CA2151071C - Bend-limiting apparatus for a cable - Google Patents
Bend-limiting apparatus for a cableInfo
- Publication number
- CA2151071C CA2151071C CA002151071A CA2151071A CA2151071C CA 2151071 C CA2151071 C CA 2151071C CA 002151071 A CA002151071 A CA 002151071A CA 2151071 A CA2151071 A CA 2151071A CA 2151071 C CA2151071 C CA 2151071C
- Authority
- CA
- Canada
- Prior art keywords
- bend
- connector
- limiting
- cable
- axial bore
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3807—Dismountable connectors, i.e. comprising plugs
- G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
- G02B6/3826—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres characterised by form or shape
- G02B6/3829—Bent or angled connectors
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3807—Dismountable connectors, i.e. comprising plugs
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/36—Mechanical coupling means
- G02B6/38—Mechanical coupling means having fibre to fibre mating means
- G02B6/3807—Dismountable connectors, i.e. comprising plugs
- G02B6/3887—Anchoring optical cables to connector housings, e.g. strain relief features
- G02B6/38875—Protection from bending or twisting
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4439—Auxiliary devices
- G02B6/4471—Terminating devices ; Cable clamps
- G02B6/4478—Bending relief means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Mechanical Coupling Of Light Guides (AREA)
- Light Guides In General And Applications Therefor (AREA)
Abstract
A bend-limiting apparatus for attachment to an optical connector has a generally cylindrical shape and includes an axial bore along its central axis for holding an optical cable. The front end of the bend-limiting apparatus attaches to the optical connector and has an outside diameter which is comparable in size to theconnector. The back end of the bend-limiting apparatus has an outside diameter which is comparable in size to the optical cable. The bend-limiting apparatus is made from a flexible material which is sufficiently stiff to accommodate heavy side loads, but includes a number of grooves that are exclusively positioned on its back half to accommodate light side loads. These grooves preferably extend from an outside surface of the apparatus into the axial bore, and also extend in a circumferential direction at least part way around the apparatus. Such a design effectively limits the minimum bend radius of an optical cable over a wide range of side loads.
Description
BEND-LIMITING APPARATUS FOR A CABLE
Technical Field This invention generally relates to a cable support device, and more particularly to apparatus for limiting the minimum bend radius of a commurlications cable.
Barl~round of the Invention Optical fiber connectors are an essential part of substantially any optical fiber communication system. For instance, such connectors may be used to join segments of fiber into longer lengths; to connect fiber to active devices such as radiation sources, 0 detectors and repeaters; or to connect fiber to passive devices such as switches and attenuators. The central function of an optical fiber connector is the maintenance of two optical fiber ends such that the core of one of the fibers is axially aligned with the core of the other fiber. When the ends are aligned properly, there will be little or no connection loss due to core mi~lignment.
However, not all of the loss in an optical fiber connection is attributable to core misalignment. Sharp bends in the optical fiber itself cause substantial loss in a lightwave signal, particularly at long wavelengths (1550 nanometers) now being used for the highest data tr~nsmis~ion speeds. When the optical fiber is bent in a curved path, the smaller the bend radius, the greater the path loss. This is especially true for matched-clad, singlemode fiber (as compared to depressed-clad, singlemode fiber). However, if the bend radius is sufficiently large, then path loss is not a concern. Bending occurs during cable placement and occasionally occurs when the cable, which contains the optical fiber, is routed around a sharp corner or becomes "kinked" due to handling. More frequently, sharp bends occur in the region where the connector is plugged into a panel, ~5 and its attached cable needs to be bent (usually by 90~) to be routed to its destination.
~ndeed, such panels are frequently equipped with access doors which, when closed, press against the back portion of the connector and cause its associated cable to bend sharply.
Such bending also occurs when a jumper (comprising an optical cable and a connector) is inserted into a receptacle and the cable is pulled in a direction which is perpendicular to the central axis of the connector. The sharp bend at the junction where the cable attaches to the connector causes excessive tr~n~mi~ion loss in the lightwave signal.
Strain-relief boots are well-known devices for transferring axial tension from the cable to the connector, and they also function to limit the amount of bending that can occur at the junction where the cable is joined to the connector. Such boots are generally cylindrical and surround the optical cable at the cable/connector junction. The diameter of the boot is approximately equal to the diameter of connector where they meet, and it tapers to the diameter of the cable where the cable enters the boot. One popular design of a strain-relief boot includes a number of bend-limiting segments which are separated from each other by a gap that is approximately equal to the width of each 5 segment. When the cable is bent, the segment portions on the inside of the bend come closer together until they finally touch, thereby limiting the minimum radius of the bend. While such designs provide acceptable results over a narrow range of side loads, they have not been completely successful over side loads that range, for example, from 0.5 to 10 pounds. Nevertheless, such wide ranges are routinely 10 encountered during normal h~ntlling Depending on the material used for the bend-limiting boot, and its pattern of segments, sharp bending will either occur at the junction where the cable meets the boot (light load), or sharp bending will occur at the junction where the boot meets the connector (heavy load). In either event, excessive tr~n~mi~ion loss will be experienced by lightwave signals traveling within 15 the optical cable when the bend is too sharp.
It is noted that bend-limiting boots can be designed to handle a very wide range of side loads if the dimensions of the boot are unconstrained. For example, a cone-shaped boot having a large diameter at one end, a narrow diameter at the other end, and a very long distance between these ends can be designecl to satisfy virtually 20 any load range. However, as a practical matter, the size (diameter) of the bend-limiting boot should be approximately equal to the size of the connector where they join together, and the boot cannot be too long. Seemingly, the prior art has notprovided a bend-limiting boot for use with optical connectors which is compact and yet capable of h~n-lling a wide range of side loads.
25 Summary of the Invention In accordance with one aspect of the present invention there is provided apparatus for limiting the bending radius of a cable that is attached to a connector, said a~dldLus comprising (i) a connector-eng~ging portion which engages the connector, and (ii) a bend-limiting portion which surrounds the cable in the region 30 where it is attached to the connector, the apparatus comprising an elongated structure having an outside surface, the a~p~dtus further comprising an axial bore which extends along a central axis of the elongated structure from a front end to a back end CA 021~1071 1998-07-30 2a thereof for supporting the cable, said al)palalus being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading; and a pluralit,v of circumferential grooves that extend at least part way around the ap~alalus and fully penetrate the bend-limiting apparatus from the outside 5 surface to the axial bore, said grooves being confined to the back half of thebend-limiting portion of the appal~ s for limiting the nfininlum bend radius of the cable under light side loading.
In accordance with another aspect of the present invention there is provided in combination, a communications cable joined to a connector and a bend-limiting 10 device, the communications cable including a signal tr~n~mi~ion medium enclosed within a plastic jacket; the connector including a plug for connecting signals from the tr~n~mi~ion medium to another connector; and the device comprising (i) a connector-eng~ging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the communications 15 cable in the region where it is joined to the connector, said device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading, said device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device for20 limiting the lllinilllum bend radius of the cable under light side loading.
In accordance with yet another aspect of the present invention there is provided in combination, an optical cable joined to an optical connector and a bend-limiting device, the optical cable comprising a light-carrying fiber enclosed within a plastic buffer material; the connector comprising (i) a fiber-holding structure 25 having an axial passageway which receives the optical fiber and which termin~tes in an end face that is perpendicular to the passageway, and (ii) a housing having int~rn~l surfaces that define a cavity and surround the fiber-holding structure; and the device comprising (i) a connector-eng~gin~ portion which engages the connector, (ii) anaxial bore along its central axis, and (iii) a bend-limiting portion which surrounds the 30 cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the optical cable under heavy side loading, said bend-limiting device including a plurality of circumferential grooves that extend at least part way around the device, extend into CA 021~1071 1998-07-30 2b the axial bore, and are confined to the back half of the bend-limiting portion of the device for limiting the minimum bend radius of the optical cable under light side loading.
In accordance with still yet another aspect of the present invention there is S provided a jumper comprising a communications cable t~rmin~te~l in a connector at each end, at least one of said connectors including a bend-limiting device having an axial bore along its central axis which holds the communications cable; the communications cable including a signal tr~n~mi~cion medium enclosed within a dielectric jacket; the connector including a plug for connecting signals from the 10 tr~n~mi~ion medium to another connector; and the device comprising (i) a connector-eng~ging portion which engages the connector, and (ii) a bend-limitingportion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiency stiff to limit the minimum bend radius of the cable under heavy side loading, said bend-limiting 15 device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device for limiting the minimllm bend radius of the cable under light side loading.
In a preferred embodiment of the invention, the outside diameter of the 20 ap~ald~ ls is tapered from front to back. At its front end, the diameter is comparable in size to the CA 021~1071 1998-07-30 ~ 2l~lo7l connector; and at its back end, the diameter of the apparatus is comparable in size to the cable.
In the preferred embodiment, the grooves of the apparatus extend into the axial bore from the outside surface, and the flexible material comprises an elastomer having a s hardness of approximately Shore 50 D. Additionally, the front end of the bend-limiting apparatus includes a portion having a generally square cross section for insertion into a mating opening of a receptacle. This square portion comprises about 20% of the length of the bend-limiting appaldl~ls and, when inserted into the receptacle, increases the amount of support to resist side loading that can be applied to the bend-limiting appalalus.
In the preferred embodiment of the invention, the bend-limiting apparatus is combined with an optical connector, and an optical cable ~,vith yarn-like strength members that surround an optical fiber within the cable. The appaldlus includes a cavity at its front end which is adapted to receive the back end of the connector capture the strength members therebetween, thus providing strain relief for the cable as well as limiting its minimum bend radius.
Brief Descril~tion of the Drawin~
The invention and its mode of operation will be more clearly understood from thefollowing detailed description when read with the appended drawing in which:
FIG. 1 is a front, top and right-side perspective view of a bend-limiting apparatus for optical fiber connectors;
FIG. 2 is a cross section of the bend-limiting apparatus of FIG. 1, and is also shown in perspective view;
FIG. 3 is a cross section of the bend-limiting apparatus of FIG. 1 shown in elevation view;
FIG. 4 is a cross section of the bend-limiting apparatus of FIG. 1, shown along a diagonal cut;
FIG. 5 is an exploded perspective view of an optical connector together with thebend-limiting appaldllls of FIG. 1-4 and an optical cable;
FIG. 6 is a partial cross section of the bend-limiting apparatus attached to an optical connector, both shown inserted into a receptacle; and FIG. 7A-7C discloses one prior art, bend-limiting device under three different load conditions in which excessive bending occurs during the application of light side loads;
FIG. 8A-8C discloses another prior art, bend-limiting device under three different load conditions in which excessive bending occurs during the application of heavy side loads, FIG. 9A-9C discloses the bend-limiting apparatus of FIG. 1-4 under three different load conditions; and FIG. 10 discloses a jumper comprising an optical connector, a bend-limiting apparatus in accordance with the invention, and an optical cable.
Detailed l)escription o Reference is made to FIG. 1 which shows a front, top and right-side perspective view of a bend-limiting apparatus 20 in accordance with the present invention. Bend-limiting devices are typically used to limit the minimum radius of a bend in a communications cable where it attaches to a connector. The apparatus of the present invention comprises a tapered cylinder having one diameter at its front end 22, and a smaller diameter at its back end 24. The bend-limiting apparatus is made from a flexible material and includes an axial bore 28 (shown in FIG. 2-4) that extends from one end to the other along a central, longitudinal axis which is designed to hold the cable. The front end of the bend-limiting apparatus includes a portion 21 having a square cross section that inserts into a mating receptacle. Portion 21 comprises about 20% of the length of ~o apparatus 20 and helps transfer bending stress from the apparatus to the receptacle. Axial bore 28 extends into a cavity 27 that is adapted to receive the back end of a connector (see FIG. 2-4). Several grooves 23 are molded into the back half portion of the apparatus and function to increase the flexibility of the apparatus when light side loads are applied to the cable. These grooves 23 are specifically confined to the back half of the apparatus ~5 so that the same flexible material can be used throughout while still elimin~ting sharp cable bends under both heavy and light side loads. In a plefelled embodiment of the invention, the grooves 23 extend into the axial bore 28 from an outside surface 29 of the apparatus, and the flexible material comprises an elastomer having a hardness ofapproximately Shore 50 D. In the preferred embodiment of the invention, the bend-limiting apparatus is also used to provide strain relief for the cable held within the axial bore, and interior flange 25 cooperates with a groove within an associated connector, as discussed in FIG. 5, to provide strain relief for the cable. And while the benefits of this design accrue mainly to cables cont~ining optical fibers, the bend-limiting apparatus may be advantageously used with cables cont~ining copper wires also. FIG. 2-4 show various cross-sectional views of the bend-limiting device of FIG. 1 to illustrate its construction in greater detail.
FIG. 5 is an exploded perspective view of an optical connector combined with an optical cable and the bend-limiting appaldl~ls shown in FIG. 1-4, illustrating their cooperative association. In particular, FIG. 5 discloses construction details of a connector 10 which includes a housing assembly 100, 110; and a fiber-holding structure comprising ferrule 140, base member 150, and spring 160 which is disposed about the base member.
Although the housing assembly is shown as two separate pieces that are bonded together, it can be constructed as a one-piece unit or a multi-piece assembly. As shown in FIG. 5, housing 110 is a generally U-shaped device having a cavity 114 for receiving the fiber-o holding structure. Once the fiber-holding structure is inserted into the cavity of housing 110, cover 100 is bonded thereto. Cover 100 includes pins 106-106 which mate with holes 116-116 in housing 110 for alignment. Once joined together, the front end of the connector has a generally square shape which fits into a receptacle 40 (see FIG. 6) that is shaped to receive same. Top surface 112 and left-side surface 101 comprise two of the four outside surfaces that form the front end of connector 10. The back end of connector 10 is conically shaped with four flat areas, spaced 90~ apart, that are used to position the back end of the connector within the front end of bend-limiting apparatus 20. Top surface 118 and left-side surface 102 comprise two of the four flat surfaces at the back end of connector 10. Housing members 100, 110 include a plurality of interior surfaces that define cavity 114 which surrounds the fiber-holding structure. The connector includes a first opening 119 at its back end which receives an optical cable 30 and a second opening 111 at its front end for enabling the end face of the fiber-holding structure to protrude therethrough. These openings 111, 119 extend into cavity 114 and are positioned at opposite ends of connector 10. Housing members 100, 110 are molded from a thermoplastic material and have been designed to be molded for straight pulls, without cams, to reduce mold and part costs. It is noted that spring latch 120 is molded into the top surface 112 of the housing 110.
Similar to the outside surface of the connector, interior cavity 114 also has a generally square shape. A flange 113 within housing 110 includes a sloped surface which is shaped to interface with chamfered surface 151 of flange 152 on the base member 150.
Moreover, flange 152 is shaped to enable it to be supported within cavity 114 in several different stable positions -- each one having a different rotational orientation with respect to the central axis of the fiber-holding structure. Flange 152 is square and thus provides 4 stable positions for orienting the fiber-holding structure so that fiber eccentricity can be changed. Compression spring 160 surrounds the back cylindrical portion of base member 150. It presses against surface 153 of the flange and against surface 115 within cavity l 14 of housing member 1 10. Spring 160 urges the end face of the fiber-holding structure through opening 111.
Ferrule 140 may be a glass, metal, ceramic or plastic cylinder having a narrow passageway (about 126 llm in diameter) through its central axis for receiving an end s portion of an optical fiber. In this illustrative connector, the ferrule has an outer diameter of about 1.25 mm and a length of about 7.0 mm. In the construction of an optical cable 30, a thin glass fiber is typically coated with two layers of ultraviolet-curable materials (polyacrylate for example) for protection. The coated fiber is then covered with a thermoplastic having sufficient stiffness to preclude fiber buckling and is referred to as a o buffered fiber 33. To withstand tensile forces that might otherwise fracture the buffered fiber, the cable is constructed with a load-bearing portion in the form of strength members 32 that surround the buffered fiber 33. Elongated slender polymeric fibers of high tensile strength, such as aramid yarn, are suitable for use in this regard. An outer jacket 31 comprising polyvinyl chloride, for example, surrounds the buffered fiber and strength members to complete the construction of optical cable 30. As the cable diameter is made smaller (with the same type fiber), path loss due to cable bending becomes more of a concern. The section modulus that affects bend performance is an exponential function of the diameter. As connectors become smaller, then cables having smaller diameters will become more common. The present invention illustratively uses a cable with a diameter of 1.6 mm -- which is substantially smaller than typical interconnection cables having diameters of 2.0 mm, 2.4 mm, and 3.0 mm.
These layers of different materials are all stripped from an end portion of the glass fiber prior to its insertion into ferrule 140. An a&esive is injected into the passageway through the central axis of ferruie 140. Then the uncoated portion of the optical fiber is inserted into the passageway of the ferrule and adhesively attached. The spring 160 is pre-compressed on the ferrule/base member subassembly 140/150 with cable, and isplaced into housing 110. Housing cover 100 is then installed and ultrasonically bonded, for example. Strength members 32 (e.g., aramid fibers) of the cable 30 are adhesively attached to the back end of connector 10 and pressed into a circumferential groove 1 17 by a mating flange 25 (see FIG. 1-4) within the bend-limiting strain-relief boot 20. Both the cable jacket 31 and the strength members 32 are "sandwiched" between the boot and the back end of connector 10. A suitable adhesive for joining the strength members together with the boot and the connector is Hysol 151 - a commercially available, two-part epoxy.
When an axial pull of up to 15 pounds is applied to cable 30, it is desirable that it remain attached to connector 10. And while adhesives are preferable, a crimping sleeve may 7 2lslo7l alternatively be used to join the strength members 32, and/or outer jacket 31 of the cable, to the connector.
Bend-limiting strain-relief boot 20 is about 38 mm long and includes a generallysquare portion at its front end whose sides are each about 4.6 mm. It is made from a suitably compliant material so that its back portion can be bent in a direction that is perpendicular to its longitudinal axis. In the preferred embodiment of the invention, the strain-relief boot is made from a thermoplastic rubber such as Santoprene(~) elastomer which is commercially available from Advanced Elastomer Systems, LP. So that thebending properties of the boot 20 are suitable for limiting the bend radius of the enclosed o cable 30 to no less than 20 mm over a prescribed load range, the preferred thermoplastic rubber is designated 253-50 and has a hardness rating of 50 D. Additionally, a portion of boot 20 is conically shaped and tapers from a maximum diameter of about 5.6 mm at one end 22 to a minimum diameter of about 3.0 mm at the other end 24. Not only does the boot 20 provide strain relief for cable 30, but it also insures that the cable can withstand repeated bends after interconnection without undue stress being imparted to the glass fiber.
At the front end of bend-limiting boot 20, a generally square portion 21 occupies approximately 20 percent of the entire length of the boot. This portion is adapted to be received into a mating opening of a receptacle 40 (see FIG. 6) to transfer bending stress ~o from the boot 20 to the receptacle, and advantageously remove stress from the connector/cable junction. The operation of grooves 23 are discussed in connection with FIG. 9A-9C.
FIG. 6 shows an optical fiber connector inserted within a duplex receptacle 40 which accommodates two such connectors. Receptacle 40 installs in a rectangular opening of a flat panel by pushing its narrow end through the opening. The receptacle is held therein by grooves 411 in spring latch 410, and may be removed from the panel by sql-ee7.ing the spring latch and pushing the receptacle forward. Typically, two identical receptacles 40-40 are joined by bonding their flanges 412 together end-to-end before insertion into the panel. Mating portions 421, 423 are used to assure proper alignment.
Nevertheless, so that the ferrules 140 within the connectors are perfectly aligned, specially designed alignment sleeves are installed in cylindrical openings 422 before the receptacles are joined. Sidewall 420 at the back end of receptacle 40 provides lateral support to the square portion 21 of bend-limiting device 20. Sidewall 420 generously extends beyond the minimum depth of the receptacle needed to hold the cormector.3s Reference is now made to FIG. 7A-7C which disclose a prior art bend-limiting device 70. In these figures the material used in the construction of device 70 is selected 8 21~1071 to handle heavy side loads better than light side loads. For example, FIG. 7A shows the rest position of bend-limiting device 70 when no downward force is applied to the optical cable 30. FIG. 7B illustrates the condition in which a light downward force FL is applied to cable 30, but bend-limiting device 70 is too rigid to yield to such light side loads, and so the optical cable itself must accommodate the bending force which results in a bend radius that is too small in the region designated 75. In this situation, lightwave signals traversing region 75 experience too much path loss. FIG. 7C illustrates the condition in which a heavy downward force FH is applied to cable 30. Here, the minimum bend radius is larger than the minimum bend radius shown in FIG. 7B which results in lower path 0 loss. Additionally, FIG. 7C is used to illustrate the me~ning of a "minimum bend radius"
which is the radius "r" of the smallest circle whose circumference is collinear with a portion of the fiber which is located approximately at the central axis 35 of the cable.
Referring now to FIG 8A-8C, bend-limiting device 80 is shown having a number of segments 81-81 that enable the bend-limiting device to yield more easily during a condition of light side loading, but is unacceptable during heavy side loads. In this prior art example, the same material is used in molding the bend-limiting device 80 as was used in molding bend-limiting device 70 (see FIG. 7A-7C). Segmentation of the bend-limiting device allows it to yield more easily to light downward forces FL as indicated in FIG. 8B. It is noted that the problem of sharp bends under light loads, as previously demonstrated in FIG. 7B, is now solved. However, as FIG. 8C illustrates, heavy downward forces FH applied to cable 30 result in too much bending in region 85, and lightwave signals traversing this region will experience too much loss. It is noted that similar results could have been achieved in FIG. 8A-8C by elimin~ting the segments and using a more flexible material for the construction of bend-limiting device 80.
FIG. 9A-9C illustrate the advantages of the present invention under different side load conditions. FIG. 9A shows the rest position of an optical cable 30 and bend-limiting apparatus 20 when no downward force is applied to the optical cable. The grooves 23 in the back half of the bend-limiting a~pdldl~ls 20 allow it to yield more readily when light downward forces FL are applied to cable 30 as indicated in FIG. 9B. In the preferred embodiment of the invention these grooves fully extend into the axial bore; and so each groove does not completely encircle the a~p~d~-ls - otherwise it would detach. In order to accommodate bending in various directions, two rows of grooves are used and the same groove pattern is repeated -- but rotated by 90~. These grooves provide a loose hinge action in bend-limiting apparatus 20 which is particularly effective for smaller 3s cables and light side loads. However, as will be illustrated in connection with FIG. 10, these grooves need not fully extend into the axial bore. Finally, FIG. 9C illustrates the 21~1071 condition in which a heavy downward force FH is applied to cable 30 in which bend-limiting apparatus 20 provides suitable results. These results are achieved by using a sufficiently stiff material to accommodate heavy side loads and grooves in the back half of the apparatus to accommodate light side loads. Such a design avoids the need for a particularly long bend-limiting apparatus. FIG. 9C also illustrates the cooperation between portion 21, at the front end of apparatus 20, and sidewall 420 of an associated receptacle which receives connector 10. It is noted that portion 21 is "sandwiched"
between the connector and the sidewall which further improves the bend-limiting apparatus by transferring bending stresses away from the cable/connector junction.
o FIG. 10 discloses a jumper comprising a cable 30 which is termin~ted at each end with an optical connector 15 and a bend-limiting device 50. In this figure, a slightly different optical connector is used (known as an ST(~-connector). Connector 15 includes a ferrule 140 having an optical fiber installed along its central axis, and a bayonet-style connection means having a c~mmin~ surface 16 for interlocking with a mating device.
s Of particular interest, however, is a second embodiment of bend-limiting apparatus 50 which includes circumferential grooves 53 that do not fully extend into the axial bore.
Nevertheless, similar to the preferred embodiment of the invention shown in FIG. 1-6, apparatus 50 comprises a sufficiently stiffmaterial to accommodate heavy side loads, and grooves confined to the back half of the apparatus for accommodating light side loads.
Although various particular embodiments of the invention have been shown and described, modifications are possible within the spirit and scope of the invention. These modifications include, but are not limited to, the use of different materials in the construction of the bend-limiting appald~us. For example, although an elastomer is disclosed, other thermoplastic materials are possible. And even though glass fibers are the primary beneficiary of the invention, other light-carrying fibers (e.g., plastic fibers) may be used. Additionally, the bend-limiting apparatus may also be used with cables having metallic conductors. Finally, the bend-limiting apparatus need not be cylindrical or tapered from front to back, but rather may comprise a substantially constant shape over its entire length.
Technical Field This invention generally relates to a cable support device, and more particularly to apparatus for limiting the minimum bend radius of a commurlications cable.
Barl~round of the Invention Optical fiber connectors are an essential part of substantially any optical fiber communication system. For instance, such connectors may be used to join segments of fiber into longer lengths; to connect fiber to active devices such as radiation sources, 0 detectors and repeaters; or to connect fiber to passive devices such as switches and attenuators. The central function of an optical fiber connector is the maintenance of two optical fiber ends such that the core of one of the fibers is axially aligned with the core of the other fiber. When the ends are aligned properly, there will be little or no connection loss due to core mi~lignment.
However, not all of the loss in an optical fiber connection is attributable to core misalignment. Sharp bends in the optical fiber itself cause substantial loss in a lightwave signal, particularly at long wavelengths (1550 nanometers) now being used for the highest data tr~nsmis~ion speeds. When the optical fiber is bent in a curved path, the smaller the bend radius, the greater the path loss. This is especially true for matched-clad, singlemode fiber (as compared to depressed-clad, singlemode fiber). However, if the bend radius is sufficiently large, then path loss is not a concern. Bending occurs during cable placement and occasionally occurs when the cable, which contains the optical fiber, is routed around a sharp corner or becomes "kinked" due to handling. More frequently, sharp bends occur in the region where the connector is plugged into a panel, ~5 and its attached cable needs to be bent (usually by 90~) to be routed to its destination.
~ndeed, such panels are frequently equipped with access doors which, when closed, press against the back portion of the connector and cause its associated cable to bend sharply.
Such bending also occurs when a jumper (comprising an optical cable and a connector) is inserted into a receptacle and the cable is pulled in a direction which is perpendicular to the central axis of the connector. The sharp bend at the junction where the cable attaches to the connector causes excessive tr~n~mi~ion loss in the lightwave signal.
Strain-relief boots are well-known devices for transferring axial tension from the cable to the connector, and they also function to limit the amount of bending that can occur at the junction where the cable is joined to the connector. Such boots are generally cylindrical and surround the optical cable at the cable/connector junction. The diameter of the boot is approximately equal to the diameter of connector where they meet, and it tapers to the diameter of the cable where the cable enters the boot. One popular design of a strain-relief boot includes a number of bend-limiting segments which are separated from each other by a gap that is approximately equal to the width of each 5 segment. When the cable is bent, the segment portions on the inside of the bend come closer together until they finally touch, thereby limiting the minimum radius of the bend. While such designs provide acceptable results over a narrow range of side loads, they have not been completely successful over side loads that range, for example, from 0.5 to 10 pounds. Nevertheless, such wide ranges are routinely 10 encountered during normal h~ntlling Depending on the material used for the bend-limiting boot, and its pattern of segments, sharp bending will either occur at the junction where the cable meets the boot (light load), or sharp bending will occur at the junction where the boot meets the connector (heavy load). In either event, excessive tr~n~mi~ion loss will be experienced by lightwave signals traveling within 15 the optical cable when the bend is too sharp.
It is noted that bend-limiting boots can be designed to handle a very wide range of side loads if the dimensions of the boot are unconstrained. For example, a cone-shaped boot having a large diameter at one end, a narrow diameter at the other end, and a very long distance between these ends can be designecl to satisfy virtually 20 any load range. However, as a practical matter, the size (diameter) of the bend-limiting boot should be approximately equal to the size of the connector where they join together, and the boot cannot be too long. Seemingly, the prior art has notprovided a bend-limiting boot for use with optical connectors which is compact and yet capable of h~n-lling a wide range of side loads.
25 Summary of the Invention In accordance with one aspect of the present invention there is provided apparatus for limiting the bending radius of a cable that is attached to a connector, said a~dldLus comprising (i) a connector-eng~ging portion which engages the connector, and (ii) a bend-limiting portion which surrounds the cable in the region 30 where it is attached to the connector, the apparatus comprising an elongated structure having an outside surface, the a~p~dtus further comprising an axial bore which extends along a central axis of the elongated structure from a front end to a back end CA 021~1071 1998-07-30 2a thereof for supporting the cable, said al)palalus being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading; and a pluralit,v of circumferential grooves that extend at least part way around the ap~alalus and fully penetrate the bend-limiting apparatus from the outside 5 surface to the axial bore, said grooves being confined to the back half of thebend-limiting portion of the appal~ s for limiting the nfininlum bend radius of the cable under light side loading.
In accordance with another aspect of the present invention there is provided in combination, a communications cable joined to a connector and a bend-limiting 10 device, the communications cable including a signal tr~n~mi~ion medium enclosed within a plastic jacket; the connector including a plug for connecting signals from the tr~n~mi~ion medium to another connector; and the device comprising (i) a connector-eng~ging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the communications 15 cable in the region where it is joined to the connector, said device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading, said device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device for20 limiting the lllinilllum bend radius of the cable under light side loading.
In accordance with yet another aspect of the present invention there is provided in combination, an optical cable joined to an optical connector and a bend-limiting device, the optical cable comprising a light-carrying fiber enclosed within a plastic buffer material; the connector comprising (i) a fiber-holding structure 25 having an axial passageway which receives the optical fiber and which termin~tes in an end face that is perpendicular to the passageway, and (ii) a housing having int~rn~l surfaces that define a cavity and surround the fiber-holding structure; and the device comprising (i) a connector-eng~gin~ portion which engages the connector, (ii) anaxial bore along its central axis, and (iii) a bend-limiting portion which surrounds the 30 cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the optical cable under heavy side loading, said bend-limiting device including a plurality of circumferential grooves that extend at least part way around the device, extend into CA 021~1071 1998-07-30 2b the axial bore, and are confined to the back half of the bend-limiting portion of the device for limiting the minimum bend radius of the optical cable under light side loading.
In accordance with still yet another aspect of the present invention there is S provided a jumper comprising a communications cable t~rmin~te~l in a connector at each end, at least one of said connectors including a bend-limiting device having an axial bore along its central axis which holds the communications cable; the communications cable including a signal tr~n~mi~cion medium enclosed within a dielectric jacket; the connector including a plug for connecting signals from the 10 tr~n~mi~ion medium to another connector; and the device comprising (i) a connector-eng~ging portion which engages the connector, and (ii) a bend-limitingportion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiency stiff to limit the minimum bend radius of the cable under heavy side loading, said bend-limiting 15 device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device for limiting the minimllm bend radius of the cable under light side loading.
In a preferred embodiment of the invention, the outside diameter of the 20 ap~ald~ ls is tapered from front to back. At its front end, the diameter is comparable in size to the CA 021~1071 1998-07-30 ~ 2l~lo7l connector; and at its back end, the diameter of the apparatus is comparable in size to the cable.
In the preferred embodiment, the grooves of the apparatus extend into the axial bore from the outside surface, and the flexible material comprises an elastomer having a s hardness of approximately Shore 50 D. Additionally, the front end of the bend-limiting apparatus includes a portion having a generally square cross section for insertion into a mating opening of a receptacle. This square portion comprises about 20% of the length of the bend-limiting appaldl~ls and, when inserted into the receptacle, increases the amount of support to resist side loading that can be applied to the bend-limiting appalalus.
In the preferred embodiment of the invention, the bend-limiting apparatus is combined with an optical connector, and an optical cable ~,vith yarn-like strength members that surround an optical fiber within the cable. The appaldlus includes a cavity at its front end which is adapted to receive the back end of the connector capture the strength members therebetween, thus providing strain relief for the cable as well as limiting its minimum bend radius.
Brief Descril~tion of the Drawin~
The invention and its mode of operation will be more clearly understood from thefollowing detailed description when read with the appended drawing in which:
FIG. 1 is a front, top and right-side perspective view of a bend-limiting apparatus for optical fiber connectors;
FIG. 2 is a cross section of the bend-limiting apparatus of FIG. 1, and is also shown in perspective view;
FIG. 3 is a cross section of the bend-limiting apparatus of FIG. 1 shown in elevation view;
FIG. 4 is a cross section of the bend-limiting apparatus of FIG. 1, shown along a diagonal cut;
FIG. 5 is an exploded perspective view of an optical connector together with thebend-limiting appaldllls of FIG. 1-4 and an optical cable;
FIG. 6 is a partial cross section of the bend-limiting apparatus attached to an optical connector, both shown inserted into a receptacle; and FIG. 7A-7C discloses one prior art, bend-limiting device under three different load conditions in which excessive bending occurs during the application of light side loads;
FIG. 8A-8C discloses another prior art, bend-limiting device under three different load conditions in which excessive bending occurs during the application of heavy side loads, FIG. 9A-9C discloses the bend-limiting apparatus of FIG. 1-4 under three different load conditions; and FIG. 10 discloses a jumper comprising an optical connector, a bend-limiting apparatus in accordance with the invention, and an optical cable.
Detailed l)escription o Reference is made to FIG. 1 which shows a front, top and right-side perspective view of a bend-limiting apparatus 20 in accordance with the present invention. Bend-limiting devices are typically used to limit the minimum radius of a bend in a communications cable where it attaches to a connector. The apparatus of the present invention comprises a tapered cylinder having one diameter at its front end 22, and a smaller diameter at its back end 24. The bend-limiting apparatus is made from a flexible material and includes an axial bore 28 (shown in FIG. 2-4) that extends from one end to the other along a central, longitudinal axis which is designed to hold the cable. The front end of the bend-limiting apparatus includes a portion 21 having a square cross section that inserts into a mating receptacle. Portion 21 comprises about 20% of the length of ~o apparatus 20 and helps transfer bending stress from the apparatus to the receptacle. Axial bore 28 extends into a cavity 27 that is adapted to receive the back end of a connector (see FIG. 2-4). Several grooves 23 are molded into the back half portion of the apparatus and function to increase the flexibility of the apparatus when light side loads are applied to the cable. These grooves 23 are specifically confined to the back half of the apparatus ~5 so that the same flexible material can be used throughout while still elimin~ting sharp cable bends under both heavy and light side loads. In a plefelled embodiment of the invention, the grooves 23 extend into the axial bore 28 from an outside surface 29 of the apparatus, and the flexible material comprises an elastomer having a hardness ofapproximately Shore 50 D. In the preferred embodiment of the invention, the bend-limiting apparatus is also used to provide strain relief for the cable held within the axial bore, and interior flange 25 cooperates with a groove within an associated connector, as discussed in FIG. 5, to provide strain relief for the cable. And while the benefits of this design accrue mainly to cables cont~ining optical fibers, the bend-limiting apparatus may be advantageously used with cables cont~ining copper wires also. FIG. 2-4 show various cross-sectional views of the bend-limiting device of FIG. 1 to illustrate its construction in greater detail.
FIG. 5 is an exploded perspective view of an optical connector combined with an optical cable and the bend-limiting appaldl~ls shown in FIG. 1-4, illustrating their cooperative association. In particular, FIG. 5 discloses construction details of a connector 10 which includes a housing assembly 100, 110; and a fiber-holding structure comprising ferrule 140, base member 150, and spring 160 which is disposed about the base member.
Although the housing assembly is shown as two separate pieces that are bonded together, it can be constructed as a one-piece unit or a multi-piece assembly. As shown in FIG. 5, housing 110 is a generally U-shaped device having a cavity 114 for receiving the fiber-o holding structure. Once the fiber-holding structure is inserted into the cavity of housing 110, cover 100 is bonded thereto. Cover 100 includes pins 106-106 which mate with holes 116-116 in housing 110 for alignment. Once joined together, the front end of the connector has a generally square shape which fits into a receptacle 40 (see FIG. 6) that is shaped to receive same. Top surface 112 and left-side surface 101 comprise two of the four outside surfaces that form the front end of connector 10. The back end of connector 10 is conically shaped with four flat areas, spaced 90~ apart, that are used to position the back end of the connector within the front end of bend-limiting apparatus 20. Top surface 118 and left-side surface 102 comprise two of the four flat surfaces at the back end of connector 10. Housing members 100, 110 include a plurality of interior surfaces that define cavity 114 which surrounds the fiber-holding structure. The connector includes a first opening 119 at its back end which receives an optical cable 30 and a second opening 111 at its front end for enabling the end face of the fiber-holding structure to protrude therethrough. These openings 111, 119 extend into cavity 114 and are positioned at opposite ends of connector 10. Housing members 100, 110 are molded from a thermoplastic material and have been designed to be molded for straight pulls, without cams, to reduce mold and part costs. It is noted that spring latch 120 is molded into the top surface 112 of the housing 110.
Similar to the outside surface of the connector, interior cavity 114 also has a generally square shape. A flange 113 within housing 110 includes a sloped surface which is shaped to interface with chamfered surface 151 of flange 152 on the base member 150.
Moreover, flange 152 is shaped to enable it to be supported within cavity 114 in several different stable positions -- each one having a different rotational orientation with respect to the central axis of the fiber-holding structure. Flange 152 is square and thus provides 4 stable positions for orienting the fiber-holding structure so that fiber eccentricity can be changed. Compression spring 160 surrounds the back cylindrical portion of base member 150. It presses against surface 153 of the flange and against surface 115 within cavity l 14 of housing member 1 10. Spring 160 urges the end face of the fiber-holding structure through opening 111.
Ferrule 140 may be a glass, metal, ceramic or plastic cylinder having a narrow passageway (about 126 llm in diameter) through its central axis for receiving an end s portion of an optical fiber. In this illustrative connector, the ferrule has an outer diameter of about 1.25 mm and a length of about 7.0 mm. In the construction of an optical cable 30, a thin glass fiber is typically coated with two layers of ultraviolet-curable materials (polyacrylate for example) for protection. The coated fiber is then covered with a thermoplastic having sufficient stiffness to preclude fiber buckling and is referred to as a o buffered fiber 33. To withstand tensile forces that might otherwise fracture the buffered fiber, the cable is constructed with a load-bearing portion in the form of strength members 32 that surround the buffered fiber 33. Elongated slender polymeric fibers of high tensile strength, such as aramid yarn, are suitable for use in this regard. An outer jacket 31 comprising polyvinyl chloride, for example, surrounds the buffered fiber and strength members to complete the construction of optical cable 30. As the cable diameter is made smaller (with the same type fiber), path loss due to cable bending becomes more of a concern. The section modulus that affects bend performance is an exponential function of the diameter. As connectors become smaller, then cables having smaller diameters will become more common. The present invention illustratively uses a cable with a diameter of 1.6 mm -- which is substantially smaller than typical interconnection cables having diameters of 2.0 mm, 2.4 mm, and 3.0 mm.
These layers of different materials are all stripped from an end portion of the glass fiber prior to its insertion into ferrule 140. An a&esive is injected into the passageway through the central axis of ferruie 140. Then the uncoated portion of the optical fiber is inserted into the passageway of the ferrule and adhesively attached. The spring 160 is pre-compressed on the ferrule/base member subassembly 140/150 with cable, and isplaced into housing 110. Housing cover 100 is then installed and ultrasonically bonded, for example. Strength members 32 (e.g., aramid fibers) of the cable 30 are adhesively attached to the back end of connector 10 and pressed into a circumferential groove 1 17 by a mating flange 25 (see FIG. 1-4) within the bend-limiting strain-relief boot 20. Both the cable jacket 31 and the strength members 32 are "sandwiched" between the boot and the back end of connector 10. A suitable adhesive for joining the strength members together with the boot and the connector is Hysol 151 - a commercially available, two-part epoxy.
When an axial pull of up to 15 pounds is applied to cable 30, it is desirable that it remain attached to connector 10. And while adhesives are preferable, a crimping sleeve may 7 2lslo7l alternatively be used to join the strength members 32, and/or outer jacket 31 of the cable, to the connector.
Bend-limiting strain-relief boot 20 is about 38 mm long and includes a generallysquare portion at its front end whose sides are each about 4.6 mm. It is made from a suitably compliant material so that its back portion can be bent in a direction that is perpendicular to its longitudinal axis. In the preferred embodiment of the invention, the strain-relief boot is made from a thermoplastic rubber such as Santoprene(~) elastomer which is commercially available from Advanced Elastomer Systems, LP. So that thebending properties of the boot 20 are suitable for limiting the bend radius of the enclosed o cable 30 to no less than 20 mm over a prescribed load range, the preferred thermoplastic rubber is designated 253-50 and has a hardness rating of 50 D. Additionally, a portion of boot 20 is conically shaped and tapers from a maximum diameter of about 5.6 mm at one end 22 to a minimum diameter of about 3.0 mm at the other end 24. Not only does the boot 20 provide strain relief for cable 30, but it also insures that the cable can withstand repeated bends after interconnection without undue stress being imparted to the glass fiber.
At the front end of bend-limiting boot 20, a generally square portion 21 occupies approximately 20 percent of the entire length of the boot. This portion is adapted to be received into a mating opening of a receptacle 40 (see FIG. 6) to transfer bending stress ~o from the boot 20 to the receptacle, and advantageously remove stress from the connector/cable junction. The operation of grooves 23 are discussed in connection with FIG. 9A-9C.
FIG. 6 shows an optical fiber connector inserted within a duplex receptacle 40 which accommodates two such connectors. Receptacle 40 installs in a rectangular opening of a flat panel by pushing its narrow end through the opening. The receptacle is held therein by grooves 411 in spring latch 410, and may be removed from the panel by sql-ee7.ing the spring latch and pushing the receptacle forward. Typically, two identical receptacles 40-40 are joined by bonding their flanges 412 together end-to-end before insertion into the panel. Mating portions 421, 423 are used to assure proper alignment.
Nevertheless, so that the ferrules 140 within the connectors are perfectly aligned, specially designed alignment sleeves are installed in cylindrical openings 422 before the receptacles are joined. Sidewall 420 at the back end of receptacle 40 provides lateral support to the square portion 21 of bend-limiting device 20. Sidewall 420 generously extends beyond the minimum depth of the receptacle needed to hold the cormector.3s Reference is now made to FIG. 7A-7C which disclose a prior art bend-limiting device 70. In these figures the material used in the construction of device 70 is selected 8 21~1071 to handle heavy side loads better than light side loads. For example, FIG. 7A shows the rest position of bend-limiting device 70 when no downward force is applied to the optical cable 30. FIG. 7B illustrates the condition in which a light downward force FL is applied to cable 30, but bend-limiting device 70 is too rigid to yield to such light side loads, and so the optical cable itself must accommodate the bending force which results in a bend radius that is too small in the region designated 75. In this situation, lightwave signals traversing region 75 experience too much path loss. FIG. 7C illustrates the condition in which a heavy downward force FH is applied to cable 30. Here, the minimum bend radius is larger than the minimum bend radius shown in FIG. 7B which results in lower path 0 loss. Additionally, FIG. 7C is used to illustrate the me~ning of a "minimum bend radius"
which is the radius "r" of the smallest circle whose circumference is collinear with a portion of the fiber which is located approximately at the central axis 35 of the cable.
Referring now to FIG 8A-8C, bend-limiting device 80 is shown having a number of segments 81-81 that enable the bend-limiting device to yield more easily during a condition of light side loading, but is unacceptable during heavy side loads. In this prior art example, the same material is used in molding the bend-limiting device 80 as was used in molding bend-limiting device 70 (see FIG. 7A-7C). Segmentation of the bend-limiting device allows it to yield more easily to light downward forces FL as indicated in FIG. 8B. It is noted that the problem of sharp bends under light loads, as previously demonstrated in FIG. 7B, is now solved. However, as FIG. 8C illustrates, heavy downward forces FH applied to cable 30 result in too much bending in region 85, and lightwave signals traversing this region will experience too much loss. It is noted that similar results could have been achieved in FIG. 8A-8C by elimin~ting the segments and using a more flexible material for the construction of bend-limiting device 80.
FIG. 9A-9C illustrate the advantages of the present invention under different side load conditions. FIG. 9A shows the rest position of an optical cable 30 and bend-limiting apparatus 20 when no downward force is applied to the optical cable. The grooves 23 in the back half of the bend-limiting a~pdldl~ls 20 allow it to yield more readily when light downward forces FL are applied to cable 30 as indicated in FIG. 9B. In the preferred embodiment of the invention these grooves fully extend into the axial bore; and so each groove does not completely encircle the a~p~d~-ls - otherwise it would detach. In order to accommodate bending in various directions, two rows of grooves are used and the same groove pattern is repeated -- but rotated by 90~. These grooves provide a loose hinge action in bend-limiting apparatus 20 which is particularly effective for smaller 3s cables and light side loads. However, as will be illustrated in connection with FIG. 10, these grooves need not fully extend into the axial bore. Finally, FIG. 9C illustrates the 21~1071 condition in which a heavy downward force FH is applied to cable 30 in which bend-limiting apparatus 20 provides suitable results. These results are achieved by using a sufficiently stiff material to accommodate heavy side loads and grooves in the back half of the apparatus to accommodate light side loads. Such a design avoids the need for a particularly long bend-limiting apparatus. FIG. 9C also illustrates the cooperation between portion 21, at the front end of apparatus 20, and sidewall 420 of an associated receptacle which receives connector 10. It is noted that portion 21 is "sandwiched"
between the connector and the sidewall which further improves the bend-limiting apparatus by transferring bending stresses away from the cable/connector junction.
o FIG. 10 discloses a jumper comprising a cable 30 which is termin~ted at each end with an optical connector 15 and a bend-limiting device 50. In this figure, a slightly different optical connector is used (known as an ST(~-connector). Connector 15 includes a ferrule 140 having an optical fiber installed along its central axis, and a bayonet-style connection means having a c~mmin~ surface 16 for interlocking with a mating device.
s Of particular interest, however, is a second embodiment of bend-limiting apparatus 50 which includes circumferential grooves 53 that do not fully extend into the axial bore.
Nevertheless, similar to the preferred embodiment of the invention shown in FIG. 1-6, apparatus 50 comprises a sufficiently stiffmaterial to accommodate heavy side loads, and grooves confined to the back half of the apparatus for accommodating light side loads.
Although various particular embodiments of the invention have been shown and described, modifications are possible within the spirit and scope of the invention. These modifications include, but are not limited to, the use of different materials in the construction of the bend-limiting appald~us. For example, although an elastomer is disclosed, other thermoplastic materials are possible. And even though glass fibers are the primary beneficiary of the invention, other light-carrying fibers (e.g., plastic fibers) may be used. Additionally, the bend-limiting apparatus may also be used with cables having metallic conductors. Finally, the bend-limiting apparatus need not be cylindrical or tapered from front to back, but rather may comprise a substantially constant shape over its entire length.
Claims (13)
1. Apparatus for limiting the bending radius of a cable that is attached to a connector, said apparatus comprising (i) a connector-engaging portion which engages the connector, and (ii) a bend-limiting portion which surrounds the cable in the region where it is attached to the connector, the apparatus comprising an elongated structure having an outside surface, the apparatus further comprising an axial bore which extends along a central axis of the elongated structure from a front end to a back end thereof for supporting the cable, said apparatus being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading; and a plurality of circumferential grooves that extend at least part way around the apparatus and fully penetrate the bend-limiting apparatus from the outside surface to the axial bore, said grooves being confined to the back half of the bend-limiting portion of the apparatus for limiting the minimum bend radius of the cable underlight side loading.
2. The bend-limiting apparatus of claim 1 wherein the outside dimensions of the elongated structure taper from the front end to the back end.
3. The bend-limiting apparatus of claim 1 wherein the flexible material comprises a thermoplastic elastomer.
4. The bend-limiting apparatus of claim 3 wherein the elastomer has a hardness of approximately Shore 50 D.
5. The bend-limiting apparatus of claim 1 further including a portion at its front end having a generally square cross section and a length which is approximately 20 percent of the overall length of the bend-limiting apparatus.
6. In combination, a communications cable joined to a connector and a bend-limiting device, the communications cable including a signal transmission medium enclosed within a plastic jacket;
the connector including a plug for connecting signals from the transmission medium to another connector; and the device comprising (i) a connector-engaging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the communications cable in the region where it is joined to theconnector, said device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading, said device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of thebend-limiting portion of the device for limiting the minimum bend radius of the cable under light side loading.
the connector including a plug for connecting signals from the transmission medium to another connector; and the device comprising (i) a connector-engaging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the communications cable in the region where it is joined to theconnector, said device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the cable under heavy side loading, said device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of thebend-limiting portion of the device for limiting the minimum bend radius of the cable under light side loading.
7. The combination of claim 6 wherein the bend-limiting device includes a tapered cylinder portion having a diameter which is greater at one end where it attaches to the connector than at the other end where it receives the communications cable.
8. The combination of claim 6 wherein the communications cable includes a light-carrying fiber.
9. The combination of claim 8 wherein the light-carrying fiber is made from glass, said cable further including a plurality of yarn-like strength members surrounding the glass fiber.
10. In combination, an optical cable joined to an optical connector and a bend-limiting device, the optical cable comprising a light-carrying fiber enclosed within a plastic buffer material;
the connector comprising (i) a fiber-holding structure having an axial passageway which receives the optical fiber and which terminates in an end face that is perpendicular to the passageway, and (ii) a housing having internal surfaces that define a cavity and surround the fiber-holding structure; and the device comprising (i) a connector-engaging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the optical cable under heavy side loading, said bend-limiting device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of thebend-limiting portion of the device for limiting the minimum bend radius of the optical cable under light side loading.
the connector comprising (i) a fiber-holding structure having an axial passageway which receives the optical fiber and which terminates in an end face that is perpendicular to the passageway, and (ii) a housing having internal surfaces that define a cavity and surround the fiber-holding structure; and the device comprising (i) a connector-engaging portion which engages the connector, (ii) an axial bore along its central axis, and (iii) a bend-limiting portion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiently stiff to limit the minimum bend radius of the optical cable under heavy side loading, said bend-limiting device including a plurality of circumferential grooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of thebend-limiting portion of the device for limiting the minimum bend radius of the optical cable under light side loading.
11. A jumper comprising a communications cable terminated in a connector at each end, at least one of said connectors including a bend-limitingdevice having an axial bore along its central axis which holds the communications cable;
the communications cable including a signal transmission medium enclosed within a dielectric jacket;
the connector including a plug for connecting signals from the transmission medium to another connector; and the device comprising (i) a connector-engaging portion which engages the connector, and (ii) a bend-limiting portion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiency stiff to limit the minimum bend radius of the cable under heavy side loading, said bend-limiting device including a plurality of circumferentialgrooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device forlimiting the minimum bend radius of the cable under light side loading.
the communications cable including a signal transmission medium enclosed within a dielectric jacket;
the connector including a plug for connecting signals from the transmission medium to another connector; and the device comprising (i) a connector-engaging portion which engages the connector, and (ii) a bend-limiting portion which surrounds the cable in the region where it is joined to the connector, the device being made from a flexible material which is sufficiency stiff to limit the minimum bend radius of the cable under heavy side loading, said bend-limiting device including a plurality of circumferentialgrooves that extend at least part way around the device, extend into the axial bore, and are confined to the back half of the bend-limiting portion of the device forlimiting the minimum bend radius of the cable under light side loading.
12. The jumper of claim 11 wherein the bend-limiting device includes a tapered cylinder portion having a diameter which is greater at one end where it attaches to the connector than at the other end where it receives the communications cable.
13 13. The jumper of claim 11 wherein the communications cable includes a light-carrying fiber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/282,936 US5461690A (en) | 1994-07-29 | 1994-07-29 | Bend-limiting apparatus for a cable |
| US282,936 | 1994-07-29 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2151071A1 CA2151071A1 (en) | 1996-01-30 |
| CA2151071C true CA2151071C (en) | 1999-01-05 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002151071A Expired - Fee Related CA2151071C (en) | 1994-07-29 | 1995-06-06 | Bend-limiting apparatus for a cable |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5461690A (en) |
| CA (1) | CA2151071C (en) |
Families Citing this family (64)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5640476A (en) * | 1995-07-14 | 1997-06-17 | Siecor Corporation | Guide sleeve for fiber optic cable |
| US5638474A (en) * | 1995-08-30 | 1997-06-10 | Lucent Technologies Inc. | Anti-snag latch assembly for a connector |
| US5710851A (en) * | 1995-11-06 | 1998-01-20 | Amphenol Corporation | Strain relief system for a fiber optic connector |
| JP4104688B2 (en) * | 1996-12-11 | 2008-06-18 | タイコエレクトロニクスアンプ株式会社 | Optical fiber cable terminal structure and cap member used therefor |
| US5889910A (en) * | 1997-02-18 | 1999-03-30 | Minnesota Mining And Manufactouring Company | Bend radius control jacket |
| US5883995A (en) * | 1997-05-20 | 1999-03-16 | Adc Telecommunications, Inc. | Fiber connector and adapter |
| US5915056A (en) * | 1997-08-06 | 1999-06-22 | Lucent Technologies Inc. | Optical fiber strain relief device |
| US6374022B1 (en) | 1998-12-23 | 2002-04-16 | Pirelli Cavi E Sistemi S.P.A. | Bend limiting device for cables |
| ES2264241T3 (en) * | 1998-12-23 | 2006-12-16 | Prysmian Cavi E Sistemi Energia S.R.L. | FLEXION LIMITATION DEVICE FOR CABLES. |
| US6196733B1 (en) | 1999-06-08 | 2001-03-06 | Lucent Technologies Inc. | Strain relief apparatus for optical connector |
| US7045695B1 (en) * | 1999-09-10 | 2006-05-16 | Wayne Cohen | Maraca with flexible handle |
| DE19944060B4 (en) * | 1999-09-14 | 2008-04-03 | The Whitaker Corporation, Wilmington | Device for kink protection of optical cables |
| US6419402B1 (en) | 1999-12-13 | 2002-07-16 | Adc Telecommunications, Inc. | Fiber optic connector and method for assembling |
| US6357934B1 (en) | 2000-01-27 | 2002-03-19 | Lucent Technologies Inc. | Optical fiber boot for a connector that provides anti-snagging and polarity identification |
| US6695490B2 (en) * | 2000-04-21 | 2004-02-24 | Yazaki Corporation | Optical ring network, optical connector, and hybrid connector |
| US6352374B1 (en) * | 2000-06-08 | 2002-03-05 | Amphenol Corporation | Fiber optic connector device |
| DE60127581T2 (en) * | 2000-07-03 | 2008-01-31 | Yazaki Corp. | Optical ring network, optical connector and hybrid connector |
| US6322386B1 (en) | 2000-09-12 | 2001-11-27 | The Jpm Company | Connector boot with integral latch release |
| JP2002341182A (en) * | 2001-05-14 | 2002-11-27 | Auto Network Gijutsu Kenkyusho:Kk | Optical connector |
| US6734435B2 (en) * | 2001-05-29 | 2004-05-11 | Rae Systems, Inc. | Photo-ionization detector and method for continuous operation and real-time self-cleaning |
| US7490997B2 (en) * | 2001-06-12 | 2009-02-17 | Robert Verhagen | Integrated bend limiter for fiber optic connectors |
| US6674951B1 (en) * | 2001-07-27 | 2004-01-06 | Ciena Corporation | Optical fiber management system and method and fiber bender thereof |
| US6672774B2 (en) * | 2001-10-05 | 2004-01-06 | Corning Cable Systems Llc | Post-connectorization boot, connectorized fiber optic cable assembly including same, and related methods |
| US20040008949A1 (en) * | 2002-06-21 | 2004-01-15 | Gang Liu | Fiber optic connection system and method of using the same |
| US7001081B2 (en) * | 2003-05-22 | 2006-02-21 | 3M Innovative Properties Company | Strain relief boot with flexible extension for guiding fiber optic cable |
| DE10342908A1 (en) * | 2003-09-17 | 2005-04-28 | Krone Gmbh | Housing for fiber optic connectors and procedures for laying fiber optic cables |
| JP2005189332A (en) * | 2003-12-24 | 2005-07-14 | Three M Innovative Properties Co | Optical connector, optical fiber with connector, optical fiber connecting apparatus and method for connecting optical fiber |
| US7147384B2 (en) * | 2004-03-26 | 2006-12-12 | 3M Innovative Properties Company | Small form factor optical connector with thermoplastic adhesive |
| JP4416591B2 (en) * | 2004-07-16 | 2010-02-17 | スリーエム イノベイティブ プロパティズ カンパニー | Optical connector and optical fiber connection system |
| JP4544928B2 (en) * | 2004-07-16 | 2010-09-15 | スリーエム イノベイティブ プロパティズ カンパニー | Optical connector and optical fiber connection system |
| US7266281B1 (en) | 2005-07-07 | 2007-09-04 | Flatau Joseph G | Optical fiber patch box |
| US7695197B2 (en) * | 2006-04-20 | 2010-04-13 | Tyco Electronics Corporation | Bend limiter |
| US7682088B2 (en) * | 2006-06-19 | 2010-03-23 | Commscope, Inc. Of North Carolina | Non-halogen fiber optic connectors |
| US7677812B2 (en) * | 2006-07-31 | 2010-03-16 | Tyco Electronics Corporation | Strain relief boot for cable connector |
| US7568844B2 (en) * | 2006-08-15 | 2009-08-04 | Corning Cable Systems Llc | Ruggedized fiber optic connector assembly |
| ES2530994T3 (en) * | 2007-06-01 | 2015-03-09 | Cooper Technologies Co | Cable connector comprising a cable cover sleeve |
| EP2279441B1 (en) | 2008-04-25 | 2016-01-27 | 3M Innovative Properties Company | Field terminable lc format optical connector with splice element |
| US8342755B2 (en) * | 2009-04-06 | 2013-01-01 | Adc Telecommunications, Inc. | Fiber optic connector and method for assembling |
| US20100284656A1 (en) * | 2009-05-07 | 2010-11-11 | Ofs Fitel, Llc | Short profile optical connector |
| US8684319B2 (en) | 2010-05-19 | 2014-04-01 | Panduit Corp. | Cable tray cable routing system |
| CH703904A2 (en) * | 2010-10-01 | 2012-04-13 | Huber+Suhner Ag | Connector. |
| US8753022B2 (en) | 2010-11-30 | 2014-06-17 | Adc Telecommunications, Inc. | LC connector and method of assembly |
| CN202995082U (en) | 2011-06-27 | 2013-06-12 | 3M创新有限公司 | Optical fiber connector for terminating optical fibers |
| US9417418B2 (en) | 2011-09-12 | 2016-08-16 | Commscope Technologies Llc | Flexible lensed optical interconnect device for signal distribution |
| US9229172B2 (en) | 2011-09-12 | 2016-01-05 | Commscope Technologies Llc | Bend-limited flexible optical interconnect device for signal distribution |
| EP2764390B1 (en) | 2011-10-07 | 2020-12-02 | CommScope Technologies LLC | Fiber optic cassette, system, and method |
| US8939655B2 (en) | 2012-06-29 | 2015-01-27 | Corning Cable Systems Llc | Dust caps, fiber optic connectors, and fiber optic splitter modules incorporating interlocking key features |
| US9146362B2 (en) | 2012-09-21 | 2015-09-29 | Adc Telecommunications, Inc. | Insertion and removal tool for a fiber optic ferrule alignment sleeve |
| US9146374B2 (en) | 2012-09-28 | 2015-09-29 | Adc Telecommunications, Inc. | Rapid deployment packaging for optical fiber |
| IN2015DN02865A (en) | 2012-09-28 | 2015-09-11 | Tyco Electronics Ltd Uk | |
| ES2792122T3 (en) | 2012-09-28 | 2020-11-10 | Commscope Connectivity Uk Ltd | Fiber optic cassette |
| US9223094B2 (en) | 2012-10-05 | 2015-12-29 | Tyco Electronics Nederland Bv | Flexible optical circuit, cassettes, and methods |
| US9435975B2 (en) | 2013-03-15 | 2016-09-06 | Commscope Technologies Llc | Modular high density telecommunications frame and chassis system |
| US9389370B2 (en) | 2013-03-21 | 2016-07-12 | 3M Innovative Properties Company | Optical connector for jacketed cables |
| US9052469B2 (en) | 2013-04-26 | 2015-06-09 | Corning Cable Systems Llc | Preterminated fiber optic connector sub-assemblies, and related fiber optic connectors, cable assemblies, and methods |
| AU2014311509A1 (en) * | 2013-08-28 | 2016-04-14 | Corning Optical Communications LLC | Optical cable cassette and drop handle with flexible radius controller |
| MX2017008276A (en) * | 2014-12-25 | 2017-10-02 | Huawei Tech Co Ltd | Connecting member and optical fibre connector. |
| EP3296785A4 (en) | 2015-05-15 | 2019-05-29 | ADC Telecommunications (Shanghai) Distribution Co., Ltd. | Alignment sleeve assembly and optical fibre adapter |
| US9857540B2 (en) * | 2016-02-16 | 2018-01-02 | Corning Optical Communications LLC | Strain relief boot and fiber optic cable assembly including the same |
| CN109906395B (en) | 2016-09-08 | 2021-06-18 | 康普连通比利时私人有限公司 | Telecommunications distribution element |
| US10261268B2 (en) * | 2016-11-14 | 2019-04-16 | Corning Optical Communications LLC | Strain relief assembly for a fiber optic connector |
| US9823428B1 (en) | 2017-01-25 | 2017-11-21 | Fluke Corporation | Optical connector and duplex connector assembly |
| US10120140B2 (en) | 2017-01-25 | 2018-11-06 | Fluke Corporation | Connector and duplex connector assembly |
| WO2019070682A2 (en) | 2017-10-02 | 2019-04-11 | Commscope Technologies Llc | Fiber optic circuit and preparation method |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4801764A (en) * | 1986-02-11 | 1989-01-31 | Cooper Industries, Inc. | Cable assembly for use under carpeting |
| US4787706A (en) * | 1987-02-03 | 1988-11-29 | American Telephone And Telegraph Company, At&T Bell Laboratories | Duplex optical fiber connector |
| US4812009A (en) * | 1987-06-30 | 1989-03-14 | American Telephone And Telegraph Company, At&T Bell Laboratories | Optical fiber connector |
| US5181267A (en) * | 1988-02-23 | 1993-01-19 | Amp Incorporated | Sheath connector for an optical cable |
| US5073044A (en) * | 1990-10-31 | 1991-12-17 | Amp Incorporated | Right angle strain relief for optical fiber connector |
| US5151962A (en) * | 1991-05-20 | 1992-09-29 | Fiber Delivery Concepts, Inc. | Fiber optic cable assemblies for laser delivery systems |
| US5138678A (en) * | 1991-09-20 | 1992-08-11 | Briggs Robert C | Connector with a variable direction strain relief |
| US5261019A (en) * | 1992-01-02 | 1993-11-09 | Adc Telecommunications, Inc. | Fiber optic connector |
| US5202942A (en) * | 1992-04-03 | 1993-04-13 | Amp Incorporated | Cable termination member for fiber optic connectors having improved strain relief |
| US5212752A (en) * | 1992-05-27 | 1993-05-18 | At&T Bell Laboratories | Optical fiber ferrule connector having enhanced provisions for tuning |
-
1994
- 1994-07-29 US US08/282,936 patent/US5461690A/en not_active Expired - Lifetime
-
1995
- 1995-06-06 CA CA002151071A patent/CA2151071C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2151071A1 (en) | 1996-01-30 |
| US5461690A (en) | 1995-10-24 |
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