描述了基于同相正交硅基光调制器的自动偏置电压控制算法理论及实现方案。首先比较了硅基光调制器与传统铌酸锂调制器的调制特性,结合同相正交硅基光调制器模型推导出了调制器输出光信号与电场信号的函数关系式,根据此关系式提出了一种基于正弦dither信号注入调制器偏置工作点并解析调制器内置低带宽监控光电二极管反馈信号频域参数的控制方案,并通过数值仿真验证方案的可行性;然后搭建自动偏置电压控制算法的测试平台,通过测试平台得出不同偏置电压条件下I(in-phase)路、Q(quadrature-phase)路与Phase(outer-phase)路调制器内置监控光电二极管的反馈信号波形,并将测试结果与仿真数据进行对比,对比结果验证了本研究假定的同相正交硅基光调制器光电传递函数模型的准确性;最后测试了128 Gb/s双偏振正交相移键控调制格式下偏置电压控制算法的精度,并通过矢量幅度误差指标得到算法所引入的光信噪比代价。

A novel automatic bias control algorithm based on in-phase quadrature-phase silicon-based optical modulator is theoretically and experimentally proposed. Firstly, we compare the modulation characteristics between silicon-based optical modulator and lithium niobate modulator. Based on the model of in-phase quadrature-phase silicon-based optical modulator, we derive the functional relationship between the output signal and the electric field signal of the modulator. A control scheme is proposed to add the sinusoidal dither signal into the bias operating point of the modulator and analyze feedback signal spectra of the low-speed monitoring photoelectric diode which is built-in modulator. The feasibility of the scheme is verified through numerical simulation. Then we build the experiment platform of automatic bias control. We obtain the test results of monitoring photoelectric diode signal spectra with different bias voltages applied to channel I (in-phase), channel Q (quadrature-phase), and channel Phase (outer-phase) by using the experiment platform. The model of the photoelectric transfer function described in this paper is supported by simulation and measurement results. Finally, we measure the control accuracy of the algorithm in 128 Gb/s dual-polarization quadrature phase shift keying modulation format and calculate the penalty factor of the optical signal-to-noise ratio by the vector magnitude error parameter.