A Kind Of Fiber Sensor Based On Fusing Tapers And Its Application In The Measurement Of Dairy Products Concentration

Since 1960-1970s, There is a big promotion of Optical fiber technology. After the appearance of the low loss fiber, a new science--fiber sensing technology, was found. The fundamental of optical fiber sensing, as follows:While a beam of light transferring in optical fiber, the changes of external environmental (such as temperature, refractive index, stress and strain, etc.), will easily affect the characteristic parameters (such as intensity, phase, polarization state, etc.) of the light inside transmission fiber. So by demodulating these characteristic parameters, we can get the environment information around the fiber. And, because of the material(silicon dioxide), the fiber sensor has many advantages compared with the traditional electrical sensors. The fiber can work in harsh conditions such as high temperature and high pressure, strong acid, strong alkali, and it can also keep high sensitivity. As the development of the fiber sensing technology, various types of fiber optic sensor was designed. Among them, the M-Z interferometer fiber optic sensor has simple structure, simple production method, the potential of mass production, gradually, become the focus of the study.One production of fiber sensor is based on fusing tapers -- a important optical fiber reprocessing technology. Which is widely used to produce fiber optic components such as couplers, wavelength division multiplexer(WDM), etc. Using this technology, we can easily make a structure of M-Z interferometer. After packaging processing, can get a compact structure, high sensitivity optical fiber sensor.Nowadays, in the industrial production of dairy products, its concentration largely affect the quality of the products. The composition of dairy products is complicated, but its concentration is directly related to its water content, and the refractive index and its water content have approximate linear relationship. Therefore, we could determined the concentration by detecting the refractive index of dairy products. However, dairy products generally belongs to the translucent or opaque colloid, the traditional refractive index measuring instrument--abbe refractometer, can only detect the refractive index of transparent liquid.This thesis The optical fiber sensors given by this thesis can solve problem very well.The topic of this thesis:a kind of fiber sensor based on fusing tapers and its application in dairy products concentration measurement. Main content is to use fusing tapers to make fiber sensors, and use the sensors to detect the refractive index of dairy products.This thesis is mainly based on experiment, theoretical analysis help to explain, the key is how to make a optical fiber sensor with high sensitivity.The innovation points of this paper as following:By introducing two bending during the tapers in the sensor, through the theoretical analysis and experimental verification, the sensitivity is about 10 times higher than that of the similar sensors,reaches 138.46nm/RI. And we also measured the sensitivity of the temperature, which is about 0.02 nm/℃, the result shows the temperature crosstalk is very small. Since the temperature changes a little while detecting of refractive index dairy products, the influence can be ignored.We come up a package type of sensing probe, by this way, the structure of the sensor are more compact. At the same time, reducing the volume of the sensor in the real sense, which permit the sensor applying in narrow mall environment, by the way, the measurement of refractive index is more convenient.This paper combining lab experiment with the practical industrial application, and provides a new method to detecting the concentration of the dairy products. Besides we built a set of refractive index measurement system, with the technology of photoelectric detection, we reduced the costs of the experimental equipment, and get the reliable results.