| There are various demodulation methods for fiber grating sensors.Interferometric demodulation methods have the characteristics of high resolution,large dynamic range,and good high-frequency response,and have become one of the most studied demodulation methods.The method of interferometric phase demodulation was first applied to the optical fiber sensing of laser light sources,and later evolved into the field of grating sensing.The interference light source also changed from a laser to a narrow-bandwidth light source with a certain width.The influence of light source intensity noise and phase noise on the resolution of the demodulation system in interferometric demodulation of the laser light source has been studied before,but the resolution of the grating interference demodulation system is subject to the grating spectrum width and interference in addition to the light source noise.Influence of instrument arm length difference and other structural parameters such as broad-spectrum light source.Therefore,this article starts with the influence of various parameters of the interference demodulation system on the system resolution,and provides an optimization solution to improve the system resolution,which provides an important theoretical basis for the practical design of the interference demodulation system in the future.Firstly,the principle of fiber grating interference demodulation technology based on 3×3 coupler is introduced,the simulation model of the interference demodulation system is given,the factors limiting the dynamic range of the system are discussed,the noise of the light source,the interferometer arm are pointed out The length difference and the grating spectral width are important factors affecting the lower limit of the dynamic range of the demodulation system.Then,theoretically analyze the constraint relationship between each parameter and resolution of the system,and find out the optimal solution of parameter selection through simulation to achieve high resolution of the system.The optimization scheme shows that the system resolution can be changed from The magnitude of 10-5 nm is increased to the magnitude of 10-6 nm.This simulation has guiding significance for subsequent optimization experiments.Finally,a fiber grating interference demodulation system based on a 3×3 coupler was built.The performance of the system was tested and experimental verification was performed according to the simulation rule.The results show that the experimental results are in good contrast with the simulation results,so different parameters can be quantitatively obtained.The influence of the noise floor of the demodulation system is conducive to the practical application of the demodulation system in the future.Moreover,it was found that there is a difference in intensity noise at different wavelengths of the optical fiber amplified spontaneous emission light source(ASE)light source.This finding has guiding significance for the selection of outdated center wavelengths of gratings in the future. |
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