Low fiber count optical cable
First Claim
Patent Images
1. A low fiber count optical fiber cable comprising:
- a hollow tubular member of dielectric material and substantially circular cross section having an inside diameter D;
the exterior surface of said tubular member being coated with a hydrophilic material;
at least one optical fiber configuration enclosed within said tubular member and having a diameter of df ;
said inside diameter D being sized for containing one or more of a plurality of any of said fiber configurations and being greater than a critical dimension dc where dc is that value of D just sufficient to enclose all of the fiber within said tubular member;
said fiber member having a length within said tubular member that is greater than the length of said tubular member by an excess length le and is given in part by the ratio dd /D, and a bend radius within the tubular member given by the ratio Db /D, where Db is twice said bend radius;
said ratio dc /D and the value of Di and of le being an optimum value regardless of the type of fiber configuration enclosed within said tubular member; and
wherein at the optimum value of D, a maximum packing density commensurate with excellent optical and mechanical performance including low bending strain and low attenuation within said tubular member results for supporting any of said fiber configurations.
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Accused Products
Abstract
A family of low optical fiber count cables which contains either optical fiber bundles, buffered fibers, or ribbon fibers housed in a core tube whose inner diameter is optimized for a cable containing two buffered fibers. The unoccupied volume of the core tube is filled with a water blocking material and the exterior surface of the core tube is coated with a hydrophilic material applied directly thereto. The core tube is encased in a dielectric jacket or in a metallic jacket. The cables thus formed can be used in a composite cable which includes an electrically conducting cable, and two abutting cables are incased in an outer sheath or jacket, forming a FIG. 8 configuration.
92 Citations
26 Claims
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1. A low fiber count optical fiber cable comprising:
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a hollow tubular member of dielectric material and substantially circular cross section having an inside diameter D; the exterior surface of said tubular member being coated with a hydrophilic material; at least one optical fiber configuration enclosed within said tubular member and having a diameter of df ; said inside diameter D being sized for containing one or more of a plurality of any of said fiber configurations and being greater than a critical dimension dc where dc is that value of D just sufficient to enclose all of the fiber within said tubular member; said fiber member having a length within said tubular member that is greater than the length of said tubular member by an excess length le and is given in part by the ratio dd /D, and a bend radius within the tubular member given by the ratio Db /D, where Db is twice said bend radius; said ratio dc /D and the value of Di and of le being an optimum value regardless of the type of fiber configuration enclosed within said tubular member; and
wherein at the optimum value of D, a maximum packing density commensurate with excellent optical and mechanical performance including low bending strain and low attenuation within said tubular member results for supporting any of said fiber configurations. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A dielectric low count optical fiber drop cable comprising:
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a core tube having an inside diameter D; at least two optical fibers of any of a plurality of fiber configurations within said core tube having a total diameter df said fiber having an excess length le ; said inside diameter D sized for containing one or more of a plurality of any of said fiber configurations and being greater than a critical diameter dc which is the minimum diameter sufficient to encompass all of said optical fibers, and having a value wherein a packing density within said core tube supports any of said fiber configurations; the outer surface of said core tube being coated with a hydrophilic powder material; first and second diametrically opposed dielectric strength members extending along the length of said core tube in a helical configuration and in contract with said hydrophilic coating material; a plurality of longitudinally extending dielectric tensile strength members in helical configuration about said core tube and in contact with said hydrophilic coating material; said first and second strength members and said tensile strength members being coated with hydrophilic powder material; and a dielectric jacket member enclosing said core tube and said strength members and being in contact with said hydrophilic material. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. An armored low count optical fiber cable comprising:
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a core tube having inside diameter D; at least two optical fibers of any of a plurality of fiber configurations within said core tube having a total diameter df ;
each fiber being an excess length le ;said inside diameter D being sized for containing one or more of a plurality of any of said fiber configurations and being greater than a critical diameter dc which is the minimum diameter sufficient to encompass all of said optical fibers and compatible for use with any of said configurations; the outer surface of said core tube being coated with a hydrophilic powder material; a sheath of metallic material surrounding said core tube in contact with said hydrophilic material; first and second diametrically opposed metallic strength members extending along the length of said core tube in contact with said metallic sheath; said first and second strength members and said metallic sheath being coated with a hydrophilic powder material; and a dielectric jacket encasing said sheath member. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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26. For use in forming a low count optical fiber drop cable having a core tube of inside diameter D, two or more optical fiber members of total outside dimensions df contained within the core tube of a length greater than the core tube, the core whereby the fibers have a bend radius given by Db /2, and a critical dimension dc diameter of the core tube sufficient to encase the fibers;
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the method of optimizing the diameter D such that one or more of a plurality of any said fiber members can be contained therein comprising; determining the packing density ratio df /dc for two buffered fibers; determining the excess fiber length relative to the core tube; determining from the excess fiber length the ratio of dc /D and the ratio Db /D; determining the fiber bending strain ε
b from the expression
space="preserve" listing-type="equation">(d.sub.f /d.sub.c)(d.sub.c /D)
space="preserve" listing-type="equation">ε
.sub.b (%)=100 (D.sub.b /D)varying the values of the ratios to produce an acceptable fiber bending strain; and
solving for D once an acceptable bending strain is achieved, said inside diameter D being sized to result in an allowable packing density for supporting said members other than said buffered fibers.
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Specification