Water level measurement via polymer-fiber Bragg grating sensor

In this paper, a new design of sensor head to monitor water level inside the tank based on fiber Bragg grating (FBG) was demonstrated. The sensor head consisted of an FBG placed under a very thin polymer plastic sheet layer. This sensor head acts as a sensitive diaphragm to sense water level based on hydrostatic pressure caused by the liquid weight. The hydrostatic pressure imposed on the sensor head produced strain in the embedded FBG, which caused a shift in Bragg wavelength detected by the optical spectrum analyzer. A calibration curve to relate liquid level and shift in the Bragg wavelength was constructed. A linear relationship between the shift in Bragg wavelength and the water level up to 70 cm height with a sensitivity of 2 pm/cm is achieved in this work

Comparison of water level measurement performance for two different types of diaphragm using fiber bragg grating based optical sensors

A sensor head incorporating a diaphragm was designed and fabricated for water level measurement. It operates in the range of 0-70 cm column height, equivalent to a pressure in atmospheric pressure of 0-6. 86 kPa. The fiber Bragg grating (FBG) was attached on the two types of diaphragm to detect the change in the hydrostatic pressure caused by water at different levels. The diaphragms performance by comparing the sensitivity in within the mentioned range. Optical spectrum analyzer (OSA) was used to record the shift in the Bragg wavelength λB at different water level. The sensitivity of water level measurement using a silicone rubber diaphragm found to be 9.81 pm/cm for 70 cm in water level, while the sensitivity for polymer plastic diaphragm found to be 2 pm/cm at the same leve

A comparative study of nanocrystalline SiC thin films on multimode optical fiber sensors, synthesized via DBD-NTP and 150 MHz VHF-PECVD

In this study, nanocrystalline SiC films were successfully synthesized on the surface of multimode fiber (MMF) sensors using 150 MHz very-high-frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) and dielectric barrier discharge nonthermal plasma (DBD-NTP) methods. The effects of the different utilized methods and various deposition times on the microstructure and chemical composition of the deposited SiC films were investigated For both methods, the SiC film thickness increased with increased deposition time. The dependency of sensitivity on the deposition time and thickness of SiC films was studied by investigating the effects of refractive index and temperature variation on the response of the MMF sensors. The SiC films deposited by 150 MHz VHF-PECVD showed more uniformity and higher sensitivity compared to those deposited using DBD-NTP. Using VHF-PECVD with a deposition time of 1 min yielded the lowest thickness (54.06 nm) and therefore the highest sensitivity (0.0240 dB/°C) for the SiC-deposited MMF sensors. Thus, the VHF-PECVD method may be a better option than DBD-NTP for the deposition of thin SiC films to improve the sensitivity of the MMF sensors