Research On Sensing Characteristics Of Optical Fiber Fabry-Perot Interferometer

As a new sensing technology,optical fiber sensor has many advantages,such as small volume,light weight,high sensitivity,long distance transmission and so on,which has been applied in many fields as diverse as health care,aerospace,energy development,Environmental monitoring,and industrial manufacturing.The combination of optical fiber microstructure and sensitive materials can not only improve the performance of optical fiber sensors,but also broaden their application fields.The purpose of this paper is to improve the coupling filling process between sensitive material and the fiber,fabricate high-performance optical fiber FabryPerot interferometer,and study its sensing characteristics.(1)A novel optical fiber Fabry-Perot interferometer based on Polydimethylsiloxane(PDMS)filled in hollow core fiber(HCF)is proposed and studied.PDMS material is filled into HCF by using the fill-ability of the HCF.In order to improve the filling efficiency,the filling process is optimized.The experimental results show that the temperature sensitivity of the interferometer is 1.2288 nm/°C and the linearity is 0.9954 in the temperature range of 28-76°C.Then,the temperature experiment is repeated three times,and the temperature sensitivities have good consistency.The filling technology is simple but effectively improves the stability of the interferometer.(2)In order to expand the application of Black Phosphorus(BP)materials in optical fiber sensing,several optical fiber interferometers are fabricated by mixing BP quantum dots(BPQDs)with Polyvinyl Alcohol(PVA)in different proportions and filling them in HCF with different thicknesses.The results of humidity experiment shows that the higher the content of BPQDs in the mixture,the higher the humidity sensitivity.In the range of 45-75 %RH,the highest humidity sensitivity is-0.7525 nm/%RH,and the response time is 1.44 s,the interferometer has the ability of acquiring humidity information quickly.The results of temperature experiments show that the lower the mixing ratio of BPQDs-PVA,the less obvious the temperature response of the interferometer,while the temperature sensitivity is as low as 0.0308 nm/℃,thus could realize temperature-insensitive humidity sensing.In the 10-day long-term stability monitoring,the humidity measurement instability standard error is only 0.07 %RH,showing its long-term stability.(3)It is found that the humidity sensitivity of the optical fiber interferometer can be further improved by increasing the filling amount of BPQDs-PVA.In order to improve the response sensitivity of the interferometer,BPQDs-PVA is filled in the middle of two single-mode fibers to increase the filling amount of BPQDs-PVA in the fibers,an optical fiber interferometer based on single Fabry-Perot cavity is fabricated.The results show that the maximum humidity sensitivity is 12.4307 nm/%RH in the range of 42-60 %RH,the humidity measurement instability standard error is 0.02 %RH,the response/recovery time of humidity are 0.78s/1.24 s,respectively.The interferometer has the advantages of high humidity sensitivity,high stability,fast response,which has great potential in some humidity monitoring fields.The above optical fiber Fabry-Perot interferometers have the advantages of simple fabrication,strong reproducibility,high sensitivity and low cost,which can meet the measurement requirements of humidity sensing and temperature sensing fields,and have certain application potential.