Issue link: https://www.e-digitaleditions.com/i/1219491
April/May/June 2020 I 13 ANSI/TIA-942-B specifies the LC connector for one or two optical fibers and MPO for more than two fibers. ISO/IEC 11801-5 and CENELEC EN 50173-5 specify the same optical fiber connectors at the equipment outlet and external network interface (LC and MPO). Unlike TIA-942-B, they permit the use of other connectors that meet the performance requirements of the standards in other areas, such as in main, intermediate and zone distributors as well as the local distribution point. Another example is the use of course wavelength division multiplexing (CWDM) or dense wavelength division multiplexing (DWDM) within the data center. Both have been used in the backhaul networks for years and are often used in delivering connectivity to the data center from the carrier's network. Course wavelength division multiplexing and DWDM allow for data to be communicated through multiple wavelengths on the same fiber, and then optical filtering is used to break out into individual channels. The connectivity solution roadmap needs to keep these in mind and provide long- term support. Fusion Splicing and Ribbon Fiber Delivering the promise of tomorrow requires millions of low loss connections. A single hyperscale data center can easily contain over 100,000 servers and 500 to 1 mil- lion connectors. This does not account for the number of splices that could be in the order of tens of thousands. If pre-terminated trunks are not being used, then the number of splices can easily expand by an order of mag- nitude. Dealing with tens to hundreds of thousands of splices is no easy challenge. This level of splice density can be equated to time-spent, making true the old adage that "time equals money." Ribbon fiber, especially a flexible gel-free ribbon product, can greatly help with this challenge. Mass fusion splicing of no-gel ribbon has been shown to reduce the overall splice time of a job by up to 87 percent (Figure 8). However, if these splices are not high quality and low loss, then any time benefit is lost by having to rework the connection. With loss budgets approaching 2 dB between any two active devices within the data center, the need to achieve splice losses of a hundredth of dB is critical. Today's leading splicers can achieve an average optical fiber splice loss of 0.03 dB. Typically, the challenge faced by low-end splicers is their ability to maintain a consis- tent fusion arc, especially across thousands of splices. Having a quality splicer alone does not guarantee suc- cess. Technicians and installers also need to follow good workmanship techniques. It begins with careful prepara- tion of the optical fiber. Ribbon stripping and cleaning the fiber is extremely important. Next, achieving a good cleave is critical for a low-loss connection. Following a good technique requires a sharp cleaver blade. Ever try cutting a tomato with a dull knife? Picture that hap- pening to the fiber if using a dull or worn cleaver blade. Except in this case, the technician or installer is cutting a thousand tomatoes. The fiber splicing process can get messy very quickly. Keeping track of the blade rotation is also crucial for consistent low-loss results. Field data discloses how the splices at the start of a job achieve a near-zero loss, and by the end of the job they can approach 0.1 dB. As previously noted, in a connection path where the total loss budget is nearing 2 dB, this FIGURE 8: Mass fusion splicing of 12-fiber ribbon. becomes a significant factor. It is for this reason that some splicer manu- facturers have integrated intelligence into their splicer and cleaver families, allowing them to communicate via Bluetooth, for example. Manufactur- ers have also incorporated a feature that auto-advances the cleaver blade after a certain number of splices or when the loss level begins to move above a pre-set threshold.