What device can be attached to a pulling line to prevent twisting of fiber-optic cables during installation?

The device that is most effective in preventing the twisting of fiber-optic cables during installation is a break-away swivel. This tool is designed to allow the pulling line to rotate independently from the fiber-optic cable itself. As installers pull the cable through conduits or across distances, any twisting motion can introduce stress and potential damage to the delicate fibers within the cable, which can lead to performance issues or cable failure. The break-away swivel mitigates this risk by ensuring that the force applied to the pulling line does not transfer twisting motion to the cable; instead, it freely rotates, maintaining the integrity of the fiber-optic installation process.

Understanding the other options provides clarity on why they are not suited for this specific application. A locking clamp does not facilitate rotation; it primarily secures cables or components, which does not address the concern of twisting. A rotating pulley can help guide the cable through bends; however, it does not necessarily prevent twisting during the pulling process itself. Finally, a protective sheath serves to protect cables from environmental damage, but it does not have any functionality regarding the rotation of the pulling line or preventing twisting during installation.