Issue link: https://www.e-digitaleditions.com/i/1192126
42 I ICT TODAY cable within 50 feet (approximate ly 15.24 meters) from its point of entry into the building to meet NEC code and NFPA requirements for a conven- tional installation. Because the blown fiber tube cables and not the fiber bundles are outdoor, plenum, riser rated and so on that meet NEC and NFPA requirements, the tube cables are connected with push-fit connec- tors allowing for a splice-free contin- uous fiber run at the point of entry into the building. When considering a blown fiber solution for this application, the conduit must be sized for the tube cable. Assuming a 7-tube outdoor tube cable will be installed, the out- side diameter is 1.7 inches. There have been concerns by some regard- ing the size of tube cable, but the advantages of the spare tubes for future growth can certainly outweigh this concern. In this instance, if 144- count fiber is required from point A to point B, two of the 7-tubes would be utilized, each with a 72-count fiber bundle. This leaves five of the seven tubes open. This would allow for up to five more fiber bundles to be installed for future use, thereby leaving the flexibility for up to 360 strands of additional fiber to be installed at a later date. In this exam- ple, the footage from point A to point B is approximately 3,000 feet (approximately 915 meters). If the customer should need to add a new fiber run, it would take only two installers around 30 minutes to blow the new fiber into the existing tubes compared to four or more installers one to two days to install/pull the fiber optic cable conventionally. Keep in mind that the setup time for either installation is not included in that timeframe. With a blown fiber system, the installer would need to set up the blowing equipment and nitrogen tanks. With a conventional installation, the installer would need to set up the reels and have proper pulling equipment in place. The cost difference for time and labor in this scenario for blown fiber can be sub- stantial to the customer, potentially saving thousands of dollars. Another scenario to consider in an outside burial application is an existing conduit situation. If there is a 4-inch conduit already in place, there would be room to install two of the 19-tube cables, yielding a total of 38 available tubes for immediate and/or future use (Figure 8). The 38 pathways through which a maximum of 72-count fiber bun- dles can be blown would give the customer the ability to install up to 2,736 strands of fiber. Assume that the customer only needs 144-strand fiber at the time of installation and is considering the conventional fiber method. The customer would have to decide whether to install the 144-strand needed now or whether to install additional strands for the future, just in case. A decision may also be made to install some type of mesh or plastic type innerduct to make future adds easier; this too will consume some of the space inside the conduit. Customers often choose to add additional fiber strands at the time of the installation and pay the additional cost up front; the fiber remains dark for long periods of time, thus costing the customer for some- thing they are not using. The advan- tage in this case with a blown fiber system is flexibility. The blown fiber system offers fiber on demand, taking the guess work out of accurately forecasting future fiber requirements and the opportunity and financial costs associated with laying either FIGURE 8: Blown fiber versus conventional conduit example. 2 - 19 Tube Cables in 4" PVC Conduit 3 - 1.25" Innerduct in 4" PVC Conduit 38 PATHWAYS VS. 3 PATHWAYS