But the survival problem of optical network is still the focus of city rail transit, especially studying and using the ring optical network.
但是光网络的生存性问题仍旧是城市轨道交通关注的焦点，特别是对环形光网络研究和应用。
2
Simulant system for training comprise of the transit instrument which has been provided by optical measure equipment without any change and the newly developed simulant sub-system for training.
模拟训练系统由原经纬仪和新研制的模拟训练分系统组成，模拟训练系统不对经纬仪做任何改动。
3
This paper introduces the principle and transformation situation of replacing cable with optical fiber for DC1500V intertrip signal transmission in Dalian Express Rail Transit No. 3 Line.