Self-Referenced Optical Fiber Sensor and Related Sensor Network

• US 20110019179A1
• Filed: 03/16/2009
• Published: 01/27/2011
• Est. Priority Date: 03/18/2008
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Huignard, Jean-Pierre, Molin, Stephanie, Morvan, Loic, Dolfi, Daniel, Doisy, Martine, Pocholle, Jean-Paul
• Granted Patent: US 8,290,316 B2
• Time in Patent Office: Days
• US Class Current: 356/32
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35312 using a Fabry Perot
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01D 5/35354 Sensor working in reflection
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: H01S 3/0007 Applications not otherwise provided for working metals or other materials by laser beam B23K26/00; using photons to produce a reactive propulsive thrust F03H3/00; optical recording of measured values in general G01D15/14; optics in general G02B; holographic processes or apparatus G03H; optical marking or sensing of data record carriers G06K7/10 - G06K7/14, G06K15/12; injection heating of plasma by laser H05H1/22; acceleration of neutral particles by electromagnetic wave pressure H05H3/04
• CPC Class Codes: H01S 3/06712 Polarising fibre; Polariser
• CPC Class Codes: H01S 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/0809 Two-wavelenghth emission
• CPC Class Codes: H01S 3/10 Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
• CPC Class Codes: H01S 3/1053 Control by pressure or deformation
• CPC Class Codes: H01S 3/1067 using pressure or deformation

Abstract

The general field of the invention is that of fiber-optic sensors comprising at least one measurement optical fiber having an optically pumped doped amplifying medium, the optical characteristics of which are sensitive to a physical quantity, the fiber having at least one Bragg grating. The fiber is designed so as to generate, in the amplifying medium, two optical waves having different optical frequencies that propagate in the same direction after reflection on the Bragg grating and are emitted by the amplifying medium, the two optical frequencies depending on the physical quantity. The two waves may be generated using either a birefringent polarization-maintaining fiber or a DBR (Distributed Bragg Reflector) laser cavity. Notably, this sensor may be used as a hydrophone.

Claims

1. A fiber-optic sensor for measuring a physical quantity, comprising at least:

a measurement optical fiber having at least one amplifying medium and a Bragg grating;

optical pumping means for pumping said amplifying medium to ensure population inversion of said medium;

wherein;

the optical fiber is a birefringent polarization-maintaining fiber, having two eigenaxes having respective refractive indices n_e and n_o;

the sensor includes means for emitting an optical wave, called a probe wave, said wave creating, by interference with itself after reflection on the Bragg grating, a dynamic gain grating generating two optical waves having different optical frequencies, the two optical frequencies depending on the physical quantity; and

the sensor includes means for analyzing the frequency difference between the two optical waves.

2. The fiber-optic sensor as claimed in claim 1, wherein the fiber-optic sensor is a strain sensor, the physical quantity to be measured being a mechanical strain applied to the fiber.

3. The fiber-optic sensor as claimed in claim 2, wherein the fiber-optic sensor is a hydrophone.

4. The fiber-optic sensor as claimed in claim 2, wherein the fiber-optic sensor has a structure substantially in the form of a cylinder around which the measurement optical fiber is wound, said cylinder being made of a material having the lowest possible Young'"'"'s modulus so as to amplify the strain exerted on the fiber.

5. The fiber-optic sensor as claimed in claim 4, wherein the material of the cylinder is polydimethylsiloxane.

6. An array of fiber-optic sensors as claimed in claim 1 wherein all the sensors are placed in series on one and the same optical fiber and in that the array includes a wavelength multiplexer placed between said fiber and the analysis means.

7. An array of fiber-optic sensors as claimed in claim 3, wherein all the sensors are placed in series on one and the same optical fiber and in that the array includes a wavelength multiplexer placed between said fiber and the analysis means.