拉曼散射分布式光纤传感器(DOFS)能有效地进行长距离温度检测，并具有抗电磁干扰强、系统结构简单和灵敏度高等优点。但其空间分辨率与检测信噪比(SNR)之间存在一定的矛盾，即在一定的光功率限制下，当增加光源脉冲宽度以提高检测信噪比时，系统的空间分辨率也会因此降低。采用Simplex编码(简称S编码)光外调制的方式来解决这一矛盾，通过理论分析和数值计算研究了S编码对拉曼散射分布式光纤传感器的作用。在实现编码光调制的分布式光纤传感器中，存在如何产生高功率编码调制光这一问题，难以应用一般的脉冲激光器或内调制。采用光源外调制加放大的方案，建立了基于S编码的4.7 km拉曼散射传感实验系统，初步实验结果验证了码长为7的S编码，对检测信号比有1.6倍左右的改善效果。

The Raman-scattering-based distributed optical fiber sensor (DOFS) can realize the continuous temperature detection in one-dimension space. It has good environmental adaptability, simple system structure, and high sensitivity. But there is a conflict between the spatial resolution and the signal sensitivity in the system, namely, when increasing pulse width of the probe pulse to improve the signal to noise ratio (SNR) of the detected signal, the spatial resolution is degraded simultaneously. Simplex code is used to overcome this conflict between the SNR and the spatial resolution. Using the theoretical analysis and numerical simulation, the Simplex code′s effect on Raman DOFS has been studied. In realizing a coding DOFS, there exits a problem of how to achieve high-power coding pump light, because the usual methods, such as pulsed-laser or internal modulation, can not be used. A method based on external modulation and optical amplifier is chosen, and a 4.7 km Simplex coding Raman DOFS experimental system has been set up. The results show that the 7-bit simplex code can improve the SNR of the detecting signal by around 1.6 times.