基于硅光调制器的混沌保密通信系统的研究

A scheme of chaos generation and synchronization based on silicon optical modulator is proposed, which will be employed to demonstrate secure communication using chaos masking. Silicon optical modulator is the key element of the scheme. On the one hand, it converts the electrical signal to optical signal. On the other hand, the nonlinear transfer function in the conversion process provides the nonlinear mapping needed by chaos generation. The optical signal produced by the electro-optical conversion will be delayed and then go through fiber amplifier, variable optical attenuator and be converted to electrical signal using photodetector and RF amplifier. This electrical signal is used to drive the silicon optical modulator to form the feedback. The strength of the feedback is adjusted by the setting of the fiber amplifier and other equipments. The combination of the nonlinear mapping and the delayed feedback forms the chaos signal generation system. The plaintext at the transmitter will be added with the chaos signal to produce noise-like hybrid signal, which is the encryption process. The chaos signal will be extracted out of the above-mentioned hybrid signal after it arrives at the receiver with a corresponding chaos system, which is the decryption process. The main research contents of this proposal consist of the design and fabrication of silicon optical modulators, the building of the chaos signal generation and synchronization system, and the demonstration of secure communication using chaos masking. The main innovation of this proposal is the implementation of chaos secure communication employing integrated optical components, which will reduce the size and improve the stability of the system.

本申请提出了一种基于硅光调制器的混沌信号产生与同步的方案，并拟利用其实现混沌掩盖保密通信的演示。硅光调制器是该方案的核心单元：一方面，它实现电信号到光信号的电光转换；另一方面，这一转换过程中的非线性传输函数提供了产生混沌所需的非线性映射。电光转换所得光信号在延迟后经过光纤放大器、可调光衰减器后被光电探测器及射频放大器转换为电信号。该电信号对硅光调制器进行驱动形成反馈，反馈强度的大小由光纤放大器等部件的设置来调节。上述非线性映射与延迟反馈的组合构成混沌信号产生系统。待传输的明文加在该混沌信号上，生成类噪声的混合信号，完成加密过程。该混合信号发送到接收机上后，再由一相应的混沌系统分离其中的混沌信号，完成解密过程。本课题的主要研究内容包括硅光调制器设计与加工、混沌信号产生与同步系统搭建、混沌掩盖保密通信演示三个方面。主要创新在于采用集成光学元件实现混沌保密通信，有利于减小系统体积并提高其稳定性。

本课题提出并实现了一种基于硅光调制器的混沌信号产生方案。硅光调制器是该方案的核心单元：一方面，它实现电信号到光信号的电光转换；另一方面，这一转换过程中的非线性传输函数提供了产生混沌所需的非线性映射。本课题通过对MZI硅光调制器的工艺参数（主要是掺杂浓度与位置以及MZI臂长等）进行优化，我们获得了静态消光比大于20dB，3dB带宽均大于12.5GHz，3 dB带宽差异小于10%的调制器。以MZI硅光调制器为核心单元，我们搭建了混沌信号产生系统。在该系统中，电光转换所得光信号在延迟后经过光纤放大器、可调光衰减器后被光电探测器转换为电信号。该电信号对硅光调制器进行驱动形成反馈，反馈强度的大小由光纤放大器来调节。延迟时间及激光波长的设置对系统的动态演化也有着重要的影响。上述非线性映射与延迟反馈的组合构成混沌信号产生系统。我们利用该系统观测到了倍周期信号、混沌信号及稳定的奇异态信号（1头至8头）。我们对该混沌信号产生系统进行了建模，基本思想是根据各组成单元的时间相应特性列出系统微分方程，然后进行差分化以模拟系统动态行为。该数值模型给出了与实验系统相近的时间演化波形。本课题所研究的采用硅基电光调制器构建的延迟反馈系统，对混沌信号的产生与同步，以及奇异态的实验研究都有着重要的意义。