Research On Microfiber Bragg Grating With Its Fabricated Technique And Refractive Index Sensing

Microfiber Bragg grating is a combination of the strong evanescent field characteristic of microfiber and better characteristic of wavelength selection of fiber Bragg grating.It overcomes the fiber Bragg grating itself limitation of insensitivity to the refractive index change,and has many merits,such as small volume,compact structure,high sensitivity and fast response and so on.Duo to the method of chemical etching fabricating microfiber Bragg grating takes longer,and not suitable for commercial production.Therefore,we study another method by combining flame-molten system and the system of the fiber Bragg grating constructed to produce microfiber Bragg grating and optimize the production parameters.Then,the refractive index sensing properties of the sensor are studied.(1)In this paper,experimental study the method of producing microfiber by using flame-molten system.After hundreds and thousands experimental research,the parameters of speed,length and hydrogen flow are optimized and several different types of tapered interferometric fiber optic sensors are fabricated under the optimized parameters.Then sensor response of the temperature and the refractive index theoretical and experimental are researched respectively.The result shows that in the measurement range from 1.3484 RIU to 1.3971 RIU refractive index change,the tapered multimode interferometric sensor with a minimum diameter of 14.37 ?m has a good linear response and its refractive sensitivity up to 539.15 nm/RIU.Such find provides the technical support for making high sensitivity sensor.At same time,a tapered single-mode interferometric sensor with a minimum diameter of 127.42 ?m is studied.The experiment find shows that the refractive index sensitivity of the sensor is 50.56 nm/RIU,and its linear fitting is as high as 99.23%.(2)The technique of phase mask composing fiber Bragg grating is experimented.Using the wavelength of 193 nm excimer laser combined with phase mask technique fabricates fiber Bragg grating in the single-mode fiber with unload hydrogen treatment.And the response characteristics of temperature of the sensor is studied.Results show that the Bragg grating sensor with this method has a good linear response characteristic to temperature change within the measurement range of 200 ?-800 ?.Hence,the sensor has a certain application value in the field of high temperature sensor.(3)By combining physical flame-molten method and the technique of fiber Bragg grating production,several different types microfiber Bragg gratings are made in the different area of the tapered microfiber,and the refractive index sensing characteristic is experimentally researched.It shows that a senor fabricated in a tapered microfiber with the minimum diameter of 11.52 ?m has a refractive sensitivity of-11.3284 dB/RIU in the refractive index measurement range of 1.3483 RIU-1.3971 RIU.Then,the sensor with a maximum diameter of 55.7 ?m in the tapered area,within the refractive index change from 1.3336 RIU-1.3683 RIU,the reflection spectrum of the sensor at 1553.7 nm has a refractive index sensitivity of-1.1273 nm/RIU.Furthermore,a microfiber Bragg grating with a tapered length of 18 mm,from the measurement refractive index range of 1.3682 RIU-1.3726 RIU,the sensor has a sensitivity up to 10.05 nm/RIU.As the refractive index sensing plays an increasingly important role the in biochemistry,medicine,food testing and environmental monitoring.In-depth studying of microfiber Bragg grating production techniques and refractive index sensing will make the sensor more practical in the field of sensing and has more industrial production value.