Issue link: https://www.e-digitaleditions.com/i/1192126
January/February/March 2020 I 37 FIGURE 1: For conventional cabling and to meet growing high-density and high-bandwidth demands, singlemode in high fiber counts is increasingly being installed, though the need for multimode for the inside plant is still very necessary. From left to right, examples include outside plant armored cable, indoor RoHS riser cable, indoor-outdoor riser, indoor interlocking armor plenum, and rollable ribbon type cable. 1 will be compared in actual OSP and inside plant installation examples so that fellow designers and installers can better understand these viable installation methods in an age when the enterprise customer confronts ever-increasing bandwidth demands and the continuous influx of emerging technologies. OPTICAL FIBER COMPARISON BETWEEN CONVENTIONAL AND THE BLOWN FIBER SYSTEM Optical fiber is categorized basically in two types: singlemode and multi- mode. Singlemode optical fiber (OS2- low water peak) has a small, narrow core of 8 to 10 microns (μm) and allows for only one mode of light to propagate, meaning that the number of reflections are decreased as the light travels through the core. This enhances performance and lowers attenuation/signal loss, thereby allowing the signal to travel further. Singlemode fiber (SMF) is optimized at the 1310 nm and 1550 nm wave- lengths. Singlemode OS1 may still be available from some manufacturers. There is another type of low-water peak singlemode optical fiber speci- fied in TIA, CENELEC and ISO/IEC standards named OS1a that has replaced the no longer recognized OS1 cable. Both OS1a and OS2 use the same low-water peak optical fibers, but OS1a is typically tight buffered for indoor use and typically a loose tube construction for outdoor use for conventional cabling installa- tions. Specifications for OS1a are for cabled optical fibers, not bare fibers. Therefore, OS2 is used with a blown fiber system. Multimode optical fiber has a larger core than singlemode that allows for multiple modes of light to propagate, allowing for increased reflections as the light passes through it. Hence, it allows more data to pass through it. However, the attenuation rate increases as well as high disper- sion causing the signal to be reduced as distances increase. Multimode fiber (MMF) is available in several grades, OM1 to OM5. Multimode OM1 is a 62.5 μm fiber and is still available but no longer recommended as often for today's high-speed networks. Multi- mode OM2 to OM5 is a 50 μm fiber with OM3 and OM4 being laser- optimized. The range of OM1 to OM4 operates at wavelengths of 850 nm to 1300 nm. Designed to work over a wide range of wavelengths between 850 nm and 950 nm, OM5 supports shortwave wavelength division multi- plexing (SWDM). For conventional cabling, both SMF and MMF for the most part are constructed in the same manner into optical fiber cables; there is the core, the cladding and the protective jacket. All three parts can vary, especially the outer jackets that must meet the plenum and riser listing require- ments of the National Electrical Code (NEC) as well as local codes. Over the years, optical cable manufactur- ers have designed cables for virtually any application, including indoor- outdoor loose-tube and ribbon, OSP cables in metallic or dielectric, gel- free, industrial cables, and a host of many other configurations. Both singlemode and multimode cables can be ordered in a variety of fiber counts from 2-to-288 fibers, along with special order counts for singlemode of 864 fibers as well as newly designed rollable ribbon-type cable of up to 3,456 fibers for high- density applications (Figure 1). Rather than housing and con- structing OS2 singlemode and OM1 to OM4 multimode into optical fiber cables, as is done for conventional cabling and the micro-cables used in