Ever increasing network speeds and tighter loss budgets ensure qualifying multimode fiber links remains a formidable challenge. Part of the challenge can stem from test instruments. In some scenarios different test instruments can produce different measurement results on the same network due to variations in launch conditions between test sources. The result is confusion and wasted time verifying actual measurement values. Wasted time means extended network downtime or delayed network starts. To help minimize test errors, standards bodies embraced encircled flux to better standardize multimode launch conditions.

Encircled Flux (EF) standards, TIA-526-14-B and IEC 61280-4-1 Ed. 2.0, define a method of controlling multimode launch conditions for optical test sources. More consistent test source launch conditions equate to more accurate and repeatable measurements. This is the goal driving the migration to encircled flux standards.