WO2002058405A2

WO2002058405A2 - Method and apparatus for converting subscriber loops for delivery of both pots services and high speed data

Info

Publication number: WO2002058405A2
Application number: PCT/CA2002/000063
Authority: WO
Inventors: Tet Hin Yeap
Original assignee: Esion Networks Inc.
Priority date: 2001-01-18
Filing date: 2002-01-18
Publication date: 2002-07-25
Also published as: CA2331551A1; WO2002058405A3; AU2002226226A1

Abstract

In order to enable both POTS and high speed data communications via a plurality of subscriber loops connected to central office by way of a junction unit and a feeder cable, a bank of POTS splitters and a high speed data interface are located adjacent the junction unit and conductors of the subscriber loops are connected to the bank of POTS splitters. Preferably, the connector blocks in the JWI are duplicated in the box containing the POTS splitters. The usual jumper conductors in the JWI are removed and the connector blocks in the JWI connected to the connector blocks in the POTS splitter box by bridging conductors. With this arrangement, it is possible to remake the connections to the subscriber loops one at a time, thus reducing disruption to service.

Description

METHOD AND APPARATUS FOR CONVERTING SUBSCRIBER

LOOPS FOR DELIVERY OF BOTH POTS SERVICES AND HIGH SPEED DATA

DESCRIPTION

TECHNICAL FIELD:

The invention relates to apparatus for connection to telephone subscriber loops to enable delivery of both so-called POTS (Plain

Ordinary Telephone System) services and high speed data via such subscriber loops, and to a method of connecting such apparatus to the subscriber loops.

BACKGROUND ART:

At present, most telephone subscribers are connected to the local central office by subscriber loops each comprising a pair of conductors, typically a so-called twisted wire pair, which convey analog telephone signals at a frequency up to about 3 kHz. Usually, groups of subscriber loops are routed to a Junctor Wiring Interface (JWI) unit where they are connected to a feeder cable which connects the JWI unit to the local central office. Typically, a local central office will serve 5,000 subscribers by way of, say, ten JWI units each to up 500 subscriber loops.

With the growth of the Internet, more and more subscribers have a need to transmit and receive data at higher speeds. Using Digital Subscriber Loops (DSL) technologies, such as Asymmetric Digital Subscriber Loop (ADSL) and Very high speed Digital Subscriber Loop (VDSL), service providers provide both POTS and high speed data communications over the same twisted wire pair. At the central office, a Digital Subscriber Loop Access Multiplexer (DSLAM) segregates incoming POTS signals from the incoming data signals, and combines outgoing POTS signals and data signals, for each of a group of subscriber loops.

In view of the relatively high data rates, the length of the twisted wire pair over which the high speed data signals can be transmitted with acceptable error rates is limited. For VDSL, the maximum length probably is likely to be less than two kilometers. Many subscriber loops, however, are more than two kilometers from the central office, and there is a need to provide high speed access to them without having to replace their existing subscriber loops. As a general rule, even though such subscribers are more than two kilometers from the central office, they are less than two kilometers from the JWI unit. Consequently, one option is to replace the JWI unit with a DSLAM which is connected to the central office by an optical fiber cable. A major disadvantage of such an approach, however, is the cost of the DSLAM and the large number of JWI units which would have to be replaced. A further disadvantage is that removal and replacement of a JWI unit would result in service to all of the 500 subscribers being discontinued for at least one day.

Even if the JWI were not removed, but a DSLAM located next to it and connected to it by bridging conductors, it would still be required to make the connections without interrupting POTS service for all of the subscribers for substantially the whole time taken to install the DSLAM.

DISCLOSURE OF INVENTION:

The present invention seeks to address this need and provide a cost-effective way of connecting subscriber loops to enable both POTS and high speed data communications, conveniently without disrupting service to large groups of subscribers.

According to the present invention, a method of converting for high speed access a plurality of subscriber loops connected to central office by way of a junction unit and a feeder cable comprises the step of locating a bank of POTS splitters and a high speed data interface adjacent the junction unit and connecting conductors of the subscriber loops to the bank of POTS splitters.

Preferably, where the junction unit has a first connector block having its terminals connected to the subscriber loop conductors and a second connector block having its terminals connected to conductors of the feeder cable, with a plurality of jumper connectors each connecting a respective one of the terminals of the first connector block with a corresponding one of the terminals of the second connector block, the method 20 further comprises the step of providing third and fourth connector blocks with the POTS splitter bank, the third connector block having terminals connected to first ports of the POTS splitters, respectively, and the fourth connector block having terminals connected to second ports of the POTS splitters, respectively, disconnecting each jumper connector and connecting in its place first and second ends of two bridging conductors, and connecting other ends of the two bridging conductors to corresponding terminals of the fourth and third connector blocks, respectively.

The high speed interface unit may comprise a complete DSLAM unit, i.e., including high speed modems, in which case both the high speed data and the voice signals could be conveyed to the central office via the same cable, the feeder cable then being redundant. Alternatively, the DSLAM could convey the high speed data via a separate cable, typically an optical fiber cable, and the POTS signals would be conveyed by the feeder cable as before. Advantageously, however, only the POTS splitter and a bank of analog interface units could be provided at the JWI and the high speed modem units provided at the central office, or even at a location remote from the central office. Such a high speed modem unit could comprise a pool of high speed modems shared by a group of subscriber loops greater than the number of modems. BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 illustrates conventional subscriber access architecture;

Figure 2 is a detail partial view of conventional connections within a JWI of Figure 1 ; Figure 3 illustrates a subscriber access architecture according to the present invention including equipment to enable high speed DSL;

Figure 4 illustrates connections between the JWI and the DSL/POTS interface apparatus within the architecture of Figure 3;

Figure 5 illustrates an alternative subscriber access architecture deploying DSL/POTS interface apparatus at a Junctor Wiring Interface and a processor pool unit at the central office; and

Figure 6 illustrates in more detail the DSL/POTS interface unit and the processor pool unit of Figure 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS:

In the drawings, items which are identical or similar have the same reference number in the different Figures, with a prime signifying a modification.

Referring to Figure 1 , a central office 10 is connected to station apparatus at subscriber's premises 12A, 12B,.., and so on, by way of a junctor wiring interface (JWI) unit 14. For convenience of illustration,

Figure 1 shows only those components of the central office 10 which are pertinent to the present invention, namely a backbone network switch 16 and a POTS switch 18. An optical link 20 connects the backbone switch 16 to other parts of the telecommunications network in known manner using, for example, SONET (Synchronous Optical Network) technology, and a link 22, typically also using SONET, connects the backbone switch

16 to the POTS switch 18. A group of feeder cables 24 comprising, perhaps, up to ten cables, each of 50 twisted pairs, connects the POTS switch 18 to JWI 14. A distribution cable 26 connected to the JWI 14 is shown as splitting into a buried cable section 26/1 and an aerial section 26/2. The depiction of one buried section and one aerial section is for purposes of illustration only. In a practical installation, of course, the cable 26 could be split into multiple sections and they could all be of the same kind, buried or aerial.

The buried section 26/1 is connected to a series of drop boxes of which only one, drop box 28B, is shown in Figure 1. Drop box 28B is connected to subscriber station apparatus (not shown) in subscriber premises 12B by a buried "drop" cable 30B. The aerial cable section 26/2, supported by poles 32, is connected to a series of aerial terminals each of which is connected to the subscriber station apparatus in a corresponding one of the subscriber premises. In Figure 1 , only aerial terminal 34A is shown, connected to station apparatus (not shown) of subscriber premises 12A by an aerial drop cable 36A. As illustrated in Figure 2, within the JWI 14, the conductors of the feeder cable 24 are connected to a bank of BIX connector blocks 38/1, 38/2, 38/3 and 38/4. Likewise, the conductors of the distribution cable 26 are connected to a second bank of BIX connector blocks 40/1 , 40/2, 40/3 and 40/4. A jumper conductor 42/1 connects the first terminal of BIX connector block 38/1 to the first terminal of BIX connector block 40/1. For simplicity, only the one jumper conductor is shown. It will be appreciated that other jumper conductors will connect other pairs of terminals of the two banks of BIX connector blocks. In a densely-built urban area, the JW1 14 might be connected to 500 subscriber loops, all less than two kilometers in length, measured from the JWI.

Figure 3 illustrates a preferred embodiment of the present invention. The installation shown in Figure 3 differs from that shown in Figure 1 because a DSL/POTS interface unit 42 is installed adjacent the JWI 14 and connected to it by a bridging cable 44 comprising a plurality of conductor pairs. An optical fiber 46 connects the DSL/POTS interface unit 42 to the backbone network switch 16, in central office 10. The JWI 14 is connected to the subscriber's premises 12A, 12B and so on as before. The DSL/POTS interface unit 42 may be of any known design able to multiplex each of the data signals from optical fiber 46 with a corresponding one of the POTS signals from the feeder cable 24 and supply the multiplexed DSL/POTS signal to a respective one of the subscriber loops via the JWI 14; or demultiplex each of the DSL/POTS signal from the subscriber loops to segregate the data signal and the POTS signal and deliver them to the optical fiber 46 and the feeder cable 24, respectively. The pertinent parts of the JWI 14 and the DSL/POTS interface unit 42 are shown in Figure 4. The JWI 14 is similar to that shown in Figure 2 in that it comprises a first bank of BIX connectors 38/1 , 38/2, 38/3 and 38/4 connected to the feeder cable 24 and a second bank of BIX connectors 40/1 , 40/2, 40/3 and 40/4 connected to the distribution cable 26. It should be noted, however, that there are no longer any jumper conductors connecting the pairs of terminals of the two banks of BIX connectors inside the JWI 14. Instead, each of the terminals of BIX connector blocks 38/1 , 38/2, 38/3 and 38/4 is connected to a respective one of the terminals of a first bank of BIX connector blocks 50/1 , 50/2, 50/3 and 50/4 in the DSL/POTS interface unit 42 by a respective one of the conductors in the bridging cable 44. Likewise, each of the terminals of the second bank of BIX connector blocks 40/1 , 40/2, 40/3 and 40/4 in the JWI unit 14 is connected to a respective one of the terminals of a second bank of BIX connector blocks 48/1 , 48/2, 48/3 and 48/4 in the DSL/POTS interface unit 42. For ease of illustration, only one pair of bridging conductors, 52/IA and 54/IA, are shown in Figure 4.

The DSL/POTS interface unit 42 includes a high speed data interface unit 56 and a POTS splitter 58. The data interface 56 provides an interface between the optical cable 46 and the (electrical) POTS splitter unit 58. The terminals of BIX connector blocks 48/1 , 48/2, 48/3 and 48/4 are connected by a first multi-conductor cable 60 to one port 62 of the POTS splitter 58 and the terminals of the second bank of BIX connectors blocks 50/1 , 50/2, 50/3 and 50/4 are connected by a second multiconductor cable 64 to a second port 66 of the POTS splitter 58. The third port 68 of the POTS splitter 58 is connected to the data interface unit 56 by a bus 70. The POTS splitter 58 comprises a bank of filters, one for each subscriber loop. The detailed construction of the interface unit 56 and the POTS splitter 58 will be known to those skilled in the art and so will not be described here.

To connect the DSL/POTS interface unit 42 to the JWI 14, the technician will remove the first jumper 42/1 (see Figure 2) from the first terminals of the BIX connector blocks 38/1 and 40/1 , respectively, and connect in its place the ends of the bridging conductors 52/IA and 54/IA. That completes the conversion of the first subscriber loop from "POTS only" to "POTS and high speed data", i.e., to become a DSL. Each of the other jumpers can be removed in turn and the corresponding bridging conductors connected in its place. Since only one subscriber loop is disconnected at any given time, and only for the time taken to remove the jumper and connect the two bridging conductors, interruption of service to the subscribers is minimal. Once the connections have been made, the POTS signals from feeder cable 24 will be routed via the BIX connector blocks 38/1 , 38/2, 38/3 and 38/4 in the JWI 14 to the BIX connector blocks 50/1 , 50/2, 50/3 and 50/4 in the DSL/POTS interface unit 42 and thence to port 66 of the POTS splitter 58. On leaving the POTS splitter 58, the POTS signals will be routed via port 62 of the splitter 58 to the BIX connector blocks 48/1 , 48/2, 48/3 and 48/4 and, from there, via the bridging conductors, to the BIX connector blocks 40/1 , 40/2, 40/3 and 40/4 in the JWI 14, and then via the distribution cable 26 to the subscribers' premises. POTS signals from the subscribers will take the opposite path. The high speed data interface unit 56 will receive optical data signals from the central office 10 via optical fiber 46, convert them to electrical signals, and supply the electrical data signals to port 70 of the POTS splitter 58, which will route them via port 62 and multiconductor cable 60 to BIX connector blocks 48/1 , 48/2, 48/3 and 48/4. From there, the data signals will be routed via the bridging conductors to BIX connector blocks 40/1 , 40/2, 40/3 and 40/4 to the distribution cable 26 and thence to the subscribers' premises. Data signals from the subscribers will follow the opposite path to the central office.

The DSL/POTS interface unit 56 could be a complete DSLAM which is installed in a box next to the JWI 14 and includes a dedicated high speed modem for each DSL. Alternatively, a DSLAM arrangement could be used which is similar to that disclosed by the present inventor in copending patent application number (Agent's file ref. AP824), and which comprises a central processor pool at the local central office, or a main central office elsewhere in the network, and a plurality of analog interface units.

Such an alternative will be described with reference to Figures 5 and 6. The installation illustrated in Figure 5 is similar to that shown in Figure 3 except that, in the DSL/POTS interface unit 42', the high speed interface unit 56 does not include the usual digital signal processors (DSPs) implementing the high speed modems. Instead, as shown in Figure 6, it comprises an analog front end unit 72 and an optical interface unit 74 interconnected by a bus 76. The central office 10 includes a processor pool unit 78 connected to the DSL/POTS interface unit 42' by optical cable 46 and connected to the backbone network switch 16 by an optical fiber link 80..

Figure 6 shows two DSL/POTS interface units, but there could be as many as the number of JWI units to be converted. Since they are identical, only the DSL/POTS unit 52 will be described. Thus, DSL/POTS interface unit 52 comprises a bank of analog interface units AFEi, ..., AFEN coupled to a session switch 82 by bus/link 76. The session switch 82 has an optical interface unit 84 connected by optical fiber 46 to the central processing pool unit 78. Within the central processor pool unit 78, the optical fiber 46 is connected to an optical interface unit 86 of a session switch 88, together with optical fibers from other DSL/POTS interface units at other JWIs. A session processor 90 monitors the session switch 88 which is connected to a bank 92 of digital signal processors (DSPs) DSPi to DSPM, which act as high speed modems. The bank of DSPs are coupled to the backbone network switch 16 by a network interface unit 94. The optical interface unit 86 converts the group of serial optical signals into electrical signals again and routes the electrical signals to the bank of DSPs via a bus 91. Memory 98 stores line codes and other data for use by the DSP's.

In the DSL/POTS interface unit 42, the optical interface unit 84 converts the digital signals of only the "active" DSLs from the corresponding group of interface units AFE-i, ..., AFEN into a serial optical signal and transmits the serial optical signal via the optical fiber 46 to the central processor pool unit 78. The active lines are detected by an activity processor 96 connected to the session switch 82. Each of the interface units AFEi, ..., AFEN in DSL interface unit 52ι is connected to the POTS splitter bank 68 (Figure 4). For more information about the construction and operation of such a twopart DSLAM, the reader is directed to copending application number (AP824) the contents of which are incorporated herein by reference.

Claims

CLAIMS:

1. A method of converting for high speed access a plurality of subscriber loops connected to central office by way of a junction unit and a feeder cable comprises the step of locating a bank of POTS splitters and a high speed data interface adjacent the junction unit and connecting conductors of the subscriber loops to the bank of POTS splitters.

2. A method according to claim 1 , further comprising, where the junction unit has a first connector block having its terminals connected to the subscriber loop conductors and a second connector block having its terminals connected to conductors of the feeder cable, with a plurality of jumper connectors each connecting a respective one of the terminals of the first connector block with a corresponding one of the terminals of the second connector block, the steps of providing third and fourth connector blocks with the POTS splitter bank, the third connector block having terminals connected to first ports of the POTS splitters, respectively, and the fourth connector block having terminals connected to second ports of the POTS splitters, respectively, disconnecting each jumper connector and connecting in its place first and second ends of two bridging conductors, and connecting other ends of the two bridging conductors to corresponding terminals of the fourth and third connector blocks, respectively.

3. A method according to claim 2, wherein the high speed interface unit comprises high speed modems, and both the high speed data and the voice signals are conveyed to the central office via the same cable.

4. A method according to claim 2, wherein the high speed interface unit conveys the high speed data via a separate cable from a feeder cable conveying conventional low speed POTS signals.

5. A method according to claim 1 , wherein the POTS splitter and a bank of analog interface units are provided at the JWI and a bank of high speed modem units are provided at a remote location.

6. A method according to claim 5, wherein the remote location is at a central office or an office connected thereto by a backbone network.

7. A method according to claim 5, wherein the high speed modem unit comprises a pool of high speed modems shared by a group of subscriber loops greater than the number of modems.

8. A method according to claim 6, wherein the high speed modem unit comprises a pool of high speed modems shared by a group of subscriber loops greater than the number of modems.

9. Apparatus for converting for high speed access a plurality of subscriber loops connected to central office by way of a junction unit and a feeder cable, the apparatus comprising a bank of POTS splitters connected to a high speed data interface unit, means for connecting a high bandwidth cable, for example an optical fiber, to the high speed data interface unit, and means for connecting the POTS splitter unit, in the junction unit, to the subscriber loops.

• 10. Apparatus according to claim 9, wherein, where the junction unit has a first connector block having its terminals connected to the subscriber loop conductors and a second connector block having its terminals connected to conductors of the feeder cable, with a plurality of

π jumper connectors each connecting a respective one of the terminals of the first connector block with a corresponding one of the terminals of the second connector block, third and fourth connector blocks are provided with the POTS splitter bank, the third connector block having terminals connected to first ports of the POTS splitters, respectively, and the fourth connector block having terminals connected to second ports of the POTS splitters, respectively.

11. Apparatus according to claim 10, wherein the high speed interface unit comprises high speed modems, and the high speed data interface unit is arranged to convey high speed data and voice signals to the central office via the same cable.

12. Apparatus according to claim 10, wherein the high speed interface unit is arranged to convey the high speed data via a separate cable from a feeder cable conveying conventional low speed POTS signals.

13. Apparatus according to claim 9, wherein the high speed interface unit comprises a bank of analog interface units and means for communicating data signals between the analog interface units and a bank of high speed modem units at a remote location.

14. A telecommunications system comprising a central office, a plurality of subscriber loops connected to the central office by way of a junction unit and a feeder cable, and bank of POTS splitters connected to a high speed data interface unit located adjacent the junction unit, a high bandwidth cable, for example an optical fiber, connecting the high speed data interface unit to the central office, and means connecting the POTS splitter unit, in the junction unit, to the subscriber loops.

15. A system according to claim 14, wherein a high speed modem unit comprising a bank of high speed modems for high speed data signals from the subscriber loops is provided at a location remote from the high speed interface unit, and the high speed data interface unit comprises a bank of analog interface units connected to the high speed modem unit.

16. A system according to claim 15, wherein the high speed modem unit comprises a pool of high speed modems for sharing by a group of subscriber loops greater than the number of modems.

17. A system according to claim 15, wherein the high speed modem unit is at the central office or an office connected thereto by a backbone network.