Hyper-stable optical frequency dissemination over 2,067 km field-deployed fiber network using bias-free phase compensation

https://www.eurekalert.org/news-releases/1138817

"severe environmental noise/ phase fluctuation overcome using RF phase recording/ intermediate optical noise purification... 2.9 X 10^-21 fractional frequency instability, maintaining continuous phase locking for >4 days without optical cycle slips... scalable multifunctional relay stations provide dynamic noise tolerance range/ virtually unlimited link extension... long-haul, continent-scale optical frequency networks, relativistic geodesy, optical atomic clock comparisons, ultra-precise distributed quantum networks"