Sensitivity normalization technique of PGC demodulation with low harmonic distortion and high stability using laser modulation to generate carrier signal

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• 作者：Shih-Chu Huang ; ^{h4431@ms18.hinet.net}&#xA0 ; [Author Vitae] ; Yuh-Fung Huang&#xA0 ; [Author Vitae] ; Zhen-Zhang Wu&#xA0 ; [Author Vitae]
• 关键词：Polarization-insensitive fiber optic Michelson interferometric sensor ; PGC demodulation ; Sensitivity normalization ; Phase scrambler ; Optical intensity modulation ; Minimum phase detection sensitivity ; Total harmonic distortion
• 刊名：Sensors and Actuators A: Physical
• 出版年：2012
• 出版时间：February 2012
• 年：2012
• 卷：174
• 期：Complete
• 页码：198-206
• 全文大小：1306 K

文摘

The phase carrier signal of the PGC demodulator can be generated by using laser current modulation to achieve all-fiber structures for long-distance and outdoor applications. However, an optical intensity modulation with carrier frequency induced from the laser modulation may cause the instability and distortion in the PGC demodulation output. In addition, optical loss may reduce the PGC demodulation output so sensitive that sensitivity compensation on demodulation circuit is needed. In this paper, we propose a novel phase scramble technique by using low frequency phase signal with amplitude 2.405 rad to achieve the sensitivity normalization, and improve the instability and distortion of the PGC demodulation output simultaneously. Experiment results show that without applying scramble signal, the maximum value of total harmonic distortion is very close to the theoretic value and it is large. After applying scramble signal which matches the theorectical optimum condition J₀(?_L) = 0, the instability and distortion of the PGC demodulation output are reduced obviously. According to the sensitivity normalization experiment results, the relative error is less than 0.6 % when the optical intensity attentuation is no more than 15 dB. Therefore, the sensitivity normalization technique proposed in our study is effective.