Research On Method Of All-fiber-optic Turbidity Detection System Based On Single Photon Detection Technique

Turbidity is the degree of turbidity of water.As defined by the International Organization for Standardization(ISO),turbidity is a measure of the reduction in the transparency of liquids due to the presence of insoluble materials.The turbidity parameters of water are not only the indicators of many reactions and the progress of the process of change,but also the major indicators of the quality testing of intermediate and final products in many industries.It is also an important indicator to judge whether water source is polluted or not.Therefore,turbidity detection is widely used in many fields such as production and living service industry,chemical industry,environmental science and medical treatment.However,the actual turbidity detection criteria are different.There may be scenarios where very low turbidity standards are required,but high turbidity standards may also be required.Therefore,based on the traditional turbidity instrument measuring range and accuracy can not completely meet the current actual production needs.In addition,the method of turbidity detection determines the size of turbidity detection system,compared to the traditional turbidity detection system,a integrated and portable turbidity instrument is the immediate need,especially for deep-sea exploration and other small working environment.Currently,the turbidity detection methods are mainly divided into transmission,scattering and combination of the two methods.For the above three detection methods,each has its own advantages and disadvantages.Compared with the traditional scattering and compound turbidity detection system,although the traditional transmission method in low turbidity condition performance is not ideal,but the transmission method is simpler than the scattering method detection,the designed system is more compact,more suitable for practical application needs.Therefore,an all-fiber transmission turbidity detection system based on single-photon detection technology is developed in this paper,which achieves wide dynamic range and high-precision measurement results.In this paper,based on the single-photon detection technology of all-fiber transmission turbidity detection method carried out in-depth study,the main research includes the following aspects:Firstly,theoretical model establishment of all-fiber transmission turbidity detection method based on single photon detection technology.According to the basic definition of turbidity,turbidity can be measured by detecting particles in the solution to be measured.The turbidity can be characterized by the amount of liquid particles detected per unit volume,that is,the concentration per unit volume.Based on the theory of light transmission,especially the Beer-Lambert Law of transmission,this paper proposes to measure the transmitted light intensity through the transmission liquid through transceiver integration transmission and reception to realize the quantitative measurement of particle number concentration.Through the research of single photon detection technology,a quantitative measurement method of weak transmitted light is found in this paper.Finally,based on the Beer-Lambert Law of transmission and the principle of single-photon detection,a new transmission turbidity detection model is established and the performance of the detection method(measurement range,stability,linearity,feasibility)were analyzed,which provided the basic theoretical basis for the design of the next turbidity detection system and the analysis of later turbidity detection experiments.Secondly,design of transmission detection system of all-fiber based on single photon detection technology.Based on the established turbidity detection model combined with the steady-state photon counting mode,a set of turbidity measurement system with all-fiber transmission and transceiver integration structure is designed.Based on the design of the system,the paper mainly studies some of the core modules,such as the light source module,the transceiver integration optical path structure of all-fiber module,the single photon detection module and the data acquisition and processing module.In order to improve the measurement range and system structure of the system,this paper first proposed a transceiver integration probe optical path based on optical fiber structure design,which changed the previous detection method of transmission method.Then,based on the optical fiber optical path structure combined with each core module,a higher accuracy turbidity measurement function of the detection system is realized and the feasibility of the measurement system is verified.Therefore,this part of the system design work for the next step of water turbidity detection test provides the basis for experimental platform.Thirdly,experimental results of an all-fiber transmission detection system based on single photon detection technology.Based on the establishment of the transmission turbidity detection model and the development of the measurement system,this paper carried out a water quality turbidity detection experiment.First,a good dispersion of a very stable and stable small particle suspension of Formazine standard turbidity solution measurement experiments were conducted to explore the detection performance of the system and analysis of the detection system measurement results.In addition,on this experimental platform,a transceiver integration all-fiber transmission turbidity measurement system is designed and implemented to carry out the preliminary detection experiments of turbidity under different turbidity liquids and light intensities.According to the test results,this paper analyzes the practical application and limitations of the current detection system design,and puts forward a new measurement method and train of thought for the future water quality testing.