Which of the following can contribute to mechanical stress in fiber optic installations?

Improper cable management is a significant contributor to mechanical stress in fiber optic installations. When fiber optic cables are not managed correctly, they can be subjected to excessive bending, twisting, or tension. This can lead to microbending or macrobending of the fibers, which in turn can cause increased signal loss or permanent damage to the fiber. Effective cable management typically includes using appropriate support and routing techniques to ensure the cables follow proper bending radii and are secured without putting stress on them.

Other choices, while they may have various effects on fiber optic performance, do not directly contribute to mechanical stress in the way that improper cable management does. Low humidity levels can affect the materials in the cable or connectors but do not directly introduce stress as a mechanical condition. Stable temperature conditions are generally beneficial for the integrity of fiber optics, contributing to a stable environment without extremes that could lead to stress. Over-length cables can lead to challenges in installation but without proper handling practices, which relates more closely to cable management issues. Hence, while they might influence performance aspects, they do not present a direct mechanical stress scenario as effectively as improper cable management.