[1]http://www.wired.com/2015/09/balloon-spy-probe-deep-sweep/
   I was thinking about something like this, about 25 years ago.  But
   rather than a free-flying balloon, I felt that an aerostat
   configuration would be better.  Further, I figured that a bidirectional
   optical fiber link would be useful, such as:
   [2]http://datainterfaces.com/sfp-modules-single-strand-bidirectional-gi
   gabit-SC.aspx?gclid=CjwKEAjw-IOwBRD1wrTC27fSjFISJABUDZ17VgezJOQe9_0o3_9
   WJIWBYvqkpJyge7-5g3ZkgT4wZBoC1vzw_wcB
   An otherwise-unjacketed optical fiber, but with a woven Kevlar strength
   covering, would be useful.
   Obviously, the FAA wouldn't approve, but that doesn't keep us from
   imagining, huh?
               Jim Bell.

References

   1. http://www.wired.com/2015/09/balloon-spy-probe-deep-sweep/
   2. http://datainterfaces.com/sfp-modules-single-strand-bidirectional-gigabit-SC.aspx?gclid=CjwKEAjw-IOwBRD1wrTC27fSjFISJABUDZ17VgezJOQe9_0o3_9WJIWBYvqkpJyge7-5g3ZkgT4wZBoC1vzw_wcB