Brillouin optoelectronic measurement method and apparatus

• US 9,116,119 B2
• Filed: 12/22/2010
• Issued: 08/25/2015
• Est. Priority Date: 12/22/2010
• Status: Active Grant

• Current Assignee: Omnisens SA (Prysmian SPA)
• Original Assignee: Omnisens SA (Prysmian SPA)
• Inventors: Le Floch, Sbastien
• Primary Examiner(s): Lyons, Michael A
• Assistant Examiner(s): Smith, Maurice
• Application Number:
  US13/991,249
• Publication Number:
  US 20130265569A1
• Time in Patent Office: 1,707 Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/35364 using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
• CPC Class Codes: G01L 1/242 the material being an optical fibre
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence

Abstract

The present invention relates to a Brillouin optoelectronic measurement method comprising the step of, providing a signal (s1) in an optical fiber (100), wherein said signal (s1) is time-frequency coded. The present invention further relates to a corresponding device for use in such a method.

Claims

1. A Brillouin optoelectronic measurement method comprising steps of:

defining a signal (s1), wherein said signal (s1) is time-frequency coded so that the signal comprises at least two code-words, and each code-word comprises at least two pulses or code-letters, and each pulse or code-letter of a code-word is associated with a different frequency;

providing said signal in an optical fibre;

measuring the optical fibre response to said signal; and

monitoring physical characteristics of an engineering structure based in part on the provided signal.

2. The Brillouin optoelectronic measurement method according to claim 1, further comprising steps of:

defining the at least two code-words, each code-word comprising at least two code-letters;

building a coding matrix (S) using the defined at least two code-words;

time-frequency coding said signal by using said coding matrix (S);

building an inverse matrix (S<sup>−

1</sup>) of the coding matrix (S); and

based on said measuring and on said inverse matrix, decoding said optical fibre response.

3. The Brillouin optoelectronic measurement method according to claim 2, wherein the coding matrix is a symmetry that is a rotation of sub-matrixes.

4. The Brillouin optoelectronic measurement method according to claim 2, wherein the measured fibre response is expressed as a matrix constructed by performing repeated acquisition of backscattered signal.

5. The Brillouin optoelectronic measurement method according to claim 1, further comprising a step of time-frequency coding each one of said two or more wavelengths when said signal (s1) comprises two or more wavelengths.

6. The Brillouin optoelectronic measurement method according to claim 1, wherein said optical system is configured to measure a stimulated Brillouin effect, the method further comprising steps of:

transmitting a first signal (s1) in a first direction along the optical fibre, wherein the first signal (s1) is a time-frequency coded signal;

transmitting a second signal (s2) in a second direction along the optical fibre, such that the first and second signals interact within the optical fibre and form a combined signal; and

probing the optical fibre at one or more probe points to measure the combined signal.

7. The Brillouin optoelectronic measurement method according to claim 1, wherein said optical system is configured to measure a spontaneous Brillouin backscattering effect, the method further comprising steps of,

transmitting a first signal (s1) in a first direction along the optical fibre, wherein the first signal (s1) is a time-frequency coded signal;

and

probing the optical fibre (100) at one or more probe points to measure a backscattered signal.

8. The method according to claim 1, further comprising a step of identifying irregularities in the optical fibre based on one or more characteristics of a measured combined signal.

9. An optoelectronic measurement device suitable for use in a Brillouin optoelectronic measurement method, the device comprising:

calculating means configured to define at least two code-words, each code-word comprising at least two code-letters, and each pulse or code-letter of a code-word is associated with a different frequency;

a transmitter configured to provide said signal in an optical fibre when carrying out the Brillouin optoelectronic measurement method; and

measurement means configured to measure the optical fibre response to said signal.

10. The optoelectronic measurement device according to claim 9, further comprising:

calculating means suitable for defining the at least two code-words, each code-word comprising at least two code-letters, for building a coding matrix (S) by using the defined at least two code-words and for calculating the inverse matrix (S<sup>−

1</sup>) of the coding matrix (S);

a frequency generator suitable for time-frequency coding said signal by using said coding matrix (S);

a decoder suitable for decoding said optical fibre response based on said measuring and on a inverse matrix (S<sup>−

1</sup>) of the coding matrix (S);

wherein the calculating means builds the inverse matrix (S<sup>−

1</sup>).

11. The optoelectronic measurement device according to claim 10, wherein, said frequency generator is configured for time-frequency coding each one of said two or more wavelengths of a signal which comprises two or more wavelengths.

12. The optoelectronic measurement device according to claim 10, wherein said frequency generator is arranged for changing the frequency at a rate equal to the duration of a code-letter.

13. The optoelectronic measurement device according to claim 12, wherein said duration is in the order of nanoseconds.

14. The optoelectronic measurement device according to claim 9, wherein said optical system is suitable for use in a stimulated Brillouin optoelectronic measurement method, the device further comprising:

a transmitter suitable for transmitting a first signal (s1) in a first direction along the optical fibre, wherein the first signal is a time-frequency coded signal;

a transmitter suitable for transmitting a second signal (s2) in a second direction along the optical fibre, such that the first and second signals interact within the optical fibre and form a combined signal; and

means suitable for probing the optical fibre at one or more probe points to measure the combined signal.

15. The optoelectronic measurement device according to claim 9, wherein said optical system is suitable for use in a spontaneous Brillouin optoelectronic measurement method, the device further comprising:

a transmitter suitable for transmitting a first signal (s1) in a first direction along the optical fibre, wherein the first signal is a time-frequency coded signal;

a detector suitable for probing the optical fibre at one or more probe points to measure a backscattered signal.

16. The optoelectronic measurement device according to claim 9, comprising:

a light source;

an electro-optic modulatory;

a Direct Digital Synthesizer;

an optical fibre;

a circulator; and

a photo-detector.

17. The optoelectronic measurement device according to claim 16, further comprising:

an optical signal processing;

an optical filtering routing;

an insulator.

18. The optoelectronic measurement device according to claim 16, further comprising at least one selected from the group comprising Fibre Bragg grating, A/D digital processing device, mixer.