基于法拉第效应的Sagnac干涉仪型光学电流互感器可精确测量电流，因此受到广泛关注。延迟线在典型的串联型电流互感器结构中起到不可或缺的作用,其长度变化会影响系统输出，从而有可能使解调出的法拉第相移引入误差。通过对琼斯矩阵得出的理想系统输出进行理论分析与数值仿真实验，研究了延迟线长度变化对尺度因子的影响。研究结果表明，在一定条件下，延迟线长度失匹配会使尺度因子误差超过0.2%，而温度变化导致的延迟线光程变化产生的尺度因子误差不够明显。因此，建议在采用典型的串联型Sagnac结构及该解调方案时，延迟线长度最好与调制圆频率相匹配，如有特殊需求，实际长度与匹配长度的偏差不要超过50 m,或者将所有器件整合在一起,采用专用线传输。

Sagnac interferometer current transformer, especially its improved inline configuration, exhibits accurate behavior in current measurement and thus attracts plenty of interest. The delay line part, which plays an indispensible role in the inline structure, has an explicit effect on the system output and may further introduce errors in the demodulated Faraday phase shift when different lengths are employed. In this paper, the theoretical analysis and numerical simulation of the ideal system output obtained by Jones matrix are prensented. And the effect of delay line length change on scale factor is studied. According to research results, the scale factor may exceed 0.2% due to delayline length mismatch under some certain conditions, while the response of temperature change induced delay line OPD in scale factor error is comparatively not obvious with other factors being equal. Consequently, it is suggested that when inline Sagnac configuration and peak-divide demodulation are implemented, the length of delay line has better to be the perfect match with the modulation frequency. Otherwise, on specific occasions, the deviation of delay line length from match value should be within 50 m, or integrate all elements together, and use specific signal transmission line.