Combining fiber Brillouin amplification with a repeater laser station for fiber-based optical frequency dissemination over 1400 km

Abstract

We investigate optical frequency dissemination over a 1400 km long fiber link in looped configuration over a pair of underground fibers between Braunschweig and Strasbourg. This fiber link is the first to combine fiber Brillouin amplifiers with a repeater laser station. Phase-coherent operation over more than five days is demonstrated. We analyze the repeatability of the performance over four campaigns and present results of 65 d in total. The weighted mean of the fractional frequency offset of the transferred optical frequency over the complete data set is (−1.1±0.4)×10 -20 . By analyzing the stabilization signals of the two individual fibers, the correlation of the phase noise on the two fibers is shown to be >98%.

Comparing ultrastable lasers at 7 × 10−17 fractional frequency instability through a 2220 km optical fibre network

“…In this work to compare the two distant lasers, each with state-of-the-art stability, we used the European metrological optical fibre link network 24 , 27 – 30 (Fig. 1 ) connecting NPL to PTB via LPL, LNE-SYRTE, and the University of Strasbourg (UoS), with a total fibre link length of 2220 km, the longest ever reported metrological optical fibre link network 21 – 30 .…”

“…In this work to compare the two distant lasers, each with state-of-the-art stability, we used the European metrological optical fibre link network 24 , 27 – 30 (Fig. 1 ) connecting NPL to PTB via LPL, LNE-SYRTE, and the University of Strasbourg (UoS), with a total fibre link length of 2220 km, the longest ever reported metrological optical fibre link network 21 – 30 . In this comparison the modified Allan deviation (MDEV) of dead-time-free -counted 34 , 35 beat frequency measurements revealed a combined flicker frequency noise floor at , from 30 s to 200 s (Fig.…”

“…Here, we show that it is possible to compare two geographically distant ultrastable lasers 21 , 22 , with state-of-the-art fractional frequency instability 17 , 18 below 1 × 10 −16 , through the longest ever reported metrological optical fibre link network 21 – 30 , at averaging times that are relevant for applications such as optical clocks.…”

A 500-km Cascaded White Rabbit Link for High-Performance Frequency Dissemination

“…In addition, we note that the ratio between the OADEVs for each span is not constant with varying integration time. It highlights that the cascaded approach provides an improvement depending on the nature of the dominant noise process at a given integration time, what we believe to be interesting is to compare to experimental observations with other optical links as for instance reported in [1], [62], [63].…”

Polarization Scramblers to Solve Practical Limitations of Frequency Transfer

“…Polarization dependent gain and polarization dependent losses introduce also a rotation of the state of polarization (SOP) that needs to be compensated for. In the frequency metrology domain, it can be simply compensated with optical amplifiers and optical repeater techniques with automatic polarization control [14]- [16]. In the quantum communication domain, QKD system has been verified over distances up to 100 km in combination with existing fiber telecommunication networks using polarizationentangled photons [13].…”