Method and an interconnecting node for use in an access network

Patent metadata

Field	Value
Publication number	US-9425983-B2
Application number	US-200913143513-A
Country	US
Kind code	B2
Filing date	Jan 16, 2009
Priority date	Jan 16, 2009
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

The invention relates to an interconnecting node for use in interconnecting a passive optical network (PON) and a copper wire xDSL access network, wherein said interconnecting node comprises an optical network unit (ONU) arranged to be connected to an optical line termination (OLT) over the PON network; and at least one xDSL access device connectable to at least one user end xDSL equipment over the copper wire xDSL access network. The interconnecting node is characterized in that it further comprises a clocking interconnect between the ONU unit and the at least one xDSL access device arranged to distribute a clock signal obtained from optical network transmissions received in the ONU unit over the PON network to an timing reference input of the at least one xDSL access device. The invention also relates to a further interconnecting node, methods for use in interconnecting nodes, a central office optical network apparatus and an access network.

First claim

The invention claimed is:

1. An interconnecting node for use in interconnecting a passive optical network (PON) and a copper wire xDSL access network, wherein said interconnecting node comprises:
an optical network unit (ONU) arranged to be connected to an optical line termination (OLT) over the PON network;
at least one xDSL access device connectable to at least one user end xDSL equipment over the copper wire xDSL access network, and
a clocking interconnect between the ONU unit and the at least one xDSL access device arranged to distribute a clock signal obtained from the rate of bits or frames of optical network transmissions received in the ONU unit over the PON network to a timing reference input of the at least one xDSL access device;
wherein said timing reference input of the at least one xDSL access device is a Network Timing Reference (NTR) input on a transceiver chip in a xDSL Transmission Unit-Central (xTU-C);
wherein, when the xDSL access device and the ONU unit are implemented in separate boxes and connects via an Ethernet-interface, said clocking interconnect between the ONU unit and the xDSL access device is either a separate copper connection or an inband signal via an Ethernet link; and
wherein the ONU unit is arranged to receive a time-of-day (ToD) information and a zero-distance equalization delay (T eqD ) from the OLT, determine a propagation delay (T p ), and update the received time-of-day information using the determined propagation delay.

2. The interconnecting node according to claim 1 , wherein said ONU unit further comprises a Clock and Data Recovery (CDR) unit arranged to determine said clock signal on a bit-level of the physical transport layer of the optical network transmissions such that a bit-level clock signal is obtained.

3. The interconnecting node according to claim 1 , wherein said ONU unit further comprises a PON framer circuitry arranged to determine said clock signal from a downstream framing structure of the physical transport layer of the optical network transmissions such that a frame-level clock signal is obtained.

4. The interconnecting node according to claim 1 , wherein said ONU unit comprises an ONU interface having a signal output arranged to output said obtained clock signal enabling additional attached equipment and systems to be synchronized using the obtained clock signal.

5. The interconnecting node according to claim 1 , wherein said PON network is a point-to-point Ethernet, a point-to-multipoint Ethernet Passive Optical Network (EPON), or a Gigabit-capable Passive Optical Network (GPON); and wherein said copper wire xDSL access network is an ADSL-, a ADSL2-, a ADSL2plus- or a VDSL2-network.

6. A method for use in an interconnecting node comprising an optical network unit (ONU) arranged to be connected to an optical line termination (OLT) over a passive optical network (PON), and at least one xDSL access device connectable to at least one user end xDSL equipment over a copper wire xDSL access network the method comprising the steps of:
receiving optical network transmissions in the ONU unit;
obtaining a clock signal from the rate of bits or frames of the received optical network transmissions in the ONU unit; and
distributing said clock signal to a timing reference input of the at least one xDSL access device;
wherein said timing reference input of the at least one xDSL access device is a Network Timing Reference (NTR) input on a transceiver chip in an xDSL Transmission Unit-Central (xTU-C);
wherein, when the xDSL access device and the ONU unit are implemented in separate boxes and connects via an Ethernet-interface, said clocking interconnect between the ONU unit and the xDSL access device is either a separate copper connection or an inband signal via an Ethernet link; and
wherein the ONU unit is arranged to receive a time-of-day (ToD) information and a zero-distance equalization delay (T eqD ) from the OLT, determine a propagation delay (T p ), and update the received time-of-day information using the determined propagation delay.

7. The method according to claim 6 , wherein the step of obtaining the clock signal uses a continuous-mode bit-level modulated transmission signal of a physical transport layer of the optical network transmissions in order to obtain said clock signal.

8. The method according to claim 6 , wherein the step of obtaining the clock signal uses a downstream framing structure of a physical transport layer of the optical network transmissions in order to obtain said clock signal.

9. An interconnecting node comprising an optical network unit (ONU) arranged to be connected to an optical line termination (OLT) over a passive optical network (PON);
wherein the ONU unit is arranged to receive a time-of-day (ToD) information and a zero-distance equalization delay (T eqD ) from the OLT termination, determine a propagation delay (T p ), and update the received time-of-day information using the determined propagation delay; and
wherein said ONU unit is further arranged to determine the propagation delay according to
T p =½·( T eqD −EqD−T res ), wherein

T egD is the zero-distance equalization delay received from the OLT termination,
EgD is an assigned equalization delay of the ONU unit, and
T res is a response time of the ONU unit.

Assignees

• Trojer Elmar
• Eriksson Per-Erik
• ERICSSON TELEFON AB L M (publ)

Inventors

• Trojer Elmar
• Eriksson Per-Erik

Classifications

• H04J3/0652

  Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] (bus network with centralized control in which slots are of a TDMA packet structure H04L12/4035) · CPC title

• H04L12/2892

  characterised by the access multiplexer architecture · CPC title

• H04J3/0647

  Synchronisation among TDM nodes · CPC title

• H04Q11/0067

  Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring · CPC title

• H04M11/062

  using different frequency bands for speech and other data · CPC title