Based on the analysis of the requirement of network communication security, the safeguard effect of optical fiber sensing and real-time monitoring technology of fiber optic cable status for network communication security is expounded. Firstly, the development history of optical fiber sensing technology and the representative optical fiber sensors are introduced, then the principle and working mode of distributed optical fiber vibration sensing system are introduced. And the demodulation method of distributed optical fiber vibration sensing system is analyzed. In order to obtain a higher SNR, the effect of delay difference on SNR in the data demodulation is analyzed through experiments. The experimental results show that the delay time is positively correlated with the SNR in a certain range.