光纤陀螺随机调制的理论分析及实验

偏置稳定性是描述陀螺性能的重要指标,而电路中的交叉干扰是导致陀螺输出漂移的重要原因.采用随机调制的方法能够减小陀螺中交叉干扰产生的输出漂移.采用快速傅立叶变换(FFT)的方法对方波调制和随机调制产生的交叉干扰进行了分析,分析结果表明,采用方波调制时,交叉干扰与方波同频,无法滤除,导致陀螺输出的偏置误差以及陀螺输出对光强的依赖性;而采用随机调制,交叉干扰与方波频率不同,能够滤除,从而减小交叉干扰带来的随机漂移.采用的随机调制为-3π/2,-π/2,π/2,3π/2调制,能够保证陀螺工作点在灵敏度最高的偏置点上,其频谱主要成分为方波基波的偶次谐波,通过陀螺电路中的滤波,能够将其滤掉,消除交叉干扰对陀螺输出带来的干扰.对方波调制和随机调制分别进行了实验,通过实验,证明了该方法的正确性,得到了随机调制能够抑制光纤陀螺中由于交叉干扰产生的输出漂移的结论.

Theory analysis and experiment of random modulation in FOG

Bias stability is an important performance of gyro. But in digital closed loop fiber optical gyro(FOG), it is influenced extremely by the electrical crosstalk in the electronics. Output drift can be reduced by using random modulation.The crosstalk of square wave modulation and random modulation was analyzed through fast Fourier transformation(FFT). When square wave modulation is used, the crosstalk result has the same square wave frequency with the photodetector analog output. So it can not be filtered in the gyro electronic and bias error arises in output. Further more , it causes the output dependence on the light intensity. When random modulation is used, the crosstalk result has different frequency with the photodetector analog output, so the output of FOG has more stablity. The random modulation point is -3π/2,-π/2,π/2,3π/2, which is the most sensitive point. The modulation wave has even harmonious of square wave frequency. Experimental results indicate that bias error can be restrained and the bias stability of output increased when random modulation is used in digital closed loop FOG.