Submittal

©2008 PANDUIT Corp. All rights reserved. www.panduit.com 9
Fiber Systems:
Polarity Best Practices
Which Method?
In complex, high-density fiber installations, the advantages of array connectors can be lost if large-scale
confusion and loss of local control result. Also, intermixing the components of these methods may result in
incorrect polarity. So, with three guideline-recognized methods from which to choose, how should network
stakeholders select the best method for ensuring polarity across their array-based fiber installation?
Table 1 summarizes the advantages and disadvantages of the three methods. The most critical consideration is
to select one method and stick with it. As stated in TIA/EIA-568-B.1 Addendum 7: “The primary consideration
faced by data center operators when choosing a method is ensuring that the same method is used throughout
all of an operator’s installations.” Therefore, the method choice should be maintained consistently throughout
the installation, and must be clearly communicated to all stakeholders.
PANDUIT endorses Method A as the most flexible and reliable method for the following reasons:
• Customers expect systems based on standards. Standards incorporate best practices and
incorporate paths to upgrade as technology advances, so system investments are better protected
from risk of obsolescence.
• Customers need flexibility. Method A provides the most flexible options for current system designs
and includes an easy path to migrate to higher data rates via parallel optics.
• Customers should have the widest choice of installation and component vendors, rather than relying
on vendors with proprietary solutions and technologists with specialist skills. Also, proprietary
methods not based on TIA/EIA guidelines will neither assure future interoperability, nor availability of
future product inventory at a time of greatest need.
Table 1. Analysis of TIA/EIA-568-B.1 Addendum 7 Fiber Polarity Methods
Method Advantages Disadvantages
A
• One cassette type, easy to produce and purchase
• Multiple sources for components
• Singlemode and multimode
• Ribbon cables can be linked (need male/female
connector)
• Compatible with many legacy systems
• Industry standard
• Standard provides migration path to parallel optics
• Requires pre-configured “A-to-A” patch
cords, or field configuration of same
B
• Single source for components
• “A-to-B” patch cord only
• Industry standard
• Standard provides migration path to parallel optics
• Remote cassette must be flipped and
re-labeled
• Identification and maintenance of
cassettes are different on each end
• Multimode only
• Not compatible with legacy systems
• Ribbon cables can only be liked using
less available (Key Up to Key Up)
adapters (need male/female cord)
• Fewest vendors
C
• One cassette type, easy to produce and purchase
• Singlemode and multimode
• Industry standard
• “A-to-B” patch cord only
• Less reliable than Method A
• Specialized ribbon cable assembly
• Does not support parallel optics
• Not compatible with legacy systems
• Less vendor support than Method A
• Difficult to extend link