High-speed demodulation of weak fiber Bragg gratings based on microwave photonics and chromatic dispersion

Abstract

A high-speed demodulation technique based on microwave photonics and chromatic dispersion is proposed for distributed weak fiber Bragg gratings (FBGs). A broadband light modulated with a frequency-swept microwave is reflected by FBGs, and the reflected signal mixes with the original microwave to produce a beat frequency. A dispersion compensation fiber (DCF) changes the beat frequency within the FBG wavelength range. With a crossing microwave sweep, all wavelengths of cascade FBGs can be quickly decoded by measuring the change of the beat frequency. The Chirp-Z + Hanning window algorithm helps to analyze the beat frequency in a single cycle. By adopting the single-peak filter as a reference, the DCF thermal drift can be also eliminated. Therefore, the wavelength detection accuracy is improved, and a higher demodulation speed of 40 kHz can be realized. We have demonstrated 105 FBGs with 0.1% reflectivity and 1 m interval, with the achieved accuracy of 8 pm.

5,6-Dimethyl-2-[(5-methyl-1,2-oxazol-3-yl)methyl]-1-(prop-2-en-1-yl)-1H-1,3-benzodiazole

“…Benzimidazole derivatives have been shown to possess various biological activities including anti-histaminic (Al Muhaimeed, 1997) anti-ulcerative (Scott et al, 2002) and anti-allergic (Nakano et al, 2000). In addition, they are effective against the human cytomegalovirus (HCMV) (Zhu et al, 2000) and are also efficient selective neuropeptide Y Y1 receptor antagonists (Zarrinmayeh et al, 1998). Isoxazole derivatives represent a unique class of nitrogen and oxygen-containing five-membered heterocycles and are the components of a variety of natural products and medicinally useful compounds (Sperry & Wright, 2005).…”

Combining SDAE Network with Improved DTW Algorithm for Similarity Measure of Ultra-Weak FBG Vibration Responses in Underground Structures

“…According to the recent research progress of distributed optical fiber-sensing technology [1][2][3][4][5][6][7], the requirement for time-and space-continuous monitoring for the geotechnical underground structures [8] has gradually become feasible. Comparisons between various commonly used sensors for underground structure monitoring were reported in [9,10], which revealed that the ultra-weak fiber optic Bragg grating (FBG) array [11] can be used for both static and dynamic measurements [12][13][14]. In the field of dynamic 2 of 15 measurement, it was reported that the distributed vibration detected by the ultra-weak FBG array can be applied to track train and identify incursion [10,15].…”

Identification of Ground Intrusion in Underground Structures Based on Distributed Structural Vibration Detected by Ultra-Weak FBG Sensing Technology

“…However, all the research is still limited to static indicators. Actually, ultra-weak FBG array is also adept to perform dynamic monitoring [28] in addition to the above positive characteristics usually witnessed in static measurement. From the reports in [15,29,30,31,32], the comparison results in Table 1 reveal that the ultra-weak FBG array can be not only used for both static and dynamic measurements, but also has higher SNR than that of DAS sensors.…”