Design And Sensing Characteristics Of Copper Ion Detection Optical Fiber Sensor

In many kinds of trace elements,copper ion as a kind of common heavy metal ions in various life activities plays a very important regulation function,but excessive intake of copper ion,the normal metabolism of human body will suffer serious interference,so the copper ion concentration in natural ecological system testing is particularly important.Among many detection methods,optical fiber sensors are widely concerned because of their advantages such as high detection limit,simple preparation process,corrosion resistance and oxidation resistance.Among the many optical fiber sensing principles,the preparation method based on Mach-Zehnder interference principle is relatively simple and the structure is more stable.Combined with the above advantages,this paper designed and produced the knotted shape fiber sensor,core-offset fiber sensor and two kinds of fiber in series structure,and carried out the sensing experiments such as temperature,refractive index and displacement double-parameter measurement and copper ion detection.According to the pre-designed fiber structure,the simulation research on the outer cladding evanescent wave,transmissive light intensity and light field mode evolution of the knotted shape fiber and core-offset fiber were carried out.Through theoretical simulation and experimental investigation,it was found that with the increase of shape variable,the energy in the core of the knotted shape fiber will decrease,and the energy of evanescent wave outside the cladding will gradually increase.Compared with other kinds of refractive index fiber sensors,the knotted shape fiber sensor had stronger cladding evanescent wave and higher refractive index sensitivity,and the fabrication method was simple and the structure was firm.Therefore,it was selected as the carrier coated with copper ion recognition materials.Double-knotted shape optical fiber sensor,knotted-core-offset optical fiber sensor,polydimethylsiloxane coated multi-thin-multimode fiber sensor and chitosan coated knotted shape fiber sensor were made by fiber fusion welding machine,respectively.According to the structural characteristics of the sensor,sensing experiment systems were established to carry out the sensing characteristic experiments.Through the refractive index and displacement double-parameter measurement experiment,sensitivities of refractive index and displacement of the double-knotted shape fiber were 290.35nm/RIU and-554.40pm/?m,respectively.The temperature and displacement sensitivities of the knotted-core-offset fiber were31.66pm/? and-537.5pm/?m,respectively.Through PDMS coating of multi-thin-multimode fiber,its temperature sensitivity was raised from 47.14pm/?to 75.04pm/?.Many experiments had proved that the sensor had the good temperature stability.The knotted shape fiber was coated with chitosan modified by glutaraldehyde,and the copper ion measurement with different concentration was detected.The detection sensitivity of copper ion was 2.46pm/ppm,and the detection stability was good.