Fabrication Of The Micro-/Nano POF And Its Optical Sensing Properties

The optical fibers with micro/nano-scale structures show some special features.As the optical fiber sensing applications, the most prominent feature of themcro-/nano optical fibers (MNFs) is the strong evanescent field around, this make theMNFs very sensitive to the outside environment (such as refractive index, temperatureand stress, etc.) and very conducive to constructing high sensitivity optical fiber sens-ing devices. However, most of the MNFs are made from silica optical fibers, few aremade from commercial plastic optical fibers (POF). The POF is easy to be melted anddrew, for the melting point of polymer materials is low. So it is very suitable for fab-ricating MNFs. Its good flexibility make it bend more easily without damage, this isconvenient for making different bending type devices.The fabrication of the micro-/nano POF and the POF couplers is introduced inthis thesis. Based on this, the macro-bending-based micro-/nano POF are used for re-fractive index and temperature sensing. The specific contents in this thesis are shownas following:A two-step taper drawing method to fabricate micro/nano POF from commercialPOF is introduced in this thesis. On the first step, the alcohol burner is used as theheater. A fiber with diameter down to about20μm and length up to tens of centime-ters can be obtained through this step. On the second step, the electric iron is used asthe heater for the further process. By this step, we can get the fiber with uniformitydiameter, smooth surface, and the fiber diameter can reach to3μm. Meanwhile, aheating and pulling method to fabricate the (1×2)，（2×2），（1×4）and (4×4) POFcouplers is also introduced in this thesis.Refractive index (RI) is one of the important optical parameters of materials. TheRI sensors which use the strong evanescent field of the MNFs have the advantages oflow cost, fast response, and simple operation. The refractive index and temperaturesensing properties of the macro-bending MNFs are investigated and analyzed in thisthesis. The results show that the macro-bending MNFs are sensitive to the low refrac-tive index range measurement of a liquid. The larger macro-bending radius of the MNFs has higher sensitivity, and for a fixed macro-bending radius, the MNFs withsmaller fiber diameter have higher sensitivity.At last, the sensing properties of the1×2MNFs coupler are investigated. Thebranch with macro-bending configuration(R=2.7mm) is used for sensing, the resultsshow the MNFs has good temperature sensitivity in the temperature interval (20-60℃), good linearity in the temperature interval (20℃-40℃) and(40-60℃), andhigher sensitivity in the temperature interval(40-60℃).