In order to complete the high-speed wavelength demodulation of output signal of Fiber Bragg Grating (FBG) sensing unit, an edge filter wavelength demodulation system is established in this paper. This wavelength demodulation system uses a reference FBG as an edge filter. First, the mathematical model of the system is built based on demodulation principle. In the model, the spectrum of FBG is simplified to Gaussian distribution. The model describes the relationship between the output voltage and input wavelength differential. According to the research above, the hardware and software of this demodulation system are developed. Besides, a calibration method of the system is proposed. Finally, experiments are carried out. According to the experiment results, the sensitivity of the wavelength demodulation system is 6.3mV/pm. When the demodulation frequency is up to 5kHz, the wavelength resolution is 0.23pm. This system has many advantages, such as simple structure, low cost and high resolution in high speed wavelength demodulation
Regardless of many researches done in recent years, most wind turbines are still unable to reach their design lifetime <sup></sup>. Failures in the gearbox, especially in the planetary stage, have been a major cause of reliability problems in the modern wind energy turbine system. The following paper proposes a fault diagnosis method based on the strain signal of the ring gear. First, the strain signal is collected from the side of the ring gear using FBG sensors in normal condition and faulty condition. Then the collected strain signal is processed and analyzed. In the time-domain analysis, traditional statistical indicators like Peak to Peak, Kurtosis, Crest factor and Peak value are adopted. The analysis results show the effectiveness of the proposed method for identifying tooth crack fault of the ring gear.