New 10-Gbit/sec 50-micron MMF standards
BY PAUL KOLESAR
With keen interest, the fiber and cabling industries are rapidly adopting a suite of standards and supporting test procedures defining the specifications of new laser-optimized 50-micron multimode fiber (MMF). While supporting low-cost 1-Gbit/sec and slower applications, this new medium also enables lowest-cost 10-Gbit/sec connectivity by extending the reach of 850-nm serial transceivers to 300 m, a distance that serves the vast majority of in-building LANs, SANs, and equipment-room interconnects. The 10-Gigabit Ethernet (IEEE 802.3ae draft standard), 10-Gbit/sec Fibre Channel (ANSI T11.2 draft standard), and OC-192/STM-64 VSR-4 Optical Internetworking Forum (OIF) specification all depend on this new medium for such connectivity.
The foundation of this effort lies within the TIA FO2.2.1 Working Group, which determined the performance requirements and accompanying new test procedure to measure the differential mode delay (DMD) property of the new fiber (see Lightwave, October 2001, p. 36). The Telecommunications Industry Association (TIA) published the test procedure, FOTP-220, in December. The ballot on a detailed fiber specification, to be published as TIA 492AAAC, closed in January.
During the past year, the United States brought these documents to the International Electrotechnical Commission (IEC) for international standardization. At its October meeting, IEC SC86A agreed to ballot the DMD test procedure, to be published as IEC 60793-1-49, and create a fiber Technical Specification, both under the fast-track method known as PAS (publicly available standard). To distinguish the new 50-micron MMF from the old, the existing 50-micron type (A1a) will be subdivided by calling the new fiber type A1a.2 and the old type A1a.1.
Structured cabling standards bodies will reference the new fiber within updates of their documents. TIA TR-42 referenced TIA 492AAAC in the ballot of ANSI/TIA/EIA-568B.3-A-1 that closed in January. ISO/IEC JTC1/SC25 WG3 and CENELEC TC 215 created new optical-fiber-cabling classes within their drafts of the second editions of ISO/IEC 11801 and EN 50173, respectively. Each defines three multimode classes distinguished by bandwidth performance. Class OM1 corresponds to 200/500-MHz-km overfilled (OFL) bandwidth (at 850/1300 nm), commonly associated with legacy 62.5/125-micron MMF. Class OM2 refers to 500/500-MHz-km OFL bandwidth, commonly associated with legacy 50/125-micron fiber. Class OM3 corresponds to the new 50-micron fiber with both 1,500/500-MHz-km OFL bandwidth and 2,000 MHz-km laser bandwidth at 850 nm. The OM3 class is the only fiber bearing laser bandwidth specifications, making it the best choice for supporting laser-based applications that deliver gigabit and higher speeds.
Paul Kolesar is a distinguished member of technical staff, and he represents OFS Fitel on several standards committees. He can be reached at tel: 732-949-1255 or fax: 732-817-2748.