Brillouin optoelectronic measurement method and apparatus

1. A Brillouin optoelectronic measurement method comprising steps of:

defining a signal (s 1 ), wherein said signal (s 1 ) 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 −1 ) 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 (s 1 ) 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 (s 1 ) in a first direction along the optical fibre, wherein the first signal (s 1 ) is a time-frequency coded signal;

transmitting a second signal (s 2 ) 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 (s 1 ) in a first direction along the optical fibre, wherein the first signal (s 1 ) 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 −1 ) 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 −1 ) of the coding matrix (S);

wherein the calculating means builds the inverse matrix (S −1 ).

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 (s 1 ) 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 (s 2 ) 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 (s 1 ) 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.