AC Modulation Low Coherence Interferometric Demodulation System
A low-coherence interference and demodulation system technology, applied in the field of optical fiber sensing, can solve the problem of low measurement accuracy and achieve the effect of improving sensing accuracy
Active Publication Date: 2016-03-30
TIANJIN UNIV
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However, due to the large half-height width of the curve in the low-coherence interference fringe, the curve near the extreme point is relatively flat, so the measurement accuracy is often low only by the envelope method and the centroid method.
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[0020] The specific implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples.
[0021] like figure 1 As shown, it is a system diagram of low-coherence interference demodulation using a birefringent crystal with electro-optical characteristics according to the present invention. Here, the method will be described in conjunction with the measurement of external atmospheric pressure.
[0022] The light emitted by the broadband light source system LED) 1 is introduced into the F-P sensor 3 through the coupler 2. The F-P sensor is a sensitive element that senses the external atmospheric pressure and converts the change of atmospheric pressure into an optical path difference. The two surfaces of the F-P cavity constitute a sensing interferometer , the optical signal modulated by the F-P sensor is derived from the outlet of the coupler 2, and sequentially transmitted through the self-focusing c...
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The invention discloses an alternating-current-modulation type low-coherence interference demodulation system and a demodulation method thereof. The low-coherence interference demodulation system comprises a broadband light source (1), a coupler (2), an F-P sensor (3), a self-focusing collimating lens (4), a polarizer (5), an alternating-current signal source (6), a modulatable birefringent wedge (7), an analyzer (8) and a linear array CCD (charge coupled device). When optical path difference generated from the modulatable birefringent wedge (7) is matched with that generated from the F-P sensor (3), low-coherence interference fringes are generated from local domains of the linear array CCD (9); the electrical source (6) can provide sinusoid alternating voltage for the modulatable birefringent wedge (7) capable of being modulated to realize modulation of refringence of o-light and e-light, so that position of the low-coherence interference fringes as a modulation result in the linear array CCD (9) can be further changed. Compared with the prior art, the system and the method have the advantages that sensing accuracy is improved; the low-coherence interference demodulation system is used not only for the low-coherence interference demodulation, but also for sensing demodulation by utilizing extreme value points of a curve, and an extreme value point can be modulated.
Description
technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a low-coherence interference demodulation method based on a modulating birefringent crystal optical wedge. Background technique [0002] Low-coherence interferometry can overcome the phase ambiguity problem in laser interferometry, and the measurement range is no longer limited to λ / 4. Theoretically, it has an unlimited measurement range, and can measure many absolute physical quantities with high precision and a large range, making low-coherence interferometry Technology has been widely used in the field of optical fiber sensing, such as the measurement of static physical quantities (temperature, pressure, displacement and refractive index), three-dimensional appearance detection of objects and optical coherence tomography. [0003] Locating the envelope peak position or center peak position of the low-coherence interference fringes is a commonly used method to obtain the tr...
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IPC IPC(8): G01D5/26
Inventor 刘铁根江俊峰张学智刘琨王双尹金德
Owner TIANJIN UNIV