The optical main distribution frame (MODF) is an important part of the optical access network, similar to the existing cable distribution frame (MDF), the optical main distribution frame mainly adopts the traditional MDF cable management method, that is, in-line The module part is the outside line side, which provides outdoor optical terminal fixation, confluence, fusion splicing and terminal functions, and the horizontal module part is the inside line side, which provides the terminal, scheduling, measurement and management functions of indoor optical fiber and cable.
MODF products combine the traditional “fiber distribution frame” and “intermediate distribution frame” to complete the following functions:
Introduction, fixation and stripping protection of optical cables, fusion splicing and protection of optical fibers, storage of pigtails, storage and management of jumper fibers, fixed connection and cross-connection of optical fibers, etc.; at the same time, optical splitters can be installed according to customer requirements. Value-added module units such as wavelength division multiplexers.
1 Necessity of Network Convergence
(1) Disadvantages of PSTN gradually appear
(2) The demand for multi-network integration continues to increase
2 Research Status of Network Convergence
International organizations such as 3GPP, ETSI, and ITU-T have carried out research on network convergence issues, which are generally in the stage of system architecture discussion.
Among them, 3GPP research hotspots focus on three aspects: how to apply IPv6 in the IMS domain to solve the address problem, so as to realize IMS as soon as possible; how to coordinate the difference between the SIP protocol in the mobile and fixed networks; Achieve higher QoS guarantee.
ETSI TISPAN is currently formulating NGN-related specifications, named TISPAN_NGNRelease1, and its overall research goals are: fixed terminals can obtain all services provided by the 3GPPIMS core network; can fully or partially replace the PSTN/ISDN services provided by the existing core network; support users or terminals Mobile; provide QoS control functions; provide business development and interoperability capabilities, and provide third-party business capabilities.
TISPAN and 3GPP also cooperate to carry out IMS-related research, focusing on subscriber identification card issues and service engine issues on the basis of reusing the IMS concept.
3 Evolution from fixed switching network to NGN
NGN is based on the idea of separating call control from bearer control, and service from control. It uses softswitch as the core technology and carries it on the packet network. It decomposes the original switch into softswitch equipment and media gateways. The protocol of IP transmission realizes the control of calls and services, and the transmission of voice and data. It not only solves the problems existing in the current switching network, but more importantly, it combines the switching network and the data network skillfully and organically. On this basis, it also A variety of flexible and rich service provision methods are proposed, making it possible for operators, equipment manufacturers, and even third parties to quickly provide integrated or personalized services. In addition, it also considers the gradual and orderly development rules of the network, so it provides a common POTS terminal access method through access gateways, integrated access devices and other equipment, and provides an effective way to communicate with PSTN networks through trunk gateways. To sum up, the fixed switching network has determined the development trend from PSTN to NGN.