Optically synchronized fiber links with spectrally pure integrated lasers

Abstract

Precision frequency and phase synchronization between distinct fiber interconnected nodes is critical for a wide range of applications, including atomic timekeeping, quantum networking, database synchronization, ultra-high-capacity coherent optical communications and hyper-scale data centers. Today, many of these applications utilize precision, tabletop laser systems, and would benefit from integration in terms of reduced size, power, cost, and reliability. In this paper we report a record low 3x10^-4 rad^2 residual phase error variance for synchronization based on independent, spectrally pure, ultra-high mutual coherence, photonic integrated lasers. This performance is achieved with stimulated Brillouin scattering lasers that are stabilized to independent microcavity references, realizing sources with 30 Hz integral linewidth and a fractional frequency instability less than or equal to 2x10^-13 at 50 ms. This level of low phase noise and carrier stability enables a new type of optical-frequency-stabilized phase-locked loop (OFS-PLL) that operates with a less than 800 kHz loop bandwidth, eliminating traditional power consuming high bandwidth electronics and digital signal processors used to phase lock optical carriers. Additionally, we measure the residual phase error down to a received carrier power of -34 dBm, removing the need to transmit in-band or out-of-band synchronized carriers. These results highlight the promise for a path to spectrally pure, ultra-stable, integrated lasers for network synchronization, precision time distribution protocols, quantum-clock networks, and multiple-Terabit per second coherent DSP-free fiber-optic interconnects.

References in corpus (12)

• A sub-40 mHz linewidth laser based on a silicon single-crystal optical cavity
• 1.5 $\mu$m lasers with sub 10 mHz linewidth
• Geodesy and metrology with a transportable optical clock
• A clock network for geodesy and fundamental science
• Integrated Waveguide Brillouin Laser
• Sub-Hz Linewidth Photonic-Integrated Brillouin Laser
• 422 Million Q Planar Integrated All-Waveguide Resonator with a 3.4 Billion Absorption Limited Q and Sub-MHz Linewidth
• Coherent optical frequency transfer at 5e-19 over a doubled 642 km fiber link
• Coherent optical phase transfer over a 32-km fiber with 1-s instability at $10^{-17}$
• All-optical link for direct comparison of distant optical clocks
• Stabilized microwave-frequency transfer using optical phase sensing and actuation
• A microrod-resonator Brillouin laser with 240 Hz absolute linewidth

Cited by in corpus (5)

• High-performance lasers for fully integrated silicon nitride photonics
• Anneal-free ultra-low loss silicon nitride integrated photonics
• Silicon nitride stress-optic microresonator modulator for optical control applications
• Compact sub-Hz Linewidth Laser Enabled by Self Injection Lock To a Sub-mL FP Cavity
• Thermal and driven noise in Brillouin Lasers