隧道能见度与行车安全有重要关系，对隧道能见度进行实时监测可以为隧道通风换气提供有力依据。基于透射法能见度检测原理，设计并搭建了一套能见度检测系统用于隧道能见度的自动检测。检测系统主要由激光二极管、分束器、硅探测器和信号处理单元等部分构成。采用高响应度硅探测器并设计了跨阻抗放大电路以满足在低能见度下测量需求。两硅探测器分别检测经光学路径衰减前后的光强并输出对应的光电流，信号处理电路对探测器两路输出进行放大滤波和A/D 转换后，反演出消光系数。使用固定透过率滤光片模拟隧道环境，在实验室环境下对该检测系统性能指标进行测试。实验结果表明：消光系数测量范围3.37 km-1～118.82 km-1，最大相对测量误差为8.4%，稳定性优于0.12 km-1。

Tunnel visibility has an important relationship with traffic safety. Real-time monitoring of tunnel visibility can provide a strong basis for ventilation and ventilation of tunnels. Based on the principle of visibility detection by transmission method, a set of visibility detection system is built for automatic detection of tunnel visibility. The detection system is mainly composed of a laser diode, a beam splitter, a silicon detector and a signal processing unit. Two silicon detectors detect the intensity of light before and after attenuation through optical path respectively and output corresponding photocurrent. The signal processing circuit amplifies and filters the output of the detector and converts the output to AD, and then calculates the extinction coefficient. Fixed transmittance filter is used to simulate tunnel environment, and the performance index of the detection system is tested in laboratory environment. The experimental results show that the measurement range of extinction coefficient is 3.37 km-1～118.82 km-1, the maximum relative measurement error is 8.4%, and the stability is better than 0.12 km-1.