Research On Miniature Low Power Spaceborne Fiber Bragg Grating Interrogation System And Key Technologies

With the rapid development of aerospace technology,the health monitoring and intelligent development requirements of aerospace structures are imminent.The traditional environmental monitoring methods based on thermistors and strain gauges have been unable to meet the health of spaceborne structures with large capacity,light weight and low power consumption requirement for monitoring.Fiber Bragg Grating(FBG)sensing technology has the characteristics of electromagnetic immunity,compact and lightweight,high reliability and sensitivity,and capabilities for distributed sensing and multiplexing.And has a wide range of applications in the aerospace field.In view of many technical difficulties such as miniaturization and low power consumption of fiber grating sensing and demodulation technology in aerospace applications,the research on a miniature low-power spaceborn FBG sensing and interrogation system based on Modulation Grating Y Branch(MG-Y)tunable semiconductor laser source is carried out.The main research contents are as follows:1.The temperature and strain sensing principle of FBG and the composition of the sensing system are studied to provide a theoretical basis for the wavelength-type demodulation method.In order to solve the problem of limited application of FBG in micro,low-power consumption and large capacity in the spaceborn environment.Various schemes of FBG demodulation and multiplexing technology are analyzed,and a demodulation method based on tunable semiconductor laser source which can be applied in the aerospace field is determined.2.The structure and control method of the tunable semiconductor laser are studied.The light source of the demodulation system is the electrically tunable semiconductor laser which has the advanges of monolithic integration,fast tuning speed and large demodulation capacity.Based on the discussion of MG-Y tunable control principle,through the comparison and analysis of two types of spaceborne optical fiber sensor demodulation systems,a interrogation method of 1*N-coupler SDM / WDM multiplexing system with tunable laser source is proposed.By studying of the mechanism of tunable laser source and FBG with different spectrum shapes,the basic parameters and wavelength calculation formula of the demodulator are determined.A characterization method of spectral measurement using a wavelength meter is proposed,and a research scheme of “wavelength-Current” precise correspondence is constructed,which solves the difficulty of deteriming the look-up table of the multi-tuned section MG-Y laser source.3.Aiming at the complex control problem of multi-tuned section lasers,the micro,low-power consumption and high-precision control method of MG-Y laser source demodulator is studied.A four-channel FBG interrogation system scheme based on ARM is proposed.The monolithic integrated constant current source system controlled by ARM and a high-precision temperature control module system are proposed.Which can achieve high-resolution,high-stability output of scanning light source.Future analyze the response range of the optoelectronic acquisition system,a photoelectric acquisition system based on the logarithmic amplifier with a wide dynamic range has been developed.System power supply and a serial communication circuit have been designed,and an FBG demodulator suitable for spaceborne environment was developed.4.A demodulation software system scheme based on MG-Y light source is proposed.The function of the underlying driver software under the ARM embedded system is studied,and the fast selection of “wavelength-current” look-up table and the fast acquisition of FBG reflection signal are realized.Aiming at the problem of traditional demodulation algorithm with consumes more resources,wavelength jitter and light source instability,a dynamic threshold with dual-centroid algorithm used in the embedded hardware system,the DGA algorithm used on host computer and a correction method based on FP etalon are proposed,which improves the accuracy and stability of wavelength demodulation.High-precision demodulator with low power consumption and wide dynamic range was realized.5.The experimental platform of FBG demodulation was established,and the performance test verification of the FBG interrogator was completed.The spectral characteristics of USFBG,core and cladding-integrated FBG,cascaded FBG and polarization-maintaining FBG were tested respectively.To meet the needs of aerospace applications,the above-mentioned FBG with different reflection spectra were inscribed by 800 nm femtosecond pulsed lasers respectively,and the temperature and longitudinal strain characteristics were tested.The developed interrogator has realized accurate demodulation of wavelength drift.In this paper,the FBG wavelength demodulation technology of the tunable laser source method is developed,and a miniature fiber-optic grating demodulator with low-power consumption based on MG-Y tunable semiconductor light source is proposed.By testing the characteristics of FBG sensors inscribed by femtosecond with different reflection spectrum shapes,it meets the requirements of miniaturization and low-power consumption spaceborne FBG sensing demodulation system.It provides a new technical means to solve the problem of safety,efficiency and intelligent perception of aerospace structure health monitoring.