In all my travels, I've never seen one of these. It appears to be a wire loop (possibly an antenna) of some kind on what I believe is a CATV line.

Seen along Hayston Ave. between E. Shields Ave. and E. Dakota Ave. in Fresno CA. USA on 06-08-20.

Any idea of what this bizarre installation is?

(Answered by G.L. -- no changes to grammar, spelling, or syntax were made):

That is fiber optic cable.

When we hang it we build in slack loops and also loops at splices so we can get the splices off the poles or down from the overhead area to slice trailers.