Identification and location of fiber optic cables

• US 6,650,798 B2
• Filed: 11/06/2002
• Issued: 11/18/2003
• Est. Priority Date: 09/21/1998
• Status: Expired due to Fees

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Russell, Stuart John, Lewis, Andrew Biggerstaff, Dakin, John Philip
• Primary Examiner(s): Ullah, Akm Enayet
• Assistant Examiner(s): CONNELLY, MICHELLE R
• Application Number:
  US10/288,431
• Publication Number:
  US 20030052258A1
• Time in Patent Office: 377 Days
• Field of Search: 385/11, 385/147, 356/5.01, 356/5.14, 356/73.1
• US Class Current: 385/11
• CPC Class Codes: G02B 6/562 locatable, e.g. using magnetic means

Abstract

In order to identify a fiber optic cable (10) a beam (14) of polarised light is caused to pass down the cable to a first site (A) at which an electromagnetic field (24) is applied to the cable (10). The electromagnetic field (24) traverses the cable (10) in an essentially transverse direction and has a time-varying component orientated along the length of the cable (10) at the first site (A), with the component varying so that the line integral thereof along the cable (10) is non-zero. This results in a variation in the polarisation of the light, which can then be detected by a polarisation discriminator (20) at a second site (B), thereby to identify the cable (10).

Claims

1. An apparatus for identifying a fibre-optic cable, comprising:

an optical detector, connected to said cable, to detect a modulation applied to a beam of light, travelling on said cable, emitted from a remote light source with a predetermined polarization, said modulation of said beam comprising a variation in said polarization of said beam received from said cable caused by the application, at a remote location, of a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable; and

an output circuit, connected to said detector, to output signals indicative of the detected variation of polarisation.

2. An apparatus according to claim 1, wherein the detector is arranged to detect modulation caused by an electromagnetic field with a frequency in the range of 10 KHz to 200 MHz.

3. An apparatus according to claim 1, wherein the detector is arranged to detect two frequencies of modulation.

4. An apparatus according to claim 3, wherein the detector is arranged to detect a first frequency of modulation, and a second frequency of modulation with a frequency of less than one tenth of the first frequency.

5. An apparatus according to claim 1, further comprising:

a signal processing unit to process the signal output by the detector; and

a further output circuit to output further signals indicative of whether or not a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable has been applied to said cable at a remote location.

6. An apparatus according to claim 5, wherein said signal processing unit further comprises:

a receiving unit to receive information indicative of the signal applied to the light at a remote source thereby to indicate whether said transverse electro-magnetic field has been applied to said cable.

7. An apparatus according to claim 6, wherein the signal processing unit is arranged to differentiate between modulations applied at two frequencies received at the detector.

8. An apparatus for identifying a fibre-optic cable, comprising a detector to detect one or more modulations applied to a beam of light carried on said cable and emitted from a remote light source with a predetermined polarization, said modulation of said beam comprising a variation in said polarization of said beam received from said cable caused by the application, at a remote location, of a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable, and to output signals indicative of the detected variation of polarisation.

9. An apparatus according to claim 8, further comprising a processor to process the signal output from the detector and to output further signals indicative of whether or not a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable has been applied to said cable at a remote location.

10. An apparatus according to claim 8, wherein the apparatus further comprises a receiver to receive information indicative of the signal applied to the light at a remote source thereby to indicate whether said transverse electro-magnetic field has been applied to the cable.

11. An apparatus for identifying a fibre-optic cable, comprising:

optical detecting means for detecting a modulation applied to a beam of light, travelling on said cable, emitted from a remote light source with a predetermined polarization, said modulation of said beam comprising a variation in said polarization of said beam received from said cable caused by the application, at a remote location, of a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable; and

outputting means, connected to said detecting means, for outputting signals indicative of the detected variation of polarisation.

12. An apparatus according to claim 11, further comprising processing means for processing the signals output from the detector;

and

outputting means for outputting further signals indicative of whether or not a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable has been applied to said cable at a remote location.

13. An apparatus according to claim 11, wherein said processing means further comprises receiving means to receive information indicative of the signal applied to the light at a remote source thereby to indicate whether said transverse electro-magnetic field has been applied to said cable.

14. A method of identifying a fibre-optic cable comprising:

detecting a modulation applied to a beam of light emitted from a remote light source with a predetermined polarization, said modulation of said beam comprising a variation of said polarisation of said beam caused by application, at a remote location, of a transverse electro-magnetic field having a time varying component with non-zero line integral orientated along the light path of said cable, and outputting signals indicative of the detected variation in polarisation.

15. A method according to claim 14, wherein electro-magnetic radiation with a frequency in the range of 10 kHz to 200 MHz is detected.

16. A method according to claim 14 wherein light detected has had a further modulation applied prior to the application of said transverse electro-magnetic field.

17. A method according to claim 16, wherein the frequency of the further modulation is less than one tenth of the frequency of said electro-magnetic field.

18. A method according to claim 14, further comprising using the detected modulation to indicate whether or not a signal has been applied to said cable.

19. A method according to claim 18, further comprising receiving information indicative of a signal applied to the light at a remote light source.

20. A method according to claim 19, wherein said detected light is compared with said information indicative of the signal applied to the light by a remote generator thereby to indicate whether said transverse electro-magnetic field has been applied to said cable.