METHOD FOR LOCALIZING AN OPTICAL TERMINATION DEVICE IN A PASSIVE OPTICAL NETWORK

• US 20110262139A1
• Filed: 12/29/2008
• Published: 10/27/2011
• Est. Priority Date: 12/29/2008
• Status: Active Grant

• Current Assignee: Telecom Italia S.p.A.
• Original Assignee: Telecom Italia S.p.A.
• Inventors: De Lutiis, Paolo, Viale, Luca, Costa, Luciana, D'Amico, Roberta
• Granted Patent: US 8,145,057 B2
• Time in Patent Office: Days
• US Class Current: 398/66
• CPC Class Codes: H04L 12/2898 Subscriber equipments DSL modems H04M11/062; cable modems H04L12/2801
• CPC Class Codes: H04Q 11/0067 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 Class Codes: H04Q 2011/0079 Operation or maintenance aspects
• CPC Class Codes: H04Q 2011/009 Topology aspects

Abstract

A method for localizing an optical network termination (ONT) of a passive optical network is disclosed. The passive optical network comprises an optical line terminal (OLT) and an optical distribution network (ODN) having a plurality of optical links. The ONT is connectable to the OLT by a given optical link of the optical distribution network. The method includes the steps of detecting that the ONT has been connected to the OLT by an optical link of the optical distribution network; determining length information indicative of a length of the optical link; comparing the length information with a reference length information indicative of a length of the given optical link; and if the length information matches the reference length information, localizing the ONT by confirming that it is connected to the OLT by the given optical link.

Claims

1. A method for localizing an optical termination device of a passive optical network, said passive optical network comprising an optical line terminal and an optical distribution network having a plurality of optical links, said optical termination device being connectable to said optical line terminal by a given optical link of said optical distribution network, said method comprising the following steps:

a) detecting that said optical termination device has been connected to said optical line terminal by an optical link of said optical distribution network;

b) determining length information indicative of a length of said optical link;

c) comparing said length information with a reference length information indicative of a length of said given optical link; and

d) if said length information matches said reference length information, localizing said optical termination device by confirming that said optical termination device is connected to said optical line terminal by said given optical link.

2. The method according to claim 1, wherein said step a) comprises:

e) performing a first ranging phase upon said optical termination device when said optical termination device is switched on for a first time;

f) measuring a first length information between said optical termination device and said optical line terminal during said ranging phase; and

g) assuming said first length information as said reference length information.

3. The method according to claim 2, wherein said step g) comprises:

h) retrieving an identifier of said optical termination device; and

i) storing an association between said reference length information and said identifier in an association table cooperating with said optical line terminal.

4. The method according to claim 3, wherein said step b) comprises:

l) repeating said ranging phase upon said optical termination device;

m) measuring said length information between said optical termination device and said optical line terminal during said repeated ranging phase;

and wherein said step d) comprises;

n) if said length information matches said reference length information, updating said reference length information by using said length information.

5. The method according to claim 4, wherein said step l) comprises:

during said repeating ranging phase, using said identifier for retrieving said reference length information stored in said association table.

6. The method according to claim 1, wherein said step d) comprises:

o) calculating an absolute value of a difference between said reference length information and said length information; and

p) when said absolute value is lower than or equal to a threshold, confirming that said optical termination device is connected to said optical line terminal by said given optical link.

7. The method according to claim 1, further comprising:

if said length information does not match said reference length information,

q) confirming that said optical termination device is not connected to said given optical link,

r) giving an alarm notifying that said optical termination device has been relocated, and

s) updating said reference length information by using said length information in order to localize a new position of said optical termination device.

8. The method according to claim 3, further comprising storing said reference length information and said identifier in an association table located at said optical line terminal.

9. The method according to claim 3, further comprising storing said reference length information, said identifier and an OLT identifier identifying an optical line terminal from which the optical termination device has been activated, in a centralized association table accessible by said optical line terminal and by a further optical line terminal belonging to another distributed passive optical network.

10. The method according to claim 6, further comprising storing said length information in a history database for statistical purposes and/or for tuning said threshold.

11. The method according to claim 1, wherein said length information is selected between a round trip delay and a fibre distance.

12. The method according to claim 1, wherein said step c) comprises determining said reference length information as an arithmetic average of previously determined values of said length information.

13. An optical line terminal for a passive optical network, said passive optical network being configured for being connectable to an optical distribution network having a number of optical links, said optical line terminal being configured for:

a) detecting that an optical termination device connectable to said optical line terminal by a given optical link of said optical distribution network has been connected to said optical line terminal by an optical link of said optical distribution network;

b) determining length information indicative of a length of said optical link;

c) comparing said length information with a reference length information indicative of a length of said given optical link and

d) if said length information matches said reference length information, localizing said optical termination device by confirming that said optical termination device is connected to said optical line terminal by said given optical link.

14. A passive optical network comprising:

an optical line terminal according to claim 13,

an optical distribution network having a number of optical links, and

an optical termination device connectable to said optical line terminal by said optical distribution network.

15. A non-transitory computer readable medium having a computer program stored thereon that, when executed on an optical line terminal for a passive optical network comprising an optical distribution network having a number of optical links, performs the steps of:

a) detecting that an optical termination device connectable to said optical line terminal by a given optical link of the optical distribution network has been connected to said optical line terminal by an optical link of said optical distribution network;

b) determining length information indicative of a length of said optical link;

c) comparing said length information with a reference length information indicative of a length of said given optical link; and

d) if said length information matches said reference length information, localizing said optical termination device by confirming that said optical termination device is connected to said optical line terminal by said given optical link.