采用外差相干技术理论上可以获得低至MHz量级甚至更高分辨率的光谱信息。介绍了一种基于外差相干技术方法实现的光谱检测系统, 并推导了90°光学混频器和平衡探测器的信号传输原理, 讨论了本振光和滤波器的性能参数与光谱检测分辨率的关系。利用光通信系统设计软件OptiSystem建立了完整的相干光谱检测系统的模型, 并使用波长扫描和迭代运算模拟了实际本振光信号的工作模式, 验证了该方案实现高分辨光谱分析的可行性和优越性。最后分析了对于频率间隔为40 MHz的被测信号, 不同的本振光扫描线宽、扫描步长和滤波器带宽参数组合实现的仿真结果, 并总结了光谱检测精度对本振光和滤波器等关键参数的要求。

The optical spectrum details could be detected theoretically even as low as MHz lever based on heterodyne interference principle. A scheme design of optical spectrum detecting system based on heterodyne interference technique was introduced, in which the signal transmission principle from the 90°optical mixer to the balanced detector was deduced. Moreover, the relationship between the settings of the local oscillator, as well as the filter intermediate frequency and the system resolution was concluded. The compact spectrum detecting system is built upon OptiSystem software, in which the wavelength sweep and iteration could be used to simulate actual local oscillator operating mode, thus the feasibility and superiority of the ultra-high resolution spectrum analysis function were verified. In the end, the simulation results of different linewidth and scanning step length of local oscillator, as well as the filtering parameters was given in 40 MHz frequency interval. The resolution requirement on the local oscillator and filter was concluded.