Bandwidth testing is done by fiber manufacturers and involves a complex laboratory test with specialized analyzers to send and measure high-powered laser pulses—it’s costly to accurately test in the field, and you don’t need to worry about it if you stick to the standard-defined length limitations.
As data speeds increase and new fiber applications emerge, there has been some confusion surrounding fiber testing parameters and whether insertion loss testing is enough to guarantee support for high-speed applications.
Other than new short-reach single mode applications that are more susceptible to reflections and therefore take connector reluctance into consideration, insertion loss testing, length and polarity are really all you need for Tier 1 certification testing.
Measured in decibels , insertion loss is the reduction in signal power that happens along any length of cable for any type of transmission.
And the longer the length, the more a signal is reduced (or attenuated) by the time it reaches the far end. In addition to length, events along the way that cause reflections also contribute to overall loss, including connectors, splices, splutters and bends.