Encircled Flux is the test method recommended by industry experts for accurate optical loss measurements for both regular multimode fiber and bend-insensitive multimode fiber. Fiber optic testing of a newly installed system not only verifies that the system meets its design requirements, but also creates a performance baseline for all future testing and troubleshooting of t at system. Corning recommends that all fiber optic systems be tested to a minimum set. Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Multi-mode links can be used for data rates up to 800 Gbit/s. The new designation in ANSI/TIA-568. Each “OM” has a minimum Modal Bandwidth (MBW) requirement. Here we look at how these different variables can affect the optical loss.