Issue link: http://www.epageflip.net/i/1043933
22 I ICT TODAY is greater than that of singlemode, it is the optics and connection costs that dominate the total cost of a network system, dwarfing variations in cable costs. 1 On average, singlemode transceivers continue to cost from one-and-a-half to five times more than multimode transceivers, depending on data rate. As faster optoelectronic technology matures and volumes increase, prices come down for both, and the cost gap between multimode and singlemode can decrease. However, singlemode optics have traditionally been more expensive than their equivalent multimode counterparts. 2 Multimode fiber is the default choice of transmission media for data centers and other high-speed enterprise applications over copper and singlemode fiber. The reasons have to do with cable size, design and cost. Multimode transceivers also consume less power than singlemode transceivers, an important consider- ation especially when assessing the cost of powering and cooling a data center. In a large data center with thousands of links, a multimode solution can provide substantial cost savings from transceiver and power/ cooling perspectives. Finally, the fact that multimode optical fiber is easier to install and terminate in the field than singlemode is an important consideration for enterprise environments where frequent moves, adds and changes are required. This advantage extends to cleaning, where a small amount of dust or contamination could create significant attenuation on a singlemode connector, but only slightly increase the loss of a multimode link. The Evolution of Multimode Fiber As shown in Table 1, there are five types of multimode fiber currently on the market. OM1 and OM2, the original 62.5 micron (µm) and 50 µm-diameter types, respectively, are considered obsolete in the ISO/IEC 11801 and TIA 568 standards, and no longer included in the main text of the documents. They are, however, allowed as grandfathered fiber types and may be used to extend legacy networks. New installations should use OM3, OM4 or OM5 multimode fiber types. OM3 multimode, introduced in 2003, was the first fiber designed for use with laser light sources at 850 nanometers (nm), primarily to support 1 and 10 Gb/s operation. OM4, standardized in 2009, offers longer link lengths supporting 10 Gb/s operation to 400 m in the standard, and up to 550 m using some engineering rules. TABLE 1: Multimode fiber types. (1) OM1 is typically a 62.5µm fiber, but can also be a 50µm fiber. (2) OM2 is typically a 50µm fiber, but can also be a 62.5µm fiber. (3) "b" designates Bend-Insensitive (4) ISO/IEC 11801 has a max. cabled attenuation of 3.5dB/km Fiber Type ISO/IEC 11801-1 Nov. 2017 IEC 60793-2-10 Aug. 2017 TIA-568.3-D Oct. 2016 TIA/EIA 492AAAx various ITU-T Dec. 2008 850nm 1300nm 850nm 1300nm 850nm 953nm 62.5/125 OM1 (1) A1b TIA 492AAAA (OM1) 492AAAA --- 3.5 1.5 200 500 --- --- 50/125 OM2 (2) A1a.1b (3) TIA 492AAAB (OM2) 492AAAB G.651.1 3.5 1.5 500 500 --- --- 50/125 OM3 A1a.2b (3) TIA 492AAAC (OM3) 492AAAC --- 3.0 (4) 1.5 1500 500 2000 --- 50/125 OM4 A1a.3b (3) TIA 492AAAD (OM4) 492AAAD --- 3.0 (4) 1.5 3500 500 4700 --- 50/125 OM5 A1a.4b (3) TIA 492AAAE (OM5) 492AAAE --- 3.0 1.5 3500 500 4700 2470 Industry Standards Attenuation— Typical Cabled Max. (dB/km) Overfilled Launch (OFLc) Effective Modal Bandwith (EMB) (also known as Laser BW) (described in the industry using primarily the ISO/IEC 11801 Designations) BANDWIDTH (MHz-km)