Study Of Optical Fiber Interferometer Sensor Based On Large Lateral Offset Fusion Splicing

Optical fiber sensing not only represents a popular direction of optical fiber application research,but also is an important part of the sensing field.Using optical fiber for information sensing,information perception,and information transmission,we can get the key information accurately and quickly.At present,the sensors are realized mainly based on gratings,resonators,interferometers,and so on.Among them,the optical fiber interferometer-based sensors have the advantages of easy integration,fast response,high sensitivity,and strong anti-interference ability.Its applications have been extended to national defense,military,industrial production,energy security,biomedicine,environmental monitoring,and etc.Two different categories of optical fiber sensors have been realized,by means of the evanescent-field interaction and the direct light-matter interaction,respectively.Sensors based on evanescent field include micro fibers,fiber gratings,and etc.Due to the weak interaction between light and the matter,there is a relatively low sensitivity and large device size.For the case of the direct light-matter interaction,however,the sensitivity can be greatly enhanced and to a great extent,the device size can be decreased.In our work,utilizing large-offset splicing structures,we study the magnetic field sensor and reflective refractive index sensor,respectively.The devices has advantages of compactness,high sensitivity,good structural stability and repeatability.The main work of this paper are as follows:(1)A magnetic field sensor by combining magnetic fluid is realized.The optical properties of magnetic fluid is modulated by the external magnetic field,so that the variations of magnetic field can be derived by monitoring the interference spectral shifts.Experiment shows that the magnetic field sensitivity can reach up to 180.0 pm/Oe within a magnetic field range of 0 to 260 Oe.The advantages for such a magnetic field sensor lies on the compact device size and high sensitivity.(2)A reflective fiber interferometer is realized by introducing a reflective fiber section to a large offset splicing fiber structure.This method can effectively reduce the size of the component.The fabricated structure is suitable for the long distance and/or closed-space measurement.The measured refractive index sensitivity is as high as 13257nm/RIU,which is higher than the counterparts in the literature.The fabricated structure shows great potential in real-world applications.