Metal trench covers are used anytime trenches are dug in roads, not just for fiberoptic cables. The following citation contains an example of the use of this phrase in a fiberoptic context:

http://www.almanacnews.com/morgue/2000/2000_05_31.elcamino.h...

“The Almanac

Issue date: May 31, 2000

Bumping along the El Camino: Cable company's trenching raises questions about future repair work.
By Alan Sissenwein, Special to the Almanac

The installation by a private cable company of fiber optic cable conduits under El Camino Real, which entailed digging a trench through the highway's left south-bound lane, has made scores of motorists' lives miserable. Nighttime drivers encountered closed lanes and traffic congestion, while daytime motorists had the bone-jarring experience of rolling over metal trench cover plates.”

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