The Study Of Specialty Fiber Sensing Devices Based On Functional Materials

Fiber-optic is the foundation of modern optical communication system.Due to the stable physical and chemical properties of fiber-optic,the light transmitting in fiber has no obvious response to the external field and biochemical substances,this will limit greatly the application of fiber-optic in other area.Combining the fiber with functional material,the performance of fiber will improve greatly.This thesis chooses special optical fiber and functional material as a breakthrough to design and fabricate the fiber-optic sensing devices.The adopted specialty optical fiber includes the simplied hollow core photonic crystal fiber(SHC-PCF),and large-core multimode fiber(MMF)in this thesis.The employed functional materials include the magnetostriction materials and fluorescent materials.The large air holes in SHC-PCF not only provide the opportunity of filling the functional material into the fiber,but also reduce the amount of quartz in fiber.The use of large-core MMF will increase the ability of collectting light.The main aspects of this thesis are listed as follows:Firstly,a fiber magnetic field sensor based on fiber intrinsic Fabry-Perot interferometer(FIFPI)and Metglas ribbon was proposed.The FIFPI was fabricated by splicing the single mode fiber(SMF)to a section of SHC-PCF at both ends by splicer.The sensor has been experimentally tested for strain by monitoring its wavelength shift.The strain sensitivity of 1.78 pm/?? was obtained.On the basis of strain response of FIFPI,the fiber magnetic field sensor was fabricated by sandwiching the FIFPI between two slices of Metglas ribbon further.The largest magnetic sensitivity is 2 pm/Oe.Secondly,a Metglas ribbon and cascaded FIFPIs-based fiber-optic magnetic field sensor was presented.Due to the slight different cavity length between two cascaded IFFPIs,the Vernier effect was obtained in this fiber structure.Through monitoring the wavelength shift of the reflected spectrum envelope,the strain and magnetic field sensitivity of the sensor are as large as 47.14 pm/?? and 71.57 pm/Oe by the Vernier effect,respectively.Besides that,through the envelope curve fitting method,continuous measurements of strain and magnetic field was realized.Thirdly,a three end face reflection-based FIFPI sensor was fabrication and characterization.Through controlling the optical path between three reflectors,similar Vernier effect was realized and the measuring sensitivity was significantly improved.The proposed fiber structure can be used to temperature,strain sensing.The fiber structure can be used to magnetic measurement by combing with Metglas ribbon.Through monitoring the wavelength shift of the reflected spectrum envelope,the obtained temperature,strain and magnetic field sensitivity are 1.019 nm/?,47.922 pml/?? and 85.46 pm/Oe,respectively.Fourthly,a highly sensitive fiber magnetic field sensor based on Terfenol-D and fiber extrinsic Fabry-Perot interferometer(FEFPI)has been demonstrated.Through combining the longer elastic length of Terfenol-D and EFFPI with smaller cavity length,the sensitivity of the proposed sensor has been improved enormously and the magnetic sensitivity is as large as 854.73 pm/Oe.Through the repeatability test,two different kinds of working scenarios are demonstrated.Finally,a fiber nitric oxide(NO)sensor based on Ru(II)complex was implemented.Due to the fluorescent intensity of Ru(II)complex increasing with the concentration of NO,the concentration of NO can be identified.The fiber NO sensor was fabricated by sol-gel or electro-static self-assembly method.Through the analysis of the experiment results,the electro-static self-assembly method has better repeatability.And through this method,the achieved NO detection limit is as low as 1 ?M/L.The sensitivity of this fiber NO sensor can be improved further and this provides an opportunity to monitor NO release from the cells in vivo.This thesis initial implemented the combination of fiber-optic and functional material,and obtained fiber magnetic field sensor and fiber NO sensor based on functional material,realized the function that the pure silica optical fiber can't implement.With the development of technology,the sensitivity of the proposed fiber sensing devices can be improved.Further,the proposed fiber sensing devices can be used in measurement in geomagnetic field and NO in vivo.