As IPTV, triple play, VoIP and other new telecommunications services rise, people find that IP-bearing agreement business has rapidly spread in most regions of telecommunications and fiber optic networks.
IP-based packet-based carrier network transformation has been become an irreversible trend. In this trend, carriers are shifting the entire network infrastructure, business anticipates the integration of optical layer integration as a foundation bearing layer, making it even more right for carrying IP/MPLS and Carrier Ethernet services group transmission network. The brand new telecom services in contrast to traditional telecom services, with increased dynamic and unpredictable, therefore have to transfer the bearer network to provide greater flexibility.
Because the same time, long-distance dense WDM mature, making the network a real business of building from the bandwidth bottleneck within the transfer to the bandwidth management, within the core network nodes, often need to deal with dozens or perhaps hundreds of wavelengths, but long-distance transmission capability and much more nodes must have more capacity to the upper minimizing wavelength. Like a basis for carrying the network inside a more competitive market environment, it needs to provide faster service and various amounts of network protection and recovery capabilities. Therefore, as the traditional physical layer of optical layer network, we must adjust to a brand new generation of packet-based bearer networks, operational, bandwidth, large granular, and dynamic networking needs.
DWDM is the most common optical layer networking technology. Through multiplexing/demultiplexing, it can achieve tens or perhaps countless wave wave transmission capacity. However in the current WDM systems, its nature is still a point-line system, most of the optical layer network only through the terminal station (TM) to achieve the optical line system construction. Later, Optical add-drop multiplexer (OADM) gradually taken point to point network to the ring from the evolution. However, due to the limited OADM functions, usually merely a fixed number of levels and wavelengths of sunshine channel, and never really flexible optical layer networking. Thus, in this way, early WDM systems do not achieve true optical layer networking, IP-based networks can not meet the business requirements and packet-based until the emergence of the situation was able to enhance the ROADM. To meet up with the needs of IP networks, it provides a new idea that gradually adopt a reconfigurable optical add drop multiplexer plug (ROADM), represented by optical layer reconfiguration technology, and in line with the construction of the bearer network.
ROADM Technical Introduction is really a similar SDHADM optical layer network element, which can be completed in one node down and up road of sunshine channels (Add/Drop), and penetrating between your optical channel wavelength-level cross-scheduling. It can be remotely controlled by software, network aspect in achieving the lower and upper road wavelength ROADM sub-system configuration and adjustment. Currently, ROADM subsystem, there are three common techniques: planar lightwave circuit (PLC), wavelength blocker (WB), wavelength selection switch (WSS).
PLC is among low-cost ROADM solution. The advantage is that multiplexer and demultiplexer technology is mature and reliable, low insertion loss within the node, down way more when costs are lower wavelength, simple to upgrade to the OXC; drawback is poor modular structure, the initial configuration and high cost, large capacity the longevity of cross matrix must be improved.
Physical factors as transmission, all-optical transmission distance is susceptible to certain restrictions, within the backbone network applications, the company flow and also the flow can not be any change, still need to accurately design and planning, increasing the complexity of network planning. Deutsche Telekom is also clear the physical limitations affecting ROADM transport network of important reasons.
Based on existing ROADM these shortcomings, the proposed to increase the cross-field power. So had a ROADM OTN equipment form. Typical applications are now, in excess of 10G (with 10G) business, the node all-optical way through or up and down, for GE/2.5G business, its first node towards the electric field under the road crossing panels, according to further 2.5G particles and electric field-drop multiplexing. This drop multiplexing mode somewhat similar to the ADM, just the first-class all-optical processing. Equipment manufacturers have previously released products, and in certain applications inside the metropolitan area.