IBM System Storage DS3500 Introduction And Implementation Manual page 63

Draft Document for Review March 28, 2011 12:24 pm
There are two core sizes of multi-mode cabling available: 50 micron and 62.5 micron. The
intermixing of the two core sizes can produce unpredictable and unreliable operation.
Therefore, core size mixing is not supported by IBM. Users with an existing optical fiber
infrastructure are advised to ensure that it meets Fibre Channel specifications and is a
consistent size between pairs of FC transceivers.
Single-mode fiber (SMF) is so thin (9 microns) that the light can barely "squeeze" through and
it tunnels through the center of the fiber using only one path (or mode). This behavior can be
explained (although not simply) through the laws of optics and physics. The result is that
because there is only one path that the light takes to the receiver, there is no "dispersion
confusion" at the receiver. However, the concern with single mode fiber is attenuation of the
signal. Table 3-1 lists the supported distances.
Table 3-1 Cable type overview
Fiber type
9 micron SMF (longwave)
9 micron SMF (longwave)
50 micron MMF (shortwave)
50 micron MMF (shortwave)
50 micron MMF (shortwave)
50 micron MMF (shortwave)
62.5 micron MMF (shortwave)
62.5 micron MMF (shortwave)
62.5 micron MMF (shortwave)
62.5 micron MMF (shortwave)
Note that the "maximum distance" shown in Table 3-1 is just that, a maximum. Low quality
fiber, poor terminations, excessive numbers of patch panels, and so on, can cause these
maximums to be far shorter.
All IBM fiber feature codes that are orderable with the DS3500 Storage System will meet the
standards.
Interfaces, connectors, and adapters
In Fibre Channel technology, frames are moved from source to destination using gigabit
transport, which is a requirement to achieve fast transfer rates. To communicate with gigabit
transport, both sides have to support this type of communication, which is accomplished by
using specially designed interfaces that can convert other types of communication transport
into gigabit transport.
The interfaces that are used to convert the internal communication transport of gigabit
transport are Small Form Factor Transceivers (SFF), also often called Small Form Pluggable
(SFP). See Figure 3-6 on page 40. Gigabit Interface Converters (GBIC) are no longer used
on current models although the term GBIC is still sometimes incorrectly used to describe
these connections.
Speed
1 Gbps
2 Gbps
1 Gbps
2 Gbps
4 Gbps
8 Gbps
1 Gbps
2 Gbps
4 Gbps
8 Gbps
Chapter 3. IBM System Storage DS3500 Storage System planning tasks
7914DS3KPlanning_090710.fm
Maximum distance
10 km
2 km
500 m
300 m
150 m
50 m
300 m
150 m
70 m
21 m
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