Patent Application
20150144377
This disclosure generally relates to a cable having a plurality of twisted pairs of conductors. At least two of the twisted pairs have different lay lengths.
Conventional data cables typically include twisted pairs of insulated conductors that are surrounded by an outer protective jacket. Twisting the pairs of conductors can alleviate crosstalk—signal interference among adjacent parallel conductors. The twisting of the conductor pairs is measured in terms of lay length—the longitudinal length along which one full twist of the conductors occurs. The lay length of a twisted pair can affect crosstalk and the signal propagation speed within the twisted pair. A twisted pair having a shorter lay length can be less susceptible to crosstalk but can experience slower signal propagation speeds than twisted pairs having a longer lay length.
As data speeds increase, twisting of the conductors into pairs has become less effective at inhibiting crosstalk, including alien crosstalk among adjacent cables. Some conventional arrangements include a shielding element, such as an aluminum tape, to alleviate alien crosstalk. However, such shielding elements require grounding and can add significant cost and weight to the cable. In some conventional arrangements the shielding element can be discontinuous to eliminate the need for grounding. However, discontinuous shielding elements can provide gaps in the shielding coverage which cause the cable to be susceptible to alien crosstalk, including Power Sum Alien Near-End (PSANEXT) Crosstalk and Power Sum Attenuation-to-Alien Crosstalk Ratio, Far-End (PSAACRF) Crosstalk.
Some conventional cable arrangements include a centrally located twisted conductor pair with other twisted pairs that surround the centrally located twisted pair. The centrally located twisted pair has a longer lay length than the other twisted pairs. The centrally located twisted pairs can accordingly have the fastest signal of all of the pairs in the cable. The other twisted pairs can be susceptible to poor signal propagation speed (e.g., due to helical loss) and high delay skew which can prevent the data cable from meeting industry standards, such as TIA 568, for example. The TIA 568 standard relates to the electrical properties of data cable and particularly delay issues. Since conductor pairs of a cable are typically twisted at different lengths, signals will arrive at the end of the cable at different times. The TIA 568 standard calls for a maximum delay skew of 45 nS. That is, once the first signal is received on one conductor pair, the last signal on a different conductor pair has 45 nS to arrive.
Providing a centrally located twisted pair having a longer lay length than other twisted pairs can adversely affect the ability of the cable to meet the TIA 568 standard, to meet the requirements for reduced internal cable crosstalk (NEXT), and to appropriately inhibit alien crosstalk. For example, although the other twisted pairs have shorter lay lengths than the center pair, those lay lengths typically are not short enough to effectively reduce alien crosstalk because the difference in the lay length of the center pair with the longest lay length and the lay lengths of the three pairs around the center pair is limited by the maximum delay skew allowed of the pair signals.
In accordance with one embodiment, a data cable comprises a core and a jacket surrounding the core. The core defines a longitudinal axis and comprises a central twisted pair of insulated conductors and a plurality of outer twisted pairs of insulated conductors. The central twisted pair of insulated conductors is disposed along the longitudinal axis and has a lay length. Each outer twisted pair of the plurality of outer twisted pairs has a lay length. Each outer twisted pair is positioned relative to the central twisted pair such that each outer twisted pair of the plurality of outer twisted pairs is disposed between the central twisted pair and the jacket. The lay length of the central twisted pair is shorter than the respective lay lengths of each outer twisted pair of the plurality of outer twisted pairs.
In accordance with another embodiment, an unshielded data cable comprises a core and a jacket surrounding the core. The core defines a longitudinal axis and comprises a central twisted pair of insulated conductors, a first outer twisted pair of insulated conductors, a second outer twisted pair of insulated conductors, and a third outer twisted pair of insulated conductors. The central twisted pair of insulated conductors is disposed along the longitudinal axis and has a central lay length. The first outer twisted pair has a first lay length. The second outer twisted pair has a second lay length. The third outer twisted pair has a third lay length. The first, second, and third outer twisted pairs are positioned relative to the central twisted pair such that the first, second, and third outer twisted pairs are disposed between the central twisted pair and the jacket. The central lay length of the central twisted pair is less than the first, second, and third lay lengths of the respective first, second, and third outer twisted pairs. The first, second, and third, lay lengths are different.
In accordance with one embodiment, a data cable comprises a core and a jacket surrounding the core. The core defines a longitudinal axis and comprises a central twisted pair of insulated conductors, a first outer twisted pair of insulated conductors, a second outer twisted pair of insulated conductors, and a third outer twisted pair of insulated conductors. The central twisted pair of insulated conductors is disposed along the longitudinal axis and has a central lay length. The first outer twisted pair has a first lay length. The second outer twisted pair has a second lay length. The third outer twisted pair has a third lay length. Each conductor of the central twisted pair of insulated conductors comprises an insulating layer. Each conductor of the plurality of outer twisted pairs comprises an insulating layer. The insulating layers of the conductors of the central twisted pair are formed of a fluoropolymer. The insulating layers of the conductors of the first, second, and third outer twisted pairs are formed of a non-fluoropolymer material.
It is believed that certain embodiments will be better understood from the following description taken in conjunction with the accompanying drawings in which:
In connection with the views and examples of
Still referring to
Each of the twisted pairs 104, 106, 108, 110 can have a respective lay length. The lay length of the central twisted pair 104 can be shorter than the respective lay lengths of each of the outer twisted pairs 106, 108, 110 (e.g., the central twisted pair 104 can be twisted tighter than the outer twisted pairs 106, 108, 110). In one embodiment, the lay lengths of the outer twisted pairs 106, 108, 110 can be different from one another. In one embodiment, the longest lay length among the outer twisted pairs 106, 108, 110 can be between about 7.75 mm and about 9.14 mm. In another embodiment, the lay length of the central twisted pair 104 can be between about 6.35 mm and about 7.75 mm. In another embodiment, the maximum difference in lay length between the central twisted pair 104 and the longest lay length among the outer twisted pairs 106, 108, 110 is about 2.8 mm.
Positioning the central twisted pair 104 between the outer twisted pairs 106, 108, 110 can overcome some of the shortcomings associated with short lay lengths. For example, the central twisted pair 104 may not be as susceptible to alien crosstalk, helical loss and signal propagation delay since it is not stranded around the other pairs in the data cable as in conventional arrangements. As such, the central twisted pair 104 can have a shorter lay length than conventional cable arrangements, which in turn can allow for the lay lengths of the outer twisted pairs 106, 108 and 110 to be reduced (e.g., relative to conventional arrangements) which can provide improved alien crosstalk performance and a delay skew that meets various industry standards, such as the TIA 568 standard. It is to be appreciated that, although the central twisted pair 104 is shown to be surrounded by three outer twisted pairs 106, 108, 110, any suitable quantity of outer twisted pairs can be provided.
In one embodiment, the insulating layer 111 of the central twisted pair 104 can be selected to encourage fast signal propagation speeds along the central twisted pair 104. For example, the insulating layer 111 can be formed of a fluoropolymer, such as FEP, a polyolefin, or any of a variety of suitable alternative materials or combination thereof that provide a suitable dielectric constant and/or insulating characteristic for inhibiting signal loss in the central twisted pair 104. In one embodiment, only the insulating layer 111 of the central twisted pair 104 can be formed of an FEP material, while the insulating layers 111 of the outer twisted pairs 106, 108, 110 can be formed of a non-FEP material. In some embodiments, the insulating layers 111 can either be formed of a solid or foamed material. For example, in one embodiment, the insulating layer 111 of the central twisted pair 104 can be formed of a foamed material and the insulating layers 111 of the outer twisted pairs 106, 108, 110 can be formed of a solid material. It is to be appreciated that foamed material can provide better insulating characteristics relative to a solid material due to the air voids imparted to the foamed material during installation.
Still referring to
An alternative embodiment of a data cable 200 is illustrated in
Another alternative embodiment of a data cable 300 is illustrated in
Another alternative embodiment of a data cable 400 is illustrated in
Another alternative embodiment of a data cable 500 is illustrated in
The foregoing description of embodiments and examples has been presented for purposes of illustration and description. It is not intended to be exhaustive nor to be limited to the forms described. The embodiment(s) illustrated in the figures can, in some instances, be understood to be shown to scale for illustrative purposes. Numerous modifications are possible in light of the above teachings. Some of those modifications have been discussed and others will be understood by those skilled in the art. The embodiments were chosen and described in order to best illustrate various principles and how the embodiments are suited to the particular use contemplated. The scope of the present disclosure is, of course, not limited to the examples or embodiments set forth herein, but can be employed in any number of applications and equivalent devices by those of ordinary skill in the art. Rather it is hereby intended the scope of the present disclosure be defined by the claims appended hereto.
The present application claims priority of U.S. provisional application Ser. No. 61/909,119, entitled REDUCED DELAY DATA CABLE, filed Nov. 26, 2013, and hereby incorporates the same application herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61909119 | Nov 2013 | US |
