Device and method for spatially resolved measurement of temperature and/or strain by Brillouin scattering

Abstract

Device for spatially resolved measurement of temperature and/or strain by Brillouin scattering, with a laser light source ( 1 ) for generating a laser radiation, an optical fiber ( 5 ) used for the measurement, into which the laser radiation can be coupled in and from which Brillouin signals generated by Brillouin scattering can be coupled out, sensors for detecting the coupled-out Brillouin signals, evaluators for determining spatially resolved from the detected Brillouin signals the temperature and/or strain of sections of the optical fiber ( 5 ), a polarization beam splitter ( 10, 11 ) capable of splitting the coupled-out Brillouin—signals into two components ( 12, 13 ) having mutually different polarizations, and an optical coupler ( 16, 17 ) for admixing a laser radiation to the Brillouin signal.

1 . A device for spatially resolved measurement of temperature and/or strain by Brillouin scattering, comprising
 at least one laser light source ( 1 ) configured to produce laser radiation,   an optical fiber ( 5 ) used for the measurement, into which the laser radiation can be coupled in and from which the Brillouin signals generated based on the Brillouin scattering can coupled out,   sensors configured to capture the coupled-out Brillouin signals,   evaluator configured to determine spatially resolved from the captured Brillouin signals the temperature and/or strain at least of sections of the optical fiber ( 5 ),   at least one optical polarization beam splitter ( 10 ,  11 ) configured to split the coupled-out Brillouin signals into two components ( 12 ,  13 ) with mutually different polarizations,   at least one optical coupler ( 16 ,  17 ) configured to admix to the Brillouin signal a laser radiation.   
     
     
         2 . The device according to  claim 1 , wherein the sensors can detect the components ( 12 ,  13 ) separate from each other. 
     
     
         3 . The device according to  claim 1 , wherein the device comprises two optical couplers ( 16 ,  17 ), each configured to admix a laser radiation to the two components ( 12 ,  13 ) of the Brillouin signal separated by the at least one optical polarization beam splitter ( 10 ,  11 ). 
     
     
         4 . The device according to  claim 1 , wherein the device comprises a beam splitter ( 2 ) configured to split off a portion ( 4 ) from the laser radiation of the laser light source ( 1 ) used for exciting the Brillouin scattering prior to coupling into the optical fiber used for the measurement, wherein this portion ( 4 ) of the laser radiation can be admixed to the Brillouin signal. 
     
     
         5 . The device according to  claim 1 , wherein the device comprises a second laser light source ( 27 ) capable of producing the laser radiation, which can be admixed to the Brillouin signal. 
     
     
         6 . The device according to  claim 5 , wherein the second laser light source ( 27 ) has a frequency different from the first laser light source ( 1 ). 
     
     
         7 . The device according to  claim 6 , wherein the device comprises an O-PLL ( 28 ), which stabilizes the different frequency between the first and the second laser light source ( 1 ,  27 ). 
     
     
         8 . The device according to  claim 1 , wherein the device comprises components for measuring Rayleigh scattering. 
     
     
         9 . The device according to  claim 8 , wherein the components for measuring the Rayleigh scattering comprise an additional laser light source ( 34 ) that is different from the first laser light source ( 1 ). 
     
     
         10 . The device according to  claim 1 , wherein the device comprises an optical fiber serving as a reference or a section of the optical fiber used for the measurement ( 5 ) serving as a reference, which is designed, as a reference coil ( 39 ) and generates a constant Brillouin signal at least over a predetermined length, so that this Brillouin signal can be detected with the sensor means and used to calibrate the sensitivity. 
     
     
         11 . A method for spatially resolved measurement of temperature and/or strain by Brillouin scattering, comprising the following steps:
 generating a laser radiation,   coupling for the measurement of temperature and train the laser ad on into an optical fiber ( 5 ),   coupling out of the optical fiber ( 5 ) Brillouin signals generated in the optical fiber ( 5 ) by the laser radiation,   splitting the coupled-out Brillouin signals into two components ( 12 ,  13 ) having mutually different polarizations,   detecting the two components ( 12 ,  13 ) of the coupled-out Brillouin signals,   evaluating and determine spatially resolved the temperature and/or strain at least of sections of the optical fiber ( 5 ) from the detected components ( 12 ,  13 ) of the Brillouin signals.   
     
     
         12 . The method according to  claim 11 , further comprising the step of
 detecting the two components ( 12 ,  13 ) of the coupled-out Brillouin signals are separately from each other.   
     
     
         13 . The method according to  claim 11 , further comprising the step of
 generating two output signals ( 25 ,  26 ) from the two detected components ( 12 ,  13 ) of the Brillouin signals, which are then suitably combined to obtain a polarization-independent output signal for determining the temperature and/or the strain,   
     
     
         14 . The device according to  claim 5 , wherein the frequency different from the first laser light source ( 1 ) about by 10 GHz. 
     
     
         15 . The device according to  claim 8 , wherein the additional laser light source ( 34 ) is also different from an optionally present second laser light source ( 27 ) for the generation of the laser radiation to be admixed to the Brillouin signal. 
     
     
         16 . The method according to  claim 11 , wherein the two generated output signals ( 25 , 26 ) are suitably combined before or after a digitization to obtain a polarization-independent output signal for determining the temperature and/or the strain.