Quasi Continuous Measurement Of Plastic Optical Fiber Liquid-level Sensor With Micro-groove

For liquid raw material or product storage and transportation process of liquid level monitoring, as well as for liquid level measurement of aircraft fuel systems, such as the liquid level sensing technology, liquid level measurement have a very wide range of application requirements such aspetroleum, chemicals, aerospace and other fields. Liquid level sensor environments typically are very complex, and often requires strong electromagnetic interference, high pressure, flammable, corrosion resistance, low temperature under special circumstances. So sensor proposed a number of high strict requirements about the ability of adaptation. At present, there are a lot more mature liquid level sensors, capacitive, magnetostrictive-type, ultrasonic type, compared with above mentioned several technology. Optical fiber liquid level sensor not only many types and each has its own characteristics, and design the most flexible for environment under the condition of complex. Optical fiber liquid level sensor meet the demand for liquid level measurementfully. Because of optical fiber sensors immune reflected electromagnetic interference, corrosion-resistant, light weight, small size, high accuracy, attract researchers in this field are more concerned.Presented with microgroove structure of quasi-continuous plastic optical fiber liquid level sensor with high resolution. The outer diameter of the fiber used to make sensor in the experiment is 1.00 mm, fiber core diameter is 0.96 mm. The core raw material for PMMA, refractive index 1.492, cladding materials for the fluorine resin, refractive index 1.417 from Japan’s Mitsubishi. Liquid level measurement in the text are the basic principles of using polymer optical fiber probe for optical power and fiber’s refractive properties of the external environment. Processing Groove by femtosecond fiber core exposed, so contact with the external environment, the core refractive index modulation optical power by external media when the medium is air or other solutions, light through micro-groove optical power will change. If the optic-fiber surface perpendicular to the axis of engraving a plurality of grooves you can receive multiple light signals to achieve the purpose of sensing liquid level. Groove dimensions and external effect of refractive index on power consumption can be explained by principles of optical fiber connection loss.It is well known that optical fiber connection loss of communication cable and equipment for connection is a very important pecifications. Micro-grooved part can be seen as two fiber connections. We discussed Groove sizes, Groove media, numerical aperture, fiber diameter, fiber optical transmission loss of impact of these factors, and numerical simulations using the principle of connection loss. You can get the following conclusions: 1, fiber optical transmission in power as the refractive index increases in groove, consumption decreases. 2, the case of media constant in the groove, Microgrooves size increases, fiber-optic transmission loss is increase too. 3, micro-Groove and Groove media under the condition of constant, small diameter optical fiber, transmission loss is smaller. 4, engraving same size micro-Groove on the same diameter of the fiber and media in the groove does not change, numerical aperture of the fiber is larger, fiber-optic transmission loss is larger.Feasibility of subsequent experimental verification of liquid-level sensor. First verify that the micro-Groove width at 25μm,50μm,75μm and micro-groove depth range from 0μm to 350μm, effect of microgroove size for optical fiber transmission characteristics, experimental results show that the connection loss will increase with the increase of Microgroove size. By increasing the microgroove size can increase the sensitivity of the sensor to measure liquid level. By considering the sensor performance, resolution, femtosecond laser micro-Groove technology and other factors, eventually decided to produce optical sensor head of the fiber liquid level sensor with micro-Groove dimensions are: groove width and groove depth is 50μm. And made different interval multiple micro-structure of sensor head, length of sensor 1cm, length of intervals between adjacent grooves is the resolution of the sensor. In this experiment the highest resolution 200 Micron, we can be observed through experiments, when the liquid level rises overwhelmed microgrooves, transmission of optical signals change too, results good linearity, high resolution continuous level measurement is realized.Finally research the effect of solution temperature and solution refractive on the sensor, through the experimental validation of the sensors have strong adaptability, sensor can detect different refraction index of solution liquid level(n= 1.33~ 1.42). when temperature 15°c-70°c,temperature will not affect groove sensing performance of optical fiber liquid level sensor.