The present disclosure relates generally to cables for use in the telecommunications industry, and various methods associated with such cables. More particularly, this disclosure relates to telecommunication cabling having twisted conductor pairs.
The telecommunications industry utilizes cabling in a wide range of applications. Some cabling arrangements include twisted pairs of insulated conductors, the pairs being twisted about each other to define a twisted pair core. An insulating jacket is typically extruded over the twisted pair core to maintain the configuration of the core, and to function as a protective layer. Such cabling is commonly referred to as a multi-pair cable.
The telecommunications industry is continuously striving to increase the speed and/or volume of signal transmissions through such multi-pair cables. One problem that concerns the telecommunications industry is the increased occurrence of crosstalk associated with high-speed signal transmissions.
In general, improvement has been sought with respect to multi-pair cable arrangements, generally to improve transmission performance by reducing the occurrence of crosstalk.
One aspect of the present disclosure relates to a multi-pair cable having a plurality of twisted pairs that define a cable core. The cable core is twisted at a varying twist rate such the mean core lay length of the cable core is less than about 2.5 inches. Another aspect of the present disclosure relates to a method of making a cable having a varying twist rate with a mean core lay length of less than about 2.5 inches. Still another aspect of the present disclosure relates to the use of a multi-pair cable in a patch cord, the cable being constructed to reduce crosstalk at a connector assembly of the patch cord.
A variety of examples of desirable product features or methods are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing various aspects of the disclosure. The aspects of the disclosure may relate to individual features as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are explanatory only, and are not restrictive of the claimed invention.
Reference will now be made in detail to various features of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring to
The conductors of the insulated conductors 14 may be made of copper, aluminum, copper-clad steel and plated copper, for example. It has been found that copper is an optimal conductor material. In one embodiment, the conductors are made of braided copper. One example of a braided copper conductor construction that can be used is described in greater detail in U.S. Pat. No. 6,323,427, which is incorporated herein by reference. In addition, the conductors may be made of glass or plastic fiber such that a fiber optic cable is produced in accordance with the principles disclosed. The insulating layer of the insulated conductors 14 can be made of known materials, such as fluoropolymers or other electrical insulating materials, for example.
The plurality of twisted pairs 12 of the cable 10 defines a cable core 20. In the illustrated embodiment of
Referring now to
In particular, the addition of the outer jacket 26 to the cable 10 reduces the capacitance of the cable 10 by increasing the center-to-center distance between the cable 10 and an adjacent cable. Reducing the capacitance by increasing the center-to-center distance between two adjacent cables reduces the occurrence of alien crosstalk between the cables. Accordingly, the outer jacket 26 has an outer diameter OD1 (FIG. 2) that distances the core 20 of twisted pairs 12 from adjacent cables. Ideally, the cores 20 of twisted pairs 12 of adjacent cables are as far apart as possible to minimize the capacitance between adjacent cables.
There are, however, limits to how far apart the double jacket 18 can place one cable from an adjacent cable. Practical, as well as economical constraints are imposed on the size of the resulting double jacket cable. A cable cannot be so large that it is impractical to use in an intended environment, and cannot be so large as to preclude use with existing standard connectors. In the illustrated embodiment, the outer diameter OD1 (
The disclosed double jacket is provided as two separate inner and outer jackets 24, 26, as opposed to a single, extra thick jacket layer. This double jacket feature reduces alien crosstalk by distancing the cores of adjacent cables, while at the same time, accommodating existing design limitations of cable connectors. For example, the double jacket 18 of the present cable 10 accommodates cable connectors that attach to a cable jacket having a specific outer diameter. In particular, the present cable 10 permits a user to strip away a portion of the outer jacket 26 (see
The inner jacket 24 and the outer jacket 26 of the present cable 10 can be made from similar materials, or can be made of materials different from one another. Common materials that can be used to manufacture the inner and outer jackets include plastic materials, such as fluoropolymers (e.g. ethylenechlorotrifluorothylene (ECTF) and Flurothylenepropylene (FEP)), polyvinyl chloride (PVC), polyethelene, or other electrically insulating materials, for example. In addition, a low-smoke zero-halogen material, such as polyolefin, can also be used. While these materials are used because of their cost effectiveness and/or flame and smoke retardancy, other material may be used in accordance with the principles disclosed.
In the manufacture of the present cable 10, two insulated conductors 14 are fed into a pair twisting machine, commonly referred to as a twinner. The twinner twists the two insulated conductors 14 about the longitudinal pair axis at a predetermined twist rate to produce the single twisted pair 12. The twisted pair 12 can be twisted in a right-handed twist direction or a left-handed twist direction.
Referring now to
In the illustrated embodiment, each of the twisted pairs 12a-12d of the cable 10 has a lay length L1 or twist rate different from that of the other twisted pairs. This aids in reducing crosstalk between the pairs of the cable core 20. In the illustrated embodiment, the lay length L1 of each of the twisted pairs 12a-12d is generally constant, with the exception of variations due to manufacturing tolerances. In alternative embodiments, the lay length may be purposely varied along the length of the twisted pair.
Each of the twisted pairs 12a-12d of the present cable 10 is twisted in the same direction (i.e., all in the right-hand direction or all in the left-hand direction). In addition, the individual lay length of each of the twisted pairs 12a-12d is generally between about 0.300 and 0.500 inches. In one embodiment, each of the twisted pairs 12a-12d is manufactured with a different lay length, twisted in the same direction, as shown in Table A below.
In the illustrated embodiment, the first twisted pair 12a (
The cable core 20 of the cable 10 is made by twisting together the plurality of twisted pairs 12a-12d at a cable twist rate. The machine producing the twisted cable core 20 is commonly referred to as a cabler. Similar to the twisted pairs, the cable twist rate of the cable core 20 is the number of twists completed in one unit of length of the cable or cable core. The cable twist rate defines a core or cable lay length of the cable 10. The cable lay length is the distance in length of one complete twist cycle.
In manufacturing the present cable 10, the cabler twists the cable core 20 about a central core axis in the same direction as the direction in which the twisted pairs 12a-12d are twisted. Twisting the cable core 20 in the same direction as the direction in which the twisted pairs 12a-12d are twisted causes the twist rate of the twisted pairs 12a-12d to increase or tighten as the cabler twists the pairs about the central core axis. Accordingly, twisting the cable core 20 in the same direction as the direction in which the twisted pairs are twisted causes the lay lengths of the twisted pairs to decrease or shorten.
In the illustrated embodiment, the cable 10 is manufactured such that the cable lay length varies between about 1.5 inches and about 2.5 inches. The varying cable lay length of the cable core 20 can vary either incrementally or continuously. In one embodiment, the cable lay length varies randomly along the length of the cable 10. The randomly varying cable lay length is produced by an algorithm program of the cabler machine.
Because the cable lay length of the cable 10 is varied, the once generally constant lay lengths of the twisted pairs 12a-12b are now also varied; that is, the initial lay lengths of the twisted pairs 12 now take on the varying characteristics of the cable core 20. In the illustrated embodiment, with the cable core 20 and each of the twisted pairs 12a-12d twisted in the same direction at the cable lay length of between 1.5 and 2.5 inches, the now varying lay lengths of each of the twisted pairs fall between the values shown in columns 3 and 4 of Table B below.
As previously described, the cable lay length of the cable core 20 varies between about 1.5 and about 2.5 inches. The mean or average cable lay length is therefore less than about 2.5 inches. In the illustrated embodiment, the mean cable lay length is about 2.0 inches.
Referring to Table B above, the first twisted pair 12a of the cable 10 has a lay length of about 0.2765 inches at a point along the cable where the point specific lay length of the core is 1.5 inches. The first twisted pair 12a has a lay length of about 0.2985 inches at a point along the cable where the point specific lay length of the core is 2.5 inches. Because the lay length of the cable core 20 is varied between 1.5 and 2.5 inches along the length of the cable 10, the first twisted pair 12a accordingly has a lay length that varies between about 0.2765 and 0.2985 inches. The mean lay length of the first twisted pair 12a resulting from the twisting of the cable core 20 is 0.288 inches. Each of the other twisted pairs 12b-12d similarly has a mean lay length resulting from the twisting of the cable core 20. The resulting mean lay length of each of the twisted pairs 12a-12d is shown in column 5 of Table B. It is to be understood that the mean lay lengths are approximate mean or average lay length values, and that such mean lay lengths may differ slightly from the values shown due to manufacturing tolerances.
Twisted pairs having similar lay lengths (i.e., parallel twisted pairs) are more susceptible to crosstalk than are non-parallel twisted pairs. The increased susceptibility to crosstalk exists because interference fields produced by a first twisted pair are oriented in directions that readily influence other twisted pairs that are parallel to the first twisted pair. Intra-cable crosstalk is reduced by varying the lay lengths of the individual twisted pairs over their lengths and thereby providing non-parallel twisted pairs.
The presently described method of providing individual twisted pairs with the particular disclosed varying lay lengths produces advantageous results with respect to reducing crosstalk and improving cable performance. In one application, the features of the present cable 10 can be used to provide an improved patch cord.
Referring now to
Referring now to
When the connector housing 32 is in place, as shown in
Referring to
In the illustrate embodiment of
Referring back to
As previously described, the jack 30 is secured to the end of the cable 10 by the clamping force of the prongs 56 on the outer diameter OD2 of the inner jacket 24. To further ensure the relative securing of the jack 30 and the cable 10, additional steps are taken. In particular, as shown in
In general, to promote circuit density, the contacts of the jacks 30 are required to be positioned in fairly close proximity to one another. Thus, the contact regions of the jacks are particularly susceptible to crosstalk. Furthermore, contacts of certain twisted pairs 12 are more susceptible to crosstalk than others. In particular, crosstalk problems arise most commonly at contact positions 3-6, the contact positions at which the split pair (e.g., 12a) is terminated.
The disclosed lay lengths of the twisted pairs 12a-12b and of the cable core 20 of the disclosed patch cord 50 reduce problematic crosstalk at the split pair 12a. Test results that illustrate such advantageous cable or patch cord performance are shown in
Referring to
The patch cord 50 of the present disclosure reduces the occurrence of crosstalk at the contact regions of the jacks, while still accommodating the need for increased circuit density. In particular, the cable 10 of the patch cord 50, reduces the problematic crosstalk that commonly arise at the split pair contact positions 3-6 of the patch cord jack. The reduction in crosstalk at the split pair (e.g., 12a) and at the contacts of the jack 30 enhances and improves the overall performance of the patch cord.
The above specification provides a complete description of the present invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, certain aspects of the invention reside in the claims hereinafter appended.
This application is a continuation of application Ser. No. 11/471,982, filed Jun. 21, 2006, which application is incorporated herein by reference.
Number | Date | Country | |
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Parent | 11471982 | Jun 2006 | US |
Child | 12121061 | US |