It’s All About Skew

Reel Time December 2008, Cabling Business Magazine

Reel Time December 2008 Skew

By: Carol Everett Oliver, RCDD, Berk-Tek, a Nexans Company

Q.  I hear a lot about “skew” as a concern in fiber optic cable.  Is this like delay skew in copper? Can you define skew as it relates to fiber cable and tell me what it means to cable performance and what I should look for when purchasing and installing fiber optic cable?

A. The skew effect in fiber is very similar to that of copper.  However, up until now, skew concerns were more with copper than with fiber because of the cable construction, transmission properties, application and speed differences.  In its simplest terms, skew is the time difference between two transmission conductors (copper or fiber), within the same jacket traveling simultaneously, reaching the same end point. The difference between the slowest and fastest is called the “skew” rate.

For copper, the four pairs each incorporate a different twist ratio, affecting the length (As mentioned in previous articles, the purpose of different lengths of copper pairs is for improved crosstalk performance between pairs).  So, the skew is the difference in time, measured in nanoseconds (ns), from the shortest (fastest) pair to the longest (slowest) reaching the termination point. 

Get the full story: Reel Time December 2008

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Carol Oliver Berk-Tek Marketing Analyst