| PGC(phase generated carrier)modulation and demodulation is an important anti-phase fading scheme and has been widely used in interference optical fiber sensing systems.Because of its excellent characteristics and wide commerciality,semiconductor lasers have become the main source of interference fiber-optic sensing systems using PGC modulation and demodulation schemes.Due to the characteristics of the semiconductor laser itself,additional intensity modulation is inevitably introduced during the modulation of the light source,resulting in unstable demodulation.Therefore,this paper analyzes the modulation characteristics of semiconductor lasers in PGC systems,and studies the additional intensity modulation suppression methods,which provides sufficient theoretical and experimental basis for the optimization of interferometric fiber-optic hydrophone systems.This paper mainly elaborates and analyzes from the following aspects:1.Based on the basic principle of PGC modulation,the additional intensity modulation mechanism of semiconductor laser due to current modulation is studied,and the modulation characteristics of semiconductor laser are tested.2.The theoretical analysis and corresponding simulation analysis of the influence of additional intensity modulation of semiconductor laser on PGC demodulation are carried out.The harmonic distortion and amplitude error are used to evaluate the demodulation effect,and the influence of parameter error on demodulation is analyzed.Verified.3.The structural phase division method is proposed to suppress the influence of additional intensity modulation on demodulation and experimental verification.From the demodulation effect,the total harmonic distortion is actually observed to decrease from about-28 dB to about-46 dB,and the amplitude error range is from A reduction of about 1.3 dB to about 0.1 dB verifies the effectiveness of the structural division method. |
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