Research On U Type Core-offset Splicing Of Single Mode Fiber Sensing Based On Sagnac Ring

In many areas of detection work,liquid level and temperature sensing detection occupies an important position,the corresponding means of detection are also varied.Compared to traditional electronic sensors,the advantages of fiber optic sensor make the fiber optic sensor rapidly develop and widely used.Among them,the Single-mode Fiber Core-offset Spliced is mixed with the Sagnac Ring to form a modal interference,using it to sense related environmental parameters can obtain high interference extinction ratio,higher interference extinction ratio results in higher measurement sensitivity,so it become a hot spot in the field of optical fiber sensing research.In this paper,we study the sensor formed by U type modification of core-offset single-mode optical fiber based on Sagnac Ring,the experimental analysis of its characteristics,and further explore its liquid level and temperature measurement applications.The sensor is low cost,simple to manufacture,easy to operate,indicating a better application prospects.The work of this paper mainly includes the following contents:1.Introduction to fiber optic sensing and related theoretical analysis.(1)To presente the background and significant of the study.Several classic optical fibers are listed.The classification of fiber optic sensor and the advantages of interference fiber optic sensor are descried.The current fiber optic sensor is facing the main problem and the research in the domestic and foreign are also described.(2)Introduce the relevant theory of Modal Interference Sensor based on Core-offset Splicing of Single Mode Fiber.(3)Then the theory shows that the Sagnac Ring can increase the interference extinction ratio,and experimental verification.2.Experimented analysis of the characteristics of the sensor.Sensor structure characteristics:(1)The experimental interference pattern of Core-offset Splicing of Single Mode Fiber sensor based on Sagnac Ring is closely related to the number of core-offset solder joints and the shape of the Sagnac Ring.(2)The number of troughs in the unit wavelength segment is closely related to the length of the sensing arm,but the fiber core-offset and the shape of the Sagnac ring do not have a significant impact on it.Sensor sensing characteristics:(1)The change of temperature causes Interference spectral line of the sensor to change.(2)The change of pressure does not have a significant effect on the sensor interference spectral line.(3)By simulation,the loss of optical power at the cladding increases with the increase of the external refractive index.In addition,soak the sensor for a long time,the Interference spectral line power will continue to decline,but stabilized with the increase of time.The wavelength of the center of the trough does not fluctuate significantly with the increase of time.3.In order to further explore the sensor,the sensor is used for the management research of liquid level and temperature.Experiments show that the two environmental parameters have a good sensing response to the center wavelength of the interference trough.Using the corresponding method to reduce the rough error in the experiment,avoid picking troughs,improve the experimental efficiency.The experimental data were processed by the corresponding method,the liquid level sensitivity is 1.72nm/cm,the temperature sensitivity is 0.689 nm/?.