SDH transmission system in the world to have a unified standard for digital transmission rate of the frame structure and standard optical interface, allowing network management system interoperability, and therefore has good lateral compatibility, is fully compatible with existing PDH, and accommodate variety of new traffic signals, the formation of a unified global standard digital transmission system, improve the reliability of the network.

SDH (Synchronous Digital Hierarchy), defined according to ITU-T recommendations, is the transmission of digital signals at different speeds to provide information on the structure of the corresponding level, including the multiplexing method and mapping method, as well as the associated synchronization method consisting of a technical system.

PTN (Packet Transport Network) refers to an optical transport network architecture and specific technologies: IP traffic between the optical transmission medium and the underlying set a level for which the packet of bursty traffic statistical multiplexing and transmission requirements Designed to packet core business and supports multiple service provider, has a lower total cost of ownership (TCO), while inheriting traditional advantages of optical transmission, including high availability and reliability, efficient bandwidth management mechanisms and traffic engineering, convenient The OAM and network management, scalable, high security.

The main advantage of OTN is fully backward compatible, it can build on existing SONET / SDH management functions on the basis of not only the existence of a fully transparent communication protocol, but also for WDM-end connectivity and networking capabilities, It provides a light layer interconnect specification ROADM, and added sub-wavelength aggregation and grooming.

This article discusses the function of WDM technology OADM based systems, the node structure and its products and applications, and its drop multiplexing tributary signals in wavelengths, called optical channel. OADM node device is one of the key equipment of all-optical network.

In 1988, the United States launched the first of a digital transmission standard, the entire network clock synchronization levels are from a very precise master clock (using expensive cesium atomic clock, accuracy better than plus or minus 10 -11 th).

Polatis all-optical switch manufacturer, today launched the network for the protection of the optical layer failures Polatis 6000n all-optical solutions to protect business switch PSS.

FTTH (Fiber To The Home), the name suggests is an optical fiber directly to the home. Specifically, FTTH refers to the optical network unit (ONU) installed at the home user or business user, a series of optical access user of the optical access network application types except FTTD (fiber to the desk) the closest off. FTTH is a distinctive feature not only provides more bandwidth, but also enhances network data format, speed, wavelength and protocol transparency, relaxes the environmental conditions and power requirements, simplifying maintenance and installation.

Automatically Switched Optical Network (ASON), also known as intelligent optical network. It is through the introduction of routing protocols and signaling mechanisms in synchronous digital hierarchy (SDH), and to promote the integration of optical switching and transport level, to provide users with a wavelength of wholesale bandwidth rental, OVPN, traffic accounting, SLA business services and so on.

Now a lot of the network, subject to the fiber aging, terrain reasons, loaded dimensional factors and other reasons, PON network led to the loss of light is too large, making it impossible to meet the receiver sensitivity between ONU or near zero cutoff, so that the terminal network connection is unstable or can not opening and so on.