Application Of Sapphire Chip And Dielectric Film On High Temperature Optical Fiber Sensor

The level of research in aerospace and other related fields has always been a manifestation of the country's top scientific and technology research strength and the strongest display of comprehensive national strength.Many products in the above areas are not only related to the construction of the national security network,but also promote and feed back the rapid development of related fields in the national economy.All countries in the world have also attached great importance to the development of aerospace science and technology,and have also continuously increased their investment in the aerospace field.However,the tests of aerospace engines and nuclear explosion tests are conducted at very high temperature,so the measurements are difficult and technical research has many difficulties.The cost of aerospace-related experiments is very high.In order to reduce the cost risk,various kinds of physics in the experiment require precise measurement,especially for temperature measurement.There is no mature technology at present.Optical fiber sensors have the advantages of stability,safety,reliability,and adaptability.They are suitable for sensing in special environments,and optical fiber sensors can realize long-distance transmission.The above advantages of fiber optic sensors also make it an important means of high-temperature sensing.Based on this research,this paper analyzes the current research of high-temperature sensors,and proposes to apply Fabry-Perot structure to high-temperature sensing,combining the characteristics of high hardness with the high temperature resistance of sapphire fiber.Temperature measurement structures are designed for use on sapphire fiber,and some of the work is already available on sapphire fiber.At the same time,the sapphire fiber does not have a cladding with high optical transmission loss characteristics,so it's meaningful to research suitable material as a sapphire fiber cladding.The main research contents and results are as follows:1.Determine the polishing process of the sapphire fiber end face.According to the characteristics of sapphire,ceramic ferrule and high-temperature ceramic adhesive,the connection method between sapphire fiber and patch is explored to determine the best paste sequence and method;2.Experimental study to determine the high temperature capability and temperature sensing performance of the 105/125 multimode fiber patch with the sapphire fiber patch F-P probe;3.The titanium oxide,silicon dioxide and alumina high-temperature dielectric materials were used to design the film system,and the F-P structure was formed on the end face of the fiber by evaporation coating to test the temperature sensing performance;4.To explore the preparation method of MgAl₂O₄,characterize the MgAl₂O₄materials prepared by different methods,and test the evaporation and film formation effects of spinel materials prepared by different methods.A series of experimental research shows:FP high-temperature probes prepared with 105/125 multimode fiber and sapphire fiber with sapphire chip,have similar temperature sensitivity of 0.02 nm/?,the limit of the measurement temperature is800?.The latter can be measured to 1400?and has good repeatability and stability;the use of evaporation coating preparation of thirteen-layer film FP high temperature probe at high temperatures,the reflection spectrum is stable,the temperature sensitivity is about 0.6-0.8 nm/?,maximum temperature measurement can reach800?,and has good reproducibility and stability;chelation and solid phase reaction method prepared in two ways magnesium aluminate spinel,the former product contains intermediates,magnesium aluminum spinel The purity is lower,the latter has the advantages of high content of magnesium aluminate spinel in the product,non-pollution of raw materials,convenient production,etc.The refractive index of the evaporated coating film is between 1.62-1.68.