In order to realize the real-time on-line monitoring of motor rotor temperature, a Fiber Bragg Grating (FBG) temperature sensing system using fiber optic rotary joint to transmit signals was built. The effects of the acceleration of the rotor and the mounting angle of the sensors chain on the central wavelength of the FBG were studied. The temperature measurement test of a rotating shaft was carried out. The following conclusions can be drawn. The central wavelength variation of the FBG is related to the linear acceleration of the rotor surface, the density and thickness of the grating coating. For the rotor whose surface linear acceleration is within 100m/s 2 , when the thickness of the coating is within 100μm, the effect of acceleration on the center wavelength of the polyimide-coated or gold-coated FBG can be ignored. For the motors with higher linear acceleration, in order to prevent the impact on the temperature measurement accuracy, the angle between the FBG sensors chain and the rotating shaft is preferably controlled within 20°. For the motors with lower linear acceleration, the installation angle can be compromised according to the rotor surface structure. The experiment shows that the FBG temperature measurement system can run stably and measure the temperature change accurately during the variable speed process of the rotor. Compared with other rotor temperature measurement systems, the FBG temperature measurement system has a simple composition, and the sensors chain is light and small. It is a very promising rotor temperature monitoring system.
The flank array of fiber laser hydrophone takes the fiber laser hydrophone as the sensitive element. A new type of fiber laser hydrophone with double diaphragms is designed, the results of anechoic tank test show that the average sound pressure sensitivity of fiber laser hydrophone is -136.9dB in the middle and high frequency range of 2.5 ~ 10kHz, and the fluctuation amplitude of sensitivity is not more than ±0.5dB. Taking the hydrophone as the sensing unit, a 64-element fiber laser hydrophone flank array is constructed based on wavelength division / time division multiplexing technology and passive homodyne interference detection technology. The lake test shows that the beam forming of the flank array is stable, the target bearing estimation is correct, and the root mean square error of horizontal target bearing estimation is 1.68°.
In order to design and fabricate high-performance fiber gratings and distributed feedback fiber lasers, the monitoring of AC and DC components of the core refractive index modulation during grating engraving was studied. Based on the Bragg equation and the coupled mode theory, the average variation and fringe visibility of the core refractive index modulation were calculated by monitoring the grating center wavelength and transmission spectrum depth. The grating engraving experiment of boron-germanium co-doped fiber, germanium-doped fiber, and erbium-doped photosensitive fiber was carried out and their refractive index modulation data was obtained. Experiment also showed that the larger pulse energy would make the average variation of core refractive index modulation increases and the fringe visibility decreases.
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