Based on the spectrum of long-period fiber grating in liquid level measurement

In this paper, we demonstrate an effective method to measure the liquid level using long period fiber grating (LPFG). First it theoretically analyzes the change rule of LPFG resonant wavelength and coupling efficiency with the surroundings fluctuating. Then the method of wavelength demodulation using long-period fiber grating to measure liquid level is proposed. LPFG, Broad band source and optical spectrum analyzer set a experimental platform. The result shows that the resonance wavelength shifts while LPFG immersed in liquid vary, and it is linear to the length of LPFG in liquid. Moreover, the method of transmission power demodulation is discussed. In contrast, the former is linear, repeatability, reliable, straight-forward, high accuracy, but certainly not the latter. The former experimental data indicates that the method can work well with high accuracy which can reach up to 0.3 mm.