title: Doppler-stabilized fiber link with 6  dB noise improvement below the classical limit.
abstract: It is known that temperature variations and acoustic noise affect ultrastable frequency dissemination along optical fiber. Active stabilization techniques are adopted to compensate for the fiber-induced phase noise. However, despite this compensation, the ultimate link performances are limited by the delay-unsuppressed noise that is related to the propagation delay of the light in the fiber. We demonstrate a post-processing approach which enables us to overcome this limit. We implement a subtraction algorithm between the optical signal delivered at the remote link end and the round-trip signal. In this way, a 6 dB improvement beyond the delay-unsuppressed noise is obtained. We confirm the prediction with experimental data obtained on a 47 km metropolitan fiber link and propose how to extend this method for frequency dissemination.
authors: C E
authors: CE
authors: Calosso
authors: E K
authors: EK
authors: Bertacco
authors: D
authors: D
authors: Calonico
authors: C
authors: C
authors: Clivati
authors: G A
authors: GA
authors: Costanzo
authors: M
authors: M
authors: Frittelli
authors: F
authors: F
authors: Levi
authors: S
authors: S
authors: Micalizio
authors: A
authors: A
authors: Mura
authors: A
authors: A
authors: Godone