High-Speed Demodulation of weak FBGs Based on Microwave Photonics and Chromatic Dispersion

TL;DR

This paper presents a novel high-speed demodulation technique for weak fiber Bragg gratings using microwave photonics and chromatic dispersion, achieving 40 kHz speed and 8 pm accuracy.

Contribution

It introduces a new method combining microwave photonics, chromatic dispersion, and advanced signal processing for rapid, accurate FBG demodulation.

Findings

Demonstrated demodulation rate of 40 kHz.

Achieved wavelength measurement accuracy of about 8 pm.

Successfully distinguished 105 FBGs with high fidelity.

Abstract

A high speed quasi-distributed demodulation method based on the microwave photonics and the chromatic dispersion effect is designed and implemented for weak fiber Bragg gratings (FBGs). Due to the effect of dispersion compensation fiber (DCF), FBG wavelength shift leads to the change of the difference frequency signal at the mixer. With the way of crossing microwave sweep cycle, all wavelengths of cascade FBGs can be high speed obtained by measuring the frequencies change. Moreover, through the introduction of Chirp-Z and Hanning window algorithm, the analysis of difference frequency signal is achieved very well. By adopting the single-peak filter as a reference, the length disturbance of DCF caused by temperature can be also eliminated. Therefore, the accuracy of this novel method is greatly improved, and high speed demodulation of FBGs can easily realize. The feasibility and performance are experimentally demonstrated using 105 FBGs with 0.1% reflectivity, 1 m spatial interval. Results show that each grating can be distinguished well, and the demodulation rate is as high as 40 kHz, the accuracy is about 8 pm.