The decision between 19- or 23-inch racks, ETSI racks or cabinets, as well as between front and rear Optical Distribution Frame (ODF) access or only front access, has implications for the operation and reliability of the ODF system.
As a rule, the larger the rack and the greater the access, the better the cable management will be. An ODF in a 19-inch enclosed cabinet with no rear access will have far less accessibility and fiber cable management features than an ODF in a 23-inch open rack with front and rear access.
This limited access space and lack of cable management features will have a direct impact on the flexibility and reconfigurability of the fiber network, as well as on the network’s long-term reliability.
Even though floor space requirements and existing practices may indicate a particular type of rack configuration, attention needs to be paid to the overall effect on fiber cable management.
As fibers are routed from the ODF to the Fiber Optic equipment, they need to be protected. In order to provide proper protection and ensure future growth and reconfiguration capabilities, all fibers routed between the ODF and the equipment should be placed in a dedicated cable raceway system.
This system is generally located at the lower level of the auxiliary framing/ ladder racking structure. Locating the raceway system there makes access for installing and routing fibers easier.
As the system is in an area of the central office in which technician activities are common, the cable raceway system needs to be durable and robust enough to handle day-to-day activities.
For example, technicians installing copper or power cables on the ladder racking can come into contact with the system.
If the system is not robust enough to withstand a technician accidentally putting his weight on it, the integrity of all the fibers in the system is in jeopardy.
A durable, properly configured raceway system with suitable cable management, especially bend radius protection, helps improve network reliability and makes network installation and reconfiguration faster and more uniform.
Cable congestion is just like traffic congestion. Put too many cars at one time onto a small road and you have traffic problems. It becomes difficult to move from one point to another, and the probability of an accident increases. The same basic rules apply to fiber congestion in an ODF’s raceway system.
If too many fibers are routed into a single trough, accessing an individual fiber becomes very difficult, and the probability of fiber damage increases. This can lead to decreased network reliability and an increase in the time it takes to reconfigure the network.
Telcordia recommends that the fiber cable in any given horizontal raceway not exceed 50 mm in depth. There are also formulas that can be used to calculate the maximum number of fibers that can be safely installed in a given cable trough.
Following the rules ensures that the fiber cables are always accessible and helps maintain the network’s long-term reliability.
The ODF system put into a central office should be capable of handling the future requirements of the network. These requirements include the addition of more fibers as well as new products such as splitters, WDMs, optical switches and the like.
The addition of any new panels, whether for splicing, termination, storage or other functions should not cause any interference with or movement of the installed fibers. This ensures that network reliability is maintained and also allows new services to be implemented quickly and cost-effectively.
This ability to add equipment as needed allows the ODF to grow as the network requirements grow, thus reducing the initial installation cost of the network while reducing the risk of network failure.
Manufacturers are developing high-density ODFs to accommodate higher and higher numbers of terminations in a smaller and smaller area. While high termination density requires less floor space, strong consideration needs to be given to the overall cost of such increased density.
A higher-density ODF does not necessarily correspond to a higher fiber count potential in the office. The focus needs to be on having a system with strong cable management features that are flexible enough to accommodate future growth while allowing for easy access to the installed fiber network.
For more information on best practices for fiber cable management explore our SP4420 Fiber Optic Infrastructure Specialist Course.