Ultimate low-loss electro-optical cable

• US 4,763,981 A
• Filed: 03/02/1981
• Issued: 08/16/1988
• Est. Priority Date: 03/02/1981
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Wilkins, George A.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Wise, Robert E.
• Application Number:
  US06/239,253
• Time in Patent Office: 2,724 Days
• Field of Search: 350/96.23, 350/96.24
• US Class Current: 385/101
• CPC Class Codes: G02B 6/4416 Heterogeneous cables
• CPC Class Codes: G02B 6/4427 Pressure resistant cables, e.g. undersea cables

Abstract

An undersea cable reliably transmits optical control signals and data. At ast one optical fiber is axially disposed in an otherwise solid electrical conductor which transmits power the length of the cable. A concentrically disposed dielectric insulating layer prevents shorting with the surrounding seawater and a load-bearing annulus coaxially contains the other elements to also protect them from environmental abuses. During deployment or towing, the load-bearing annulus shares part of the load with the solid electrical conductor and a coaxially disposed sleeve encloses all of the other elements for preventing a leaching action of seawater and to defocus externally originating, concentrated forces.

Claims

1. A deep ocean cable having essentially no voids therein for transmitting power and data comprising:

at least one optical fiber axially extending for optically transmitting control and data signals;

a tube-shaped solid conductor having a coaxial bore sized to encase, isolate and hermetically seal the at least one optical fiber for electrically transmitting d.c. power through the deep ocean cable;

a tube-like dielectric cylinder coaxially disposed about the tube-shaped solid conductor for encasing it and dielectrically insulating the tube-shaped solid conductor from the surrounding seawater;

means coaxially disposed about the tube-like dielectric cylinder for armoring the at least one optical fiber, the tube-shaped solid conductor, and the tube-like dielectric cylinder and for tensiley bearing the load imposed by the cable, the armoring and bearing means further guards the tube-like dielectric cylinder from abrasion and penetration; and

means coaxially disposed about the armoring and bearing means for protecting it from the leaching action of seawater and to defocus externally originating concentrated forces, the tube-shaped solid conductor and the armoring and bearing means are selected from materials and dimensioned to provide a stress safety factor of about two in combination and, with the other means, to have a specific gravity of about one point five, the tube-shaped solid conductor and the armoring and bearing means are selected from materials that, when simultaneously strained a pretermined percent, share the load of the cable;

further including means interposed in contact with the at least one optical fiber and within the tube-shaped solid conductor for buffering the at least one optical fiber to help isolate stress therefrom and the coaxial bore of the cylindrically-shaped solid conductor is sufficiently sized to receive the buffering means without any voids therein;

the optically transmitting means is at least one optical fiber and the electrically transmitting means is a cylindrically-shaped solid conductor having a coaxial bore sized to receive the optically transmitting means and the buffering means to make a one-way d. c. path along the cable;

the tube-like dielectric cylinder is a high density plyethylene;

the armoring and bearing means is a multitude of aromatic polyamide filaments in an annular resin matrix;

the tube-shaped solid conductor is fabricated from materials to share equally in the tensile load imposed by the cable when both the tube-shaped solid conductor and the aromatic polyamide filaments are strained to a one percent strain;

the aromatic polyamide filaments are disposed in a contrahelix configuration with a relatively long lay length for torque balance; and

the outer and inner diameters D₃ and D₂ of the tube-shaped solid conductor, the outer diameter of the tube-like dielctric cylinder D₄ and the outer diameter D₅ of the armoring and bearing means have the following relationship upon said one percent strain;

space="preserve" listing-type="equation">S(1%)=(π

/4)S.sub.c (D.sub.3.sup.2 -D.sub.2.sup.2)+S.sub.k (D.sub.5.sup.2 -D.sub.4.sup.2)

where S_c is the tube-shaped solid conductor ultimate tensile stress at 1% strain of 4500 KGF/CM² and S_k is the armor and bearing means tensile stress at 1% strain of 11250 KGF/CM².

2. An apparatus according to claim 1 in which the specific gravity of the armoring and bearing means is about one point four five to assure the stress safety factor of about two and specific gravity of about one point five.

3. An apparatus according to claim 2 in which the diameter D₅ of the armor and bearing means is less than one point six centimeters.

4. An apparatus according to claim 1, in which said one percent strain is maintained for a power delivered to instrumentation of between ten and two hundred fifty kilowatts with the outer diameter D₆ of the cable less than two point five centimeters.