Unidirectional absolute optical attenuation measurement with OTDR

Patent metadata

Field	Value
Publication number	US-9419707-B2
Application number	US-200913143043-A
Country	US
Kind code	B2
Filing date	Dec 10, 2009
Priority date	Dec 31, 2008
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

Devices and methods for optical measurements in point-to-point and point-to-multipoint networks, e.g. like PON networks with splitters are described in which reflected power from some known reflections at the end of the lines is used to determine the attenuation and stability of the attenuation of each line. Also a reference reflection is used at the beginning of the network so that an absolute loss measurement between the points of reflection and the reference reflection can be made. In a further aspect wavelength selective stable reflections and reflectors are used, to provide reflections in a wavelength range that does not interfere with normal operation.

First claim

The invention claimed is:

1. A monitoring device for monitoring absolute loss between two points in an optical network, said optical network comprising an optical transmission path having a head end and at least one remote end, the optical network carrying data traffic using at least light of a first wavelength, wherein the monitoring device comprises:
an optical signal returning device at a first location in the optical network;
a reference optical signal returning device at a second location in the optical network;
optical test equipment for communicating with the head end, the optical test equipment optically connected to the optical network at a location spaced apart from at least the first location and configured to:
send a test signal at a test wavelength, different from the first wavelength; and
receive a first returning signal from the optical signal returning device and a second returning reference signal from the reference optical signal returning device, both the first returning signal and the second returning reference signal being derived from the test signal; and
compare the first returning signal and the second returning reference signal to derive therefrom a value related to the absolute loss between the first and second locations in the optical network, wherein at least one of the optical signal returning device and the reference optical signal returning device is a wavelength selective device, wherein the test signal travels with the data signal remains spaced apart from the reference optical signal returning device.

2. The monitoring device according to claim 1 , wherein the optical signal returning device and/or the reference optical signal returning device returns a signal that has a different wavelength than the first wavelength.

3. The monitoring device according to claim 1 , wherein the test signal is an OTDR signal.

4. Monitoring device for monitoring absolute loss between two points in an optical network, said network comprising an optical transmission path having a head end and at least one remote end, an optical signal returning device at a first location in the network and a reference optical signal returning device at a second location in the network, wherein the monitoring device comprises:
equipment for communicating with the head end for sending a test signal and for receiving a first returning signal from the optical signal returning device and a second returning reference signal from the reference optical signal returning device, both the first returning signal and the second returning reference signal being derived from the test signal, the equipment having means for comparing the first returning signal and the second returning reference signal and for deriving therefrom a value related to the absolute loss between the first and second locations in the network, wherein at least one of the optical signal returning device and the reference optical signal returning device is a wavelength selective device, wherein the equipment is coupled to the reference optical signal returning device via an asymmetrical splitter, the asymmetrical splitter splitting the test signal into a first portion sent to the optical signal returning device and a second portion sent to the reference optical signal returning device, first portion being unequal to the second portion, wherein the first portion of the test signal exits the asymmetrical splitter along a first axis and the second portion of the test signal exits the asymmetrical splitter along a second axis, the first returning signal from the optical signal returning device entering the asymmetrical splitter along the first axis and the second returning reference signal from the reference optical signal returning device entering the asymmetrical splitter along the second axis.

5. The monitoring device according to claim 1 , wherein the equipment is coupled to the optical network via a WDM.

6. The monitoring device according to claim 1 , wherein the optical network comprises a splitter and branch fibers connected to the splitter.

7. The monitoring device according to claim 1 wherein at least one of the optical signal returning device and the reference optical signal returning device is a passive device.

8. An optical fiber network comprising the monitoring device according to claim 1 .

9. Unidirectional method of monitoring absolute loss between two points in an optical network, said optical network comprising an optical transmission path having a head end and at least one remote end, an optical signal returning device at a first location in the optical network and a reference optical signal returning device at a second location in the optical network, the optical network carries data traffic using at least light of a first wavelength, wherein the method comprises:
sending a test signal from the head end at a test wavelength different from the first wavelength while the optical network is carrying the data traffic using at least light of the first wavelength,
receiving a first returning signal from the optical signal returning device and a second returning reference signal from the reference optical signal returning device, both the first returning signal and the second returning reference signal being derived from the test signal, and the data signal remains spaced apart from the reference optical signal returning device,
comparing the first returning signal and the second returning reference signal and
deriving therefrom a value related to the absolute loss between the first and second locations in the optical network, wherein at least one of the first returning signal and the second reference returning signal is a wavelength selective signal.

10. The method according to claim 9 , further comprising
coupling the equipment to the reference optical signal returning device via an asymmetrical splitter, the asymmetrical splitter splitting the test signal into a first portion sent to the optical signal returning device and a second portion sent to the reference optical signal returning device, first portion being unequal to the second portion.

11. The method according to claim 9 , wherein the test signal is an OTDR signal.

12. A machine readable signal storage device tangibly storing a computer program product that when executed on a processing engine, can provide a method of monitoring absolute loss between two points in an optical network, wherein the optical network comprises an optical transmission path having a head end and at least one remote end, an optical signal returning device at a first location in the optical network and a reference optical signal returning device at a second location in the optical network, the optical network carries data traffic using at least light of a first wavelength, the computer program product providing for:
sending a test signal from the head end at a test wavelength different from the first wavelength while the optical network is carrying the data traffic using at least light of the first wavelength,
receiving a first returning signal from the optical signal returning device and a second returning reference signal from the reference optical signal returning device, both the first returning signal and the second returning reference signal being derived from the test signal, the data signal remains spaced apart from the reference optical signal returning device,
comparing the first returning signal and the second returning reference signal and deriving therefrom a value related to the absolute loss between the first and second locations in the optical network, wherein at least one of the first returning signal and the second reference returning signal is a first wavelength s

Assignees

• Daems Daniel
• CommScope Connectivity Belgium BVBA

Inventors

• Daems Daniel

Classifications

• H04B10/071 Primary

  using a reflected signal, e.g. using optical time domain reflectometers [OTDR] · CPC title

• G01M11/3136

  for testing of multiple fibers · CPC title