Font Size: a A A

Research On Mode Field Mismatch Optical Fiber Liquid Level Sensor

Posted on:2021-03-14Degree:MasterType:Thesis
Country:ChinaCandidate:D J FengFull Text:PDF
GTID:2428330602977581Subject:Photoelectric information acquisition and processing
Abstract/Summary:PDF Full Text Request
Optical fiber,as a high-quality optical signal transmission waveguide,has received widespread attention since its inception.In addition to being used in the field of optical communications,optical fibers are also used in the manufacture of various fiber sensors.This is mainly due to the fiber's own composition material and the special properties of light,which makes fiber optic sensors have a wide range of applications in the fields of refractive index,temperature,pressure,gas,heavy metal ions,electromagnetic fields,and liquid levels.Liquid level parameters are used in the petrochemical field for the control and detection of liquid raw materials or finished product reserves.Too high or too low liquid levels will affect the smooth production of the factory and even cause production accidents.In the field of liquid level measurement,the traditional electrical and mechanical level sensor technology has matured.Because electrical and mechanical liquid level sensors must be charged or work with metal materials or mechanical structures,there are still many defects,such as electromagnetic interference,line breaks may generate sparks,resistance to corrosion or large structures.In this paper,liquid level sensing has been targeted.The application of mode field mismatched optical fiber sensors in liquid level measurement has been studied.Different types of mode field mismatched optical fiber liquid level sensors have been studied.The main work of this paper is as follows:1.The performance of a Michelson level sensor with a coreless fiber as an optical coupler is studied.The sensor is divided into a light-guiding single-mode optical fiber 1and a sensor no-core optical fiber + sensing single-mode optical fiber 2.The end face of the sensing single-mode optical fiber 2 Silver reflection layer is added to increase the core fiber is used as both the sensor beam coupler and the sensor area.The sensor monitors the movement of the characteristic interference valley to obtain the liquid level information,which belongs to the phase modulation type.The optimal length of the no core optical fiber and the sensor single-mode optical fiber 2 was explored through a combination of simulation and experiments.It was found that two sections of sensing fiber with different structures exhibited the same sensitivity in the liquid level measurement.Based on the simulation results,it was found that the optical field distribution of the no core fiber coupled into the single-mode fiber 2 cladding would affect the sensorperformance.The thesis explores the liquid level sensitivity and linearity of the sensor under different refractive index environments,and the stability and temperature stability in a static environment,all of which have obtained good results.2.Intensity-modulated fiber-optic liquid level sensors have the advantage of low demodulation cost in the current technical environment.In this paper,cheap no core fiber and single-mode fiber are used as sensor elements,and relatively inexpensive handheld optical power meters are used as demodulation devices.In this paper,a single-mode series intensity-modulated liquid level sensor for dual no core optical fibers is proposed.The sensor converts the wavelength shift of a single no core fiber into the output light intensity change of the entire sensing arm.A reference arm is added to the sensor to eliminate the influence of light source light power fluctuations.The article explores the relationship between the self-image distance and the wavelength of the no core fiber used in the experiment.The experiment tested the relationship between the output light intensity and the liquid level of the sensor under different refractive index liquid environments,and explored the stability of the sensor system under the change of the light power of the light source.The output of the liquid temperature was stable under the static environment and the 20 mm liquid level.And the repetitiveness of the rising and falling liquid levels.The principle that the sensor has better temperature stability below 60 ? and the reason why the sensor is unstable above 60 ? are given.The idea of widening the measurement range of liquid level is given.
Keywords/Search Tags:Liquid-level sensor, no core fiber, Mode field mismatch, phase modulation, intensity modulation
PDF Full Text Request
Related items