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Research On Temperature Optical Fiber Sensor Based On Two Kinds Of Fibers With Opposite Temperature Response Characteristics

Posted on:2022-08-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2518306542460694Subject:Optical Engineering
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With the development of the times,optical fiber sensor has the advantages of simple structure,high precision,electrical insulation,strong anti-interference ability and other excellent performance.It is widely used in building safety,bridge monitoring,aerospace and other fields.Among the many optical fiber sensors,the fiber intermodal sensor can achieve interference conditions in single fiber.Compared with the traditional optical fiber sensors,the structure is more compact,the design is more flexible,and the cost is relatively lower.Therefore,the fiber intermodal sensors have attracted extensive attention in the measurement of important parameters such as temperature,torsion,strain and refractive index.In the process of measuring non-temperature parameters,in order to effectively suppress the cross-sensitivity between temperature and other measurements,the temperature sensitivity of the sensor should be reduced.In the process of temperature parameter measurement,it is hoped that the temperature detection sensitivity of the sensor can be effectively improved.Therefore,it is of great significance to develop a fiber intermodal sensor with controllable temperature response sensitivity.Based on this,the following research works are carried out in this paper:1.Based on two optical fibers with opposite temperature response characteristics,a novel method that can control the temperature sensitivity of the intermodal fiber sensor is proposed,and a temperature-insensitive sensor is fabricated.Based on the opposite response characteristics of single-mode fiber(SMF)and photosensitive fiber(PSF)to temperature,the control of temperature sensitivity has been realized via adjusting the proportion of PSF to SMF in the sensing part.The temperature sensitivity as high as-192 pm/°C,and as low as-2.6 pm/°C can be obtained,satisfying the demand in both research and application.Based on this method,a temperature insensitive sensor has been successfully fabricated.The torsion sensor is taken as an example to illustrate feasibility of this method,showing no evident interference in the measurement of torsion parameters.The proposed method is not only simple in operation and low in cost,but also the principle of the method is universal in the application of fiber intermodal sensors.It can be applied to more fiber intermodal sensors.2.Based on the cascaded Mach-Zehnder interferometer(MZI),a highly sensitive temperature sensor is proposed,which has an enhanced vernier effect.The Mach-Zehnder interferometer consists of two cascaded tapers,and the sensing parts of the two cascaded interferometers are photosensitive fiber and single-mode fiber.The temperature sensor based on the vernier effect will reduce the temperature sensitivity if the two interferometers have the same response characteristics to the temperature.In order to ensure the high sensitivity of the sensor,it is necessary to desensitize one of the two interferometers to make it as a reference interferometer.Desensitization requires special optical fibers or structures,or the reference interferometer can be encapsulated,which increases the complexity of the system.However,the sensor prepared in this paper has opposite response characteristics of the two interferometers to temperature,so it will not only enhance the temperature sensitivity of the vernier effect,but also has a simple structure and does not need complex working conditions.In this paper,four interferometers composed of SMF were fabricated,with sensing length of10.2 cm,10.6 cm,10.9 cm and 11 cm,respectively.Four temperature sensors are obtained by cascading them with an interferometer with a length of 10.4 cm,which is composed of photosensitive optical fiber.The experimental results show that the temperature sensitivity of a single SMF interferometer is 0.045 nm/°C,and the temperature sensitivity of a single PSF interferometer is-0.169 nm/°C.The temperature sensitivities of the four cascaded sensors are as high as-2.002 nm/°C,-2.524 nm/°C,-4.167 nm/°C and-5.588 nm/°C.The sensitivities are magnified about 12,15,25 and 34 times compared with the single PSF interferometer.Temperature sensitivity has been significantly improved.
Keywords/Search Tags:Photosensitive fiber, Single-mode fiber, Intermodal interference, Temperature insensitivity, Vernier effect
PDF Full Text Request
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