CA2266991A1 - Water blocking components for fiber optic cable - Google Patents
Water blocking components for fiber optic cable Download PDFInfo
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- CA2266991A1 CA2266991A1 CA002266991A CA2266991A CA2266991A1 CA 2266991 A1 CA2266991 A1 CA 2266991A1 CA 002266991 A CA002266991 A CA 002266991A CA 2266991 A CA2266991 A CA 2266991A CA 2266991 A1 CA2266991 A1 CA 2266991A1
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- Prior art keywords
- water absorbent
- fiber optic
- optic cable
- water
- entity
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- 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
- G02B6/4401—Optical cables
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
- G02B6/44384—Means specially adapted for strengthening or protecting the cables the means comprising water blocking or hydrophobic materials
Abstract
Water blocking components (31, 35, 51, 55) for blocking the flow of water in fiber optic cables (10, 40, 70) and methods of making the components. Each water blocking component (31, 35, 51, 55) includes a respective plastic substrate (32, 36, 52, 55) that includes a water absorbent entity, for example, a water absorbent layer (60). The water absorbent layer is a mixture of a water absorbent substance and an adhesive substance. The cross sectional profiles of water blocking components (31, 35, 51, 55) permit a distribution of the water absorbent substance, and the adhesive substance stabilizes the position of the water absorbent substance, thereby advantageously establishing the water blocking effectiveness of components (31, 35, 51, 55).
Additionally, the bulk of the substrates themselves substantially fill the grooves and thereby effectuate a water blocking function. A method of making water blocking components (31, 35, 51, 55) includes the application of water absorbent layer (60) as a thin surface treatment, i.e., it is not impregnated into the substrates but, rather, it is adhered to the smooth, non-porous surfaces of the substrates. Substrates (32, 36, 52, 55) may be in the form of foamed rods. Figures 1-2.
Additionally, the bulk of the substrates themselves substantially fill the grooves and thereby effectuate a water blocking function. A method of making water blocking components (31, 35, 51, 55) includes the application of water absorbent layer (60) as a thin surface treatment, i.e., it is not impregnated into the substrates but, rather, it is adhered to the smooth, non-porous surfaces of the substrates. Substrates (32, 36, 52, 55) may be in the form of foamed rods. Figures 1-2.
Description
WATER BLOCKING COMPONENTS FOR FIBER OPTIC CABLES
The present invention relates to fiber optic cables and, more particularly, to water blocking components of fiber optic cables.
Fiber optic cables include optical fibers which transmit information in cable television, computer, power, and telephone systems. A fiber optic cable may be installed in an environment where the cable is exposed to water. The migration of water in a fiber optic cable is a problem which 1o may occur where the cable jacket has been cut or otherwise breached and water enters the cable. The migration of water in a cable may cause the flooding of a cable passageway or enclosure, and/or it may negatively affect the performance of the optical fibers. For example, fiber optic cables of the slotted rod or loose tube types present potential water migration paths.
To block the flow of water in a cable, known fiber optic cables may include hardened resin walls, a hard to remove flooding or filling compound, or a more craft-2o friendly, dry water absorbent chemical. US-A-4381140 discloses a slotted core type fiber optic cable wherein optical fibers are fixed to the slotted core by hardened walls of polyurethane resin that define solid barriers against the migration of water. This solution to the water migration problem is disadvantageous because it makes the cable heavy and stiff. An additional disadvantage is that, upon bending of the cable, stress may flow from the slotted core to the hardened polyurethane and thence to the optical fibers therein, whereby the optical fibers may experience 3o breakage, macrobending, or microbending.
As noted above, flooding or filling compounds may be used to block the flow of water in a fiber optic cable. US-A-4752113 and US-A-4701015 disclose slotted rod type cables that include a hard to remove polybutylene flooding compound or jelly. Loosely applied damp-proof powder is disposed between spaced masses of the jelly. This solution to the problem of water migration is disadvantageous because the jelly is hard to remove. An additional disadvantage is that the application of loose powder and spaced masses of jelly hinder manufacturing processes and result in high production costs. Moreover, the jelly is expensive and it makes the cable heavy and difficult to route through cable passageways. Further, the damp-proof powder is subject to a variable distribution in the grooves of the slotted rod which may leave sections of the cable unprotected from water 1o migration.
As noted above, a dry water absorbent chemical is more craft-friendly than hardened resin walls or a hard to remove and messy flooding or filling compound. A typical water absorbent chemical includes a polymer chain with reaction sites that react with water, thereby transforming the water absorbent chemical into an expanded mass of viscous gel.
The viscous gel acts as a physical barrier to the migration of water. The water absorbent chemical is typically impregnated in a yarn or a non-woven tape. Such water 2o blocking tapes and yarns may be disadvantageous because, rather than being generally distributed in a slotted core groove, the water absorbent chemical is localized within the immediate area of tape or yarn, e.g., in a small cross sectional area of the groove. As described in more detail below, the localized distribution of the water absorbent chemical may limit the water blocking effectiveness of the tape or yarn.
For example, the water blocking effectiveness of conventional water absorptive tapes may be limited in 3o slotted rod type cables. US-A-5179611 discloses a slotted rod type fiber optic cable that includes a dry water absorptive tape wrapped around the slotted rod. Prior art described therein is a water absorbent tape placed between optical fiber ribbons located in a groove of the slotted rod. The prior art solution to the water blocking problem is stated to be cumbersome and time-consuming, resulting in a lowering of the production efficiency of the fiber optic cable. The tape disclosed in US-A-5179611 is a non-woven fabric, a paper or other sheet-like object, which is topically coated or impregnated with a combination of a thermoplastic elastomer binding agent, and a water absorptive resin combined with a water soluble resin.
However, the water absorptive tape localizes the water absorbent chemical in the area surrounding the slotted core) which may negatively affect the water blocking effectiveness 1o of the tape. For example, upon gelation of the water absorbent chemical, the gel may not extend to radially inner interstices of the grooves.
The water blocking effectiveness of a water absorbent powder may be limited by a non-uniform distribution of the powder in the cable. US-A-4401366 discloses a slotted rod type cable wherein each groove of the slotted rod includes optical waveguides and a mixture of a hydrophilic powder and a hydrophobic powder. The hydrophilic powder is a high molecular weight polyacrylamide powder, and the hydrophobic zo powder is a calcium carbonate powder, the particles of which are coated with stearic acid. The polyacrylamide powder is designed to prevent the optical waveguides from being subjected to compression by ice in the grooves, whereby attenuation in the waveguides is not increased. The powdery mixture is disadvantageous because it may create microbending, it is expensive, and it is subject to movement in the grooves along the cable length. This results in a variable distribution of the powders along the cable length, whereby, upon gelation of the water absorbent chemical, 3o sections of the grooves may not be protected from the migration of water.
In view of the foregoing, the localized distributions of water absorbent tapes, and the variable distribution of water absorbent powders, may not be effective to block the flow of water in slotted core cables because, even though the water absorbent chemicals may swell, nevertheless water migration paths may exist in unprotected areas of the grooves. As a further illustration, US-A-4596443 discloses a water detection system including a slotted rod type fiber optic cable having a slot with a signaling optical conductor herein. The signaling optical conductor is located in a particular groove of the slotted rod, which groove includes a wave-shaped pattern and a significant quantity of localized water swellable material. When water enters the particular groove, the water swellable material may swell 1o thereby forcing the wave shaped pattern into pressing engagement with the signaling conductor. The signaling conductor is deformed whereby it experiences a detectable increase in attenuation that indicates that water has penetrated into the groove. This arrangement is disadvantageous because a significant amount of water swellable material is required to support the forcing function of the wave pattern, i.e., beyond that which is needed to block the flow of water. Moreover, water may migrate through the cable without contacting the localized 2o water swellable material.
As noted above, water blocking yarns localize the water absorbent chemical and may have limited water blocking effectiveness. For example, fibrous braids restrict water absorbent chemicals to a sparse cross sectional area which may cause potential leak paths. US-A-4703998 discloses a slotted rod type fiber optic cable having optical fibers disposed in respective grooves of the slotted rod. Each optical fiber includes a water absorbent yarn wrapped therearound. A disadvantage of this solution is that, since 3o the fibrous braid occupies only a sparse cross sectional area of the groove, the fibrous braid restricts the distribution of the water absorbent chemical to the small cross sectional area thereof. The localized distribution of the water absorbent chemical in the grooves limits the water blocking effectiveness of the fibrous braids.
Obiects of the Invention In view of the foregoing, it is an object of the present invention to provide a fiber optic cable comprising a slotted rod having at least one groove, the groove including at least one optical fiber, the cable further including a water blocking component disposed in one of the grooves, the water blocking component comprising a foamed substrate which defines a profile, at least portions of the 1o profile comprise a stabilized water absorbent entity for effective water blocking in the groove.
It is another object of the present invention to provide a loose tube fiber optic cable having at least one tube including at least one optical fiber therein, and a water blocking component disposed adjacent to the at least one tube, the water blocking component comprising a plastic substrate which defines a profile, at least portions of the profile comprising a stabilized water absorbent layer for blocking water adjacent the tube, the water absorbent layer comprising a mixture of a water absorbent substance and an adhesive substance, wherein the adhesive substance stabilizing the position of the water absorbent substance on the profile.
It is a further object of the present invention to z5 provide a fiber optic cable having at least one optical fiber and a water blocking component, wherein the water blocking component comprising a plastic material that defines a non-porous profile, at least portions of the profile comprising a stabilized water absorbent entity 3o thereon for effective water blocking.
It is another object of the present invention to provide a method of installing a water absorbent component in a cable core, comprising the steps of passing a water blocking component in the form of a plastic substrate having 35 a stable water absorbent layer thereon through a rotatable stranding device and stranding the water blocking component into a cable core. The water blocking component may be stranded into a groove of a slotted rod, or stranded with buffer tubes into a loose tube cable core.
brief Description of the Drawings Figure 1 is an isometric view of a fiber optic cable according to an embodiment of the present invention.
Figure 2 is a cross sectional view of the fiber optic cable of Figure 1 taken along line 2-2.
1o Figure 3 is a cross sectional view of a fiber optic cable according to a second embodiment of the present invention.
Figure 4 is a quarter section of a fiber optic cable according to a third embodiment of the present invention.
Figure 5 is a cross sectional view of an extrusion head for use in the making of water blocking components in accordance with the present invention.
Figure 6 is a part sectional view of a stranding device for use in the manufacture of fiber optic cables according 2o to the present invention.
Detailed Description of the Invention In achieving the foregoing objects, the present invention provides water blocking components for blocking the flow of water in fiber optic cables and methods of making the components. Each water blocking component includes a respective substrate that includes a water absorbent entity. In an embodiment of the present invention, the substrate is a rod formed of a plastic polymeric material, and the water absorbent entity is a io water absorbent layer. The water absorbent layer is a mixture of a water absorbent substance and an adhesive substance. The cross sectional profiles of water blocking components distribute the water absorbent substance, and the adhesive substance stabilizes the position of the water is absorbent substance, thereby advantageously controlling the location and distribution of the water blocking substance and avoiding undesirable localization and variable distribution of the water blocking substance. Additionally, the bulk of the rods themselves substantially fill the 2o grooves and thereby effectuate a water blocking function. A
method of making the water blocking components includes the application of a water absorbent layer to a rod as a thin surface treatment, i.e., it is not impregnated into the rod but, rather, it is adhered to the smooth, non-porous 25 surfaces of the rod. The rod may be formed of a foamed or a non-foamed plastic.
Referring to Figures 1 and 2, a fiber optic cable 10 according to an embodiment of the present invention will be described. Fiber optic cable 10 includes a slotted rod 12 3o with a central dielectric strength member 11 and buffer tubes 13 disposed in helical or SZ-shaped grooves 25.
Slotted rod 12 includes ribs 12a that distribute radially applied crushing loads from one side of cable 10 to another while avoiding the application of crushing loads to buffer 35 tubes 13 and thereby protecting optical fibers in ribbon stacks 14. A slotted rod suitable for use in the present invention is disclosed in commonly assigned patent US-A-4784461, which patent is hereby incorporated by reference in its entirety. Buffer tubes 13 may be surrounded by a water swellable material 16 comprising a conventional water blocking substance within grooves 25 (Figure 1).
Slotted rod 12 may be surrounded by a conventional water blocking tape 18. Tape 18 typically comprises a substrate, e.g. a non-woven tape, which is impregnated with a conventional water swellable material. Tape 18 also 1o performs the function of holding buffer tubes 13 in grooves 25. Surrounding tape 18 is a metallic tape 20 which may include corrugations and longitudinally overlapping edges.
A ripcord 19 may be disposed along the inner or outer surface of tape 20. An outer jacket 21 surrounds metallic tape 20, and jacket 21 may bond with tape 20 during extrusion of jacket 21 around tape 20.
Water blocking components according to the present invention will now be described. Where the fiber count of fiber optic cable 10 does not require all of grooves 25 to 2o contain buffer tubes and/or optical fiber ribbons; water blocking components according to the present invention, used as filler rods, may be placed in the non-fiber containing grooves 25 to prevent the migration of water therein. For example, water blocking components 31,35 are disposed in respective grooves 25 and include respective substrates, for example, rods 32,36. At least portions of rods 32,36 are treated with a water absorbent entity in the form of a water absorbent layer 60, as further described below.
As shown in Figure 3, water blocking components 3o according to the present invention may be installed in a slotted core type fiber optic cable 40. Fiber optic cable 40 includes a slotted rod 43 with a central member 44 and slots 45 having optical fiber ribbons 42 therein. A
conventional water absorbent tape 47 surrounds slotted rod 43, and a jacket 48 surrounds water absorbent tape 47.
Water blocking components 51,55 are disposed in respective slots 43 and include respective substrates, for example, rods 52,56. At least portions of water blocking components 51,55 are treated with a water absorbent layer 60.
Water absorbent layers 60 comprise a mixture of an adhesive substance and at least one water absorbent substance. Water absorbent layers 60 are a surface treatment on the respective rods which are preferably not impregnated with the water absorbent substance. The water absorbent substance may be, for example, commercially io available potassium polyacrylate particles or sodium polyacrylate particles, as disclosed in US-A-5684904, which patent is incorporated by reference herein in its entirety.
The adhesive substance may be an elastomer, e.g. a latex binder, as disclosed in US-A-5689601, a water soluble or water absorptive resin as disclosed in US-A-5179611, or a water soluble hot melt adhesive as disclosed in US-A-5649041, which patents are incorporated by reference herein in their respective entireties. Additionally, water absorbent layer 60 may be a plastisol) an ultraviolet (UV)_ light curable resin, as described in US-A-5684904, which patent is incorporated by reference herein in its entirety.
Moreover) water absorbent layers 60 may include a mixture of two distinct water absorbent substances. One of the water absorbent substances is characterized by a very fast swell rate, i.e., it has a relatively lightly plastic polymeric structure. The other superabsorbent substance is characterized by a high gel strength, i.e., it has a relatively highly plastic polymeric structure. Suitable superabsorbent substances having a very fast swell rate are 3o made commercially available by Sumitomo Chemicals, e.g.
formulation No. J550, and by Chemdal Cabdry, e.g.
formulation Nos. 130 or 150. Suitable superabsorbent substances having a high gel strength are made commercially available by Stockhausen, e.g. formulation Nos. 85-13 or 88-13 sieved. Furthermore, water absorbent layers 60 may include an anti-freezing chemical that is effective to Aio23 9 depress the freezing point of water. Anti-freeze chemicals are disclosed in US-A-5410629, US-A-5321788, and US-A-4401366, which patents are hereby incorporated by reference.
The cross sectional profiles of water blocking components 31,35,51,55 permit a distribution of the water absorbent substance in each quadrant of a respective groove, and the adhesive substance stabilizes the position of the water absorbent substance, thereby advantageously establishing the water blocking effectiveness of components 31,35,51,55. For example, as shown by the distribution of portions of layer 60 of rod 55 about reference axes X-X,Y-Y
(Figure 3), portions of layer 60 are stabilized in each quadrant of groove 45 thereby avoiding undesirable localization of the water absorbent substance. Under normal 1s operating conditions, vibration or bending of the cable will not redistribute the water absorbent substance thereby avoiding an undesirable variable distribution of the water absorbent substance along the cable length. A stable distribution of the water absorbent substance is thus 2o achieved, thereby establishing the water blocking effectiveness of components 31,35,51,55. The stable distribution of the water absorbent substance may extend in each quadrant of the groove, symmetrically or asymmetrically, and/or along the full length of the water 25 blocking component.
Additionally, the bulk of the rods themselves substantially fill the grooves and thereby effectuate a water blocking function. For example, the profile of rod 32 has a cross sectional shape that is complementary to the 3o cross sectional shape of the groove, but loosely fits in the groove. The loose fit between layer 60 and the walls of the groove permits easy relative movement between the rod and the groove during cable bending, thereby avoiding undue contributions to the stiffness of the cable. Alternatively, 35 a water blocking component, for example as shown by the profile of rod 52 (Figure 3), may be sized so that water absorbent layer 60 more tightly fits, and may press against, the walls of the groove.
The amount of surface area treated with the water absorbent substance of layer 60 is an important factor s because it bears on the degree of exposure of the water absorbent substance to water in the groove. For example, the profile of rod 35 includes a geometry that includes angles which define a capacious surface area that maximizes the degree of exposure of water absorbent layer 60 in each 1o quadrant of the groove. The circular profile of water blocking component 55 likewise defines a capacious surface area, and rod 56 thereof has the added advantage of being a commercially available item from the Aeroquip Corporation.
Manufacturing aspects of rods 32,36,52,56 will now be 1s described. Rods 32,36,52,56 may be made with an extrusion head (not shown) having a suitable extrusion profile. Rods 32,36,52,56 may be formed of a non-foamed polyethylene, or a medium density polyethylene that is foamed 20~-30~ with a physical or a chemical foaming agent. The post extrusion, 2o surface finish of the rods is such that it is smooth and non-porous. Such rods exhibit suitable flexibility and are not easily compressed. Alternatively, one or more of the rods may be foamed to 30~-50~ or more to reduce costs, increase flexibility, and/or to increase compressibility.
25 During manufacture of water blocking components 31,35,51,55 water absorbent layer 60 is applied as a thin surface treatment, i.e.) it is not impregnated into the rods but, rather, it is adhered to the smooth, non-porous surfaces of the rods. For example, as shown in Figure 5, a 3o coating die 200 with an inlet port 202 is used to apply a thin water absorbent layer 60 to rod 55. In this example, water absorbent layer 60 is a compound of a water absorbent substance and an adhesive substance which is fed under pressure and heat through inlet port 202. Alternatively, 35 extrusion head 200 may be adapted to co-extrude the plastic of rods 32,36,52,56 with respective water absorbent layers 60. In either event, the water absorbent layer is cured after extrusion whereby the position of the water absorbent substance becomes stabilized.
An exemplary manufacturing operation for installing water s blocking components 31,35,51,55 in a slotted rod will now be described. A stranding device 300 (Figure 6) may be used to install water blocking components 31,35,51,55 in respective grooves 25,45 of fiber optic cables 10,40. Device 300 is made and used generally in accordance with the stranding 1o devices described US-A-4154049 and/or US-A-4195468, which are hereby incorporated by reference in their respective entireties. Stranding device 300 includes a rotatable plate 301 mounted to a stationary plate 302 with thrust bearings 303. Rotatable plate 302 includes distribution holes 305, 15 guide members 306, and a central aperture 307. In the exemplary manufacturing operation, during a manufacturing step in the manufacture of fiber optic cable 40, slotted rod 43 (Figure 3) passes through central hole 307 as water blocking component 55 is fed through distribution hole 30~
20 (Figure 6). Guide member 306 guides the component into groove 45 and rotatable plate is free to rotate as component 55 is guided into the groove.
The present invention has thus been described with reference to the foregoing embodiments, which embodiments 25 are intended to be illustrative of the inventive concepts rather than limiting. Persons of skill in the art will appreciate that variations and modifications of the foregoing embodiments may be made without departing from the scope of the appended claims. For example, although the 3o invention has been described with reference to slotted rod type cables, water blocking components 31,35,51,55 of the present invention may be used with other fiber optic cable types as well. For example, water blocking component 55 may be installed in a cable 70 (Figure 4) having a loose tube 35 type cable core, for example as disclosed in commonly assigned co-pending Application No. 08/885,575 which is incorporated by reference herein in its entirety, whereby water absorbent layer 60 is effective to block the flow of water between buffer tubes 73. Water blocking component 55 may be stranded with buffer tubes 73 in a loose tube cable manufacturing process, for example, as disclosed in US-A-5283014) which patent is incorporated by reference herein.
Although rods 32,36,52,55 have been described with particular reference to a medium density foamed polyethylene, other densities may be used well. In io addition, the rods may be formed of suitable alternative materials, for example, foamed or non-foamed polypropylene, polyurethane, elastomers, or polyvinylchloride.
Moreover, water absorbent layer 60 may be applied to only pre-selected portions of the rods. For example, a side of a rod that faces a water blocking tape may be left untreated by water absorbent layer 60. Further, water absorbent layer 60 may be applied intermittently in the form of annular bands, or in the form of longitudinal or helical stripes. A rod according to the present invention may have 2o a hollow portion. A water blocking component according to the present invention may share the same groove with one or more optical fibers. where it is not desirable to use a water absorbent layer 60, water absorbent entities, for example) in the form of yarns 62 (Figure 3) or a tape 64 (Figure 2) may be placed adjacent a rod to define a water blocking component 37 or 57, respectively.
Aio23 13
The present invention relates to fiber optic cables and, more particularly, to water blocking components of fiber optic cables.
Fiber optic cables include optical fibers which transmit information in cable television, computer, power, and telephone systems. A fiber optic cable may be installed in an environment where the cable is exposed to water. The migration of water in a fiber optic cable is a problem which 1o may occur where the cable jacket has been cut or otherwise breached and water enters the cable. The migration of water in a cable may cause the flooding of a cable passageway or enclosure, and/or it may negatively affect the performance of the optical fibers. For example, fiber optic cables of the slotted rod or loose tube types present potential water migration paths.
To block the flow of water in a cable, known fiber optic cables may include hardened resin walls, a hard to remove flooding or filling compound, or a more craft-2o friendly, dry water absorbent chemical. US-A-4381140 discloses a slotted core type fiber optic cable wherein optical fibers are fixed to the slotted core by hardened walls of polyurethane resin that define solid barriers against the migration of water. This solution to the water migration problem is disadvantageous because it makes the cable heavy and stiff. An additional disadvantage is that, upon bending of the cable, stress may flow from the slotted core to the hardened polyurethane and thence to the optical fibers therein, whereby the optical fibers may experience 3o breakage, macrobending, or microbending.
As noted above, flooding or filling compounds may be used to block the flow of water in a fiber optic cable. US-A-4752113 and US-A-4701015 disclose slotted rod type cables that include a hard to remove polybutylene flooding compound or jelly. Loosely applied damp-proof powder is disposed between spaced masses of the jelly. This solution to the problem of water migration is disadvantageous because the jelly is hard to remove. An additional disadvantage is that the application of loose powder and spaced masses of jelly hinder manufacturing processes and result in high production costs. Moreover, the jelly is expensive and it makes the cable heavy and difficult to route through cable passageways. Further, the damp-proof powder is subject to a variable distribution in the grooves of the slotted rod which may leave sections of the cable unprotected from water 1o migration.
As noted above, a dry water absorbent chemical is more craft-friendly than hardened resin walls or a hard to remove and messy flooding or filling compound. A typical water absorbent chemical includes a polymer chain with reaction sites that react with water, thereby transforming the water absorbent chemical into an expanded mass of viscous gel.
The viscous gel acts as a physical barrier to the migration of water. The water absorbent chemical is typically impregnated in a yarn or a non-woven tape. Such water 2o blocking tapes and yarns may be disadvantageous because, rather than being generally distributed in a slotted core groove, the water absorbent chemical is localized within the immediate area of tape or yarn, e.g., in a small cross sectional area of the groove. As described in more detail below, the localized distribution of the water absorbent chemical may limit the water blocking effectiveness of the tape or yarn.
For example, the water blocking effectiveness of conventional water absorptive tapes may be limited in 3o slotted rod type cables. US-A-5179611 discloses a slotted rod type fiber optic cable that includes a dry water absorptive tape wrapped around the slotted rod. Prior art described therein is a water absorbent tape placed between optical fiber ribbons located in a groove of the slotted rod. The prior art solution to the water blocking problem is stated to be cumbersome and time-consuming, resulting in a lowering of the production efficiency of the fiber optic cable. The tape disclosed in US-A-5179611 is a non-woven fabric, a paper or other sheet-like object, which is topically coated or impregnated with a combination of a thermoplastic elastomer binding agent, and a water absorptive resin combined with a water soluble resin.
However, the water absorptive tape localizes the water absorbent chemical in the area surrounding the slotted core) which may negatively affect the water blocking effectiveness 1o of the tape. For example, upon gelation of the water absorbent chemical, the gel may not extend to radially inner interstices of the grooves.
The water blocking effectiveness of a water absorbent powder may be limited by a non-uniform distribution of the powder in the cable. US-A-4401366 discloses a slotted rod type cable wherein each groove of the slotted rod includes optical waveguides and a mixture of a hydrophilic powder and a hydrophobic powder. The hydrophilic powder is a high molecular weight polyacrylamide powder, and the hydrophobic zo powder is a calcium carbonate powder, the particles of which are coated with stearic acid. The polyacrylamide powder is designed to prevent the optical waveguides from being subjected to compression by ice in the grooves, whereby attenuation in the waveguides is not increased. The powdery mixture is disadvantageous because it may create microbending, it is expensive, and it is subject to movement in the grooves along the cable length. This results in a variable distribution of the powders along the cable length, whereby, upon gelation of the water absorbent chemical, 3o sections of the grooves may not be protected from the migration of water.
In view of the foregoing, the localized distributions of water absorbent tapes, and the variable distribution of water absorbent powders, may not be effective to block the flow of water in slotted core cables because, even though the water absorbent chemicals may swell, nevertheless water migration paths may exist in unprotected areas of the grooves. As a further illustration, US-A-4596443 discloses a water detection system including a slotted rod type fiber optic cable having a slot with a signaling optical conductor herein. The signaling optical conductor is located in a particular groove of the slotted rod, which groove includes a wave-shaped pattern and a significant quantity of localized water swellable material. When water enters the particular groove, the water swellable material may swell 1o thereby forcing the wave shaped pattern into pressing engagement with the signaling conductor. The signaling conductor is deformed whereby it experiences a detectable increase in attenuation that indicates that water has penetrated into the groove. This arrangement is disadvantageous because a significant amount of water swellable material is required to support the forcing function of the wave pattern, i.e., beyond that which is needed to block the flow of water. Moreover, water may migrate through the cable without contacting the localized 2o water swellable material.
As noted above, water blocking yarns localize the water absorbent chemical and may have limited water blocking effectiveness. For example, fibrous braids restrict water absorbent chemicals to a sparse cross sectional area which may cause potential leak paths. US-A-4703998 discloses a slotted rod type fiber optic cable having optical fibers disposed in respective grooves of the slotted rod. Each optical fiber includes a water absorbent yarn wrapped therearound. A disadvantage of this solution is that, since 3o the fibrous braid occupies only a sparse cross sectional area of the groove, the fibrous braid restricts the distribution of the water absorbent chemical to the small cross sectional area thereof. The localized distribution of the water absorbent chemical in the grooves limits the water blocking effectiveness of the fibrous braids.
Obiects of the Invention In view of the foregoing, it is an object of the present invention to provide a fiber optic cable comprising a slotted rod having at least one groove, the groove including at least one optical fiber, the cable further including a water blocking component disposed in one of the grooves, the water blocking component comprising a foamed substrate which defines a profile, at least portions of the 1o profile comprise a stabilized water absorbent entity for effective water blocking in the groove.
It is another object of the present invention to provide a loose tube fiber optic cable having at least one tube including at least one optical fiber therein, and a water blocking component disposed adjacent to the at least one tube, the water blocking component comprising a plastic substrate which defines a profile, at least portions of the profile comprising a stabilized water absorbent layer for blocking water adjacent the tube, the water absorbent layer comprising a mixture of a water absorbent substance and an adhesive substance, wherein the adhesive substance stabilizing the position of the water absorbent substance on the profile.
It is a further object of the present invention to z5 provide a fiber optic cable having at least one optical fiber and a water blocking component, wherein the water blocking component comprising a plastic material that defines a non-porous profile, at least portions of the profile comprising a stabilized water absorbent entity 3o thereon for effective water blocking.
It is another object of the present invention to provide a method of installing a water absorbent component in a cable core, comprising the steps of passing a water blocking component in the form of a plastic substrate having 35 a stable water absorbent layer thereon through a rotatable stranding device and stranding the water blocking component into a cable core. The water blocking component may be stranded into a groove of a slotted rod, or stranded with buffer tubes into a loose tube cable core.
brief Description of the Drawings Figure 1 is an isometric view of a fiber optic cable according to an embodiment of the present invention.
Figure 2 is a cross sectional view of the fiber optic cable of Figure 1 taken along line 2-2.
1o Figure 3 is a cross sectional view of a fiber optic cable according to a second embodiment of the present invention.
Figure 4 is a quarter section of a fiber optic cable according to a third embodiment of the present invention.
Figure 5 is a cross sectional view of an extrusion head for use in the making of water blocking components in accordance with the present invention.
Figure 6 is a part sectional view of a stranding device for use in the manufacture of fiber optic cables according 2o to the present invention.
Detailed Description of the Invention In achieving the foregoing objects, the present invention provides water blocking components for blocking the flow of water in fiber optic cables and methods of making the components. Each water blocking component includes a respective substrate that includes a water absorbent entity. In an embodiment of the present invention, the substrate is a rod formed of a plastic polymeric material, and the water absorbent entity is a io water absorbent layer. The water absorbent layer is a mixture of a water absorbent substance and an adhesive substance. The cross sectional profiles of water blocking components distribute the water absorbent substance, and the adhesive substance stabilizes the position of the water is absorbent substance, thereby advantageously controlling the location and distribution of the water blocking substance and avoiding undesirable localization and variable distribution of the water blocking substance. Additionally, the bulk of the rods themselves substantially fill the 2o grooves and thereby effectuate a water blocking function. A
method of making the water blocking components includes the application of a water absorbent layer to a rod as a thin surface treatment, i.e., it is not impregnated into the rod but, rather, it is adhered to the smooth, non-porous 25 surfaces of the rod. The rod may be formed of a foamed or a non-foamed plastic.
Referring to Figures 1 and 2, a fiber optic cable 10 according to an embodiment of the present invention will be described. Fiber optic cable 10 includes a slotted rod 12 3o with a central dielectric strength member 11 and buffer tubes 13 disposed in helical or SZ-shaped grooves 25.
Slotted rod 12 includes ribs 12a that distribute radially applied crushing loads from one side of cable 10 to another while avoiding the application of crushing loads to buffer 35 tubes 13 and thereby protecting optical fibers in ribbon stacks 14. A slotted rod suitable for use in the present invention is disclosed in commonly assigned patent US-A-4784461, which patent is hereby incorporated by reference in its entirety. Buffer tubes 13 may be surrounded by a water swellable material 16 comprising a conventional water blocking substance within grooves 25 (Figure 1).
Slotted rod 12 may be surrounded by a conventional water blocking tape 18. Tape 18 typically comprises a substrate, e.g. a non-woven tape, which is impregnated with a conventional water swellable material. Tape 18 also 1o performs the function of holding buffer tubes 13 in grooves 25. Surrounding tape 18 is a metallic tape 20 which may include corrugations and longitudinally overlapping edges.
A ripcord 19 may be disposed along the inner or outer surface of tape 20. An outer jacket 21 surrounds metallic tape 20, and jacket 21 may bond with tape 20 during extrusion of jacket 21 around tape 20.
Water blocking components according to the present invention will now be described. Where the fiber count of fiber optic cable 10 does not require all of grooves 25 to 2o contain buffer tubes and/or optical fiber ribbons; water blocking components according to the present invention, used as filler rods, may be placed in the non-fiber containing grooves 25 to prevent the migration of water therein. For example, water blocking components 31,35 are disposed in respective grooves 25 and include respective substrates, for example, rods 32,36. At least portions of rods 32,36 are treated with a water absorbent entity in the form of a water absorbent layer 60, as further described below.
As shown in Figure 3, water blocking components 3o according to the present invention may be installed in a slotted core type fiber optic cable 40. Fiber optic cable 40 includes a slotted rod 43 with a central member 44 and slots 45 having optical fiber ribbons 42 therein. A
conventional water absorbent tape 47 surrounds slotted rod 43, and a jacket 48 surrounds water absorbent tape 47.
Water blocking components 51,55 are disposed in respective slots 43 and include respective substrates, for example, rods 52,56. At least portions of water blocking components 51,55 are treated with a water absorbent layer 60.
Water absorbent layers 60 comprise a mixture of an adhesive substance and at least one water absorbent substance. Water absorbent layers 60 are a surface treatment on the respective rods which are preferably not impregnated with the water absorbent substance. The water absorbent substance may be, for example, commercially io available potassium polyacrylate particles or sodium polyacrylate particles, as disclosed in US-A-5684904, which patent is incorporated by reference herein in its entirety.
The adhesive substance may be an elastomer, e.g. a latex binder, as disclosed in US-A-5689601, a water soluble or water absorptive resin as disclosed in US-A-5179611, or a water soluble hot melt adhesive as disclosed in US-A-5649041, which patents are incorporated by reference herein in their respective entireties. Additionally, water absorbent layer 60 may be a plastisol) an ultraviolet (UV)_ light curable resin, as described in US-A-5684904, which patent is incorporated by reference herein in its entirety.
Moreover) water absorbent layers 60 may include a mixture of two distinct water absorbent substances. One of the water absorbent substances is characterized by a very fast swell rate, i.e., it has a relatively lightly plastic polymeric structure. The other superabsorbent substance is characterized by a high gel strength, i.e., it has a relatively highly plastic polymeric structure. Suitable superabsorbent substances having a very fast swell rate are 3o made commercially available by Sumitomo Chemicals, e.g.
formulation No. J550, and by Chemdal Cabdry, e.g.
formulation Nos. 130 or 150. Suitable superabsorbent substances having a high gel strength are made commercially available by Stockhausen, e.g. formulation Nos. 85-13 or 88-13 sieved. Furthermore, water absorbent layers 60 may include an anti-freezing chemical that is effective to Aio23 9 depress the freezing point of water. Anti-freeze chemicals are disclosed in US-A-5410629, US-A-5321788, and US-A-4401366, which patents are hereby incorporated by reference.
The cross sectional profiles of water blocking components 31,35,51,55 permit a distribution of the water absorbent substance in each quadrant of a respective groove, and the adhesive substance stabilizes the position of the water absorbent substance, thereby advantageously establishing the water blocking effectiveness of components 31,35,51,55. For example, as shown by the distribution of portions of layer 60 of rod 55 about reference axes X-X,Y-Y
(Figure 3), portions of layer 60 are stabilized in each quadrant of groove 45 thereby avoiding undesirable localization of the water absorbent substance. Under normal 1s operating conditions, vibration or bending of the cable will not redistribute the water absorbent substance thereby avoiding an undesirable variable distribution of the water absorbent substance along the cable length. A stable distribution of the water absorbent substance is thus 2o achieved, thereby establishing the water blocking effectiveness of components 31,35,51,55. The stable distribution of the water absorbent substance may extend in each quadrant of the groove, symmetrically or asymmetrically, and/or along the full length of the water 25 blocking component.
Additionally, the bulk of the rods themselves substantially fill the grooves and thereby effectuate a water blocking function. For example, the profile of rod 32 has a cross sectional shape that is complementary to the 3o cross sectional shape of the groove, but loosely fits in the groove. The loose fit between layer 60 and the walls of the groove permits easy relative movement between the rod and the groove during cable bending, thereby avoiding undue contributions to the stiffness of the cable. Alternatively, 35 a water blocking component, for example as shown by the profile of rod 52 (Figure 3), may be sized so that water absorbent layer 60 more tightly fits, and may press against, the walls of the groove.
The amount of surface area treated with the water absorbent substance of layer 60 is an important factor s because it bears on the degree of exposure of the water absorbent substance to water in the groove. For example, the profile of rod 35 includes a geometry that includes angles which define a capacious surface area that maximizes the degree of exposure of water absorbent layer 60 in each 1o quadrant of the groove. The circular profile of water blocking component 55 likewise defines a capacious surface area, and rod 56 thereof has the added advantage of being a commercially available item from the Aeroquip Corporation.
Manufacturing aspects of rods 32,36,52,56 will now be 1s described. Rods 32,36,52,56 may be made with an extrusion head (not shown) having a suitable extrusion profile. Rods 32,36,52,56 may be formed of a non-foamed polyethylene, or a medium density polyethylene that is foamed 20~-30~ with a physical or a chemical foaming agent. The post extrusion, 2o surface finish of the rods is such that it is smooth and non-porous. Such rods exhibit suitable flexibility and are not easily compressed. Alternatively, one or more of the rods may be foamed to 30~-50~ or more to reduce costs, increase flexibility, and/or to increase compressibility.
25 During manufacture of water blocking components 31,35,51,55 water absorbent layer 60 is applied as a thin surface treatment, i.e.) it is not impregnated into the rods but, rather, it is adhered to the smooth, non-porous surfaces of the rods. For example, as shown in Figure 5, a 3o coating die 200 with an inlet port 202 is used to apply a thin water absorbent layer 60 to rod 55. In this example, water absorbent layer 60 is a compound of a water absorbent substance and an adhesive substance which is fed under pressure and heat through inlet port 202. Alternatively, 35 extrusion head 200 may be adapted to co-extrude the plastic of rods 32,36,52,56 with respective water absorbent layers 60. In either event, the water absorbent layer is cured after extrusion whereby the position of the water absorbent substance becomes stabilized.
An exemplary manufacturing operation for installing water s blocking components 31,35,51,55 in a slotted rod will now be described. A stranding device 300 (Figure 6) may be used to install water blocking components 31,35,51,55 in respective grooves 25,45 of fiber optic cables 10,40. Device 300 is made and used generally in accordance with the stranding 1o devices described US-A-4154049 and/or US-A-4195468, which are hereby incorporated by reference in their respective entireties. Stranding device 300 includes a rotatable plate 301 mounted to a stationary plate 302 with thrust bearings 303. Rotatable plate 302 includes distribution holes 305, 15 guide members 306, and a central aperture 307. In the exemplary manufacturing operation, during a manufacturing step in the manufacture of fiber optic cable 40, slotted rod 43 (Figure 3) passes through central hole 307 as water blocking component 55 is fed through distribution hole 30~
20 (Figure 6). Guide member 306 guides the component into groove 45 and rotatable plate is free to rotate as component 55 is guided into the groove.
The present invention has thus been described with reference to the foregoing embodiments, which embodiments 25 are intended to be illustrative of the inventive concepts rather than limiting. Persons of skill in the art will appreciate that variations and modifications of the foregoing embodiments may be made without departing from the scope of the appended claims. For example, although the 3o invention has been described with reference to slotted rod type cables, water blocking components 31,35,51,55 of the present invention may be used with other fiber optic cable types as well. For example, water blocking component 55 may be installed in a cable 70 (Figure 4) having a loose tube 35 type cable core, for example as disclosed in commonly assigned co-pending Application No. 08/885,575 which is incorporated by reference herein in its entirety, whereby water absorbent layer 60 is effective to block the flow of water between buffer tubes 73. Water blocking component 55 may be stranded with buffer tubes 73 in a loose tube cable manufacturing process, for example, as disclosed in US-A-5283014) which patent is incorporated by reference herein.
Although rods 32,36,52,55 have been described with particular reference to a medium density foamed polyethylene, other densities may be used well. In io addition, the rods may be formed of suitable alternative materials, for example, foamed or non-foamed polypropylene, polyurethane, elastomers, or polyvinylchloride.
Moreover, water absorbent layer 60 may be applied to only pre-selected portions of the rods. For example, a side of a rod that faces a water blocking tape may be left untreated by water absorbent layer 60. Further, water absorbent layer 60 may be applied intermittently in the form of annular bands, or in the form of longitudinal or helical stripes. A rod according to the present invention may have 2o a hollow portion. A water blocking component according to the present invention may share the same groove with one or more optical fibers. where it is not desirable to use a water absorbent layer 60, water absorbent entities, for example) in the form of yarns 62 (Figure 3) or a tape 64 (Figure 2) may be placed adjacent a rod to define a water blocking component 37 or 57, respectively.
Aio23 13
Claims (40)
1. A fiber optic cable, comprising:
a slotted rod having at least one groove, said groove including at least one optical fiber; and a water blocking component disposed in one of said grooves, said water blocking component comprises a foamed substrate which defines a profile, at least portions of said profile comprise a stabilized water absorbent entity for effective water blocking in said groove.
a slotted rod having at least one groove, said groove including at least one optical fiber; and a water blocking component disposed in one of said grooves, said water blocking component comprises a foamed substrate which defines a profile, at least portions of said profile comprise a stabilized water absorbent entity for effective water blocking in said groove.
2. The fiber optic cable of claim 1, wherein said water absorbent entity is in the form of a water absorbent layer.
3. The fiber optic cable of claim 1, wherein said water absorbent entity is generally distributed on said profile in each quadrant of said groove.
4. The fiber optic cable of claim 1, wherein said water absorbent entity is generally distributed along the full length of the water blocking component.
5. The fiber optic cable of claim 1, wherein said water absorbent entity comprises a mixture of a water absorbent, substance and an adhesive substance.
6. The fiber optic cable of claim 5, wherein the adhesive substance stabilizes the position of the water absorbent substance on said profile.
7. The fiber optic cable of claim 1, wherein the bulk of the substrate substantially fills the groove and thereby effectuates a water blocking function.
8. The fiber optic cable of claim 1, wherein said profile defines a cross sectional shape that is complementary to the cross sectional shape of the groove
9. The fiber optic cable of claim 1, wherein said substrate loosely fits in said groove thereby permitting easy relative movement between the substrate and the groove during cable bending.
10. The fiber optic cable of claim 1, wherein said profile is sized so that said water absorbent entity tightly fits against walls of said groove.
11. The fiber optic cable of claim 1, wherein said profile includes a geometry which defines a capacious surface area that maximizes the degree of exposure of said water absorbent entity.
12. The fiber optic cable of claim 1, wherein said substrate is flexible.
13. The fiber optic cable of claim 1, wherein said substrate is compressible.
14. The fiber optic cable of claim 1, wherein said profile includes a round geometry.
15. The fiber optic cable of claim 1, wherein said water absorbent entity is a non-impregnated surface treatment.
16. The fiber optic cable of claim 1, wherein said substrate comprises non-porous surfaces, said water absorbent entity is adhered to said non-porous surfaces.
17. The fiber optic cable of claim 1, wherein said water absorbent entity is in the form of a water absorbent yarn.
18. The fiber optic cable of claim 1, wherein said water absorbent entity is in the form of a water absorbent tape.
19. The fiber optic cable of claim 1, wherein said substrate is in the form of a rod.
20. The fiber optic cable of claim 1, wherein said substrate is formed of a foamed plastic.
21. A loose tube fiber optic cable, comprising:
at least one tube including at least one optical fiber therein; and a water blocking component disposed adjacent said at least one tube, said water blocking component comprising a plastic substrate which defines a profile, at least portions of said profile comprising a stabilized water absorbent layer for blocking water adjacent said tube, said water absorbent layer comprising a mixture of a water absorbent substance and an adhesive substance, said adhesive substance stabilizing the position of the water absorbent substance on said profile.
at least one tube including at least one optical fiber therein; and a water blocking component disposed adjacent said at least one tube, said water blocking component comprising a plastic substrate which defines a profile, at least portions of said profile comprising a stabilized water absorbent layer for blocking water adjacent said tube, said water absorbent layer comprising a mixture of a water absorbent substance and an adhesive substance, said adhesive substance stabilizing the position of the water absorbent substance on said profile.
22. The fiber optic cable of claim 21, wherein said water blocking component is disposed between a plurality of tubes.
23. A fiber optic cable, comprising:
at least one optical fiber; and a water blocking component, said water blocking component comprising a plastic material that defines a non-porous profile, at least portions of said profile comprising a stabilized water absorbent entity thereon for effective water blocking.
at least one optical fiber; and a water blocking component, said water blocking component comprising a plastic material that defines a non-porous profile, at least portions of said profile comprising a stabilized water absorbent entity thereon for effective water blocking.
24. The fiber optic cable of claim 23, wherein said plastic material is foamed.
25. The fiber optic cable of claim 23, wherein said water absorbent entity is in the form of a water absorbent layer.
26. The fiber optic cable of claim 23, wherein said water absorbent entity is generally distributed along the full length of the water blocking component.
27. The fiber optic cable of claim 23, wherein said water absorbent entity comprises a mixture of a water absorbent substance and an adhesive substance.
28. The fiber optic cable of claim 27, wherein the adhesive substance stabilizes the position of the water absorbent substance on said profile.
29. The fiber optic cable of claim 23, wherein said profile includes a geometry which defines a capacious surface area that maximizes the degree of exposure of said water absorbent entity.
30. The fiber optic cable of claim 23, wherein said substrate is flexible.
31. The fiber optic cable of claim 23, wherein said substrate is compressible.
32. The fiber optic cable of claim 23, wherein said profile includes a round geometry.
33. The fiber optic cable of claim 23, wherein said water absorbent entity comprises a non-impregnated surface treatment.
34. The fiber optic cable of claim 23, wherein said substrate comprises non-porous surfaces, said water absorbent entity is adhered to said non-porous surfaces.
35. The fiber optic cable of claim 23, wherein said water absorbent entity is in the form of a water absorbent yarn.
36. The fiber optic cable of claim 23, wherein said water absorbent entity is in the form of a water absorbent tape.
37. A method of making a water blocking component for use with a fiber optic cable, comprising the steps of:
depositing a water absorbent layer on a plastic substrate so that at least portions of said plastic substrate including said water absorbent layer; and curing the water absorbent layer whereby a water absorbent substance in said water absorbent layer becomes stabilized.
depositing a water absorbent layer on a plastic substrate so that at least portions of said plastic substrate including said water absorbent layer; and curing the water absorbent layer whereby a water absorbent substance in said water absorbent layer becomes stabilized.
38. A method of installing a water absorbent component in a cable core, comprising the steps of:
passing a water blocking component in the form of a plastic substrate having a stable water absorbent layer thereon through a rotatable stranding device; and stranding said water blocking component into a cable core.
passing a water blocking component in the form of a plastic substrate having a stable water absorbent layer thereon through a rotatable stranding device; and stranding said water blocking component into a cable core.
39. The method of claim 38, wherein the water blocking component is stranded into a groove of a slotted rod.
40. The method of claim 38, wherein the water blocking component is stranded with buffer tubes into a loose tube cable core.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5233798A | 1998-03-31 | 1998-03-31 | |
| US09/052,337 | 1998-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2266991A1 true CA2266991A1 (en) | 1999-09-30 |
Family
ID=21976967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002266991A Abandoned CA2266991A1 (en) | 1998-03-31 | 1999-03-26 | Water blocking components for fiber optic cable |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH11326717A (en) |
| CA (1) | CA2266991A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011008194A1 (en) * | 2009-07-13 | 2011-01-20 | Ben Wells | Optical fiber cable having dummy rods with non-circular cross-section |
| CN113985546A (en) * | 2021-10-09 | 2022-01-28 | 富通集团（嘉善）通信技术有限公司 | Water-resistant optical cable |
| CN114460702A (en) * | 2022-02-18 | 2022-05-10 | 浙江富春江光电科技有限公司 | Novel asymmetric optical fiber directional bending type optical cable |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100420174B1 (en) * | 2001-04-26 | 2004-03-02 | 엘지전선 주식회사 | Optical fiber cable containing ribbon units |
| US6922512B2 (en) * | 2002-10-17 | 2005-07-26 | Alcatel | Non-round filler rods and tubes with superabsorbent water swellable material for large cables |
| CN104035173B (en) * | 2014-06-27 | 2017-01-25 | 中国电子科技集团公司第八研究所 | Fully-dry type nonmetal optical cable and machining technology thereof |
-
1999
- 1999-03-26 CA CA002266991A patent/CA2266991A1/en not_active Abandoned
- 1999-03-31 JP JP11093168A patent/JPH11326717A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011008194A1 (en) * | 2009-07-13 | 2011-01-20 | Ben Wells | Optical fiber cable having dummy rods with non-circular cross-section |
| US8781277B2 (en) | 2009-07-13 | 2014-07-15 | Prysmian S.P.A. | Optical fiber cable having dummy rods with non-circular cross-section |
| AU2009349709B2 (en) * | 2009-07-13 | 2015-05-07 | Prysmian S.P.A. | Optical fiber cable having dummy rods with non-circular cross-section |
| CN113985546A (en) * | 2021-10-09 | 2022-01-28 | 富通集团（嘉善）通信技术有限公司 | Water-resistant optical cable |
| CN113985546B (en) * | 2021-10-09 | 2023-09-15 | 富通集团（嘉善）通信技术有限公司 | Water-resistant optical cable |
| CN114460702A (en) * | 2022-02-18 | 2022-05-10 | 浙江富春江光电科技有限公司 | Novel asymmetric optical fiber directional bending type optical cable |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11326717A (en) | 1999-11-26 |
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