One-femtosecond, long-term stable remote laser synchronization over a 3.5-km fiber link

Abstract

Long-term stable timing distribution over a 3.5-km polarization maintaining (PM) fiber link using balanced optical cross-correlators (BOC) for optical-to-optical synchronization is demonstrated. Remote laser synchronization over 40 hours showed a residual timing jitter and drift of 2.5 fs for the whole locking period and only 1.1 fs integrated from 100 μHz to 1 MHz. This result corresponds to the lowest jitter and drift achieved to date for a multi-km fiber link and remote timing synchronization operating continuously over multiple days. Yan, J. M. Fini, and F. X. Kärtner, "Long-term stable, sub-femtosecond timing distribution via a 1.2-km polarization-maintaining fiber link: approaching 10

Laser-to-laser remote transfer and synchronization with sub-fs precision over a 3.5 km fiber link

“…Sub-fs precision for link-stabilization and remote laser locking over km distances has been reported before [6], [9]; however, this is the first demonstration of sub-fs precision for remote synchronization achieved under realistic facility conditions. We believe that the demonstrated timing link can be deployed in the European X-FEL to achieve femtosecond level timing distribution over the full length of the facility, helping to both monitor and control the electron bunch creation and hard X-ray pulse generation, to ultimately push the limits of spatial and temporal X-ray diffractive imaging.…”

“…Finally, the power spectral density is converted to jitter spectral density by using the timing sensitivity of the BOC which was measured to be 0.36 mV/fs with a balanced photodetector (BPD) of 2x10 3 V/A transimpedance gain and 1-MHz bandwidth in this experiment. From a simple feedback-loop analysis, the locking bandwidth of the BOC can be calculated as [6]:…”

Applications of femtosecond lasers in microwave photonics

“…Among many other fields, distributing stable timing signals is particularly important for modern large-scale scientific facilities, such as X-ray free-electron lasers [4][5].…”

High Precision Synchronization of a Large-scale Microwave Network over Stabilized Fiber Links

“…On the other hand, a mode locked laser (MLL) has an inherent advantage to simultaneously provide low jitter time markers and generate high performance microwave signals encoded in its repetition rate; it is therefore a promising candidate to serve as a timing reference for all antennas in this microwave network. In the past decade, we have developed a high precision timing distribution system using MLLs and balanced optical cross-correlators (BOC) [3] and demonstrated 1-fs precision local optical-to-microwave synchronization using balanced optical-microwave phase detectors (BOMPD) [4]. In this paper, we remotely synchronize two independent microwave sources over a 4.7-km fiber link network.…”