共路徑非等光程偏光干涉儀及其在多工式光纖光柵感測器之應用

A Nonequal- and Common-path Polarization Interferometer and Its Application for Multiplexing of Fiber Grating Sensor

張浩銘(How-Min Chang)

指導教授 ： 林世聰

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2009年)

摘要

本文提出一套創新的波長位移量測用的干涉儀，它包含偏極片、雙折射晶體、四分之一波板、旋轉分析板及與之同步旋轉之斷光板。偏極片為使入射光之水平與垂直偏振態具相同分量，藉由使用雙折射晶體造成其兩個偏振態在同一路徑上產生相位差，使得量測的訊號具有共路徑與非等光程之特性，再利用由四分之一波板、旋轉分析板及斷光板所組成的移頻機制，使得量測與參考信號產生頻差，最後由光偵測接受。因上述之特點，使本干涉儀具有高穩定性與高靈敏度的特點，並以旋轉分析板產生外差光源之設計，使光路架設容易，且具即時與非破壞性的量測為其優點。
利用鎖相放大器與波長計對本干涉儀進行靈敏度及穩定度量測，其結果分別為K=271.11 degree/nm與4.74×10-4 nm。實驗應用上，將使用本干涉儀針對光纖光柵感測器受靜態應變的負載量測及動態伸縮量量測，前者為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，也證實本論文所提出偏光干涉儀的正確性。動態量測為將光纖末稍兩端分別貼附於PZT驅動平台的兩側後，量測PZT動態伸縮所造成光纖光柵的光柵週期變化而引起的相位變化。最後，我們將做
串接式及並接式光纖光柵的多工式感測實驗，實驗結果可證實本干涉儀在光纖光柵的動態與靜態多工感測上的可應用性與實用性。

關鍵字

波長位移 ； 光纖光柵 ； 旋轉分析板

並列摘要

This paper has put for a set of innovative interferometer to measure the shift of wavelength, which includes polarizer, calcite,1/4 wave plate, rotating analyzer, and chopper plate of concurrent rotation. To render the horizon and vertical polarization of the injected light from the polarizer be given with identical amount, the calcite is used to create phase difference of the two polarization on the same path so that signals measured are found with the features of nonequal- and common-path. Then, 1/4 wave plate, rotating analyzer, and frequency-shift mechanism from chopper plate are employed so that phase difference is created for measurement and referential signals. At the end, it will be detected and accepted by light. As of above-mentioned features, it has rendered this interferometer be found with the characteristics of high stability and sensitivity, while the design of heterodyne light source as generated from rotating analyzer has helped it easier for optical path to be installed, with the advantages of real-time and non-destructive measurement.
Lock-in amplifier and wavelength meter are exploited to conduct the measurement of sensitivity and stability upon this interferometer, and the results obtained are K=271.11 degree/nm and 4.74×10-4 nm respectively. In experiment application, this interferometer is used to measure the load and dynamic warping volume as affected by static strain upon the fiber bragg grating sensor. For the former, 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. On the other hand, dynamic will have the two ends of optic-fiber separately attached to the rear on the two sides of the PZT drive-platform so that the phase change generated from the grating period brought about on fiber bragg grating sensor by PZT dynamic warping. Lastly, we will conduct in-line and cascode fiber bragg grating sensor of multi-agent sensor experiment, and the experiment results have further proved the practicality and applicability of this interferometer in terms of dynamic and static multi-agent sensing and measurement for fiber bragg grating sensor.

並列關鍵字

wavelength shift technique ； fiber Bragg grating ； rotating analyzer method

參考文獻

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