Three reasons not to mix 50- and 62.5-micron multimode fibers

March 26, 2010
Problems arise from the signal's inability to get from one fiber core to the other.

In an article he authored for Cabling Installation & Maintenance magazine, OFS's John Kamino details how and why network managers may make the switch from 62.5-micron to 50-micron multimode fiber. If and when users choose to make the switch, he warns that they should avoid mixing 50- and 62.5-micron cables in a single system, for three primary reasons.

  1. The difference in core sizes could cause high loss when transmitting from the 62.5-micron into the 50-micron fiber.
  2. The bandwidth of 62.5-micron fibers is typically much lower than that of 50-micron, further degrading system performance.
  3. Even if a low-speed application operates over a link made up of mixed fiber types, upgradability will be severely compromised.

"The elevated loss problem occurs when transmitting from the larger-core 62.5-micron fiber into a smaller 50-micron core," Kamino writes. "It is comparable to a 4-inch water pipe connecting to a 3-inch pipe. There is no problem going from the smaller pipe to the larger pipe, but going in the opposite direction can lead to a lot of lost water, or in this case, light."

He adds that the amount of connection loss users experience is about 4 dB for LED-based systems, and can be anywhere from 0 to 4 dB for a VCSEL-based system. He adds, "Since most optical loss test sets use LEDs, you should plan for the worst and assume you'll see a 4-dB loss in one direction."

Look for the full article in the May issue of Cabling Installation & Maintenance.

Sponsored Recommendations

March 28, 2025
Bringing University of Tennesee's campus up to speed.
March 28, 2025
CommScope’s FiberGuide® Design Pro helps you design a complete fiber raceway for your data center or central office using 2D and 3D technology. This video guides you through the...
March 28, 2025
CommScope and Equinix work hand in hand to provide client connectivity across the globe