为了提高异面腔四频差动激光陀螺(NFMDLG)的精度，提出了一种利用互易偏频的零偏补偿技术。根据气体激光器经典理论，推导了NFMDLG的互易偏频和零偏的表达式。分析了NFMDLG中的左旋陀螺分别位于增益曲线左、右侧时其输出零偏的特点，指出磁圆二向色性差损导致的零偏在这两种情况下大小相同符号相反。搭建了一套可同时测量互易偏频和零偏的实验系统，通过改变NFMDLG的放电电流和腔体温度验证了理论分析。在此基础上提出利用互易偏频补偿温度和电流变化导致零偏的方案。实验结果表明，温度变化50 ℃时，采用该补偿方法后零偏在±0.01 Hz内波动；放电电流变化0.2 mA时，补偿后的零偏降低了4/5。因此互易偏频可有效补偿模牵引效应导致的零偏误差。

In order to improve the precision of Nonplanar Four Mode Differential Laser Gyros (NFMDLG), a compensation method by using reciprocal biasing is proposed. Expressions of reciprocal biasing and bias of the NFMDLG are derived according to the classic theory of a gas laser. The bias characteristics of the left circularly polarized gyro in the NFMDLG on the left and right sides of a gain curve are analyzed for two cases, respectively. Then,it points out that the bias caused by a magnetic circular dichroism loss is identical in number while reverse in sign for the two cases. An experimental system is established to measure the reciprocal biasing and bias synchronously,which verifies the theoretical analysis by varying the discharge current and temperature. Finally,a method is proposed to compensate the bias error of NFMDLG with reciprocal biasing. Experiments show that the bias drift resulted from temperature variation in the range of 10-60 ℃ is less than 0.01 Hz,and that resulted from 0.2 mA current variation is reduced by four-fifths after compensation. In conclusion,the reciprocal biasing can compensate effectively the bias caused by the mode pulling effect.