Research On Modal Interferometer Sensor Based On Peanut-shape Splice

In the recent decades, the fiber optical sensors have been developed for afew distinguished features such as small dimensioning, electromagnetic immunity,and resistance to corrosive, light quality and high sensitivity. Therefore, the sensorsbased on modal interferometer have been widely provided. In this paper, a series ofnovel modal interferometers based on waist-enlarge have been proposed. And theirpractical applications in sensing field were verified by experiment.The main work of this thesis as follows:1. The modal interferometer based on peanut-shape splice with all SMF has beenproposed. After applying arc discharge, the fiber tips are softened and become sphere.Then the two spheres are spliced to become a peanut-shape structure. A easymanufacture, low cost, and hard robustness modal interferometer is generated bythe two peanut-shape structures. We discuss the relationship of the sensitivity and thesize of peanut-shape and simulate mode field distribution of the sensor. Then thecurve fitting is plot. Temperature, strain, bending and refractivity index are measuredby the sensor. The results show that the sensor based on peanut-shape splice has ahigh sensitivity. And different lengths of sensors have been experimented.2. The modal interferometer based on fiber tapered cascaded with apeanut-shape structure has been proposed. The character of fiber is change aftertapering, it can bend to a large degree and generate cladding mode. In addition, thepeanut-shape can recoup the cladding mode. So this sensor can measure angle via theinterference peaks shift.3. A new simultaneous measurement of the refractive index (RI) andtemperature mode interferometer sensor is introduced. This type of sensor is consistof a LPG and two peanut-shape structures. A section of LPG is spliced withpeanut-shape structures between two SMFs to construct a modal interferometer.Thesensor can measure the double parameter at the same time, so it can eliminate the influence of temperature on the other physical quantities in the daily practicalproduction and engineering structure. The sensor can measure refractive index andtemperature at the same time, thus expands the practical application.