UNIDIRECTIONAL ABSOLUTE OPTICAL ATTENUATION MEASUREMENT WITH OTDR

• US 20110268438A1
• Filed: 12/10/2009
• Published: 11/03/2011
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: Commscope Connectivity Belgium BVBA (CommScope Holding Company, Inc.)
• Original Assignee: Tyco Electronics Raychem BVBA (TE Connectivity Ltd. (United Kingdom))
• Inventors: Daems, Daniel
• Granted Patent: US 9,419,707 B2
• Time in Patent Office: Days
• US Class Current: 398/16
• CPC Class Codes: G01M 11/3136 for testing of multiple fibers
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]

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.

Claims

1. 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.

2. The monitoring device according to claim 1, wherein the network carries data traffic using at least light of a first wavelength and 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. The monitoring device according to claim 1, wherein the equipment is coupled to the reference optical signal returning device via an asymmetrical splitter.

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

6. The monitoring device according to claim 1, wherein the 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 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 method comprises:

sending a test signal from the head end,

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,

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 network, wherein at least one of the first returning signal and the second reference returning signal is a first wavelength selective signal.

10. The method according to claim 9, further comprising transmitting data traffic using at least light of a second wavelength and the first wavelength selective signal has a different wavelength than the first wavelength.

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

12. An optical device comprising:

a first port for connection to a first optical fiber,

a second port for connection to a second optical fiber,

a third port connected to an optical signal returning device, wherein when an optical signal is fed to the first port, the optical device returns a signal back through the first port that is wavelength selective.

13. 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 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 network and a reference optical signal returning device at a second location in the network, the computer program product providing for:

sending a test signal from the head end,

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,

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 network, wherein at least one of the first returning signal and the second reference returning signal is a first wavelength selective signal.

14. A machine readable signal storage device storing the computer program product of claim 13.