System and method for monitoring environmental effects using optical sensors

• US 20040245441A1
• Filed: 01/27/2004
• Published: 12/09/2004
• Est. Priority Date: 01/27/2003
• Status: Active Grant

• Current Assignee: Newport Corporation (MKS Instruments Incorporated)
• Original Assignee: Bookham Incorporated (Oclaro (North America), Inc.)
• Inventors: Nguyen, Hoang, Pieterse, Jan-Willem, Cordes, Andrew H., Abriam, Rosemary O.
• Granted Patent: US 7,119,325 B2
• Time in Patent Office: Days
• US Class Current: 250/227.14
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01D 5/35354 Sensor working in reflection
• CPC Class Codes: G01J 3/1895 using fiber Bragg gratings or gratings integrated in a waveguide
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/433 Modulation spectrometry; Derivative spectrometry

Abstract

An apparatus and method for determining a physical parameter affecting an optical sensor or a number of sensors in a network. The apparatus uses a narrow linewidth source at an emission wavelength λ_e and an arrangement for varying the emission wavelength λ_e of the radiation. An analysis module with curve fitting is used to generate a fit to the response signal obtained from the optical sensor. The physical parameter is determined form the fit rather than from the response signal. The apparatus can be employed with Bragg gratings, etalons, Fabry Perot elements or other optical sensors.

Claims

1. An apparatus for determining a physical parameter affecting an optical sensor, said apparatus comprising:

a) a source for emitting a radiation having a narrow linewidth at an emission wavelength λ

_e;

b) a means for varying said emission wavelength λ

_e;

c) an optical path for guiding said radiation to said optical sensor and guiding a response radiation from said optical sensor;

d) a detector for generating a response signal to said response radiation; and

e) an analysis module for fitting said response signal and determining therefrom said physical parameter.

2. The apparatus of claim 1, wherein said source is a narrow linewidth laser.

3. The apparatus of claim 2, wherein said narrow linewidth laser is a tunable laser selected from the group consisting of External Cavity Diode lasers, Distributed Bragg Reflector lasers, fiber lasers.

4. The apparatus of claim 1, wherein said analysis module comprises a curve fitting module for fitting a best fit curve to said response signal.

5. The apparatus of claim 1, wherein said optical sensor is selected from the group consisting of Bragg Gratings and Fabry-Perot elements.

6. The apparatus of claim 5, wherein said optical path comprises an optical fiber and said Bragg Grating is a Fiber Bragg Grating.

7. The apparatus of claim 1, wherein said means for varying said emission wavelength λ

_e comprise a laser tuner.

8. The apparatus of claim 7, wherein said laser tuner comprises a scanner for scanning said emission wavelength λ

_e.

9. The apparatus of claim 7, wherein said laser tuner comprises a sweeper for sweeping said emission wavelength λ

_e.

10. The apparatus of claim 1, wherein said optical path comprises a waveguide.

11. The apparatus of claim 1, further comprising a tap for tapping said radiation and a wavelength meter for monitoring said emission wavelength λ

_e.

12. A method for determining a physical parameter affecting an optical sensor, said method comprising:

a) emitting a radiation having a narrow linewidth at an emission wavelength λ

_e;

b) providing an optical path for said radiation to said optical sensor and for a response radiation from said optical sensor;

c) varying said emission wavelength λ

_e;

d) generating a response signal from said response radiation; and

e) determining said physical parameter from a fitting of said response signal.

13. The method of claim 12, wherein said optical sensor produces said response radiation by a varying a property of said radiation, said property being selected from the group consisting of transmittance, reflectance, absorbance and polarization.

14. The method of claim 12, wherein said emission wavelength λ

_e is varied continuously.

15. The method of claim 14, wherein said emission wavelength λ

_e is swept.

16. The method of claim 12, wherein said emission wavelength λ

_e is varied discontinuously.

17. The method of claim 16, wherein said emission wavelength λ

_e is scanned.

18. The method of claim 12, wherein said fitting comprises a best curve fit of said response signal.

19. The method of claim 18, wherein said fitting further comprises an analysis method selected from the group consisting of peak detection, Full Width Half Maximum (FWHM) determination, centroid detection.

20. The method of claim 18, wherein said fitting comprises a fit selected from the group consisting of a polynomial fit, a Lorentzian fit and a Gaussian fit.

21. The method of claim 12, wherein said physical parameter is selected from the group consisting of temperature, strain and pressure.

22. The method of claim 12, further comprising tapping said radiation and monitoring said emission wavelength λ

_e.