OPTICAL METHOD AND DEVICE FOR A SPATIALLY RESOLVED MEASUREMENT OF MECHANICAL PARAMETERS, IN PARTICULAR MECHANICAL VIBRATIONS BY MEANS OF GLASS FIBERS
The invention relates to a device for a spatially-resolved measurement of mechanical parameters, in particular mechanical vibrations, comprising at least one optical fiber ( 3 ) for measuring at least one mechanical parameter with spatial resolution, at least one laser light source ( 1 ), the light from which can be coupled into the optical fiber ( 3 ), wherein in the optical fiber ( 3 ), backscattered portions of the light generated by the laser light source ( 1 ) can be coupled out of the optical fiber ( 3 ), tuning means ( 2 ) that can tune the laser light source ( 1 ) within a time period of less than 50 ms, detection means that can detect the portions of the backscattered light that are coupled out of the optical fiber ( 3 ), and analysis means that can determine at least one mechanical parameter of the optical fiber ( 3 ) in a spatially-resolved manner from the captured portions of the backscattered light.
1 . A method for spatially resolved measurement of mechanical vibrations, comprising the following steps:
generating light with a laser light source ( 1 );
tuning the laser light source ( 1 ) within a time period of less than 50 ms;
coupling the light into an optical fiber ( 3 );
coupling the portions of the light that were coupled into the optical fiber and are backscattered in the optical fiber ( 3 ) out of the optical fiber ( 3 );
measuring the portions of the backscattered light coupled out of the optical fiber ( 3 ); and
evaluating the measured portions of the backscattered light for spatially resolved determination of at least one mechanical parameter of the optical fiber ( 3 ).
2 . The method according to claim 1 , wherein the tuning step causes beat signals which are evaluated.
3 . The method according to claim 1 , wherein the method is an OFDR method (Optical Frequency Domain Reflectometry).
4 . The method according to claim 1 , wherein the tuning step occurs within a time period of less than 10 ms.
5 . The method according to claim 1 , wherein the tuning range is between 0.1 GHz and 50 GHz.
6 . The method according to claim 1 , wherein the coupling step provides portions of the backscattered light coupled out of the optical fiber ( 3 ) which are measured with a sampling rate of at least 1 Ms/s.
7 . The method according to claim 1 , further comprising the step of evaluating the measured portions including a Fourier transform.
8 . The method according to claim 7 , the wherein the Fourier transform is performed with between 1024 and 131,072 sampling points.
9 . The method according to claim 7 , wherein the Fourier transform is performed in a time interval of less than 10 ms.
10 . A device for spatially resolved measurement of mechanical parameters, comprising:
at least one optical fiber ( 3 ) for the spatially resolved measurement of at least one mechanical parameter;
at least one laser light source ( 1 ), the light of which is coupled into the optical fiber ( 3 ), wherein the portions of the light generated by the laser light source ( 1 ) and backscattered in the optical fiber ( 3 ) is coupled out of the optical fiber ( 3 );
tuning means ( 2 ) capable of tuning the portions of the backscattered light coupled out of the optical fiber ( 3 );
analyzer for determining from the measured portions of the backscattered light the at least one mechanical parameter of the optical fiber ( 3 ) with spatial resolution.
11 . The device according to claim 10 , wherein the laser light source ( 1 ) is constructed such that the bandwidth of the light emitted by the laser light source ( 1 ) is less than 500 kHz.
12 . The device according to claim 10 , wherein the laser light source ( 1 ) is constructed such that the coherence length of the light emitted by the laser light source ( 1 ) is longer than 1 km.
13 . The device according to claim 10 , wherein the analyzer comprises a digital signal processor (DSP) or a field programmable gate array (FPGA).
14 . The device according to claim 13 , wherein the analyzer comprises an A/D converter ( 11 ) arranged before the digital signal processor (DSP) or the field programmable gate array (FPGA).
15 . The device according to claim 10 , wherein the tuning means ( 2 ) comprise a wavelength modulator provided with a piezo-based control.
16 . The method according to claim 4 , wherein the tuning step occurs within a time period of less than 5 ms.
17 . The method according to claim 4 , wherein the tuning step occurs within a time period between 0.8 ms and 1.2 ms.
18 . The method according to claim 5 , wherein the tuning range is 0.5 GHz and 20 GHz.
19 . The method according to claim 5 , wherein the tuning range is between 1 GHz and 10 GHz.
20 . The method according to claim 6 , wherein the sampling rate is at least 10 Ms/s.
21 . The method according to claim 6 , wherein the sampling rate is at least 100 Ms/s.
22 . The method according to claim 7 , wherein the Fourier transform is performed with between 4096 and 65,536 sampling points.
22 . The method according to claim 7 , wherein the Fourier transform is performed with sampling points equal to 2 n , with n=1, 2, 3, . . . .
23 . The method according to claim 7 , wherein the Fourier transform is performed in a time interval of less than 10 ms.
24 . The method according to claim 7 , wherein the Fourier transform is performed in a time interval of less than 2 ms.
25 . The method according to claim 7 , wherein the Fourier transform is performed in a time interval of between 0.2 ms and 1.0 ms.
26 . The device for spatially resolved measurement of mechanical parameters according to claim 1 , wherein the mechanical parameter are mechanical oscillations.
27 . The device according to claim 11 , wherein the bandwidth of the light emitted by the laser light source ( 1 ) is less than 200 kHz.
28 . The device according to claim 12 , wherein the bandwidth of the light emitted by the laser light source ( 1 ) is less than 100 kHz.
29 . The device according to claim 12 , wherein the laser light source ( 1 ) is longer than 5 km.
30 . The device according to claim 12 , wherein the laser light source ( 1 ) is between 10 km and 100 km long.
31 . The device according to claim 15 , wherein the wavelength modulator is a fiber Bragg grating (FBG).