Fiber optic cables and assemblies for fiber toward the subscriber applications

Disclosed are fiber optic cables and assemblies for routing optical networks closer to the subscriber. The fiber optic cables have a robust design that is versatile by allowing use in aerial application with a pressure clamp along with use in buried and/or duct applications. Additionally, the fiber optic cables and assemblies have a relatively large slack storage capacity for excess length. Assemblies include hardened connectors such as plugs and/or receptacles suitable for outdoor plant applications attached to one or more ends of the fiber optic cables for plug and play connectivity.

FIELD OF THE INVENTION

The present invention relates to fiber optic cables and assemblies suitable fiber optic networks such as fiber to the subscriber or fiber to the node applications. More particularly, the present invention relates generally to fiber optic cables having a robust design with a relatively large slack storage capacity for excess length along with associated assemblies for plug and play connectivity.

BACKGROUND OF THE INVENTION

Communications networks are used to transport a variety of signals such as voice, video, data and the like to subscribers. Service providers are routing optical fiber deeper into communication networks, thereby increasing the bandwidth available to subscribers for receiving the desired content. More specifically, service providers are routing optical fiber to the premises of subscribers instead of copper, thereby dramatically increasing the bandwidth available to subscribers for emerging applications.

FIG. 1schematically illustrates two preconnectorized fiber optic cables10and10′ being routed to a premise of a subscriber using two different exemplary installation techniques. Specifically,FIG. 1shows a first preconnectorized fiber optic cable10being routed to premises20in an aerial installation and a second preconnectorized fiber optic cable10′ being routed to premises20in a buried installation. In the aerial installation, a first end10aof preconnectorized cable10is attached at a first interface device12located at, or near, a pole11and a second end10bof preconnectorized cable10is attached at a second interface device14located at premise20. By way of example, first interface device12may be a closure, multiport (a device having multiple receptacles), or the like and second interface device14may be a closure, network interface device (NID), optical network terminal (ONT), or the like. In the aerial installation, the craft typically uses a pressure clamp19(i.e., a p-clamp) as schematically shown inFIG. 1for securing fiber optic cable10under tension at, or near, pole11and/or premises20, thereby avoiding undue sag in fiber optic cable10along the aerial span.

FIG. 2depicts a 2 PR pressure clamp19such as available from Reliable Power Products of Franklin Park, Ill. as well as from others with a portion of fiber optic cable10disposed therein. Pressure clamp19includes a body19a, a grip19b, and a wedge19cfor clamping (i.e., squeezing) the fiber optic cable with increasing frictional force as the tension on the fiber optic cable is increased. Body19areceives fiber optic cable10between grip19band wedge19cand squeezes it therebetween as tensile forces are applied. Body19aalso includes a loop end used for attaching it to pole11, premises20, or other structure. Simply stated, the frictional force on the fiber optic cable increases as tension force of the fiber optic cable pulls wedge19ctighter onto the fiber optic cable, thereby preventing the fiber optic cable from pulling out of the pressure clamp. It is possible for the clamping (i.e., frictional) force from pressure clamp19to plastically deform the fiber optic cable therein or even severely damage the same since grip19bhas dimples and body19ahas ridges. Pressure clamp19can not be used with all fiber optic cable designs since it may cause damage and/or elevated levels of optical attenuation. Consequently, other types of devices that do not clamp the optical portion of the fiber optic cable are also used for securing fiber optic cables such as wire vises, winding posts, and the like. Simply stated, conventional fiber optic cables used with in pressure clamp19uses a buffer tube for protecting the optical fibers while allowing use within while maintaining acceptable optical performance and reliability.

In buried or duct applications, the first and second ends of preconnectorized cable10′ are respectively connected to an interface device16located at a field location18such as inside a pedestal, a manhole, a handhole or the like and second interface device14. The interface devices may include at least one receptacle (not visible) for making the optical connection with a plug end of preconnectorized fiber optic cable10. Like aerial applications, buried or duct applications can also require a rugged fiber optic cable design. For instance, the fiber optic cable can encounter rough terrain such as being pushed against rocks, or the like or rough handling during installation such as pulling into a duct. Thus, for fiber to the subscriber applications the preconnectorized fiber optic cable should be robust enough to handle either an aerial, buried, and/or duct installations while maintaining suitable optical performance and reliability.

Further, the distance between pole11, or field location18, to the second interface device14at premises20varies with each specific installation. By way of example, if the distance between pole11and second interface device is 30 meters, then the craftsman may select a 50 meter preconnectorized fiber optic cable10for managing the length of cable for slack storage (i.e., the storage of excess 20 meter length). For instance, the slack cable length may be stored behind the second interface device14, or other suitable location. Because this excess length for slack storage can take a substantial amount of space, may look unsightly, and/or there may be a limited space available, the craft, generally speaking, selects a length of preconnectorized fiber optic cable from his inventory that minimizes the length for slack storage for the particular installation. Consequently, the craft carries many different lengths of preconnectorized fiber optic cables into the field to accommodate these varying distances while accommodating the slack storage limitation. For instance, the craft may carry up to fifteen different lengths of preconnectorized fiber optic cables into the field, which creates complexity issues for the craft, the service provider, and the manufacturer.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. When practical, the same reference numerals will be used throughout the drawings to refer to the same or like parts.FIG. 3is a cross-sectional view of a fiber optic cable30having at least one optical fiber32, a first and a second strength component34, and a cable jacket38. First and second strength components34are disposed on opposite sides of optical fiber32and generally aligned along a common plane A-A, thereby providing a preferential bend characteristic to fiber optic cable30. As depicted, cable jacket38contacts the optical fiber32and first and second strength members34. Cable jacket38has a medial height MH disposed about optical fiber32that is less than an end height EH of fiber optic cable30, which is advantageous for preserving optical performance during clamping within pressure clamp19as discussed herein. Fiber optic cable30is also advantageous because it has a relatively small cross-sectional footprint compared with conventional fiber optic drop cables used for fiber to the subscriber, or node, applications, thereby providing a relatively large slack storage capacity for excess length while still being robust.

For comparison purposes,FIG. 4schematically depicts a cross-sectional footprint42of fiber optic cable30(represented by solid lines) superimposed onto a cross-sectional footprint44for a conventional fiber optic cable (represented by phantom lines with outlines of the buffer tube and strength members also shown) for fiber to the subscriber applications. As shown, the cross-sectional footprint42of fiber optic cable30is substantially smaller than the cross-sectional footprint44of conventional fiber optic cable while still providing a robust design for use within a 2PR pressure clamp19. Remarkably, cross-sectional footprint42is about 42% of the cross-sectional footprint44(e.g., about 13.2 millimeters squared compared to about 31.5 millimeters squared) while still working within pressure clamp19. Cross-sectional footprint42is substantially smaller than cross-sectional footprint44since it does not require a buffer tube (represented by the middle circle in phantom) for housing and protecting optical fiber32when used within pressure clamp19like the conventional fiber optic cable. Moreover, fiber optic cable30does not require special installation procedures such as separation or isolation of the optical fiber from the clamping force of pressure clamp19such as with other device for aerial applications. Simply stated, the portion of fiber optic cable30having optical fiber32therein can be placed within pressure clamp19while maintaining suitable optical performance without having a buffer tube (or other similar structure) for protecting the optical fiber. Likewise, fiber optic cable30can also withstand the requirements of buried and/or duct applications.

By way of example, fiber optic cable30has a height H of about 3.0 millimeters and a width W of about 5.3 millimeters while still providing suitable optical performance when subjected to the clamping force of pressure clamp19. The concepts of the present invention may be used with fiber optic cables having other suitable dimensions and/or shapes as shown in Table 1. Moreover, the smaller cross-sectional footprint of fiber optic cable30allows for a smaller coil diameter compared with the conventional fiber optic cable. Consequently, fiber optic cable30advantageously allows storing relatively long lengths of the same in a relatively small volume (i.e., space) such as at the network interface device at the subscriber's premise, closure, pedestal, or other suitable locations. Moreover, since longer lengths of fiber optic cable30can be stored in smaller spaces the craft can carry fewer lengths of preconnectorized assemblies into the field while still accommodating limited storage space constraints. In other words, fiber optic cable30allows relatively large lengths of slack storage in small spaces for aerial installations and/or buried installations, while still providing suitable optical performance within pressure clamp19. Moreover, the service provider and manufacturer can advantageously stock fewer lengths of preconnectorized fiber optic cables such as a short length and a long length.

Fiber optic cable30is also advantageous because it has a relatively low weight and small footprint for ice and wind loading such as under NESC heavy loading conditions. As such, lower tensile forces are required for maintaining suitable sag for fiber optic cable30in aerial installations, which results in lower tensile forces being applied to subscriber's premises from tension forces applied to the pressure clamp. Illustratively, a 1% sag of fiber optic cable30in a 150 foot aerial span may be achieved with a tensile force of about 20 pounds (about a 30% reduction in tensile force compared with the conventional fiber optic drop cable shown inFIG. 4), which also makes fiber optic cable30easier for the craft to install. Table 1 compares characteristics (i.e., the overall dimensions, coiling capacity, and weight) of fiber optic cable30with the conventional fiber optic cable schematically illustrated inFIG. 4in the first two rows. Table 1 also includes size variations of fiber optic cable30listed as fiber optic cable30′ and fiber optic cable30″ for illustrating the ranges of the characteristics. Because conventional fiber optic cable ofFIG. 4has one or more optical fibers within a 3.0 millimeter buffer tube it has an overall cable width of about 8.1 millimeters and cable height of about 4.4 millimeters.

Specifically, the first two rows of Table 1 shows that 60 meters of the fiber optic cable30can be coiled and stored in a space having a volume of about 4300 cubic centimeters or less, which is half of the volume (i.e., space) required for the same length with the conventional fiber optic cable. Part of the reason for the increase in slack storage is that fiber optic cable30can be coiled into a smaller diameter compared with the conventional fiber optic cable (i.e., fiber optic cable has a smaller bend radius). By way of example, fiber optic cable using 1.25 millimeter glass-reinforced plastic can begin being coiled with a diameter of about 12.5 centimeters or less, whereas the conventional fiber optic cable can begin being coiled with a diameter of about 16 centimeters. The other reason that fiber optic cable30has a dramatic increase in the slack storage characteristic is because the cross-sectional area of fiber optic cable30is much smaller (i.e., about 42% of the conventional fiber optic cable area as depicted inFIG. 4). Moreover, fiber optic cable30has a considerable reduction in weight compared with the conventional fiber optic cable. Specifically, fiber optic cable30has a weight of about 15 kilograms or less per kilometer of length compared with a weight of about 31 kilograms per kilometer of length for the conventional fiber optic cable schematically illustrated inFIG. 4. This is a dramatic reduction in weight and increase in storage capacity which is surprising for fiber optic cables that are capable of being GR-20, RDUP, IEC, or ICEA compliant. Thus, the slack storage and weight characteristics along with the performance of fiber optic cable30within pressure clamp19(as discussed below) provide the craft with a versatile fiber optic cable design for fiber optic networks.

Table 1 also lists size variations for fiber optic cable30and how changes in size affect the storage capacity and weight of the design. As shown by fiber optic cable30′, if the size increases slightly, then the storage capacity decreases and the weight increases to about 19 kilograms per kilometer or less. Likewise, if the size decreases slightly, then the space for storage capacity of 60 meters decreases to about 3760 cubic centimeters or less and the weight per kilometer decreases as shown by fiber optic cable30″. Additionally, fiber optic cables according to the invention are useful for other applications in optical networks such as a tether cable that forms a portion of a distribution fiber optic cable assembly, as a jumper cable assembly, attached to a multiport device, or the like.

Generally speaking, strength members34are much larger in size than optical fiber32and are selected to provide the desired tensile strength requirements for fiber optic cable30. By way of example, strength members34are dielectric members such as glass-reinforced plastic (GRPs) having a diameter of about 1.25 millimeters, but other sizes, shapes, and/or materials are possible for the strength members. For instance, strength members34can have an oval, rectangular, or other shape and/or be formed from steel or the like. If strength members34are formed from steel, then the fiber optic cable is no longer a dielectric design, but the cable may be able to be wrapped around structures for tie-down since the steel or metal strength members have a shape memory. If fiber optic cable30is intended for use with pressure clamps, then strength members34should be suitably bonded with cable jacket38; otherwise, cable jacket38may be pulled from strength members34by pressure clamp19which can cause catastrophic failure. To promote bonding with cable jacket38, strength members34may include one or more adhesion promoters35thereon such as selected from the ethylene-acrylic family such as an ethylene-acrylic acid (EAA), but other materials or mechanisms. For instance, bonding can be mechanical bonding by using a strength component with a rough surface or the like. Likewise, if intended for use with pressure clamp19, strength members34should have a spacing S of about 1 millimeter apart between inner surfaces to keep the clamped cable jacket38from moving into the optical fiber zone and pressing against optical fiber32, thereby causing elevated levels of optical attenuation. More specifically, spacing between inner surfaces of strength members34should be in the range of 0.8 millimeters to about 1.5 millimeters, thereby leaving a wall thickness of between about 0.4 to about 0.75 disposed about a single optical fiber when exposing and removing strength members34as shown inFIG. 15a. Spacing S being relatively small also helps with the relatively large storage capacity of the fiber optic cables according to the invention.

As discussed above, cable jacket38has a narrower waist portion compared with the end portions of fiber optic cable30(i.e., medial height MH is smaller than end heights EH) for inhibiting the transfer of crushing forces to optical fiber32when fiber optic cable is disposed within pressure clamp19. By way of example, medial height MH is about between about 0.1 to 1.0 millimeters smaller than end height EH, and more preferably, between about 0.2 and 0.8 millimeters smaller. A height ratio is defined as the medial height to end height (MH/EH) of the fiber optic cable. Fiber optic cables according to the present invention may have a height ratio in the range of about 0.6 to about 0.9 while still working within pressure clamp19, but the closer the range is to 1.0 the more optical performance is affected. Fiber optic cable30has a nominal height ratio of about 0.8 (2.5 mm/3.0 mm), but this value can vary within the range such as the height ratio being between about 0.6 (1.8 mm/3.0 mm) to about 0.9 (2.7 mm/3.0 mm). In other words, the shape of cable jacket38inhibits/reduces bend losses of optical fiber32due to crushing forces applied by pressure clamp19. Other variations of the fiber optic cable can have a uniform thickness for the cable jacket, but these designs may not be suitable for use within pressure clamp19since elevated optical attenuation may occur and the optical fiber may even go “dark.” More specifically, when tensioned within pressure clamp19the end portions (i.e., end height EH) of fiber optic cable30absorb the majority of the clamping forces and reduce the clamping force transferred to optical fiber32.

FIGS. 4a-4cshow various cross-sections of fiber optic cables within pressure clamp19as the height ratio changes. Specifically,FIG. 4adepicts a cross-sectional view of fiber optic cables within pressure clamp19with wedge19cproviding clamping of the cables between grip19band body19ato show the details of clamping. More specifically,FIG. 4ashows outlines of two fiber optic cables with a height ratio of 0.9 and 1.0 (e.g., the 0.9 profile is shown as a solid line and the 1.0 profile) is shown as dashed line at the medial height over optical fiber32. A longitudinal section is taken along line b-b respectively through medial height MH of the respective fiber optic cables with two different height ratios as shown respectively inFIGS. 4band4c. Wedge19cis not shown inFIGS. 4band4cfor clarity, but pushes down on grip19bduring clamping. As shown by the detail inFIGS. 4band4c, grip19bhas dimples (not numbered) and body19ahas ridges (not numbered) for deforming fiber optic cable and increasing the gripping strength as the cable is being clamped therebetween. Specifically,FIG. 4bshows the longitudinal section of a fiber optic cable with a height ratio of 1.0 and the deformation of cable jacket48created by the dimples of grip19band the ridges on body19a.FIG. 4balso shows that deformation and/or forces of pressure clamp19affects optical fiber32, which affect optical performance. Conversely,FIG. 4cshows the longitudinal section of a fiber optic cable with a height ratio of 0.6 and the lack of deformation of cable jacket48over optical fiber32from the dimples of grip19band the ridges on body19a, but other height ratios up to 0.9 can also benefit by preserving optical performance. Simply stated, if the height ratio is about 0.9 or less, deformation of cable jacket38into the optical fiber zone is reduced when disposed within pressure clamp19. Additionally, cable jacket38may be formed from any suitable polymer or blends such as a polyethylene, flame-retardant polyethylene, flame-retardant PVC, PVDF, and/or other suitable materials depending on intended use of the fiber optic cable (e.g., indoor, indoor/outdoor, or outdoor).

FIG. 5illustrates a graph showing an average delta optical attenuation for fiber optic cables with different height ratios when disposed within pressure clamp19at a reference wavelength of 1625 nanometers for comparison purposes. Specifically, the graph illustrates the delta optical attenuation for fiber optic cable30(i.e., a height ratio of about 0.8) and a similar comparison fiber optic cable with the height ratio of one. More specifically, the graph depicts an average delta optical attenuation for the fiber optic cables with different height ratios in pressure clamp19as the tensile load on fiber optic cables is increased from 0 pounds to 300 pounds, after the tensile load is released from the respective fiber optic cables with the pressure clamp19still attached, and finally when pressure clamp19is removed from the respective fiber optic cables. The tensile load is increased up to 300 pounds to model very extreme aerial installations within the pressure clamp19along with heavy wind and ice loading.

A line52and a line54respectively represent an average delta optical attenuation for fiber optic cable30and the comparison fiber optic cable over the given tensile range and other conditions. As shown, line52is generally flat at around 0.02 dB, which is within the noise of the measuring equipment. For the purpose of illustration, line52is generally shown as being generally zero across the tensile range and other conditions. On the other hand, line54has a relatively low delta optical attenuation until the tensile force reaches about 175 pounds and then dramatically increases with tensile force to unacceptable levels. After the tensile force of 300 pounds is released the attenuation still increases since the pressure clamp is still clamped and the cable jacket material relaxes within pressure clamp19. Additionally, if strength components are not bonded to the cable jacket the optical fiber will probably break as the tensile force is increased to 300 pounds. Simply stated, if strength members34are not bonded, then pressure clamp19causes cable jacket38to plastically deform by necking down on one side of pressure clamp19and accordion on the other side, resulting in catastrophic failure. However, fiber optic cable30is advantageous since it is robust enough to handle the extreme installation tensile loads and long spans under heavy wind and ice loads that can be experienced in aerial installations using pressure clamp19without undue levels of optical attenuation or catastrophic failure. By way of example, an aerial span of 150 feet of fiber optic cable30experiences a tensile load of about 220 pounds under NESC heavy loading (i.e., wind and ice). The relatively low tensile load under NESC heavy conditions is due to its relatively small cross-sectional footprint of fiber optic cable30. Moreover, as shown byFIG. 5fiber optic cable30can advantageously handle extreme tensile loading beyond NESC heavy loading while disposed within pressure clamp19(e.g., such as up to 300 pounds) without experiencing elevated levels of optical attenuation.

Additionally, since cable jacket38contacts optical fiber32a water-swellable or water-blocking component is not necessary since there are no gaps (i.e., pathways) for water to migrate along fiber optic cable30. Stated another way, cable jacket38is tightly drawn onto optical fiber32, but it does not bond to the same. It is believed that bonding of the cable jacket38with to optical fiber32is inhibited due to the relatively small amount of polymer required for the cable jacket38cross-section, which cools quickly during manufacturing since it has a relatively low amount of thermal energy to dissipate. Simply stated, the cross-section of fiber optic cable30is smaller because a buffer tube is not required for protecting the optical fiber (i.e., no buffer tube is necessary for inhibiting crushing forces and/or inhibiting sticking of the optical fiber to the cable jacket). The relatively small amount of polymer for cable jacket38can be quantified using a cable jacket envelope to strength component area ratio. The cable jacket envelope to strength component is defined as the total area of the cable jacket envelope (minus the area for the strength component(s)) to the total area for all of the strength components. For instance, the cable jacket envelope to strength component area ratio of fiber optic cable30is about 4.5:1, whereas the ratio for the conventional fiber optic cable ofFIG. 4is about 5.5:1. Size variations of fiber optic cable30can alter the ratio to about 5:1 or less.

Optical fiber32should provide the desired performance for the intended application. For instance, if the cable is intended for aerial applications, then the optical fiber32within fiber optic cable30should have an delta optical attenuation of about 0.3 dB or less when disposed in pressure clamp19with a tensile load of 300 pounds and preferably about 0.1 dB or less. Likewise, if the fiber optic cable has strength components with shape memory and is intended to be wrapped about structures for tie-down, then optical fiber32should be a bend resistant optical fiber to accommodate small bend diameters as known in the art. Additionally, if desired optical fiber32may include an optional coating33that becomes part of the optical fiber to improve the handability by the craft and/or robustness. By way of example, coating33can be any suitable material such as a UV-curable upcoating disposed on the optical fiber such as up to 500 microns or other desired size like 900 microns, but other sizes are possible like 700 microns. Polymer coatings such as a PVC, PVDF, or the like are also possible, but bonding between the polymer coating and cable jacket38should be avoided to preserve optical attenuation. Optical fiber32has a relatively low excess fiber length (EFL) such as 0.1% or less since cable jacket38contacts the same and higher levels of EFL can cause elevated optical attenuation levels. Additionally, optical fiber32may be proof tested to higher strength levels than normal (e.g., over 100 KPSI) such as proof tested to 200 KPSI or other suitable value for making the fiber optic cable compliant with GR-20 optical fiber strain requirements.

Fiber optic cable designs according to the concepts of the present invention can have any suitable number of optical fibers therein in a bare, colored, coated, or ribbonized format.FIGS. 6 and 7respectively are cross-sectional views of a fiber optic cable60and a fiber optic cable70according to the present invention that are similar to fiber optic cable30, but the fiber optic cables include multiple optical fibers32. As shown fiber optic cable60includes two bare optical fibers32disposed between strength members34, thereby forming a multi-fiber version of the fiber optic cable. Other structures are also possible such as using optical fiber ribbons for creating multi-fiber cable variations. Illustratively, fiber optic cable70depicts a fiber optic ribbon71having four optical fibers32therein.

Additionally, tonable variations similar to fiber optic cable30are possible according to the concepts of the present invention such as shown inFIGS. 8-10. Specifically, fiber optic cables according to the present invention can include a tonable element81such as a conductive wire, strip, or the like for locating the fiber optic cable such as when it is buried so it can be located and/or marked to prevent inadvertent damage. Tonable element81may be any suitable conductive material useful for determining the location of the fiber optic cable such as a small copper wire, copper-clad steel, or the like. By way of example, tonable element81is a copper wire having a gauge between 20-42 AWG. For instance,FIG. 8depicts a fiber optic cable80having a tonable element81disposed within a tonable lobe83that is separable from a main cable body85. Specifically, tonable lobe83is attached to main cable body85by a web87that is easily separable by hand, thereby making it craft-friendly. Web87can also include a preferential tear portion/geometry (not numbered) for controlling the location of the tear in the web near main cable body85, thereby resulting in a “clean” separation. Main cable body85and tonable lobe83are typically extruded using the same extrusion tooling. Other variations locate tonable element81within the main cable body. By way of example, fiber optic cable90includes tonable element81disposed within cable jacket38at a location near the outer surface of the same, thereby making accessing tonable element81relatively easy. Fiber optic cable100shows another variation where tonable element is disposed within cable jacket38, but disposed adjacent to one of the strength members34. Fiber optic cables90and100may also include marking indicia for indicating which side of the cable includes the tonable element81. In other variations, tonable element81can be disposed within one of the strength members or the strength component could be a tonable element.

Fiber optic cables of the present invention can be preconnectorized in the field or the factory on one or more ends with a hardened optic connector, thereby making a preconnectorized fiber optic cable or assembly suitable for plug and play connectivity by the craft. As used herein, a hardened connector refers to a robust fiber optic connector that is weatherproof, thereby making it suitable for use in the outside plant environment, but it is possible to use the hardened connector indoors. For instance, the craft may route the preconnectorized fiber optic cable having the hardened connector to a premises, a multi-port device, a network interface device (NID), optical network terminal (ONT), a closure, or the like.FIGS. 11a-11cshow an exemplary fiber optic mating assembly during the various stages of mating of an end of a preconnectorized fiber optic cable.

More specifically,FIGS. 11a-11cdepict a preconnectorized fiber optic cable110(i.e., the assembly includes fiber optic cable30with one or more hardened connectors150) being mated with a complementary receptacle130. Specifically,FIG. 11ashows receptacle130detached from preconnectorized fiber optic cable110. Moreover, preconnectorized fiber optic cable110and receptacle130are depicted with their respective protective caps on. Protective cap168is used for shielding a connector assembly152(FIG. 13), and in particular, the end face of a connector ferrule152bof the hardened connector from the elements and/or damage. Specifically, installed protective cap168isolates connector ferrule152bfrom the elements and prevents it from being damaged during transportation and handling.FIG. 11bshows protective cap168removed from the end of preconnectorized fiber optic cable110. Likewise, the respective cap (not numbered) of receptacle130is also removed. Preconnectorized fiber optic cable110is positioned to engage the complimentary portions of receptacle130. Specifically, an alignment indicia160cof preconnectorized fiber optic cable110is positioned to its complementary indicia130cof receptacle130.FIG. 11cshows a mated connection between the preconnectorized fiber optic cable110and receptacle130, thereby making an optical connection therebetween. As readily apparent, no special equipment, training, or skill is required to make the optical connection. Thus, the labor cost of deploying the optical network to the premises, or other location, is cost effective and efficient. In this case, the mating between the hardened connector (i.e., the plug connector) and the receptacle is secured using a threaded engagement, but other suitable means of securing the optical connection are possible. For instance, the securing means may use a quarter-turn lock, a quick release, a push-pull latch, or a bayonet configuration.

FIG. 12depicts a perspective view of an assembled preconnectorized fiber optic cable110′ with a toning element81. Specifically, preconnectorized fiber optic cable110′ is an assembly that includes fiber optic cable80with a hardened connector150(i.e., optical plug connector) mounted upon one end of fiber optic cable80. Recall that fiber optic cable80has toning element81disposed within tonable lobe83that is connected by a web portion87to the main cable body85. As shown, a portion of tonable lobe83is separated from main cable body85and coiled before attaching hardened connector150, thereby keeping it out of way and allowing grounding of tonable element81if necessary. Hardened connector150uses a connector assembly152of the SC type, but other types of connector assemblies such as LC, FC, ST, MT, and MT-RJ are contemplated by the present invention by using a suitable crimp housing. Thus, suitable hardened connectors may be used with suitable cables according to the concepts of the present invention, thereby resulting in numerous fiber optic cable/hardened connector assembly combinations.

FIG. 13depicts a partially exploded view of preconnectorized fiber optic cable110showing the components of hardened connector150. As shown, hardened connector150includes an industry standard SC type connector assembly152having a connector body152a, a ferrule152bin a ferrule holder (not numbered), a spring152c, and a spring push152d. Hardened connector150also includes a crimp assembly (not numbered) that includes a crimp housing155having at least one shell155aand a crimp band154, a shroud160(FIGS. 14aand14b) that receives one or more O-rings159, a coupling nut164, a cable boot166, a heat shrink tube167, and protective cap168secured to boot166or other suitable portion of the assembly by a lanyard169.

Generally speaking, most of the components of hardened connector150are formed from a suitable polymer. By way of example, the polymer is a UV stabilized polymer such as ULTEM2210available from GE Plastics; however, other suitable materials are possible. For instance, stainless steel or any other suitable metal may be used for various components.

As best shown inFIG. 15d, the crimp assembly includes crimp housing155and crimp band154. Crimp housing155has two shells155athat are held together by crimp band154when the preconnectorized fiber optic cable is assembled. Although, two identical shells are shown, it is to be understood that other suitable shell configurations are possible such as shells that are greater than or less than half of the crimp housing or more than two shells. Crimp band154is preferably made from brass, but other suitable crimpable materials may be used. Crimp housing155is configured for securing connector assembly152as well as providing strain relief to fiber optic cable30by securing one or more strength members34. Additionally, an epoxy, adhesive, glue, or the like may be used for securing strength members34within crimp housing155. This advantageously results in a relatively compact connector arrangement using fewer components. Moreover, the crimp assembly allows preconnectorized fiber cable110to be assembled quickly and easily. Of course, other embodiments are possible according to the present invention. For instance, connector body152amay be integrally molded into crimp housing155in a ST type configuration so that a twisting motion of the crimp housing secures the ST-type connector with a complementary mating receptacle.

FIGS. 15a-15ddepict several steps during the process of attaching the crimp assembly155to fiber optic cable30.FIG. 15ashows fiber optic cable30with strength members34and optical component42extending from the end of fiber optic cable30. Preparing the end of fiber optic cable30is relatively easy since a cutting blade can be run adjacent to strength members34at the top and bottom removing portion of cable jacket38and then strength members34can be pulled apart leaving optical fiber(s)32encased in a portion of cable jacket38to provide protection the same for routing and the like. Thereafter, the remainder of cable jacket38on strength members34can be easily removed along with the desired length of remaining cable jacket38on optical fiber(s)32.FIG. 15bshows the inner surface of one shell155a. In this case, only one shell155ais illustrated since two symmetrical shells are used for crimp housing155. In other embodiments there may be a first shell and a second shell, which are different. For instance, one shell may have two alignment pins, rather than each half-shell having a single alignment pin or one shell may be less than half of crimp housing155.

As shown inFIG. 15b, shell155aincludes a first end155bfor securing connector assembly152and a second end155cthat provides strain relief by securing one or more strength members34. A longitudinal axis A-A is formed between first end155band second end155cof shell155anear the center of crimp housing155, through which half of a longitudinal passage is formed. When assembled, optical fiber(s)32passes through the longitudinal passage and is held in a bore of ferrule152b. Additionally, shell155aincludes a cable clamping portion156and a connector assembly clamping portion157.

Specifically, cable clamping portion156has two outboard half-pipe passageways156aand a central half-pipe passageway156bthat is generally disposed along longitudinal axis A-A. Half-pipe passageways156amay include at least one rib156cfor securely clamping strength members34and may further include injecting an epoxy, adhesive, glue, or the like into the cable clamping portions, then crimp band154is crimped, thereby completing the crimp assembly. Moreover, half-pipe passageways156aare sized for the components of fiber optic cable30such as strength components34and optical fiber(s)32, but the passageways can be sized for different cable configurations.

Likewise, shell155ahas a connector assembly clamping portion157that is sized for attaching connector assembly152. Specifically, connector assembly clamping portion157has a half-pipe passageway157athat opens into and connects central half-pipe passageway156band a partially rectangular passageway157b. Half-pipe passageway157ais sized for securing spring push152dand may include one or more ribs for that purpose. Rectangular passageway157bholds/secures a portion of connector body152atherein and inhibits the excess rotation between connector assembly152and the crimp housing155.FIG. 15cdepicts prepared fiber optic cable30ofFIG. 15ahaving connector assembly152attached and positioned in a first shell155a. The alignment of the two shells is accomplished by inserting pins157cinto complementary bores157dof the two shells.FIG. 15dshows both half-shells155aof crimp housing155disposed about fiber optic cable30before crimp band154is installed thereover. Additionally, shells may include one or more bores156dthat lead to one of half-pipe passageways156aor156b. Bores156dallow for inserting an epoxy, adhesive, glue, or the like into the crimp housing155, thereby providing a secure connection for strain relief.

As shown inFIG. 12, when fully assembled at least a portion of the crimp assembly fits into shroud160. Additionally, crimp housing155is keyed to direct the insertion of the crimp housing/crimp assembly into shroud160. In this case, shells155ainclude planar surfaces157e(FIG. 15d) on opposites sides of crimp housing155to inhibit relative rotation between crimp housing155and shroud160. In other embodiments, the crimp assembly may be keyed to the shroud using other configurations such as a complementary protrusion/groove or the like.

As best shown inFIGS. 14aand14b, shroud160has a generally hollow cylindrical shape with a first end160aand a second end160b. Shroud160generally protects connector assembly152and may also key hardened connector150with the respective mating receptacle130. Shroud160includes a through passageway between first and second ends160aand160bfor receiving a portion of the crimp housing. As discussed, the passageway of shroud160is keyed so that crimp housing154is inhibited from excess rotation when hardened connector150is assembled. Additionally, the passageway has an internal shoulder (not visible) that inhibits the crimp assembly from being inserted beyond a predetermined position.

Additionally, first end160aof shroud160includes at least one opening (not numbered) defined by shroud160. The at least one opening extends from a medial portion of shroud160to first end160a. More specifically, shroud160includes a pair of openings on opposite sides of first end160a, thereby defining alignment portions or fingers161a,161b. In addition to aligning shroud160with receptacle during mating, alignment fingers161a,161bmay extend slightly beyond connector assembly152, thereby protecting the same. As shown inFIG. 14b, alignment fingers161a,161bhave different shapes so hardened connector150and receptacle130only mate in one orientation. This orientation can be marked on shroud160using alignment indicia160cso that the craftsman can quickly and easily mate preconnectorized fiber optic cable110with receptacle130. In this case, alignment indicia160cis an arrow molded into the top alignment finger of shroud160, however, other suitable indicia may be used. As shown, the arrow is aligned with complimentary alignment indicia130cdisposed on receptacle30(FIG. 11b), thereby allowing the craftsman to align indicia160c,130cso that alignment fingers161a,161bcan be seated into receptacle130. Thereafter, the craftsman engages the external threads of coupling nut164with the complimentary internal threads of receptacle130to make the optical connection as shown inFIG. 11c.

A medial portion of shroud160has one or more grooves162for seating one or more O-rings159. O-ring159provides a weatherproof seal between hardened connector150and receptacle130or protective cap168. The medial portion also includes a shoulder160dthat provides a stop for coupling nut164. Coupling nut164has a passageway sized so that it fits over the second end160bof shroud160and easily rotates about the medial portion of shroud160. In other words, coupling nut164cannot move beyond shoulder160d, but coupling nut164is able to rotate with respect to shroud160. Second end160bof shroud160includes a stepped down portion having a relatively wide groove (not numbered). This stepped down portion and groove are used for securing heat shrink tubing167. Heat shrink tubing167is used for weatherproofing the preconnectorized fiber optic cable. Specifically, the stepped down portion and groove allow for the attachment of heat shrink tubing167to the second end160bof shroud160. The other end of heat shrink tubing167is attached to cable jacket38, thereby inhibiting water from entering hardened connector150.

After the heat shrink tubing167is attached, boot166is slid over heat shrink tubing167and a portion of shroud160. Boot166is preferably formed from a flexible material such as KRAYTON, but other materials and/or configurations are possible. Heat shrink tubing167and boot166generally inhibit kinking and provide bending strain relief to fiber optic cable30near hardened connector150. Boot166has a longitudinal passageway (not visible) with a stepped profile therethrough. The first end of the boot passageway is sized to fit over the second end of shroud160and heat shrink tubing167. The first end of the boot passageway has a stepped down portion sized for fiber optic cable30and the heat shrink tubing167and acts as stop for indicating that the boot is fully seated. After 1 boot66is seated, coupling nut164is slid up to shoulder160cso that lanyard169can be secured to boot166. Specifically, a first end of lanyard169is positioned about groove166aon boot166. Thus, coupling nut164is captured between shoulder160cof shroud160and lanyard169on boot166. This advantageously keeps coupling nut164in place by preventing it from sliding past lanyard169down onto fiber optic cable30.

A second end of lanyard169is secured to protective cap168using a snap-fit into a groove (not numbered) on a front end of protective cap168. Consequently, protective cap168is prevented from being lost or separated from preconnectorized fiber optic cable110. Additionally, protective cap168can also include at an eyelet168a. Eyelet168ais useful for attaching a fish-tape or other pulling device so that preconnectorized fiber optic cable110can be pulled through a duct or the like. Protective cap168has internal threads for engaging the external threads of coupling nut164to secure it in place when not making an optical connection. Moreover, one or more O-rings159provide a weatherproof seal between hardened connector150and protective cap168when installed. When threadly engaged, protective cap168and coupling nut164of the hardened connector may rotate with respect to the remainder of preconnectorized fiber optic cable110, thereby inhibiting torsional forces during pulling of the same.

Preconnectorized fiber optic cable110may have any suitable length desired, however, preconnectorized fiber optic cable110can have standardized lengths. Moreover, preconnectorized fiber optic cable110may include a length marking indicia for identifying its length. For instance, the length marking indicia may be a marking located on the cable such as a colored stripe or denoted in a print statement. Likewise, the length marking indicia may be a marking located on hardened connector150. In one embodiment, length marking indicia may be denoted by a marking on coupling nut164or protective cap168such as a colored stripe. In any event, the length marking indicia should be easily visible so the craftsperson may identify the preconnectorized fiber cable length. By way of example, a red marking indicia on coupling nut164denotes a length of about 150 feet while an orange marking indicia denotes a length of about 300 feet.

The described explanatory embodiment provides an optical connection between the hardened connector150and its complementary receptacle130that can be made in the field without any special tools, equipment, or training. Additionally, the optical connection is easily connected or disconnected by merely mating or unmating the ends of preconnectorized fiber optic cable110with the respective receptacle by threadly engaging or disengaging coupling nut164and pulling hardened connector150from the complementary receptacle130. Thus, the preconnectorized fiber optic cables of the present invention allow deployment of optical waveguides toward the subscriber or other location in an easy and economical manner, thereby providing the end user with increased bandwidth. Furthermore, the concepts of the present invention can be practiced with other hardened connectors and/or other preconnectorized fiber optic cable configurations.

For instance,FIG. 16depicts an exploded view of another preconnectorized fiber optic cable210according to the present invention using a hardened connector250attached to fiber optic cable30that is similar to hardened connector150. In other words, hardened connector250is suitable for mating with complementary receptacle130like hardened connector150, but uses a different structure for securing fiber optic cable30and connector assembly52. Hardened connector250also includes a retention body255, a shroud260that receives one or more O-rings259, an optional shroud end piece260a, a coupling nut264, a cable boot266, a heat shrink tube254, and protective cap268secured to boot266or other suitable portion of the assembly by a lanyard269.

Fiber optic cable30is prepared for connectorization with hardened connector150in a manner similar to that shown inFIG. 15a. The exposed strength members34of fiber optic cable are secured to retention body255. Retention body255includes a central bore (not visible) for passing optical fiber32of fiber optic cable30therethrough for insertion into the ferrule of connector assembly152. Additionally, retention body255has two bores disposed outboard of the central bore sized for receiving strength members34therein. One method for securing strength members34to retention body255uses a radiation curable, heat curable epoxy, adhesive, glue, or the like for securing the same. If a radiation curable substance is used such as a light or UV curable epoxy, then retention body should be translucent for allowing the radiation for curing to reach and cure the radiation curable substance in a suitable manner. The front end of retention body255is used for securing connector assembly152thereto. Specifically, connector assembly152snap-fits to retention body255using resilient fingers or the like, but other suitable structures are possible for securing connector assembly152to retention body. Additionally, connector assembly152may be secured to retention body255in a manner that allows for some rotational movement. Thereafter, the retention body255assembly at least partially fits within shroud260and is keyed to shroud260inhibit rotation therebetween. The other components of hardened connector250are similar to hardened connector150.

As shown, retention body255is a monolithic structure, but it may have a structure that includes more that one piece. For instance, strength members34could have a mechanical attachment to retention body255instead of using an epoxy, adhesive, glue, or the like for securing the same. Specifically, retention body255can have wedges (i.e., one-way grips like a Chinese finger toy) that secure strength members34as they are inserted into the same. Hardened connector150is also suitable for use with automated assembly techniques.

Other hardened connectors can be used with the fiber optic cables of the present invention.FIG. 17illustrates complementary preconnectorized fiber optic cables310and320that are suitable for mating together. Specifically,FIG. 17shows a partially exploded view of a preconnectorized fiber optic cable310using a hardened connector350on a first fiber optic cable30along with a partially exploded view of its complementary preconnectorized fiber optic cable320having hardened connector390on a second fiber optic cable30. Hardened connector350and390are similar hardened connectors (i.e., some components are the same or similar thereby reducing complexity) that are intended to have opposing ferrules mate through an alignment sleeve354that is a portion of hardened connector350, instead of mating with a complementary receptacle like hardened connectors150and250. In other words, a coupling nut364of hardened connector350connects to the coupling sleeve365of hardened connector390for making the optical connection therebetween.

Hardened connector350includes a spring351, a ferrule assembly352, an inner housing353, alignment sleeve354, a retention body355, one or more O-rings359, an outer housing360, a coupling nut364, a boot366, and a cap368. Hardened connector350is similar to hardened connector250in that it has a retention body355having a central bore (not numbered) therethrough for passing optical fiber32therethrough and outboard bores (not numbered) for receiving and attaching strength members34of fiber optic cable30using an epoxy, glue, adhesive, or the like. However, ferrule assembly352does not snap-fit to retention body355; instead, spring351biases ferrule assembly352forward and inner housing353snap-fits to retention body355using resilient arms (not numbered), thereby positioning ferrule assembly352relative to retention body355. Specifically, inner housing355includes a centrally located hole therethrough sized to allow a portion of the ferrule to protrude beyond the front of inner housing355when assembled. As shown, hardened connector350includes two different sized O-rings359. The smaller O-ring is sized to attach to a medial shoulder (not numbered) portion of retention body355and the larger O-ring is sized to attach to outer housing360at a medial shoulder (not numbered) for sealing portions of the hardened connector. When assembled, the retention body355(along with the attached components) slides back into outer housing360and is secured therein by alignment sleeve354.

As shown, alignment sleeve354includes one or more resilient fingers (not numbered) that cooperates with one or more windows (not numbered) on outer housing360to secure the components together in the proper position. Retention body355is keyed to outer housing360using appropriate keying geometry to inhibit rotation therebetween. Outer housing360also includes a keying slot (not numbered) as best shown inFIG. 19for aligning hardened connector350with hardened connector390and alignment sleeve354also includes a keying portion (not visible) such as a recess that aligns with keying slot of outer housing360. Hardened connector350may also include a heat shrink tubing254to form a seal between retention body355and fiber optic cable30. Thereafter, boot366is attached to outer housing36using an epoxy, glue, adhesive, or the like, thereby keeping coupling nut364in place. In other words, coupling nut364is trapped between a shoulder of outer housing360and a shoulder of boot366while being free to rotate. When assembled, a portion of outer housing360extends beyond coupling nut364for insertion into hardened connector390. As shown, cap368can include an eyelet (not numbered) for attaching a pulling device to hardened connector350and when installed protects the end portion of hardened connector350. Additionally, the assembly can optionally include a lanyard (not shown) with one end secured onto boot366below coupling nut364and the other end of lanyard being attached to cap368for keeping it from being lost or misplaced.

Hardened connector390includes many of the same components as hardened connector350. For instance, hardened connector390includes spring351(not visible), ferrule assembly352, inner housing353(not visible), retention body355, one or more O-rings359, heat shrink tube (not visible), and boot366. Hardened connector390also has components that are similar to hardened connector350such as a coupling sleeve365(instead of coupling nut364) and a cap369that attaches to coupling sleeve365for protection; however, no outer housing or similar component is used. Instead, coupling sleeve365receives retention body355and is keyed to the same to inhibit rotation therebetween; otherwise, hardened connector390is similar to hardened connector350and assembled in a like fashion. Moreover, retention body355is set back a distance from the front end of coupling sleeve365to receive an extending portion of hardened connector350during mating of the two hardened connectors. Thus, the craft can quickly and easily make a reliable optical connection (or break an optical connection) between the optical fibers of the first and second fiber optic cable.

The concepts of hardened connector350and390are advantageous because a whole family of hardened connectors can be constructed by simply changing and/or adding a few components, thereby making the hardened connectors adaptable to fiber optic cables having other fiber counts. For instance, by changing the inner housings and the adapter the hardened connectors may be configured for securing more than one ferrule assembly or other types of ferrules, thereby allowing preconnectorization of fiber optic cables having other fiber counts.

By way of example,FIG. 18depicts complementary preconnectorized fiber optic cables410and420that are suitable for mating together. Specifically,FIG. 18shows a partially exploded view of preconnectorized fiber optic cable410using a hardened connector450on a first fiber optic cable60along with a partially exploded view of its complementary preconnectorized fiber optic cable420having hardened connector490on a second fiber optic cable60. In other words, hardened connectors450and490are suitable for fiber optic cables having two optical fibers32. The components of hardened connector450are similar to hardened connector350, except for inner housing453on both hardened connectors and adapter454. Simply stated, inner housing453is similar to inner housing353, but it includes two spaced apart holes for receiving two respective ferrules352therethrough. Likewise, adapter454is similar to adapter354, but it has two spaced apart bores to allow the two ferrules of each hardened connector to mate, instead of a centrally disposed bore.

In other variations, hardened connectors similar to hardened connectors350and390may include one or more multi-fiber ferrules for preconnectorizing fiber optic cable70or other similar fiber optic cables. For instance,FIG. 19depicts complementary preconnectorized fiber optic cables510and520that are suitable for mating together. Specifically,FIG. 19shows a partially exploded view of preconnectorized fiber optic cable510using a hardened connector550on a first fiber optic cable70along with a partially exploded view of its complementary preconnectorized fiber optic cable520having hardened connector590on a second fiber optic cable70. In other words, hardened connectors550and590are suitable for fiber optic cables having multiple optical fibers32such as four, eight, twelve, or other suitable fiber counts. The components of hardened connector550are similar to hardened connector350, except for inner housing553on both hardened connectors, spring (not visible), and adapter554. Simply stated, inner housing553is similar to inner housing353, but it includes a rectangular opening for receiving a multi-fiber ferrule552therethrough. Likewise, adapter454is similar to adapter354, but it has a rectangular bore to allow the rectangular multi-fiber ferrule of each hardened connector to mate, instead of a centrally disposed bore. Other variations of hardened connectors according to the invention are possible such as multiple multi-fiber ferrules or the like

Many modifications and other embodiments of the present invention, within the scope of the claims will be apparent to those skilled in the art. For instance, the concepts of the present invention can be used with any suitable composite cable designs and/or optical stub fitting assemblies. Thus, it is intended that this invention covers these modifications and embodiments as well those also apparent to those skilled in the art.