闭环光纤陀螺调制非线性度的测试方法研究

Research on testing method of modulation nonlinearity in closed-loop fiber optic gyroscope

反馈调制回路是闭环光纤陀螺的重要组成部分,反馈回路器件本身以及温度变化造成的调制非线性直接影响光纤陀螺的调制解调过程。为了实现对反馈回路调制非线性度的精确测量,提出了一种新颖的六态波调制方案。利用第二闭环解调序列与第一闭环解调序列正交的原理,消除陀螺输入角速度对反馈回路调制非线性度测试的影响;利用数字式平均处理,消除温度漂移的影响;利用调制波幅值较大的优势,激发出反馈回路微弱的非线性误差。进而,分析了六态波调制方案测试反馈回路非线性度的原理,并推导出解调值与非线性误差的关系。实验结果表明,新的六态波调制方案对于反馈回路非线性度的测试有效,简单易行,对于促进光纤陀螺标度因数线性度的改善具有重要的意义。

The feedback is the core component of the closed-loop fiber optic gyroscope( FOG). The nonlinear effects of the device’s material and temperature directly affect the modulation and demodulation process of the FOG. In order to accurately measure the modulation nonlinearity of the feedback,a novel six-state wave modulation scheme is proposed. The interference induced by the input angular velocity is nulled out because the second closed-loop demodulation sequence is orthogonal to the first closed-loop demodulation sequence;The temperature drift is eliminated by using the digital averaging process;A weakly nonlinear error of the feedback loop is excited by the six-state modulation wave with a large modulation amplitude. Furthermore,the test method of modulation nonlinearity by the six-state modulation scheme is analyzed,and the nonlinearity of the demodulation result and modulation phase is derived. The experimental results present that the new six-state wave modulation scheme is effective for testing of the modulation nonlinearity. This testing method is very advantageous because of its convenience.