A high speed quasi-distributed demodulation method based on the microwavephotonics and the chromatic dispersion effect is designed and implemented forweak fiber Bragg gratings (FBGs). Due to the effect of dispersion compensationfiber (DCF), FBG wavelength shift leads to the change of the differencefrequency signal at the mixer. With the way of crossing microwave sweep cycle,all wavelengths of cascade FBGs can be high speed obtained by measuring thefrequencies change. Moreover, through the introduction of Chirp-Z and Hanningwindow algorithm, the analysis of difference frequency signal is achieved verywell. By adopting the single-peak filter as a reference, the length disturbanceof DCF caused by temperature can be also eliminated. Therefore, the accuracy ofthis novel method is greatly improved, and high speed demodulation of FBGs caneasily realize. The feasibility and performance are experimentally demonstratedusing 105 FBGs with 0.1% reflectivity, 1 m spatial interval. Results show thateach grating can be distinguished well, and the demodulation rate is as high as40 kHz, the accuracy is about 8 pm.
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