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。

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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。

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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.

本文详细介绍了大连快轨三号线牵引供电系统中直流1500V联跳信号的传输由电缆改为光缆的原理和改造情况。

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"By bringing optical fibres in some of the networks, by just closing the loops, you will avoid excessive Internet transit costs, bringing down the cost by two-thirds, " he said.

UNESCO: Communication and Information