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在分析光纤色散导致的相位-强度调制转换的基础上,提出了一种利用电光相位调制的光纤色散扫频测量方法。方法的原理为光纤色散使相位调制信号获得附加相移并产生周期性衰落,从衰落曲线的特征性凹陷频率确定出光纤色散。实际运用中,由于凹陷频率附近的信号弱,因此噪声大且不稳定。为了解决这一问题,通过衰落曲线的多项式拟合,进一步提高凹陷频率和光纤色散的测量精度。实验中,对长光纤或者短光纤分别测试以验证本文方法对于不同色散的适应性。实验结果表明,本文方法的相对误差小于0.22%。使用矢量网络分析仪(VNA)和相位调制器进行测试,可工作于不同光波长,适用于测量不同种类的光纤的色散;并且可以利用简单的实验系统,实现光纤色散的大小和符号的测量。
Based on the analysis of phase-intensity modulation conversion caused by fiber dispersion, a fiber-optic dispersion sweep measurement method using electro-optical phase modulation is proposed. The principle of the method is that the fiber dispersion obtains additional phase shift and periodic fading of the phase-modulated signal, and determines the fiber dispersion from the characteristic recess frequency of the fading curve. In practice, the noise is large and unstable due to the weak signal near the recess frequency. In order to solve this problem, the polynomial fitting of the fading curve further improves the measurement accuracy of the sag frequency and the dispersion of the optical fiber. In the experiment, long fiber or short fiber were tested separately to verify the adaptability of the method to different dispersion. Experimental results show that the relative error of this method is less than 0.22%. Using VNA and phase modulator for testing, it can work at different light wavelengths, suitable for measuring the dispersion of different kinds of optical fibers. And it can use simple experimental system to measure the size and symbol of optical fiber dispersion.