As a new type of DBR tunable laser, Modulated Grating Y-branch (MG-Y) laser has great advantages in the field of optical fiber sensing and demodulation. However, due to the complex tuning relationship of MG-Ylaser and the wavelength switching interval of 50GHz cannot meet the requirements of the existing FBG demodulators, this paper proposes a characterization method of MG-Y laser based on k-means clustering combined with combinatorial optimization algorithm, which the final test time is about 8 hours. Theoretical and experimental tests show that the designed MG-Y laser has an wavelength interval of 0.02nm in the 40nm range, with a better wavelength stabilitythan0.006nm and an output power flatness within 1.6dBm. Compared with the direct traversal current method, this method reduces the amount of test data by 90% and improves efficiency by more than 50%.
An identical weak reflection FBGs demodulation system based on a FDML laser is proposed. The laser is developed to output a continuous wavelength-swept spectrum in the scanning frequency of 120 kHz over a spectral range of more than 10nm at 1.54 μm. Based on this high-speed wavelength-swept light and the optical transmission delay effect, the demodulation system obtains the location and wavelength information of all identical weak FBGs by the reflected spectrum within each scanning cycle. By accessing to a high-speed FPGA processing module, continuous demodulation of 120 kHz is realized. The system breakthroughs the bandwidth of the laser to expand the sensors capacity and greatly improves the demodulation speed of a TDM sensing network. The experiments show the system can distinguish and demodulate the identical weak FBGs and measure the 4 kHz vibration at 120 kHz demodulation speed.
A high-speed fiber Bragg grating (FBG) interrogation system is realized by using the high-speed sweep characteristic of Distributed feedback (DFB) laser to constitute a high-speed wavelength-swept laser. To solve the problem of narrow scanning width of the DFB laser and low reuse capacity of the system, the method of building a time division multiplexing (TDM) sensor network with identical weak fiber Bragg grating is proposed. By using the transmission delay of light between the gratings to separate the grating reflection spectrum in time-domain and demodulating the reflection scanning spectrum of each grating to realize the wavelength demodulation. Experimental results show that, under a constant interrogation frequency on 100kHz of the system, 10 identical weak FBGs with the center wavelength of 1553.7nm and reflectivity of 1% have achieved demodulation in a single fiber. And within the temperature range from 25°C to 79°C the linearity of each FBG’s center wavelength varying with the temperature reaches 0.99 .
This paper presents a spiral bevel gear strain measurement using optical fiber gratings. High-speed and heavy-duty spiral bevel gear (SBG) is the key component of the power transmission of intersection axes. Its dynamic mechanical properties greatly influence the working performance of the machine. By building a strain detecting system based on FBG demodulation, we carried out real-time measurements of the distributed strain in the SBG with different torques and different rotation speed. The experimental results show a complete strain waveform from gear-in to gear-out, verifying the feasibility of measuring the strain of SBG using optical fiber gratings.
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