Which of the following best describes insertion loss testing?

Insertion loss testing is primarily concerned with quantifying the loss of signal power as light passes through a connector or splice in a fiber optic system. This measurement is crucial because high levels of insertion loss can lead to poor signal quality and decreased system performance. By determining how much signal power is lost due to connectors, splices, or any other component in the optical path, technicians can make informed decisions on optimizing the system and ensuring that it operates within acceptable parameters.

Other options, while related to fiber optics, do not accurately define insertion loss testing. Measuring the speed of signal transmission pertains to bandwidth and latency rather than loss of signal power. Checking the alignment of fiber connectors focuses on physical connection quality rather than the quantification of power loss. Assessing the minimum bend tolerance is related to the physical characteristics of the fiber cable and not its performance in terms of insertion loss. Thus, the option describing the quantification of signal power loss through a connector or splice is the most appropriate representation of insertion loss testing.