High-speed railway that has been progressing very quickly is one of the greatest techniques in present time because of its high speed, economy, comfort, environment benefits and other advantages. And among all of these, safe is the backbone and lifeline, so the chief task in developing high-speed railway is to establish safety guarantee system. Also in this safety guarantee system, train control is one of the key techniques to guarantee safe train operation and to advance ability of transportation, so operation safe is located in the hardcore position. That is to say, it is imperative to set up a safe, real-time and reliable automatic train control system. And we can easily find out that this kind of system is now developed and applied in many countries. Important information related to train control, such as the received and transmitted information of track-sided equipment, is called safe information, because it deals with train operation's safe, reliability, and even directly with people's life and wealth. It is so important that if there were some kind of fault with its making, transmission, or processing, fatal accident would occur. So to some degree, it is impossible to transmit and process this information through present railway communication network because of the former's extreme importance and the latter's no safe capability. Therefore, a specific communication network that mainly considers about safe transmission and management should be established in order to realize the specific function for this specific information. High-speed railway safe information transmission optical LAN, which adopts optical fiber as transmission media and transmits safe information, is a kind of LAN designed for the request for safe, real-time and highly reliable automatic train control system in the process of our country's high-speed railway construction and commonly train speed. In this paper, after analyzing the characteristics of automatic train control system and the structure, status and function of the safe information transmission optical LAN, we analyze the main factors which affect the network's safe transmission performance based on the principle of safe design. Then, on the foundation of the elementary principle of the concept, fail-safe, in railway signal field, we discuss the real network's safety and realization of the software and hardware. The final experiment indicates that the real network works robustly, performs reliably, and achieves the designed aim. When some kind of faults occur which produced by hardware, software or transmission media, the network can easily and reliably deal with them and transfer to safety mode that will ensure the train's operation. The analysis and design of this network is a meaningful step in constructing our country's railway special communication network and also the network can be used in other similar conditions that demand extreme safe.
Propose coupling equation between counter-propagating signal and control pulse in nonlinear optical loop mirror (NOLM). Study the nonlinear phase shift deference between the co- propagating and the counter-propagating signal in transmission process. Analyze the switching characteristics of Gaussian and non-return zero (NRZ) pulse. Get the first best de- multiplexing lengths, switch windows, output waveform and so on, which are important in practical usage.