the connector body <NUM> to secure the aramid fibers <NUM> to the connector <NUM>. Avoiding this step in forming the cable assembly <NUM> may not only save time and cost (e.g., by not needing a crimping tool), but may also avoid potential damage to the connector body <NUM>.

As can be appreciated, although the molding step may be needed to form the cable assembly <NUM>, multiple steps that are traditionally required can be avoided. Manufacturing process flows can be streamlined, and the total amount of equipment needed for forming the cable assembly can be reduced.

Advantageously, the molding may be performed using thermoplastic materials having properties suitable for low pressure molding (LPM). This type of molding may be characterized by relatively low pressures and temperatures. For example, the material of the boot <NUM> may be kept at a temperature below <NUM> and at a pressure less than <NUM> kPa during the molding process. Molding may be performed relatively fast, with the boot <NUM> being formed in less than <NUM> seconds, or even in less than <NUM> seconds in some embodiments.

Examples of thermoplastic materials that may be suitable for low pressure molding include polyamide-based materials, such as TECHNOMELT® PA <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> (Henkel Corp. , Dusseldorf, Germany). These materials have viscosities in the range of about <NUM> mPa:s to about <NUM> mPa:s at <NUM>, glass transition temperatures of no greater than -<NUM>, and service temperatures that range from no less than about -<NUM> to no greater than about <NUM>. A glass transition temperature is the point at which a material goes from a hard brittle state to a flexible or soft rubbery state as temperature is increased. A common method for determining glass transition temperature uses the energy release on heating in differential scanning calorimetry. In certain embodiments, service temperature of a thermoplastic material may be determined by compliance with one or more industry standards for telecommunication fiber reliability testing, such as (but not limited to): ITU-T G. <NUM>, IEC <NUM>-<NUM>, Telcordia GR-<NUM>-CORE, and TIA/EIA-<NUM>.

Claim 1:
A fiber optic cable assembly, comprising:
a fiber optic cable (<NUM>) having at least one optical fiber (<NUM>), a cable jacket (<NUM>) surrounding the at least one optical fiber (<NUM>), and aramid fibers (<NUM>) between the cable jacket (<NUM>) and the at least one optical fiber (<NUM>); and
a fiber optic connector (<NUM>) installed on an end of the fiber optic cable (<NUM>), the fiber optic connector (<NUM>) including:
a connector body (<NUM>) having a back-end portion (<NUM>), wherein the at least one optical fiber (<NUM>) extends through the back-end portion (<NUM>) of the connector body (<NUM>);
the cable jacket (<NUM>) includes a jacket end portion (<NUM>) defining an end of the cable jacket (<NUM>) that is spaced from the back-end portion (<NUM>) of the connector body (<NUM>); and
at least some of the aramid fibers (<NUM>) extend beyond the end of the cable jacket (<NUM>) and over the back-end portion (<NUM>) of the connector body (<NUM>);
a tube (<NUM>) having a first portion (<NUM>) positioned over the back-end portion (<NUM>) of the connector body (<NUM>) and a second portion (<NUM>) positioned over the jacket end portion (<NUM>) of the cable jacket (<NUM>), wherein the at least some of the aramid fibers (<NUM>) extend between the first portion of the tube (<NUM>) and the back-end portion (<NUM>) of the connector body (<NUM>); and
a boot (<NUM>) molded over the back-end portion (<NUM>) of the connector body (<NUM>) and the jacket end portion (<NUM>) of the cable jacket (<NUM>) such that the boot (<NUM>) is also molded over the tube (<NUM>), wherein the tube (<NUM>) is configured to prevent material of the boot (<NUM>) from entering into space between the end of the cable jacket (<NUM>) and the back-end portion (<NUM>) of the connector body (<NUM>).