Bragg grating temperature/strain fiber sensor having combination interferometer/spectrometer output arrangement
First Claim
1. An arrangement for optically determining an absolute physical state variable in an optical fiber with the aid of an optical spectral analyzer for determining different Bragg wavelengths of fiber gratings which have different mean wavelengths and at which the light traversing the optical fiber is reflected, as well as means for calculating the absolute physical quantity from the determined Bragg wavelengths, comprising:
- an optical spectral analyzer in the form of a spectrometer having an imaging, spectrally dispersive element;
a first linear receiver arrangement;
a first input light bundle being arranged with reference to said dispersive element such that the light spectrally dispersed at said dispersive element is projected onto said first linear receiver arrangement;
a second linear receiver arrangement;
an additional second input light bundle being directed onto said dispersive element in said spectrometer, whose spectrally dispersed light falls onto said second linear receiver arrangement, parallel to the first one;
a broadband light source;
said two input light bundles being fed light from said broadband light source which has been reflected by at least two optical fiber gratings with different mean wavelengths;
an interferometer arrangement with phase modulation and different arm lengths being present at least in the light path of the second input light bundle upstream of the spectral dispersion by said dispersive element;
said interferometer arrangement having an evaluation section which is arranged downstream of said second receiver arrangement assigned to said input light bundle;
a signal processing module for determining the absolute Bragg wavelengths of the optical fiber gratings and for calculating a physical variable dependent thereon being connected downstream of said first receiver arrangement; and
phase demodulation modules arranged downstream of said second receiver arrangement being provided for evaluating interferometer signals for determining relative changes in the Bragg wavelengths of the optical fiber gratings, and for calculating the relative changes in a physical quantity.
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Accused Products
Abstract
An arrangement for simultaneous optical determination of temperature and strain fluctuations in an optical fiber for precisely determining the changes in environmental influences and/or fiber loads is disclosed. The arrangement performs two different measurement tasks of the absolute measurement of a stationary quantity, such as temperature and the relative, high-resolution measurement of quickly varying quantities of fluctuation processes with comparable accuracy in a single optical The arrangement which is achieved using a spectrometer with an imaging, spectrally dispersive element, a first input light bundle being arranged with reference to the dispersive element such that the light spectrally dispersed at the dispersive element is projected onto a first linear receiver The arrangement, and an additional second input light bundle is directed onto the dispersive element in the spectrometer, whose spectrally dispersed light falls onto a second linear receiver The arrangement, parallel to the first one, the two input light bundles are fed light from a broadband light source which has been reflected by at least two optical fiber gratings with different mean wavelengths, and an interferometer The arrangement with phase modulation and different arm lengths is present at least in the light path of the second input light bundle upstream of the spectral dispersion by means of the dispersive element, whose evaluation is performed via the second receiver. The arrangement by means of phase modulation modules with reference to relative changes in the Bragg wavelengths, while a CCD evaluation module for determining the absolute Bragg wavelengths of the optical fiber gratings is arranged downstream of the first receiver The arrangement.
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Citations
24 Claims
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1. An arrangement for optically determining an absolute physical state variable in an optical fiber with the aid of an optical spectral analyzer for determining different Bragg wavelengths of fiber gratings which have different mean wavelengths and at which the light traversing the optical fiber is reflected, as well as means for calculating the absolute physical quantity from the determined Bragg wavelengths, comprising:
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an optical spectral analyzer in the form of a spectrometer having an imaging, spectrally dispersive element; a first linear receiver arrangement; a first input light bundle being arranged with reference to said dispersive element such that the light spectrally dispersed at said dispersive element is projected onto said first linear receiver arrangement; a second linear receiver arrangement; an additional second input light bundle being directed onto said dispersive element in said spectrometer, whose spectrally dispersed light falls onto said second linear receiver arrangement, parallel to the first one; a broadband light source; said two input light bundles being fed light from said broadband light source which has been reflected by at least two optical fiber gratings with different mean wavelengths; an interferometer arrangement with phase modulation and different arm lengths being present at least in the light path of the second input light bundle upstream of the spectral dispersion by said dispersive element; said interferometer arrangement having an evaluation section which is arranged downstream of said second receiver arrangement assigned to said input light bundle; a signal processing module for determining the absolute Bragg wavelengths of the optical fiber gratings and for calculating a physical variable dependent thereon being connected downstream of said first receiver arrangement; and phase demodulation modules arranged downstream of said second receiver arrangement being provided for evaluating interferometer signals for determining relative changes in the Bragg wavelengths of the optical fiber gratings, and for calculating the relative changes in a physical quantity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification