CA2429765A1

CA2429765A1 - Cable termination bar

Info

Publication number: CA2429765A1
Application number: CA002429765A
Authority: CA
Inventors: Alain Quenneville; Michel Bohbot; Antoine Tazbaz
Original assignee: Nordx CDT Inc
Current assignee: Nordx CDT Inc
Priority date: 2003-05-23
Filing date: 2003-05-23
Publication date: 2004-11-23

Description

TITLE OF THE INVENTION
CABLE TERMINATION MODULE AND METHOD OF USE
FIELD OF THE INVENTION
The present invention relates to a cable termination module which serves as a guide for wires between the end of the cable and a connector. In particular, the present invention relates to cable termination module for arranging 'the individual twisted pairs of wires exiting the end of a telecommunications cable, their connection to a connector and the method of use of the termination module in order to improve performance of the cable/connector assembly.
BACKGROUND
The development of the Category 6 standard (ANSI/TIA/EIA-56$-B.2-1) and its subsequent wide acceptance by the telecommunications industry has raised the transmission requirements for electrical signals in telecommunications cables to a higher level than ever. Category 6 is a performance classification for twisted pair cables, connectors and systems which is specified up to 250 MHz.
In many installations, in particular office buildings and the like, telecommunications cables are installed behind walls or in the plenum ceiling and floor spaces. These cables are typically terminated at a first end in a patch bay close to servers or other networking equipment and terminated at a second end at a receptacle in proximity to the user. At both ends the individual wires emerging from the end of the cable are spliced into the back of an appropriate connector with the front side of the connector being exposed to provide easy access for the insertion and removal of patch cables. In order to test the installed cables to assess whether or not they meet the specifications as dictated by the applicable standards, a testing equipment is attached to the front of the connector located at the patch bay and the front of the connector located at the receptacle. Measurement of the performance of length of cable, therefore, includes not only the length of cable but also the connectors through which access to the cable is gained.
As higher transmission frequencies give rise to complex changes in the behaviour of the various components, not only the performance of the individual components, in this case the cable and the two connectors, is important but also the manner in which these components are interconnected.
A number considerations must be taken into account when installing telecommunications cables in order to ensure that they will meet the requisite testing specifications following installation. In particular, the cable termination on the back of the connector is an important factor and the conduction of an installation in a casual manner can lead to a significant degradation of performance.
One important electrical characteristic by which the performance of a telecommunications cable is measured is Near-End-Crosstalk, or NEXT. As is well known in the are, crosstalk is the undesired coupling from signal carrying wire to a collocated signal carrying wire. Crosstalk gives rise to undesirable interference which can severely affect transmission performance. For its part, NEXT is a measurement of crosstalk between two wire pairs of wires and is measured as the difference in signal strength between the interfering pair and the interfered pair. NEXT is directly affected by the manner in which the cable is terminated, and arises when the wires of two pairs are crossed. Crossing of wires can arise due to a number of reasons including failure to take appropriate care during installation or physical forces brought to bear on the cable or connector, for example during the installation of other cables.

Additionally, failure to take appropriate care when stripping the jacket from the length of cable as well as untwisting the twisted pairs can create a loop which can also affect performance. Therefore, installation of the cable on the back of each connector becomes very sensitive to the manner in which the installation is carried out by the installer.
SUMMARY OF THE INVENTION
In order to address the above and other drawbacks, the present invention provides for a termination module for insertion between a telecommunications cable, the cable comprising a cable jacket enclosing a plurality of twisted pairs of wires, and a connector. The termination module comprises a plurality of spaced apertures into which the twisted pairs of wires are inserted. The apertures maintain the twisted pairs of wires in an arrangement and separate and isolate the twisted pairs of wires from one another.
There is also provided a method for attaching a telecommunications cable to a connector, the cable comprising a cable jacket enclosing a plurality of twisted pairs of wires. The method comprises the steps of:
~ removing a section of cable jacket from the end of the cable thereby exposing the twisted pairs;
~ arranging the twisted pairs so that the wires of a first twisted pair do not cross the wires of a second twisted pair;
~ inserting the arranged twisted pairs into a termination module until the termination module abuts against the cable jacket;
~ bending the wires perpendicularly so that they can be inserted into a corresponding slot in the connector;
~ untwisting the twisted pairs of wires after the bend; and ~ inserting the wires into the corresponding slots while cutting any excess away from the end of the wires.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is an exploded front perspective view of a connector in accordance with an illustrative embodiment of the present invention;
Figure 2 is an exploded rear perspective view of a connector in accordance with an illustrative embodiment of the present invention;
Figure 3 is a perspective view of a communications cable having four pairs of twisted pair conductors in accordance with an illustrative embodiment of the present invention;
Figures 4a and 4b are cross sectional views of the cable of Figure 1 taken across lines 4-4;
Figure 5 is a rear perspective view of an assembled connector in accordance with an illustrative embodiment of the present invention;
Figure 6 is a schematic diagram illustrating the manner in which twisted pairs may become crossed during installation;
Figure 7a is a perspective view of a termination module in accordance with an illustrative embodiment of the present invention;
Figure 7b is a side plan view of a termination module in accordance with an illustrative embodiment of the present invention;

Figure 7c is a top plan view of a termination module in accordance with an illustrative embodiment of the present invention;
Figure 8 is a schematic diagram illustrating the manner in which the twisted 5 pairs must be arranged prior to insertion into the termination module in accordance with an illustrative embodiment of the present invention; and Figure 9 is a rear perspective view of an assembled connector and cable with a termination module interposed between the cabled end and the connector in accordance with an illustrative embodiment of the present invention;
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
Referring to Figure 1, a connector assembly, generally referred to using the numeral 10, for insertion into a patch bay or receptacle cover (both not shown) is disclosed. The connector assembly 10 is typically comprised of a front plate 12 having moulded into its front side 14 a socket 16 into which a patch cable having the requisite connector plug (both not shown) can be inserted. The front plate is typically manufactured from a dielectric material which is easily cast such as plastic. Moulded into the rear side 18 of the front plate 12 is a receptacle 20 for receiving a snap in interconnection module 22 and snap on cover 24.
Referring to Figure 2 in addition to Figure 1, the interconnection module 22 for the ANSIlTIA/EIA-568-B.2-1 standard is comprised of a series of eight (8) conductors as in 26 which are each terminated at a first end by a straight bendable portion as in 28 and at a second end by a bifurcated contact plate as in 30. Typically the contact plates 30 are arranged in two opposing parallel rows of four (4) contact plates 30 each.

Referring to Figure 3, a category 6 communications cable, in this case an Unshielded Twisted Pair (UTP) cable and generally referred to by the reference numeral 32, is disclosed. Category 6 cables have evolved from the lower performance Category 5 and Category 5e cabling systems, and consist of four (4) pairs of 18 to 26 AWG gauge wires as in 34 manufactured from suitable conducting material such as copper. Each wire 34 is individually wrapped in a colour coded outer sheath 36, typically manufactured from polyethylene (PE).
As shown in Figure 3, the two wires 34 of each pair are wound helically around one another to form the ubiquitous twisted pairs well known to persons of ordinary skill in the art. As stated above, twisted pairs significantly reduce the crosstalk which would otherwise arise as a result of the capacitative interference between two parallel transmission lines. Furthermore, as is also well known in the art, performance of a cable comprised of multiple twisted pairs of wires can be increased by varying the lay lengths of the twists between adjacent pairs (lay lengths typically range from 0.25 to about 1.5 inches for telecommunications cables).
Category 6 cables may include an isolating separator 38 between each of the four (4) pairs of wires 34. The communications cable 32 also includes a cable jacket 40, typically manufactured from polyvinylchloride (PVC). As will be clear on referring to Figure 4a, the isolating separator 38 divides the chamber defined by the inner wall 42 of the cable jacket 40 into a series of four compartments as in 44. Each compartment contains the two wires 34 belonging to one twisted pair. The isolating separator 38 is typically manufactured from a polymer material such as PVC or PE. The use of an isolating separator 38 further reduces cross talk thereby improving the performance characteristics of the cable.
Referring back to Figure 2, each bifurcated contact plate 30 has sharp opposed edges 46. As is well known to persons of ordinary skill in the art, pressing a sheathed wire (as in 34 in Figure 3) into the bifurcation causes the sharp edges 46 to sever the outer sheath 36 thereby bringing the conductor as in 26 into electrical contact with the wire 34. On assembly, the interconnection module is inserted into the cover 24 such that each contact plate 30 is arranged proximally to a corresponding slot 48 in the cover 24.
Referring now to Figure 5, once assembled, each slot 48 allows a wire as in 34 to be inserted between the sharp edges 46. Typically individual wires and their corresponding sheaths 36 are inserted between the sharp edges 46 of the bifurcated contact plate 30 by means of a suitable tool which simultaneously removes any excess from the end of the wire 34. A space 50 is provided for between the two rows of slots 48 to allow the wires 34 to be bent such that they may be pressed flat into the slots 48.
As is well known to those of ordinary skill in the art, the sheaths 36 of each wire are colour coded in order to aid the installer during installation of cables onto the connectors. ANSIlTIA/EIA-568 provides for four standardised colours, that is blue, orange, green and brown, for colour coding the sheaths 36 of the individual wires 34. As is also well known in the art, one wire 34 of each pair typically has a solid coloured sheath 36 while the second wire 34 of each pair has a white sheath 36 into which a stripe having the same colour as the other wire of the pair has been imbedded along the length thereof.
In fabricating a cable 32 the twisted pairs are arranged around the core of the cable such that if the cable 32 is cut a cross section the order of the twisted pairs is predetermined. The order as defined by ANSI/TIA/EIA-568 when looking at a first end of the cable and proceeding clockwise is blue, orange, green and then brown, or alternatively when looking from the other end the reverse, i.e. blue, brown, green and then orange. In this regard, referring now back to Figure 4b, the twisted pairs are referenced using the numerals I, II, III

and IV. Applying the order as defined in ANSI/TIA/EIA-568 the colours could be assigned to each twisted pair in the following manner: I - blue, II - orange, III -green and IV - brown or alternatively (if viewed from the other end) I - blue, I I -brown, I II - green and IV - orange.
Referring again to Figure 5, the wires 34 of each twisted pair are inserted into adjacent slots according to the requirements of the particular standard being implemented. ANSI/TIA/EIA-568B, for example, requires that twisted pair I
(blue) be inserted in the two slots 48 located in the right lower quadrant of the snap on cover 24, twisted pair II (orange) be inserted in the two slots 48 located left lower quadrant, twisted pair III (green) be inserted in the two slots 48 located left upper quadrant, and twisted pair IV (brown) be inserted in the two slots 48 located left lower quadrant. ANSI/TIA/EIA-568A, on the other hand, requires that the green and orange twisted pairs are reversed.
As stated above, NEXT is directly affected by the manner in which the cable 32 is terminated at that connector 10 and in particular NEXT can be introduced when the wires of different twisted pairs cross one another. Referring to Figure 6, a schematic diagram of the various ways in which the wires 34 of a cable can be attached to a connector in accordance with ANSIITIA/EIA-568A and 568B. Note that in Figure 6 reference numeral I indicates blue, II orange, III
green and IV brown. Different termination sequences can be obtained depending on the standard desired (T568A or T568B) and the end of the cable which is being connected. As is apparent from the diagram, three out of four possibilities involve the crossing of the wires of different twisted pairs which can give rise to unwanted NEXT.
It should also be pointed out that NEXT is also affected by the manner in which the individual twisted pairs are terminated. For example, the steps of unjacketing a portion of the cable to reveal the twisted pairs and untwisting the pairs in order to insert them in the slots 48 creates a loop opening. Effort must be made to maintain the untwisting to a minimum.
It will now be apparent from the above that in order to ensure that every installation meets the requisite performance requirements as laid down in the applicable standards, it is necessary to proceed during attaching the wires 34 to the connector 10 using a rigorous and systematic approach. Therefore, the provision of any methods or tools which ensure that the installer proceeds in a systematic fashion can serve to greatly improve the performance of the installed interconnection.
As stated above, NEXT is directly affected by the manner in which the cable is terminated, and arises when the wires of two pairs are crossed. Therefore, the ideal solution is to avoid crossing the pairs as the cable approaches the connector. Referring now to Figures 7a, 7b and 7c, in order to aid the installer during installation and prevent the crossing of the wires of different twisted pairs, regardless of the various configurations, a termination module, generally referred to using the reference numeral 52, is inserted between the connector 10 and the cable 32 in order to maintain an advantageous spacing between the twisted pairs. In this manner, the termination module 52 minimises any variations in performance which may be introduced as the result pour quality installation practices, by imposing a uniform and systematic way of terminating the cable 32 on the connector 10.
In the present illustrative embodiment, the termination module 52 comprises four (4) apertures 54 machined or cast, etc., through the upper surface 55 of the termination module and into which the twisted pairs (not shown in Figures 7a, 7b or 7c) can be inserted. The termination module 52 can be manufactured not only from a suitable rigid dielectric material such as plastic, but also cast from a shielding material such as metal (e.g. zinc), a composite material or a ferro-magnetic material. The twisted pairs exit the termination module 52 via a series of exits as in 56 machined, cast, etc., at right angles to and intersecting the apertures 54. Referring back to Figure 5, once the twisted pairs have been inserted through the apertures 54 in the termination module 52 and the wires of 5 the twisted pairs are protruding out of their respective exits 56, the termination module is inserted into the space 50 located between the opposing roles of slots 48 in the cover 24. It will be apparent now to one of ordinary skill in the art that the wires 34 of the twisted pairs which protrude from the exits are in position to intersect with the slots 48 into which they are then inserted.
Prior to inserting the twisted pairs in the apertures 54, however, the twisted pairs must first be aligned in the correct straight sequence such that no crossing of the pairs occurs. Referring to Figure 8, a schematic diagram of the conversion from a round sequence (for a round cable) to a straight sequence.
It should be noted that in Figure 8 the reference numeral 1 indicates the blue twisted pair, 2 indicates orange, 3 indicates green and 4 indicates brown.
Depending on the configuration, by moving the twisted pairs in the directions indicated by the arrows the correct align of the twisted pairs to avoid crossing can be achieved. Notice that although twisted pairs 2 (orange) and 3 (green) are inverted between the T568A and T568B schemes, no crossing of the wires of different twisted pairs occurs. It is rather a transposition from their respective vertical position to a horizontal position.
The use of a termination module is not applicable to only the round UTP cables as commonly used. The same termination module may be used with other cables included both the Screened Twisted Pair (ScTP) or Shielded Twisted Pair (STP), in both round and flat configurations. Use of the termination module is also not limited by colour coding of the twisted pairs nor their sequence within the cable.

Referring back to Figures 7a, 7b and 7c, the installation method consists of exposing the end of the cable to reveal the twisted pairs, arranging the twisted pairs according to the correct sequence as shown in Figure 8, sliding the termination module 32 onto the twisted pairs until the upper surface 55 of termination module 32 abuts the with the end of the cable jacket 40, while maintaining the twisted pairs in the sequence according to Figure 8. Once a sufficient amount of wire is exposed below the lower surface 58 of the termination module 52, the twisted pairs are bent perpendicularly such that they pass through their respective exits 56.
Still referring to Figures 7a, 7b and 7c, the four apertures 54 on the termination module 52 retain the twisted pairs in the correct sequence according to Figure 8. The two raised abutments 60 serve to provide a maximum separation between the external twisted pairs. The two dividing abutments 62 serve to isolate the twisted pairs as they continue out of the exits 56 to their insertion points in the slots 48 thereby reducing cross-talk between them. The outer walls 64 serve to isolate the twisted pairs from exterior interterence, especially in the that event another connector is installed in close proximity. This external crosstalk is known as "alien crosstalk".
Additionally, the termination module 52 is designed in such a way to minimise the distance between the unjacketed section of the cable and the connection.
Figure 9 discloses a UTP cable 32 terminated by a connector 10 using the termination module 52. The bending of the wires as in 32 in the exits 56 prevents the untwisting of the pairs through the termination module 32 and underneath the cable jacket 40. Therefore, the portion of each twisted pair which must be untwisted is minimised. Additionally, by forcing the cable termination module 52 upwards such that it abuts with the lower end of the cable jacket 40, the cable jacket 40 will be held as close as possible to the connector 10 thereby exposing a minimal portion of each twisted pair. This, combined with minimising the untwisting of the twisted pairs at the connector, can greatly improve the return loss, another important electrical parameter.
In brief, termination module 32 allows for a systematic installation of a connector following simple steps thereby optimising the installation time and the performance of the electrical transmission parameters.
Other advantages are also associated with the termination module 52. For example, the termination module 52 may be rigidly attached to the connector whereby it will provide additional mechanical support thereby improving cable retention and reducing those negative effects related to the manipulation of the cable (for example, excessive bending). Given its compact dimension, the termination module can also be easily integrated into existing designs. The termination module may also be used on a connector during a mated performance qualification session, to eliminate the variance related to the installation.
A number of variations to the termination module can also be foreseen. For example, the termination module can be modified to be adapted to an already installed cable without removing the connections, for example by dividing the termination module longitudinally into two separate parts which clip together around the twisted pairs.
Additionally, the basic concept of the termination module can be easily adapted for use on a number of different connector types including those where the slots 48 are arranged in four straight pairs, two rows of two pairs, etc., by simply modifying the location of the exits 56. Furthermore, it is not necessary that the apertures 54 be linearly aligned as illustrated in the figures. The apertures 54 could, for example, alternatively be arranged in a square pattern (i.e. with four twisted pairs in a 2 by 2 arrangement) provided the exits 56 are aligned in order to maintain the requisite arrangement. Also, the device can be used in conjunction with a termination {punch) tool or it can be adapted to a "tool-less" connector, where pressure ensures the contact.
Finally, different materials could be used to optimise the performance of the termination module 52. For example, it is possible to add some conductive material to the material used to fabricate the termination module 52 to use it as an electrical shield.
Although the present invention has been described hereinabove by way of an illustrative embodiment thereof, this embodiment can be modified at will without departing from the spirit and nature of the subject invention.

Claims

1. A termination module for insertion between a telecommunications cable and a connector, the cable comprising a cable jacket enclosing a plurality of twisted pairs of wires, the termination module comprising:

a plurality of spaced apertures into which the twisted pairs of wires are inserted, said apertures maintaining the twisted pairs of wires in an aligned arrangement and isolating said twisted pairs of wires from one another.

2. The termination module according to claim 1 wherein the module is manufactured from a shielding material.

3. A method for attaching a telecommunications cable to a connector, the cable comprising a cable jacket enclosing a plurality of twisted pairs of wires, comprising the steps of:

removing a section of cable jacket from the end of the cable thereby exposing the twisted pairs;

arranging the twisted pairs so that the wires of a first twisted pair do not cross the wires of a second twisted pair;
inserting the arranged twisted pairs into a termination module as defined in claim 1 until the termination module abuts against the cable jacket;
bending the wires perpendicularly so that they can be inserted into a corresponding slot in the connector;
untwisting the twisted pairs of wires after the bend; and inserting the wires into the corresponding slots while cutting any excess away from the end of the wires.