本論文研究新提出的光子微波干涉儀,旨在增加光學干涉儀的 Non-Ambuguity
Range (NAR)。我們利用訊號產生器產生 6 GHz (Λ = 5 cm)的微波訊號,對半導體 雷射做直接調製將微波訊號載在光訊號上,作為干涉儀的探測光源,待探測訊號 於待測物反射並與參考訊號干涉後,待測物之位移可藉由擷取微波訊號的相位而 得知。研究中亦嘗試了兩種相位擷取方法,分別為鎖相法(Lock-in method)以及正 交偵測法(Quadrature detection method),並分析了不同光路架構下的相位穩定度, 也討論了訊號強度與相位的關係。於本研究中,此技術成功將 NAR 增加至 2.5 cm,且由於訊號產生器產生的微波訊號有著極細的線寬與極穩的頻率,加上使用 對稱的光路架構減少環境擾動對相位的影響,我們成功的使位移量測的解析度(五 次量測的標準差)達到了 12 μm,亦即 Λ/4000。

In this study, we proposed a photonic microwave interferometry which aims to extend Non-Ambiguity Range (NAR) of the typical interferometer. A 6 GHz microwave signal (Λ = 5 cm) was generated by a signal generator and was carried by light through direct modulation to the semiconductor laser. The microwave carried by light, so-called photonic microwave, was used as the optical source of the interferometer. After the testing signal returning from the target and interfering with the reference signal, the phase of the microwave was directly extracted and the displacement of the target was resolved. We also tested two different phase extraction methods, which are lock-in method and quadrature detection method. The phase stability under different experimental setup and the relation between signal strength and phase are also discussed. By using the microwave as the actual detecting signal, we extend the NAR to 2.5 cm. Since the microwave signal has narrow linewidth and stable frequency, 12 μm resolution of displacement measurement (standard deviation of 5 measurements) is achieved, which is equivalent to Λ/4000.

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