Before measuring end-to-end attenuation, what must be considered?

To measure end-to-end attenuation accurately, it is essential to ensure that the light source and optical power meter are referenced together prior to conducting any field measurements. This means that both devices need to be calibrated and aligned to ensure accurate baseline readings.

When the light source and optical power meter are referenced together, any inherent losses or variations in the devices' readings can be accounted for, leading to a more precise measurement of the attenuation in the optical fiber. If this step is skipped, the measurements taken could reflect errors caused by the mismatch in calibration between the two devices rather than the actual performance of the fiber.

The other options, while they may have some relevance in different contexts, do not address the primary requirement of referencing the devices for accurate measurements. The impact of ambient temperature on fiber optics performance is important, but without properly referenced equipment, temperature variations won't provide reliable information on attenuation. Calibration of only the optical power meter disregards the entirety of the measurement system, and using multiple light sources could complicate the measurement process without guaranteeing improved accuracy unless they are also referenced properly.