Extended distribution of ADSL signals

• US 6,886,181 B1
• Filed: 07/07/2000
• Issued: 04/26/2005
• Est. Priority Date: 07/07/2000
• Status: Expired due to Fees

• Current Assignee: Critical Telecom Corp. (BATM Advanced Communications Ltd.)
• Original Assignee: Critical Telecom Corp. (BATM Advanced Communications Ltd.)
• Inventors: Cruder, Oliver, Labbe, Mark, Dodds, David E.
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): SHANG, ANNAN Q
• Application Number:
  US09/612,445
• Time in Patent Office: 1,754 Days
• Field of Search: 725/106, 725/118, 725119-122, 725/127, 725/129, 370352-354, 370/395, 370/401, 370/486, 370/487, 370/493, 370/498
• US Class Current: 725/119
• CPC Class Codes: H04L 25/4908 using mBnB codes
• CPC Class Codes: H04Q 11/04 for time-division multiplexing H04Q11/0001 takes precedence
• CPC Class Codes: H04Q 2213/1301 Optical transmission, optical switches
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/13039 Asymmetrical two-way transmission, e.g. ADSL, HDSL
• CPC Class Codes: H04Q 2213/1305 Software aspects
• CPC Class Codes: H04Q 2213/1309 Apparatus individually associated with a subscriber line, line circuits
• CPC Class Codes: H04Q 2213/13099 Loop multiplexer
• CPC Class Codes: H04Q 2213/1319 Amplifier, attenuation circuit, echo suppressor
• CPC Class Codes: H04Q 2213/13214 Clock signals
• CPC Class Codes: H04Q 2213/13291 Frequency division multiplexing, FDM
• CPC Class Codes: H04Q 2213/13292 Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13305 Transistors, semiconductors in general
• CPC Class Codes: H04Q 2213/1332 Logic circuits
• CPC Class Codes: H04Q 2213/13322 Integrated circuits
• CPC Class Codes: H04Q 2213/13332 Broadband, CATV, dynamic bandwidth allocation
• CPC Class Codes: H04Q 2213/1336 Synchronisation

Abstract

A plurality of metallic telephone lines carrying both baseband POTS (plain old telephone service) and DSL (digital subscriber line) or ADSL (asymmetric digital subscriber line) signals originate at customer premises and pass through a common field cabinet enroute to a telephone central office. Baseband POTS signals flow in an undisturbed manner through the field cabinet and maintain the normal, highly reliable, communication between the subscriber premises and the central office telephone switch. At the field cabinet, DSL/ADSL signals are removed from the metallic telephone line and are then communicated between the field cabinet and the central office using fiber optic broadband transmission. Fiber optic transmission increases the allowed distance between the ADSL transceiver located at the customer location and the respective ADSL transceiver located in the telephone central office. In the optical fiber, DSL and ADSL signals are retained in their 2B1Q, DMT, QAM or CAP analog format and are simply frequency translated in the process of frequency division multiplex (FDM) transmission. The arrangement allows the provision of ADSL service to customers beyond the distance limit normally imposed by a completely metallic telephone line. It is understood that this arrangement is equally applicable to a variety of DSL (digital subscriber line) signals.

Claims

1. Apparatus for distributing ADSL signals to customer premises from a central office, comprising:

a central office having a POTS switching system and ADSL terminals that connect to a data network;

a plurality of customer locations at least some of which have at least one voice frequency POTS terminal and at least one ADSL terminal;

a field cabinet remote from the central office associated with the plurality of customers;

a plurality of individual metallic telephone lines each extending from a respective one of the customers to the field cabinet;

a trunk cable containing a large number of metallic telephone lines and extending from the field cabinet to the central office;

the field cabinet including a plurality of connections for connecting the individual telephone lines to the trunk cable for connection of signals between the customer locations and the central office;

the individual metallic telephone lines each being arranged to transmit both voice frequency POTS signals and ADSL signals between the respective customer location and the field cabinet;

a bi-directional link separate from the trunk cable for the broadband transmission of ADSL signals in a modulated analog form in pre-selected frequency bands between the central office and the field cabinet;

the ADSL terminals at the central office including ADSL modems arranged to communicate the ADSL signals in their modulated analog form over the bi-directional link;

a splitter and interface module at the field cabinet, remote from the central office having;

a plurality of signal splitting coupler units each associated with a respective one of the individual telephone lines and each arranged to separate the ADSL signals and the voice frequency POTS signals from the respective telephone line;

a plurality of connectors each arranged to connect the separated voice frequency POTS signals between the respective individual telephone line and the trunk cable;

a plurality of interface and frequency translation units each associated, with a respective one of the coupler units for receiving the separated ADSL signals from the coupler unit and for communicating the bi-directional ADSL signals in their analog form on the bi-directional link between the central office and the respective individual telephone line in a pre-selected one or more of the frequency bands that are associated with the respective individual telephone line; and

a plurality of frequency translation and interface units at the telephone central office each of which is associated with the pre-selected band or bands on the bi-directional link associated with a respective individual telephone line and each of which provides an interface between the respective ADSL signals on the bi-directional link and the ADSL modem of the ADSL terminal of the central office.

2. The apparatus according to claim 1 wherein the signal splitting coupler includes a filter that couples to the connectors substantially only voice frequency signals in the frequency band below 4 kHz and couples to the interface and frequency translation units substantially only signals in the frequency range above 20 kHz.

3. The apparatus according to claim 1 wherein the bi-directional link includes a fiber optic link between the field cabinet and the central office, an optical transceiver at the field cabinet and a second optical transceiver at the central office.

4. The apparatus according to claim 3 wherein the fiber optic link includes two unidirectional fiber optic links and wherein the interface and frequency translation units each contain a directional hybrid coupler to interface the bi-directional metallic telephone line to the unidirectional fiber optic link.

5. The apparatus according to claim 3 wherein the fiber optic link includes a fiber optic cable and a metallic conductor pair for supplying power from the central office to the interface and frequency translation units.

6. The apparatus according to claim 1 wherein the frequency translators are arranged such that the frequency bands are each located within a respective 6 MHz frequency band communicated on the bi-directional link.

7. The apparatus according to claim 1 wherein each frequency translator from the ADSL signals to the frequency band includes a CATV modulator arranged to locate the respective ADSL signals within a respective video channel frequency band which is then communicated on the bi-directional link.

8. The apparatus according to claim 7 wherein each frequency translator includes a first translator element arranged to translate to an intermediate frequency by double side band transmitted carrier amplitude modulation (AM-DSB-TC) of a radio frequency carrier at the intermediate frequency and wherein the CATV modulator is arranged to translate from the intermediate frequency to the respective video channel frequency band.

9. The apparatus according to claim 8 wherein the first translator element is arranged to effect direct translation from the ADSL signals to the pre-selected frequency band by AM-DSB-TC modulation of a radio frequency carrier.

10. The apparatus according to claim 8 wherein each frequency translator includes a first tuner element arranged to translate from the pre-selected frequency band to the intermediate frequency band and the tuner to be followed by envelope detection of the AM-DSB-TC signal so as to translate the signal from the intermediate frequency band to the ADSL signal band on the metallic telephone line.

11. The apparatus according to claim 1 wherein the bi-directional link includes a coaxial cable link.

12. The apparatus according to claim 11 wherein the means in each frequency translator communicating the bi-directional ADSL signals via the co-axial cable comprises at least one transmitter and at least one receiver arranged to transmit and receive the bi-directional signals at respective frequencies.

13. The apparatus according to claim 12 wherein said frequency translator at the telephone central office is tuned to transmit signals at a respective frequency in a first frequency band for a downstream transmission direction on the coaxial cable, and the said frequency translator at field cabinet is tuned to transmit signals at a respective frequency in a second frequency band for an upstream transmission direction on the coaxial cable.

14. Apparatus for distributing ADSL signals to customer premises from a central office, comprising:

a central office;

the central office having a POTS switching system;

the central office having ADSL connection terminals that connect to a data network;

a plurality of customer locations at least some of which have at least one voice frequency POTS terminal and at least one ADSL terminal;

a field cabinet remote from the central office associated with the plurality of customer locations;

a plurality of individual metallic telephone lines each extending from a respective one of the customer locations to the field cabinet;

a trunk cable containing a large number of metallic telephone lines and extending from the field cabinet to the central office;

the field cabinet including a plurality of connections for connecting the individual telephone lines to the trunk cable for connection of signals between the customer locations and the central office;

the individual metallic telephone lines each being arranged to transmit both voice frequency POTS signals and ADSL signals between the respective customer location and the field cabinet;

a bi-directional link separate from the trunk cable for the transmission of ADSL signals in a modulated analog form between the field cabinet and the central office for connection to the data network; and

the ADSL terminals at the central office including ADSL modems arranged to communicate the ADSL signals in their modulated analog form over the bi-directional link;

a splitter and interface module at the field cabinet, remote from the central office having;

a plurality of signal splitting coupler units each associated with a respective one of the individual telephone lines and each arranged to separate the ADSL signals and the voice frequency POTS signals from the respective telephone line;

a plurality of connectors each arranged to connect the separated voice frequency POTS signals between the respective individual telephone line and the trunk cable; and

a plurality of interface units each associated with a respective one of the coupler units for receiving the separated ADSL signals from the coupler unit and for communicating the bi-directional ADSL signals on the bi-directional link between the central office and the respective individual telephone line.

15. The apparatus according to claim 14 wherein the central office includes an interface module arranged to transport the ADSL signals on the bi-directional link in a modulated format intended for transmission on the metallic telephone lines and wherein these the interface module at the central office location is arranged to modulate a high frequency carrier and where this carrier is demodulated at the field cabinet to recover the DSL signal which is then transmitted on the metallic telephone line to the customer location.

16. The apparatus according to claim 15 where the ADSL signal is transported without significant amplitude change.

17. The apparatus according to claim 14 wherein the interface units are arranged such that multiple ADSL signals from respective customer locations are combined to a single broadband signal through the use of frequency division multiplexing.

18. The apparatus according to claim 14 wherein the interface units are arranged such that a plurality of ADSL signals individually modulate a respective plurality of high frequency carriers separated in frequency by an amount that avoids interference between the individual DSL signals.

19. The apparatus according to claim 14 wherein the interface units are arranged such that power failure or failure in the DSL transmission equipment does not impair the POTS service and where.

20. The apparatus according to claim 14 wherein the interface units are arranged such that the DSL signals are not concentrated, as in statistical multiplexing, and that all customers may simultaneously utilize the full ADSL bit rate.

21. The apparatus according to claim 14 wherein the field cabinet receives its power supply from the central office through paired metallic telephone lines including wire pairs that would otherwise be used for voice frequency transmission.