在基于外差方案的干涉型光纤检波器中,正交载波的获取是其中的一个重要环节。谐波失真和相对幅度误差是评价解调信号质量的重要指标,正交载波之间存在的相位偏差会导致解调信号的谐波失真和相对幅度误差增大。分析了正交载波的相位偏差与解调结果的谐波失真、相对幅度误差之间的关系,运用级数分解和贝塞尔函数展开式进行数学推导,并进行了仿真验证。分析结果表明,正交载波的相位偏差与谐波失真/相对幅度误差呈正相关,当要求谐波失真优于-40 dB、相对幅度误差小于1%时,需要控制相位偏差在1.6×10 ^-2 rad以下。最后搭建了实验测试系统,实验结果验证了理论的正确性。

The acquisition of quadrature carriers is important for interferometric fiber-optic seismometer with heterodyne scheme. Harmonic distortion and relative amplitude error are the major parameters for quality evaluating. The existence of phase bias between quadrature carriers will lead to the harmonic distortion of demodulation result and increase the relative amplitude error. Relationship among phase bias of quadrature carriers, harmonic distortion and relative amplitude error is analyzed. Mathematical derivation is carried out with series decomposition and Bessel function expansion, and simulation verification is carried out. Analysis results show that the relative amplitude error and the harmonic distortion are both positively correlate with the phase bias of quadrature carriers. The phase bias should be controlled under 1.6×10 -2 rad to ensure relative amplitude error lower than 1% and harmonic distortion better than -40 dB. A experimental system is established, and experiments are conducted. The experimental results are consistent with the theoretical results.