The Research On Optical Fiber Temperature Sensor Based On Printed Quantum Dot Fiber

Optical fiber sensors are obviously different with traditional electrical sensors in sensing methods,sensing principles,signal detection and data processing.It's playing an irreplaceable role in some areas where the traditional electrical sensors can't be used.In addition,optical fiber sensors are easily to form an intelligent distributed sensor network with high density and large capacity.if we can try making new sensing fiber from new materials and realize its application in optical fiber sensors,that will be of great significance for the optical fiber sensor's development.Recent years,the synthesis process of quantum dots gradually become mature.Compared with bulk materials,due to the quantum size effect and surface effect,it shows lots of unique optical properties and electrical properties.Therefore,it has received wide attention from the researchers in the research fields of material science,biomedicine and optoelectronics.The changing of ambient temperature and chemical composition can affect the fluorescent spectrum and intensity of the QDs.So as a kind of novel sensing material,it has been used for various optical sensors.Based on its properties,this thesis mainly does research on a new way of manufacturing polymer quantum dot sensing fiber by printing method,and applies the printed quantum dot fiber into the optical fiber sensors,finally achieve the temperature measurement.The research contents are shown in the following aspects.At first,the thesis shows the research status of quantum dot fiber and quantum dot fiber sensor.In view of the shortcomings of current manufacturing process of quantum dot fiber,a new method for manufacturing quantum dot fiber is proposed.In second chapter,the basic theory of optical fiber is introduced and then we make the quantum dot fiber by printing.Its size is close to that of multimode fiber,which proves the new producing method has advantages of high accuracy and good repeatability.By aligning the quantum dot fiber to multimode fiber,the excitation light is successfully introduced into two kinds of quantum dot fibers,the fluorescence in 633 nm and 530 nm band is excited,and the transmission loss of the quantum dot fiber is analyzed.The transmission loss is less than 0.35dB/mm@633nm.The third chapter studies the single-point quantum dot fiber temperature sensor.First,a CdSe/ZnS quantum dot fiber with a length of 3mm and a diameter of about 125 um is printed.By aligning and coupling with the multimode fiber,a 375 nm excitation light is introduced into quantum dot fiber and the fluorescent in 630 nm band is excited.Then the quantum dot fiber was placed in a temperature control box,and we recorded the drift of fluorescent wavelength while the temperature is changed.The results show that the center wavelength of the fluorescent has a good linear relationship with the ambient temperature the temperature,sensitivity reaches 121.43pm/?.In addition,the effect of axial tensile stain on the quantum dot fiber is also tested.It was found that the intensity of the fluorescent gradually became weaker with the increase of strain,but the center wavelength of the fluorescence didn't shift during the test.The result shows that the fluorescent wavelength of quantum dot fiber is insensitive to strain.Chapter 4 designs and manufactures a cascaded quantum dot fiber and realizes the measurement of temperature at two points.At first,by optimizing printing parameters,a cascaded quantum dot fiber is fabricated,then the sensor is coupled with a multimode fiber,the excitation light is coupled into the cascaded quantum dot fiber.Finally the fluorescence in two different band is excited.Among them,the quantum dot fiber 1 is 1.7mm long and its fluorescent band is at 630 nm.The quantum dot fiber 2 is 1.7mm long and its fluorescent band is at 530 nm.In the experiment,the change of fluorescent center wavelength was recorded while the cascaded quantum dot fiber was heated.An analysis result shows that the sensitivity of the quantum dot fiber 1 is 141.9pm/?,the sensitivity of the quantum dot fiber 2 is 134.3pm/?.With the structure,quasi-distributed temperature measurement at two points can be realized at the same time,and the spatial resolution is 1.7mm which is the same as the length of the single quantum dot fiber.Based on the above experimental results,a three-stage cascaded quantum dot fiber is also made for measurement,which provides a reference for the later production of quasi-distributed quantum dot fiber sensor based on printing technology.At the end of the thesis,the current experimental results are summarized and analyzed,and the future development direction is proposed.