- 學位論文
共路徑波長偏移量測干涉儀及其應用
A Common-path Interferometer for Determining Wavelength Shifting and Its Application
摘要
本文提出兩套創新的波長位移量測用的干涉儀。兩套干涉儀皆具有共路徑及異光程的特色，並配合由四分之一波板及旋轉分析板組成的移相機制，得到參考以及量測兩週期性訊號。以量測參考訊號與量測訊號之間的相位變化，此相位變化為量測光波長的函數，故可得到量測光波長的微小位移量。 架構一是以雷射二極體(λ0=638nm)為光源，利用麥克森干涉儀量測二極體雷射波長位移量，本干涉儀量測出穩定度為4.7×10-4nm。靈敏度在d=5mm及d=8mm時，波長改變0.01nm 就分別有88.4°及143.5°的相位差。架構二是以紅外波段 (λ=1530~1560nm)的光為光源，使用保偏光纖造成其兩個偏振態在同一路徑上產生相位差，使量測的訊號具有共路徑與非等光程之特性，本實驗量測結果在保偏光纖分別為5m及10m時，具有298.72°/nm的靈敏度及596.49°/nm的靈敏度。穩定度分別為5.608×10-3 nm及3.394×10-3 nm。本干涉儀具有高穩定性與高靈敏度的特點，系統光路架設容易，且具即時與非破壞性的量測為其優點。 實驗應用上，將使用架構二之干涉儀針對光纖光柵感測器受靜態應變的負載量測，將光纖光柵貼附於四點彎曲樑上後施力，藉由相位變化量及干涉儀的靈敏度，換算而求得波長漂移量後，光纖光柵受力產生的應變即可測得，接著利用應變規作為量測參考標準，量測結果與參考標準值具有相當的一致性，也驗證本論文所提出偏光干涉儀的正確性。
並列摘要
This paper has put for two sets of innovative interferometers to measure the shift of wavelength, which have the features of unequal- and common-path. The Phase-shifting method with a quarter-wave plate and a rotatable analyzer are employed so that periodic signal is created for measurement and referential signals. We can obtain a wavelength shift of the light source to measure the phase difference as a function of wavelength between measurement and referential signals. This experiment used a Michelson interferometer to measure a wavelength shift of the laser diode (λ=638nm) as light source for the first structure. From the experimental results, the sensitivity of interferometer are 88.4°and 143.5° per 0.01nm when d=5mm and d=8mm respectively, and stability is 4.7×10-4 nm. Structure of the second used Infrared (λ=1530~1560nm) light as light source, the PMF is used to create phase difference of the two polarization on the same path so that signals measured are found with the features of unequal- and common-path. From the experimental results, the sensitivity of interferometer are 298.72°and 596.49°per 1nm and stability is 5.608×10-3 nm and 3.394×10-3 nm when PMF length equal 5m and 8mm respectively. As of above-mentioned features, it has rendered this interferometer be found with the characteristics of high stability and sensitivity, and easier for optical path to be installed, with the advantages of real-time and non-destructive measurement. In experiment application, this interferometer of the second is used to measure the load by static strain upon the fiber bragg grating sensor. The fiber bragg grating sensor is attached to four-point bending beam before export is exerted, and then the wavelength drift volume can be obtained and translated through the sensitivity of the interferometer and phase change volume. Thus, the strain generated from the fiber bragg grating sensor as exerted can then be detected. Afterwards, the strain gauge is employed as the reference criteria of measurement, while the measurement results and criteria value of reference are found with certain consistency, which has further substantiated the accuracy of polarizing interferometer.