結合光纖光柵與Mach-Zehnder光干涉量測結構振動

The Measurement Of Structural Vibration By Combining Fiber Bragg Grating With Mach-Zehnder Interferometry

謝文斌(Wen-Pin Hsieh)

指導教授 ： 何旭川

元智大學/工程學院/機械工程學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00259

摘要

近年來光纖感測技術的日益純熟，及光纖具有直徑小、重量輕、韌性強、抗腐蝕、抗電磁干擾等優點，已使其成為未來感測技術不可或缺的主要角色。本文以短週期光纖光柵結合Mach-Zehnder干涉光路組成感測系統量測結構振動，量測方法為藉由觀察干涉光路之光強度變化與應變規之應變變化，瞭解光強度與應變之關聯性包含振動週期、相位與振幅等參數。實驗結果顯示光強度與應變具相同之週期與相位，振幅則呈現線性關係，本研究即應用此特性，以光纖感測所得光強度訊號量測結構振動，並與應變規量測值比較。將此光纖感測系統應用於量測懸臂樑振動，包含自由振動、基座激振與強制振動等三種不同振動模式，設定之頻率則涵蓋共振、非共振、單一頻率與雙頻率等多種不同組合。實驗結果顯示光纖感測所得懸臂樑振動應變與應變規量測值，趨勢相當吻合數值雖有些許誤差，但皆在可接受之範圍，驗證此光纖感測系統量測結構振動的準確度與可行性。

關鍵字

光纖光柵 ； Mach-Zehnder干涉儀 ； 自由振動 ； 基座激振 ； 強制振動

並列摘要

Fiber-optic sensors with small size, light weight and immunity to the electro-magnetic interference have the advantages over the conventional sensors. In this investigation, the fiber bragg grating is incorporated with the Mach-Zehnder interferometry to measure the dynamic strain of a vibrating structure. Period, amplitude and phase shift are the three major parameters to characterize the vibration. Experimental results show that the Mach-Zehnder interferometric intensity and the dynamic strain have the same period and phase, and linear relation between the amplitudes. Using these relations, the integrating fiber-optic sensor is employed to measure the dynamic strain of a cantilever beam subjected to either free vibration, base excitation or forced vibration. The selected frequencies for the vibration test include resonance, non-resonance, single frequency and double frequencies. The dynamic strains measured by the fiber-optic sensor are compared with the results of strain gauge. Good correlations demonstrate that the integrating fiber-optic sensor is capable of measuring the dynamic response of a vibration structure.

並列關鍵字

fiber Bragg grating ； Mach-Zehnder interferometry ； free vibration ； base excitation ； forced vibration

參考文獻

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