TWO-CORE OPTICAL FIBERS FOR DISTRIBUTED FIBER SENSORS AND SYSTEMS

• US 20140042306A1
• Filed: 10/24/2012
• Published: 02/13/2014
• Est. Priority Date: 08/09/2012
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Hoover, Brett Jason, Li, Ming-Jun, Li, Shenping
• Granted Patent: US 9,574,911 B2
• Time in Patent Office: Days
• US Class Current: 250/227.14
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35364 using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
• CPC Class Codes: G01D 5/35383 using multiple sensor devices using multiplexing techniques
• CPC Class Codes: G01J 5/0821 Optical fibres
• CPC Class Codes: G01K 11/32 using changes in transmittance, scattering or luminescence in optical fibres
• CPC Class Codes: G01K 11/3206 at discrete locations in the fibre, e.g. using Bragg scattering
• CPC Class Codes: G01K 11/322 using Brillouin scattering
• CPC Class Codes: G01L 1/242 the material being an optical fibre
• CPC Class Codes: G01N 2021/638 Brillouin effect, e.g. stimulated Brillouin effect
• CPC Class Codes: G01N 21/636 using an arrangement of pump beam and probe beam; using the measurement of optical non-linear properties; non-linear optics per se G02F1/35
• CPC Class Codes: G01N 2201/088 Using a sensor fibre
• CPC Class Codes: G02B 6/02042 Multicore optical fibres
• CPC Class Codes: G02B 6/0281 Graded index region forming part of the central core segment, e.g. alpha profile, triangular, trapezoidal core G02B6/0288, G02B6/0286 take precedence
• CPC Class Codes: G02B 6/0365 arranged - - +

Abstract

A two-core optical fiber is provided for use in Brillouin distributed fiber sensor applications and systems. The two-core fiber includes a first and second core. Each core is configured to exhibit a Brillouin frequency shift greater than 30 Mhz relative to the other core. Further, each core possesses temperature and strain coefficients that differ from the other core. The cores can be configured to produce Brillouin frequency shift levels of at least 30 Mhz relative to one another. These differences in shift levels may be effected by adjustment of the material compositions, doping concentrations and/or refractive index profiles of each of the cores. These optical fibers may also be used in BOTDR- and BOTDA-based sensor systems and arrangements.

Claims

1. A fiber sensor, comprising:

an optical fiber having a first core, a second core, and a cladding surrounding the cores,

wherein each core is configured to exhibit a Brillouin frequency shift of at least 30 Mhz relative to the other core.

2. The fiber sensor according to claim 1, wherein each core is further configured with a refractive index profile that differs from the refractive index profile of the other core.

3. The fiber sensor according to claim 1, wherein each core is further configured with a doping concentration that differs from the doping concentration of the other core.

4. The fiber sensor according to claim 1, wherein each core is configured to exhibit a Brillouin frequency shift of at least 80 Mhz relative to the other core.

5. The fiber sensor according to claim 1, wherein the optical fiber further comprises a refractive index ring configured to surround at least one of the cores.

6. The fiber sensor according to claim 1, wherein the cores are configured such that the relative refractive index of the cores to the cladding is between about 0.2% to 2%.

7. The fiber sensor according to claim 1, wherein the cores have differing compositions.

8. The fiber sensor according to claim 1, wherein the cores have a plurality of operating wavelengths and differing mode field diameters at the plurality of operating wavelengths.

9. The fiber sensor according to claim 1, wherein the optical fiber further comprises a radius of 500 μ

m or less.

10. The fiber sensor according to claim 1, wherein the optical fiber is configured such that crosstalk between the cores is −

20 dB/km or less.

11. The fiber sensor according to claim 2, wherein the refractive index profile for each core is selected from the group consisting of step-shaped and graded index profiles.

12. The fiber sensor according to claim 3, wherein each core is doped with germania.

13. The fiber sensor according to claim 12, wherein each core is doped with approximately 1 to 10 mol % germania.

14. The fiber sensor according to claim 5, wherein a trench separates the refractive index ring from the at least one of the cores.

15. The fiber sensor according to claim 6, wherein the cores are further configured such that the distance between the center of the cores is at least 25 μ

m.

16. The fiber sensor according to claim 15, wherein the distance between the center of the cores is at least 40 μ

m.

17. A Brillouin distributed fiber sensor system, comprising:

an optical fiber having a first core and a second core, wherein each core is configured to exhibit a Brillouin frequency shift of at least 30 Mhz relative to the other core;

at least one pump laser configured to launch test light into the optical fiber; and

a receiver element configured to receive a Brillouin scattered component of test light from each core and evaluate the Brillouin frequency shift of each core based at least in part on the received test light.

18. The Brillouin distributed fiber sensor system according to claim 17, further comprising a beam splitter element configured to direct test light into each core of the fiber.

19. A Brillouin distributed fiber sensor system, comprising:

an optical fiber having a first core and a second core, wherein each core is configured to exhibit a Brillouin frequency shift of at least 30 Mhz relative to the other core;

at least one pump laser configured to launch pump test light into the optical fiber;

at least one probe laser configured to launch probe test light into the optical fiber; and

a receiver element configured to receive pump and probe test light from each core and evaluate the Brillouin frequency shift for each core based at least in part on the received test light.

20. The Brillouin distributed fiber sensor system according to claim 19, further comprising a plurality of beam splitter elements configured to direct the pump and probe test light into each core of the fiber.