A Method for Determining Fiber Bragg Resonance Wavelength Based on Periodic Modulation

Abstract

The invention discloses a fiber grating Bragg resonance wavelength determination method based on period modulation. According to the invention, by imposing periodical strain on a cantilever beam, a periodically changed reflection spectrum is obtained; by carrying out Fourier transform on curves of change of an intensity value at each wavelength point of each spectrum along with the modulation time, the specific value of second harmonic generation components and fundamental components therein is solved; by use of the specific value at each wavelength point, the spectrum of narrowing down of half-height is reconstructed, so the position of a peak point of the fiber grating reflection spectrum is quite precisely acquired; and high precision demodulation of the fiber grating is achieved. Compared with the prior art, the spectrum of narrowing down of half-height is reconstructed finally, and demodulation precision is further improved.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a method for accurately determining the Bragg resonance wavelength of an optical fiber grating based on periodic modulation. Background technique [0002] Fiber Bragg Grating (FBG) sensors are widely used in many fields due to their advantages of small size, light weight, strong anti-electromagnetic interference and easy modulation. The demodulation of the fiber grating sensor adopts wavelength coding, which makes the demodulation of the fiber grating free from the fluctuation of the light intensity of the light source and the loss caused by other devices, and has become the most widely used demodulation technology. FBG obtains changes in parameters such as temperature, vibration, dynamic and static strain, etc. by demodulating wavelength information. The common demodulation methods are: spectrum method, edge filter method, interference method, tunable narrowband light sourc...

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Problems solved by technology

[0004] In order to solve the problems encountered by the traditional demodulation method, the present invention proposes a method for determining the fiber Bragg resonance wavelength based on periodic modulation, which does not directly demodulate the original spectrum, but imposes a periodic Vibration, obtain a periodically changing spectrum, reconstruct a spectrum with the same central wavelength as the previous reflection spectrum, use the principle that the extreme point of the curve corresponds to the point where the first derivative is zero, and directly calculate the reconstruction The position where the first derivative of the spectral curve is zero, ultimately improving the accuracy of the demodulation

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