Selection Of Configuration Structure For Optical Access Network

The selection of configuration structure for optical access networks depends on numerous factors, which are very complex and require detailed analysis, comparison, and comprehensive calculation. Below are only a few basic considerations and principles for readers to consider.

(1) User type

The user type is the first factor to consider when selecting a configuration structure, and if the positioning is not accurate, there will naturally be no reasonable choice. Usually, different types of users require different structures to be configured. For example, the number of user lines required by enterprise users is always greater than that of residential users. Therefore, FTTO and FTTC can be used for this type of user. The former is suitable for large enterprise users with high business volume requirements, while the latter is mainly suitable for small enterprise and residential users. Residential users usually only need one or two user phone lines, so they must adopt structures with greater sharing capabilities, such as FTTC, FTTB, and FTTR. FTTC is more suitable for dispersed users, while FTTB is more suitable for concentrated apartment and residential users. In the long run, FTTH is the direction.

(2) Cost

Cost is the key to the success of user access network technology, and the level of cost largely depends on the extent to which ONU costs can be shared and shared among users. Obviously, FTTH has the lowest degree of sharing, and the user side needs to install an ONU dedicated to one user, which has the highest initial installation and maintenance costs. The cost model calculation results of Raynet Company in the United States indicate that the cost is optimal when the ONU can be shared by 24-32 users. Compared to FTTC and FTTB, the cost of FTTH is much higher, and the current plan to install FTTH can only be due to other non cost considerations. For a considerable period of time, FTTC and FTTB will become the most economically feasible residential user line solutions. For large enterprise users, due to the large number of required user lines, the average cost per line decreases, so the FTTO structure is the most economically feasible solution. New office buildings, restaurants, and large companies in cities can now directly adopt FTTO structures without the need to lay a large number of copper cable user lines.

When considering costs, it is not only necessary to consider the initial cost, but also the cost of the entire life cycle, including the cost of future line growth or renovation, as well as operating costs (supply, maintenance, and power supply, etc.). In this way, the benefits of FTTH are demonstrated. According to the research results of Bell Communications Research Institute in the United States, although the initial cost of FTTH is much higher than FTTC, the power supply cost can be saved by 75% to 90%, the supply cost can be saved by more than 20%, and the business assurance cost can be saved by 25% to 40%. Therefore, the total life cycle cost can be compared with other methods.

(3) Integrated with local exchange

With the advancement of switching technology and fiber optic transmission technology, especially the significant decrease in fiber optic transmission costs, most telephone companies are reorganizing and configuring their access networks. The main trend is to reduce the number of local switches, increase switch capacity, and expand the coverage of the access network. Installing an optical access network often forms part of the aforementioned network reconfiguration plan. If remote switching and centralized functions can be integrated into the ONU, it will make the above network reconfiguration plan easier to implement. However, at this point, the ONU must be able to serve a large number of users in order to be economically viable. Preliminary research and analysis results indicate that an ONU should be able to serve 256 users in order to be economically viable. At this point, the SDH ring structure can integrate the integrated FTTC/FTTB/FTTR access network.

(4) Service flexibility

Service flexibility is often a characteristic that enterprise and public users attach great importance to. The FTTO structure can quickly and flexibly provide or cut off business on request, which is very suitable for the activity characteristics of enterprise and public users. Usually, as the number of users sharing ONUs decreases, the ability to provide special services to each user will correspondingly increase. For large enterprise users, and due to the high demand for business volume, FTTO provides the most flexible services.

(5) Business type

From a long-term perspective, optical access networks must be able to provide broadband image services, including interactive and distributed image services. Obviously, a configuration structure suitable for providing interactive low-speed services (telephone and data) may not necessarily be suitable for providing broadband image services, especially distributive image services. In this regard, pure light FTTH and FTTO structures have the best business transparency. In addition, the closer the ONU is set to the user's location, the easier it will be for future upgrades and updates. Of course, there are other considerations that cannot be elaborated on here.