Abstract: Due to appealing properties such as high bandwidth, low latency and power consumption, optical network is one of the development trends of the new generation communication networks. To enhance optical network's availability and reliability, and guarantee the network to be normal and highly effective working, the fault diagnosis for optical network is an issue that needs to be studied urgently. For optical network, this article sketches its research significance, research trends and development, and points out four aspects including enhanced communication modes, the topological structure properties, different diagnosis abilities and efficient fault self-diagnosing algorithms for optical network to analyze their fault diagnosis in the future.