Study of a liquid level sensor based on a tilted long period grating imprinted on a plastic optical fiber

A tilted long period grating (LPG) fabricated on a commercial plastic optical fiber (POF) by a simple mechanical die-press-print method was proposed for liquid-level sensing. The liquid level sensing performances of the sensor with different structural parameters were studied theoretically and experimentally. The LPG fabricated on the POFs with different diameters (0.25, 0.50, and 1.00mm) were evaluated. And the liquid-level sensing performances of the so-obtained LPGs imprinted on a thinner POF with a diameter of 0.25mm, and with the period of 300 mu m, the tilted angle of 0-30 degrees and the groove depth of 30-75 mu m were investigated. The results show that when the LPG with the tilted angle of 30 degrees and the groove depth of 75 mu m, the highest sensitivity of -0.4631dB/mm was obtained in the level range of 20mm. In addition, the influence of temperature on the liquid level sensing performances of sensors was also studied. It was found that the sensitivity of the sensor was decreased with the increase of temperature.