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Journal of Zhejiang University SCIENCE C

ISSN 1869-1951(Print), 1869-196x(Online), Monthly

Residual intensity modulation in resonator fiber optic gyros with sinusoidal wave phase modulation

Abstract: We present how residual intensity modulation (RIM) affects the performance of a resonator fiber optic gyro (R-FOG) through a sinusoidal wave phase modulation technique. The expression for the R-FOG system’s demodulation curve under RIM is obtained. Through numerical simulation with different RIM coefficients and modulation frequencies, we find that a zero deviation is induced by the RIM effect on the demodulation curve, and this zero deviation varies with the RIM coefficient and modulation frequency. The expression for the system error due to this zero deviation is derived. Simulation results show that the RIM-induced error varies with the RIM coefficient and modulation frequency. There also exists optimum values for the RIM coefficient and modulation frequency to totally eliminate the RIM-induced error, and the error increases as the RIM coefficient or modulation frequency deviates from its optimum value; however, in practical situations, these two parameters would not be exactly fixed but fluctuate from their respective optimum values, and a large system error is induced even if there exists a very small deviation of these two critical parameters from their optimum values. Simulation results indicate that the RIM-induced error should be considered when designing and evaluating an R-FOG system.

Key words: Resonator fiber optic gyro, Phase modulation, Residual intensity modulation

Chinese Summary  <38> 基于正弦波相位调制的谐振式光纤陀螺中的残余强度调制

研究目的:相位调制器是谐振式光纤陀螺系统中的一种重要的信号处理器件。当采用电压调制信号驱动相位调制器时,会伴随引入残余强度调制,这将影响陀螺性能。本文拟深入分析一种采用正弦波相位调制技术的谐振式光纤陀螺中的残余强度调制效应。
创新要点:通过谐振式光纤陀螺解调曲线在残余强度调制下的特性分析,研究了残余强度调制效应对谐振式光纤陀螺系统性能的影响。发现残余强度调制会在陀螺系统中引入零点偏移,该零点偏移引起的误差会随残余强度调制系数及调制频率的变化而变化。得到最佳残余强度调制系数及调制频率,使得残余强度调制引起的误差为零。
方法提亮:如图5所示,通过仿真残余强度调制引入的陀螺误差与调制频率FCCW与FCW的关系,可以发现,存在最佳调制频率使得残余强度调制引入的误差为零。然而,在实际系统中,所选取的调制频率往往与抑制残余强度调度误差的最佳值不同。以FCW=101 kHz为例,当FCCW偏离其最佳值约10.2 kHz时,将引入大约253.4 deg/h的误差,这将严重影响一个中等精度谐振式光纤陀螺的检测精度。
重要结论:在设计及评估谐振式光纤陀螺系统时,需要考虑残余强度调制引入的误差。

关键词组:谐振式光纤陀螺;相位调制;残余强度调制


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DOI:

10.1631/jzus.C1400036

CLC number:

TN253

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On-line Access:

2014-06-06

Received:

2014-02-06

Revision Accepted:

2014-03-26

Crosschecked:

2014-05-04

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