Which of the following describes optical time domain reflectometer (OTDR) nonreflective signatures?

The correct answer highlights that optical time domain reflectometer (OTDR) nonreflective signatures are associated with fusion splices, macrobends, and microbends. These signatures reflect changes in the optical fiber infrastructure that do not return significant reflected signals, meaning they represent issues that can be detected by the ongoing evaluation of light traveling through the fiber.

Fusion splices represent points where two fiber ends have been melted together, creating a smooth transition that limits reflections. Macrobends and microbends are bending events in the fiber where the light path is altered, also resulting in minimal reflection and the possibility of signal loss or degradation.

The other options mention different testing methodologies or phenomena related to optical fiber but do not address nonreflective signatures. For instance, optical return loss measurements focus on quantifying the amount of light that is reflected back toward the source, which is not applicable when discussing nonreflective events. Wavelength propagation delays pertain to the time it takes for light signals to travel through the fiber at specific wavelengths, rather than identifying nonreflective aspects. Light intensity variations can signify overall signal integrity but are not specifically linked to the nonreflective characteristics deduced from OTDR.