Method and system for optical fiber sensing

• US 10,641,622 B2
• Filed: 04/24/2019
• Issued: 05/05/2020
• Est. Priority Date: 06/16/2014
• Status: Active Grant

• Current Assignee: Ariel Scientific Innovations, Ltd.
• Original Assignee: Ariel Scientific Innovations, Ltd.
• Inventors: Sternklar, Shmuel, Mermelstein, David
• Primary Examiner(s): Luu, Thanh
• Application Number:
  US16/392,692
• Publication Number:
  US 20190250015A1
• Time in Patent Office: 377 Days
• CPC Class Codes: G01D 5/35361 using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
• CPC Class Codes: G01D 5/35377 Means for amplifying or modifying the measured quantity
• CPC Class Codes: G01D 5/36 Forming the light into pulses
• CPC Class Codes: G01M 11/3109 Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR
• CPC Class Codes: G01M 11/319 Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/302 in an optical fibre

Abstract

A method of optical sensing is disclosed. The method comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal; coupling the backscattered signal into a second optical fiber, spatially separated from the first optical fiber; and optically amplifying the backscattered signal in the second optical fiber, thereby generating a sensing signal.

Claims

1. A method of optical sensing, comprising:

coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal;

coupling said backscattered signal into a second optical fiber, spatially separated from said first optical fiber by at least one optical coupler; and

optically amplifying said backscattered signal in said second optical fiber, thereby generating a sensing signal;

wherein said optically amplifying comprises employing at least one of Brillouin amplification and Raman amplification by coupling a CW pump light beam into said second optical fiber.

2. The method according to claim 1, further comprising transmitting said sensing signal into a signal analyzer, for analyzing said sensing signal so as to identify a change in at least one property along said first fiber.

3. The method according to claim 2, wherein said at least one property is selected from the group consisting of a mechanical property, a thermal property and a chemical property.

4. The method according to claim 1, further comprising transmitting said sensing signal into a signal analyzer, for analyzing said sensing signal so as to identify a spatially-resolved change in at least one property along said first fiber.

5. The method according to claim 1, wherein said excitation optical signal is a pulsed optical signal.

6. The method according to claim 5, wherein a characteristic duty cycle of said pulsed optical signal is less than 10%.

7. The method according to claim 1, wherein said optical amplification is an on-resonance optical amplification.

8. The method according to claim 1, wherein said optical amplification is an off-resonance optical amplification.

9. The method according to claim 8, wherein a detuning frequency of said off-resonance optical amplification is from about 0.1X to about 0.9X, where X is a characteristic on-resonance bandwidth of said optical amplification.

10. A system for optical sensing, comprising:

a light source system configured for generating an excitation optical signal selected to induce Rayleigh backscattering, and a CW pump light beam selected to amplify said Rayleigh backscattering by at least one of Brillouin amplification and Raman amplification;

an arrangement of optical couplers arranged for coupling said excitation optical signal into a first optical fiber thereby providing a backscattered signal, and for coupling said backscattered signal and said pump light beam into a second optical fiber, spatially separated from said first optical fiber by at least one of said optical couplers, to thereby generate an optically amplified sensing signal; and

a signal analyzer, for analyzing said sensing signal so as to identify a change in at least one property along said first fiber.

11. The system according to claim 10, wherein said signal analyzer is configured for analyzing said sensing signal so as to allow identifying a spatially-resolved change in at least one property along said first fiber.

12. The system according to claim 10, wherein said at least one property is selected from the group consisting of a mechanical property, a thermal property and a chemical property.

13. The system according to claim 10, wherein said excitation optical signal is a pulsed optical signal.

14. The system according to claim 13, wherein a characteristic duty cycle of said pulsed optical signal is less than 10%.

15. The system according to claim 10, wherein said pump light beam is selected to induce an on-resonance optical amplification.

16. The system according to claim 10, wherein said pump light beam is selected to induce an off-resonance optical amplification.

17. A method of optical sensing, comprising:

coupling an excitation optical signal into an optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal;

optically amplifying said backscattered signal in said optical fiber, thereby generating a sensing signal; and

transmitting said sensing signal into a signal analyzer, for analyzing said sensing signal so as to identify a change in at least one property along said first fiber;

wherein said optically amplifying is by pump light beam at intensity I that is satisfying gI≥

K+2α

, said α

being a Rayleigh scattering coefficient characteristic to said fiber, said g being a gain coefficient characteristic to said fiber, and said K being a predetermined variation rate which larger than −

0.01 m<sup>−

1</sup>.