O Terra

Brillouin amplification in phase coherent transfer of optical frequencies over 480 km fiber.

G Grosche, H. Schnatz, G. Grosche, 2010, Optics express.

A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th Decimal Place

T. Hänsch, T. Udem, R. Holzwarth, 2012, Science.