Cisco Cisco DWDM Transceiver Modules Libro blanco
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Figure 1. Distribution of Gigabit Ethernet vs. 10 Gigabit Ethernet Interfaces
Source: Cisco internal analysis.
Multimode Fiber Types: An Overview
The main challenge in upgrading 1-Gbps links to 10-Gbps links is the variety of fiber types already
deployed in the installed base. The main property of a multimode fiber is its capability to transmit a
certain amount of information over a certain distance. This property is known as “modal bandwidth”
and is expressed in MHz*km.
In general, an inverse linear relationship between the data rate and the maximum distance
achievable is considered at a certain modal bandwidth. As an example, this means that an
increase of the data rate from Gigabit Ethernet to 10 Gigabit Ethernet (which represents a factor of
ten) will result in a tenfold reduction of achievable distance on the same fiber and under the same
launch conditions. However, some complex nonlinear parameters need to be taken into account to
calculate the exact reach possible at a certain data rate, and standard bodies such as IEEE define
minimum transmission distance requirements for various combinations of data rate and fiber
modal bandwidth. Please refer to Table 1 for a list of various fiber types defined by major
international standard bodies.
Table 1.
Various Types of Multimode Optical Fibers
Standard Body
Document
Notes
492AAAA
62.5
fibers with 160/500 MHz.km OFL BW
492AAAB
50
fibers with 500/500 MHz.km OFL BW
TIA—
Telecommunications
Industry Association
Telecommunications
Industry Association
492AAAC
Laser-optimized 50
fibers with 2000 MHz.km EMB at 850 nm
A1a.1 fiber—50
fibers with a range of OFL BW
A1a.2 fiber—Laser-optimized 50
fibers with 2000 MHz.km EMB at 850 nm
IEC—International
Electrotechnical
Commission
Electrotechnical
Commission
60793-2-10
A1b fiber—62.5
fibers with a range of OFL BW
OM1 fiber—200/500 MHz.km OFL BW
(in practice OM1 fibers are 62.5
(in practice OM1 fibers are 62.5
fibers)
OM2 fiber—500/500 MHz.km OFL BW (in practice OM2 fibers are 50
fibers)
ISO—International
Standards Organization
Standards Organization
11801
OM3 fiber—Laser-optimized 50
fibers with 2000 MHz.km EMB at 850 nm