What is the primary use of a wavelength-isolating power meter?

The primary use of a wavelength-isolating power meter is indeed best aligned with point-to-multipoint FTTx installations. In these systems, different wavelengths are used to deliver services to multiple subscribers from a single optical fiber. The wavelength-isolating power meter measures the power of specific wavelengths, enabling technicians to ensure that the correct services are being delivered to the right endpoints and that there is minimal crosstalk or interference between channels. This specificity is crucial in FTTx applications, where maintaining high-quality service over shared infrastructure is a vital part of network management.

In contrast, the other options relate to different contexts in which power measurements are made but do not emphasize the wavelength-specific measurement aspect. For example, while testing fiber integrity is important in laboratory settings, it does not typically require wavelength isolation. Similarly, measuring power in long-distance cables and troubleshooting side-access points does not necessarily focus on the varying wavelengths, which is critical for managing point-to-multipoint setups effectively.