Optic fibre sensing

Patent metadata

Field	Value
Publication number	US-10928546-B2
Application number	US-201615532202-A
Country	US
Kind code	B2
Filing date	Feb 5, 2016
Priority date	Feb 6, 2015
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A fibre sensing apparatus ( 100 ) comprises an interrogation unit ( 104 ) to interrogate a sensing fibre with optical radiation, and to detect an optical signal returned from the fibre, and processing circuitry ( 114 ). A portion of the fibre may be excited with a test signal. The processing circuitry comprises an assessment module ( 115 ) to analyse the optical signal returned from the excited portion of fibre, and to determine at least one operational characteristic of the apparatus based on the detected optical signal.

First claim

The invention claimed is:

1. A method of assessing at least one operational characteristic of a sensing apparatus comprising:
interrogating an optical fibre with optical radiation;
detecting optical radiation returned from a portion of an optical fibre which is excited by an acoustic test signal having at least one attribute of an anticipated signal, wherein the acoustic test signal comprises at least one of a variation in frequency or a variation in amplitude corresponding to the anticipated signal, and wherein the assessment module is configured to compare at least one characteristic derived from the detected optical signal from the excited portion to a signature characterising at least one acoustic signal or acoustic signal type, and wherein the interrogation unit is configured to recalibrate if the detected optical signal from the excited portion does not match at least one acoustic signal or acoustic type; and
analysing the detected optical radiation from the excited portion to determine at least one operational characteristic of the sensing apparatus.

2. A method according to claim 1 in which the test signal has one or more known characteristics and the step of analysing comprises determining if the detected optical signal is indicative of an acoustic signal having at least one known characteristic of the test signal.

3. A method according to claim 1 which comprises determining if the determined characteristic meets at least one predetermined standard.

4. A method according to claim 3 comprising, if a determined characteristic does not meet at least one predetermined standard, changing at least one operational parameter of the sensing apparatus.

5. A method according to claim 1 in which the sensing apparatus is for use in monitoring a system and the test signal comprises at least one acoustic signal having at least one attribute of at least one anticipated acoustic signal for the system.

6. A method according to claim 5 in which at least one anticipated acoustic signal is a signal indicative of one or more of (i) a fault, or (ii) a safety critical scenario in the system.

7. A method according to claim 1 in which the step of analysing the detected signal comprises at least one of:
determining if an acoustic signal has been received;
comparing at least one characteristic of a detected signal to at least one characteristic based on the test signal; or
comparing a detected signal to one or more characteristic based on a signal type.

8. A method according to claim 1 further comprising carrying out acoustic sensing for portions of the fibre other than the portion of the fibre which is excited by the acoustic test signal by detecting optical radiation returned from such other portions of the fibre.

9. A method according to claim 1 in which the test signal comprises at least one of (i) a characteristic amplitude and/or frequency, (ii) a characteristic varying amplitude and/or frequency, (iii) a series of pulsed vibrations capable of providing a digital signal, (iv) a pseudo random signal, or (v) a repeated sequence of acoustic impulses.

10. A method according to claim 1 which further comprises applying a test signal.

11. A method according to claim 10 which comprises varying at least one characteristic of the test signal over time.

12. A fibre sensing apparatus comprising:
an interrogation unit to interrogate a sensing fibre with optical radiation, and to detect an optical signal returned from the fibre, and
processing circuitry comprising an assessment module to analyse the optical signal returned from a portion of the fibre which is excited with an acoustic test signal having at least one attribute of an anticipated signal, and to determine at least one operational characteristic of the apparatus based on the detected optical signal;
wherein the assessment module is configured to compare at least one characteristic derived from the detected optical signal from the excited portion to a signature characterising at least one acoustic signal or acoustic signal type;
wherein the interrogation unit is configured to recalibrate if the detected optical signal from the excited portion does not match at least one acoustic signal or acoustic type; and
wherein the acoustic test signal comprises at least one of a variation in frequency or a variation in amplitude corresponding to the anticipated signal.

13. Fibre sensing apparatus according to claim 12 further comprising:
sensing fibre; and
an actuator to excite the portion of the fibre with the acoustic test signal.

14. Fibre sensing apparatus according to claim 13 in which the assessment module is arranged to compare at least one characteristic derived from the detected optical signal from the excited portion to at least one predetermined characteristic.

15. Fibre sensing apparatus according to claim 14 in which the assessment module is arranged to compare at least one characteristic of the detected optical signal from the excited portion to one or more characteristics derived from an actuator test signal.

16. Fibre sensing apparatus according to claim 13 in which the actuator comprises a vibrational acoustic source.

17. Fibre sensing apparatus according to claim 13 in which the actuator comprises a controller arranged to control the acoustic signal generated thereby.

18. Fibre sensing apparatus according to claim 12 in which the operational characteristic is at least one of:
an indication that the sensing apparatus is functional; or
an indication that the sensing apparatus is non functional.

19. Fibre sensing apparatus according to claim 12 in which the operational characteristic is at least one of:
an indication of the sensitivity of the apparatus over at least one operational range; or
an indication of the calibration of the apparatus.

20. Fibre sensing apparatus according to claim 12 in which the assessment module is arranged to analyse the signal detected and, based on the analysis, optimize interrogation unit performance over one or more operational range.

21. Fibre sensing apparatus according to claim 12 in which the assessment module is arranged to analyse the signal detected and, if a determined characteristic does not meet at least one predetermined standard, the apparatus is arranged to vary at least one operational parameter based on the analysis.

22. Fibre sensing apparatus according to claim 12 in which the assessment module is arranged to produce an output indicative of at least one operational characteristic.

23. Fibre sensing apparatus according to claim 12 in which the processing circuitry further comprises an alert module, and, if the determined operational characteristic(s) do not meet a predetermined standard, the alert module is arranged to produce an alert.

24. Fibre sensing apparatus according to claim 12 in which the interrogation unit is arranged to carry out sensing in relation to other fibre portions.

25. Fibre sensing apparatus according to claim 12 which comprises a Distributed Acoustic Sensor (DAS).

Assignees

• Optasense Holdings Ltd

Inventors

• Lewis Andrew

Classifications

• B61L27/57

  for vehicles or trains, e.g. trackside supervision of train conditions · CPC title

• B61L1/166

  Optical · CPC title

• B61L1/20

  Safety arrangements for preventing or indicating malfunction of the device, e.g. by leakage current, by lightning · CPC title

• G01V8/16 Primary

  using optical fibres · CPC title

• G01V13/00

  Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00 · CPC title