Frequency comb-based microwave transfer over fiber with 7×10^−19 instability using fiber-loop optical-microwave phase detectors

Abstract

We demonstrate a remote microwave/radio frequency (RF) transfer technique based on the stabilization of a fiber link using a fiber-loop optical-microwave phase detector (FLOM-PD). This method compensates for the excess phase fluctuations introduced in fiber transfer by direct phase comparison between the optical pulse train reflected from the remote site and the local microwave/RF signal using the FLOM-PD. This enables sub-fs resolution and long-term stable link stabilization while having a wide timing detection range and less of a demand in fiber dispersion compensation. The demonstrated fractional frequency instability between 2.856 GHz RF oscillators separated by a 2.3 km fiber link is 7.6×10(-18) and 6.5×10(-19) at 1000 and 82,500 s averaging times, respectively.

Microwave synthesis and remote transfer using attosecond-jitter mode-locked fiber lasers

“…We could show that 2.856-GHz microwave signal transfer over a 2.3-km fiber with 6.5×10 -19 fractional frequency instability (see Fig. 3) [7]. This instability level is about an order of magnitude improved result from the previous record [8], and so far the lowest for the microwave transfer by frequency combs over km-scale fiber links.…”

“…First, we show how ultralowjitter optical pulse train can be used for microwave phase detection with sub-femtosecond resolution and long-term stability: the use of a differential-biased Sagnac fiber-loop culminated in a new class of phase detector named the fiberloop optical-microwave phase detector (FLOM-PD) [5]. We used the FLOM-PDs for sub-femtosecond stability lasermicrowave synchronization (Section II), ultralow phase noise microwave signal synthesis (Section III) [6], and remote transfer of highly stable microwave over kilometer-scale fiber links (Section IV) [7].…”

High-Precision Distribution of Highly Stable Optical Pulse Trains with 8.8 × 10−19 instability

“…Similar with the system in Ref. 40, the performance of our system is also limited by polarization mode dispersion. In future studies, the techniques proposed in this work could be applied to the distribution of time and frequency signals over free space to reduce the effect.…”

“…Compared with Ref. 40, we did longer distance and lower noise optical-pulse-train distribution, which is more suitable for that of optical clocks. Meanwhile, the system is potentially suitable for use in timing synchronisation for the next generation of XFELs and particle accelerators, various parts of which may need to be distantly located to achieve sufficient accelerating distance while working in tightly synchronised conditions.…”

10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources

“…As a result, FLOM-PDs working at 1550-nm telecommunication wavelength have been widely used in photonic microwave/RF generation19, RF phase transfer over fibre links2021, time synchronization fibre links22, and laser stabilisation23. More recently, a 800-nm-version FLOM-PD was demonstrated and successfully employed in a single-electron UED system for fs-precision timing diagnostics between a 6.2-GHz microwave signal and a 5-MHz Ti:sapphire laser24.…”