MXPA00012280A - An optofibre cable - Google Patents

Abstract

The present invention relates to a method for producing an optofibre cable, and to an optofibre cable produced in accordance with the method. Optofibre cables are used for transmitting optosignals and will often include a plurality of optofibres housed in tubular elements or pipes enclosed in a protective casing. With the intention of simplifying manufacture and handling of optofibre cables and with the intention of preventing the ingress of water into such cables and to connected components, there has been produced an optofibre cable which includes one or more tubular elements (3) that contain one or more optofibres (4), a central strain relief (1) bonded to the optofibre-containing pipes with a glue layer (8), an intermediate porous filling material (7), all enclosed in a protective casing in the form of a pipe (6) or the like. The purpose of the porous filling material is to fill the space between the pipes, the glue surface on the strain relief and the casing so as to fixate the pipes around the strain relief and to make the optofibre cable watertight along its length. The use of porous filling material results in low material consumption and therewith an optofibre cable of low weight.

Description

OPTIC FIBER CABLE FIELD OF THE INVENTION The present invention relates to a method for producing a fiber optic cable and an optical fiber cable produced according to the method and, particularly, a fiber optic cable for optical signal transmission and comprising a plurality of optical fibers. of optical fibers contained in tubular elements or tubes contained in a protective cover.

BACKGROUND OF THE INVENTION It is known in several different contexts, the use of fiber optic cables that include plastic tubular elements containing optical fiber that are wound and attached to a voltage reliever and contained in a protective cover. The tubular element is filled in the interior spaces with filling material to fix the tubular elements in the cable and make the cable watertight all along. The problem with this type of optical cable is that it is possible to form capillaries between the filler material and the plastic tubular elements, thereby making it possible for the water to enter the entire length. The filler material also tends to be too heavy and inflexible cable.

COMPENDIUM OF THE INVENTION With the intention of simplifying the manufacture and handling of fiber optic cables and also with the intention of preventing the entry of water into the fiber optic cables connected to the components, a fiber optic cable has been produced that it includes one or more tubular elements that store one or more optical fibers, a central stress reliever connected to said tubular elements, and an intermediate porous filler material, all of which are contained in a protective coating in the form of an insulating tube. The tubular elements that contain the optical fiber are glued to the tension reliever. The purpose of the porous filler material is to fill the space between the tubular elements, the gummy surface in the tension reliever and the liner and to fix the tubular elements around said tension reliever, still allowing the propagation of the gummy connection to all or long fiber optic cable. The use of a porous filler material means that less material is used than in known cases and this results in a lighter weight cable. In spite of being porous, the filler material is still capable of helping the mutual fixing of the plastic tubular elements in the cable and producing the stable and hermetic form of the cable throughout. The glue bond between the tension reliever and the plastic tubular elements can be made stronger, by applying a thick layer of sizing agent to increase the contact surface area between the plastic tubular elements and the sizing layer, thereby obtaining better adhesion and better union of the plastic tubular elements with the tension reliever. The risk of capillary formation between the plastic tubular elements, the sizing layer and the filler material is also reduced with this thicker sizing layer, thus avoiding the risk of water leaking along the length of the cable. In addition to making the thicker glue layer in the stress reliever, an increase in the use of glue will allow the plastic tubular elements to be provided with an outer glue layer instead of an outer plastic sleeve, thereby allowing one or more Arrangements of the plastic tubular elements with the intermediate porous filler material to be arranged and the assembly to be contained by an outer protective liner, such as a plastic cover. The invention will now be described in more detail with reference to the preferred embodiments thereof and also with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a cross-sectional view of an inventive fiber optic cable comprising a series of plastic tubular elements containing optical fibers. Figure 2 is a cross-sectional view of an inventive fiber optic cable having a plurality of plastic tubular elements containing optical fiber and a thicker sizing layer. Figure 3 is a cross-sectional view of an inventive fiber optic cable including two series of plastic tubular elements containing optical fiber and thicker sizing layers. Figure 4 is a cross-sectional view of an optical fiber cable of the invention that includes three series of plastic tubular elements containing optical fiber and layers of thicker sizing.

DESCRIPTION OF THE PREFERRED MODALITIES Figure 1 is a cross-sectional view of a fiber optic cable of the inventive and shows the construction of the cable. The core of the cable 1 forms the tension reliever of the cable, and may consist of a fiber-reinforced plastic material. In the manufacture of the cable, adhesive material, such as a layer of sizing 2, is applied around the core. The functions of this sizing layer are to connect the core with one or more helically applied tubular elements 3 containing optical fibers 4, whereby tensile forces are transferred from the core to the tubular elements. The tubular elements 3 that store the optical fibers can be composed of a plastic material, such as polyamide plastic, and can store one or more optical fibers, for example 6 or 8 fibers, and can optionally also include a filler 5, such as a thixotropic gel that acts in the space between the optical fibers and a wall of internal tubular elements. The space is delimited by the outer surface of the core coated with sizing, the outer surfaces of the tubular elements, and an inner surface of a surrounding covering or lining 6 is filled with porous filler material 7, such as a porous plastic of the TEP type , which makes the cable watertight all along and helps in fixing the tubular elements in the cable. The choice of a porous filler material that results in a lighter cable still producing the watertight cable all along. The flexibility of the filling material will not impede the actuation and propagation of the gummy bond between the outer surface of the core and the outer surfaces of the tubular elements. The surrounding cover can be made of a plastic material, such as a polyethylene plastic, and preferably will be black. The fiber optic cable is first produced by winding the helical plastic tubular elements 3 containing optical fibers 4 around the core covered with sizing 1 and then the porous filler material 7 is applied, where the coating material 6 is then applied. 2 is a cross-sectional view of a fiber optic cable similar to the view shown in Figure 1, but where the sizing layer in the stress reliever has been made thick and identified by the reference numeral 8. The thickness of the sizing layer 8 will penetrate higher between the plastic tubular elements 3 in view of said tubular elements being fixed to the core, thereby obtaining a greater contact area between the sizing layer in the core and the plastic tubular elements. The thicker sizing layer 8 does not produce capillary gradients between the plastic tubular elements and the sizing layer in the core. The filling material would be unable to fill such capillaries, which could result in the formation of cavities in the cable and thereby facilitate the penetration of water into the fiber optic cable throughout. The fiber optic cable is manufactured in the same way as the fiber optic cable shown in Figure 1, otherwise, which has been shown by the use of essentially the same reference signs. Figure 3 illustrates a further development of the fiber optic cable concept described above with the thicker sizing layer 8, by virtue of the application of a thicker layer of sizing agent around the plastic tubular elements 3 and the porous filler material intermediate 7 to form an outer coating, whereby the additional sizing layer 9 can also be attached to the plastic tubular elements 3. Several plastic tubular elements containing optical fiber 10 can then be wound helically in the sizing layer 9, with this the thickness of said additional sizing layer 9 can be such as to allow the plastic tubular elements to be compressed within the sizing layer, to obtain a greater contact surface area between the plastic tubular elements 10 and the glue layer 9 and thereby eliminate the possibility of capillary formation between the tubular elements and said layer. The space between the plastic tubular elements 10 in the second series of tubular elements outside the sizing layer can be filled with a porous filler material 11. An outer protective plastic layer, such as a black polyethylene layer, is then applied to The second series of plastic tubular elements and the intermediate filling material for use. Figure 4 is a cross-sectional view of another example of an optical fiber cable including several concentric layers or series of plastic tubular elements containing optical fiber. In this embodiment, a glue layer 13 applied to the second series of plastic tubular elements 10 has been used as a base on which a third concentric series of plastic tubular elements containing optical fiber 14 has been applied, together with a porous filler intermediate 15. The sizing layer has also become thicker, which contributes to obtaining a better connection between the sizing layer 13 and the tubular elements containing optical fibers 14. A protective plastic layer 16, such as a polyethylene layer black, has been applied outside the third series of plastic tubular elements 14 and the intermediate porous filler 15. The mutually concentric rubbery layers bonded to the plastic tubular elements containing optical fiber and intermediate porous filler impart mechanical strength, stability in shape and low weight to the cable, and also make the cable watertight all along. The concentric structure of the fiber optic cable with tubular elements joined with the gummy layers facilitates the construction of a multi-layer fiber optic cable with gummy layers and intermediate porous filling, where the concentric layers of the porous filler between the concentric series of tubular elements make the water-tight fiber optic cable all the way through, while providing a lighter cable than it might otherwise be. It should also be understood that the invention is not restricted to the above-described and illustrated embodiments thereof, and that modifications may be made within the scope of the accompanying claims.

Claims (4)

1. A method for manufacturing a fiber optic cable proposed for the transmission of optical signals and comprising a plurality of tubular elements wound around a tension relieving core, an outer coating and filling material, wherein each tubular element contains at least one optical fiber, and wherein the filling material is arranged in the spaces between the outer sheath, the core and the tubular elements, which is characterized by the core covered with sizing; winding one or more tubular elements around the core covered with sizing such as to join with glue the tubular element or tubular elements to said core and thereby form in the core a first series of tubular elements; filling the spaces between the tubular elements with a porous filler material, said bonding with sizer provides a tension reliever between the core and the tubular elements and said tubular elements are held fixed around the core by the porous filler material; joining the tubular elements with intermediate filling material to the first series of tubular elements with intermediate filling material by means of one or more concentric layers of sizing agent; and coating the outermost concentric series of tubular elements and filler material in coating material, to obtain a multilayer fiber optic cable containing several series of fiber optic tubular elements, where the bonding with glue between the different series of tubular elements provides a tension reliever between said series of tubular elements and the core, said filling material makes the cable watertight throughout, in addition to fixing the tubular elements in the different series of tubular elements. The method according to claim 1, characterized in that the glue layers are provided with a thickness such that when the tubular elements containing optical fiber are wound around the core and when the series of tubular elements that are placed are rolled up outwardly, said tubular elements will be compressed within the respective glue layers to obtain greater contact surface and joint contact between the tubular elements and the glue layers. 3. An optical fiber cable for transmission of optical signals, comprising a plurality of tubular elements wound around a tension mitigating core, a surrounding coating, and filler material, wherein each tubular element contains at least one optical fiber, and wherein the filling material is deposited in the spaces between the surrounding lining, the core and the tubular elements, characterized in that the core (1) is joined to a first series of tubular elements (3) by means of sizing (2); wherein one or more concentric layers of sizer (1) with tubular elements attached thereto is provided (n) outside the first series of tubular elements (3) and with sizer are attached thereto; in that the filling material (7) is porous, whereby a tension reliever is obtained between the core and the various series of tubular elements by virtue of said glued joints, and wherein the filling material functions to fix the tubular elements in the different series of tubular elements and makes the fiber optic cable watertight all along. 4. The fiber optic cable according to claim 3 characterized in that the layers of sizing agent (8) applied to the core / tension reliever (1), and the additional layers of sizing agent have a thickness such that when applied to the tubular plastic elements (3) and the tubular elements are joined, the formation of capillaries between the sizing layers and the plastic tubular elements containing optical fiber while obtaining a stable fiber optic cable that is water-tight is avoided. Throughout.