Patent Application
20050213901
This invention relates to a communications cable. Particularly, this invention relates to fiber optic cable. More particularly, this invention relates to a method for identifying optical fibers and buffer tubes in a cable.
Optical fiber cables have been a very popular medium for communications and data transmission due to their high speeds and suitability over long distances. The transmission medium of optical fiber cables consist of thin optical fibers protected from external forces and elements by precisely designed and manufactured cable structures. One common cable structure used is the loose-tube cable. The loose-tube cable contains one or more buffer tubes arranged around a central strength member. The buffer tubes loosely encase one or more optical fibers, either in bundles or ribbons, thereby providing sufficient room for the fiber(s) to move within the buffer tube in response to applied stresses. The space inside the buffer tubes between the fibers and the buffer tube is filled with a waterblocking filling material to protect the fibers from water penetration. The buffer tubes can then be wrapped with binders, tapes, or yarns to provide additional strength and protection. Finally, the cable assembly is encased within a cable jacket to provide mechanical strength and protection from the environment.
The loose-tube cable design permits easy drop-off of groups of fibers at intermediate points without interfering with other buffer tubes being routed to other locations. Since not all fibers, or groups of fibers, will always be routed to the same location or terminal application, it is necessary to be able to identify and distinguish among the various groups of fibers and among individual fibers. Because of the vast quantity of optical fibers that may be contained in an optical fiber cable, a color coding scheme is most commonly used to identify the buffer tubes and the individual optical fibers therein. This color-coding scheme generally consists of color-coding the buffer tubes and individual fibers. Usually the color-coding complies with EIA/TIA-598 color specifications.
Traditionally, individually colored buffer tubes are produced by adding and mixing a colorant in an extruder or other high pressure mixing device prior to extrusion of each individual tube. Coloring buffer tubes requires mixing the buffer tube material with a color concentrate, or colorant, in an extruder or other high temperature and high pressure mixing device prior to extrusion each time a different tube color is desired. This results in substantial delays and down times just to change the tube color. Tube colorants can also be quite expensive. These colorants typically contain a pigment, dye or other coloring concentrate carried in a base resin. The buffer tube material and the base resin for the color concentrate should be the same type of material because of material incompatibility. Since the buffer tube material generally comprises polybutylene terephthalate (PBT), polyester elastomer, nylon, fluoropolymer, acetal resin or polycarbonate, the colorants that can be used become quite expensive.
Finally, color-coding buffer tubes is not suitable for cables having a high number of buffer tubes. The buffer tubes of cables having more than twelve buffer tubes are marked by the placement of rings, bands, stripes or identification threads/tapes around or in the buffer tubes. These cables are expensive to produce, and require cutting away substantial portions of the outer jacket to locate any such marking.
This specification describes a method and system for identifying buffer tubes in a cable by including at least one colored filling material within a transparent or translucent buffer tube.
The products and processes described herein will be understood in light of the drawings, wherein:
The following description includes specific details in order to provide a thorough understanding of the novel cable and buffer tube and fiber identification and management system. The skilled artisan will understand, however, that the products and methods described below can be practiced without employing these specific details. Indeed, they can be modified and can be used in conjunction with products and techniques known to those of skill in the art. For example, this specification describes the novel cable and identification system with respect to loose-tube cables. The principles taught herein, however, may be applied to other types of cables, such as optical fiber ribbon cables, or any cable or device employing a filling material.
It should be understood that the term “different color,” as used in the present specification and appended claims, refers to a color or shade of a color that is visually distinguishable from another color or shade of a color, unless otherwise noted. The term “same color” refers to colors or shades of a color that are visually indistinguishable, unless otherwise noted.
This specification describes a fiber optic cable and a method of manufacture that makes use of a colored filling material injected into a translucent or transparent fiber buffer tube or tubes. This allows for the identification of fiber optic buffer tubes and management of the individual fibers without coloring the buffer tube itself. This fiber optic cable is created by mixing a colorant into the filling material just prior to its injection into the buffer tube. The process eliminates the need for tube coloring and allows the use of less expensive and more manufacturing-friendly color concentrates that are mixed into the filling material itself, not the buffer tube material. The colored filling material can be visible through the translucent or transparent fiber buffer tube material, thus allowing identification and classification of the various buffer tubes within the cable.
In loose-tube cables the individual fibers are typically grouped into groups of six or twelve fibers, and each group is placed inside a buffer tube, separate from fibers in other buffer tubes. The filling material contained within a buffer tube serves a variety of functions. For example, the filling material inhibits water migration into the tube, and protects the fiber(s) within the tube from water absorption. The filling material that may be used includes any filling material known to those skilled in the art, such as gels, greases, petroleum jelly compounds, oils, and the like.
As shown in
In an embodiment, the color-coding scheme complies with EIA/TIA-598 color specifications, which are incorporated herein by reference. According to these specifications, the filling material used within buffer tubes may be one of twelve colors: blue, orange, green, brown, slate, white, red, black, yellow, purple, rose, or aqua. The fibers within these buffer tubes may also be color-coded, typically according to EIA/TIA-598 specifications. Thus, a cable may contain up to twelve buffer tubes, each containing filling material of a different color. In another embodiment, each tube contains up to twelve differently colored individual fibers. Other color-coding schemes besides EIA/TIA-598 may also be followed, according to the desired application or other applicable rules and standards. Generally, though, no two buffer tubes of the same color will contain filling material of the same color. While most cables typically contain six or twelve optical fibers in each buffer tube, the cable described herein also contemplates buffer tubes having more or fewer fibers in each buffer tube.
The filling material is colored by adding and mixing a colorant, such as a dye or pigment, into the filling material prior to its injection into a buffer tube. This process provides significant savings in money and processing time. The colorants for filling material are cheaper and easier to use because they do not require an expensive base resin, unlike the colorants used in prior art buffer tube materials.
Suitable dyes that may be used include, but are not limited to, azo dyes, diazodyes, pyrazolones, quinolones, quinophthalones, anthraquinones and nigrosines. Useful pigments include any substance that imparts a desired color to the filling material. Suitable pigments include, but are not limited to, organic pigments such as benzimidazolones (yellow, red, orange), phthalocyanimes (blue, green), quinacsidones (violet, red, orange), dioxanes (violet), isoindolinones (yellow, red, orange), disazos (yellow, red), pyrazalones (orange, red), diarylides (yellow, orange), dianisidines (orange); inorganic pigments such as titanium dioxide (white), lead chromates (yellow, orange), iron oxides (brown, red, maroon, yellow, black), chromium oxide (green), cadmium sulfoselenides (maroon, red, orange), lithopone (white), ultramarine blue (aluminosilicate complex with sulfur), nickel titanate (yellow), cobalt aluminate (blue), zinc chromate (yellow), lead molybdate (orange), cadmium sulfide (orange); lake pigments; pearlescent colorants; and daylight fluorescent colorants.
Using color-coded fibers and color-coded filling material thus provides a two-level buffer tube and fiber identification and management system for optical fiber cables. The buffer tubes in such a two-level fiber identification and management system may consist of any one color. In an embodiment, as shown in
Transparent or translucent buffer tubes provide significant advantages and benefits to colored buffer tubes. They significantly decrease costs of making the buffer tubes, and since they are not colored they eliminate the need for expensive colorants having a base resin made from the buffer tube material. Also, producing transparent or translucent buffer tubes requires the use of only one buffer tube material, thereby eliminating the step of changing and mixing the colorant. This substantially decreases the processing time and associated costs.
The buffer tubes may also be color-coded, and need not be transparent or translucent, as shown in
To provide additional methods and systems of identifying and managing optical fibers in a cable, different combinations of color-coded buffer tubes and color-coded filling material may be used.
Furthermore, other techniques known to those in the art may be used in combination with the principles described herein. For example, a third-level of identification of buffer tubes can be achieved by using ring or band markings around one or more buffer tubes at various or regular intervals, in addition to using color-coded filling material and color-coded fibers. This can be suitable for cables having high numbers of buffer tubes.
The cable of the present invention is made in a manner that substantially decreases the time and costs associated with processing buffer tubes and fiber optic cables. Generally, the filler material colorant is mixed into the filler material prior to injection of the filler material into the buffer tubes to create a colored filler material. The buffer tubes can then be extruded around the optical fibers. In an embodiment, the buffer tube material contains no added colorants, thereby creating a transparent or translucent buffer tube when extruded. The steps of adding and mixing colorant into the buffer tube material, and then changing the buffer tube material for a subsequent tube extrusion, can be eliminated, increasing the processing time. In another embodiment, the buffer tube material is also colored by adding and mixing a tube colorant to the buffer tube material prior to extrusion. The buffer tube is extruded around the fibers while the colored filler material is injected into the buffer tubes. Those skilled in the art will recognize that methods other than those described above, but known to those of skill in the art, may also be employed to make transparent or translucent, or colored buffer tubes.
The novel cable can also include other components to provide additional strength, protection, durability, and other desirable properties. For example, the cable may include yarns, tapes, binders, armors, shields, flooding material, strength members, jackets and other cable components known to those of skill in the art.
The preceding description has been presented only to illustrate and describe exemplary embodiments of the novel cable and buffer tube and fiber identification and management system. It is not intended to be exhaustive or to limit the products and processes to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the products and processes be defined by the following claims.
