Polarity Matters

Kirt Griffis November 29, 2012

Data centers are in a constant state of change. No data center is ever really static. The reality is that most data center professionals operate in an environment where priorities and projects are constantly shifting to meet user demands.

Because of this, understanding polarity in MPO connector-based fiber optic infrastructure is so important. As changes are made and networks are upgraded from today's 10-gigabit Ethernet to tomorrow's 40- and 100-gigabit Ethernet, data center owners need to maximize their spending and provision a path that does not require a forklift upgrade.

The polarity management challenge is that there are three different, mutually incompatible methods of polarity with MPO fiber systems: Method A, Method Band Method C.

CommScope uses Method B. Polarity in Method B is achieved simply through the position of the MPO adapter (key up to key up approach) and, as such, polarity can be easily solved by simply flipping over the module within the fiber panel or shelf so that “alpha” is on one end and “beta” on the other. Standard patch cords are used on both ends of the channel.

Methods A and C require the use of special pair-reversed cables (meaning your main investment, the trunk, cannot be re-used) or unique polarity cords (meaning you can't use your standard patch cords). This is time-consuming for a data center manager to map out, as well as costly from the standpoint of having expensive parts that are suddenly obsolete in an upgrade cycle.

Customers said the beauty of Method B is it offers them the easiest and lowest cost upgrade option to 40- and 100- gigabit Ethernet. Simply remove the duplex LC-LC patch cords, replace the LC-MPO transition module with an inexpensive MPO bulkhead adapter, leave the fiber trunk in place and complete the circuit with MPO patch cords. You are now 40- and 100-gig ready!

About the Author

Kirt Griffis

Kirt Griffis is a technical manager for the Pacific Northwest Region at CommScope. Kirt joined CommScope in 2007 after more than 15 years of communication experience with various companies including Verizon as a BICS sales engineer III. Kirt holds a BS in Management Information Systems from the University of Idaho.