Hybrid fiber links for accurate optical frequency comparison

• DOI: 10.1007/s00340-017-6736-5
• Publication Date: 2017-05-02T01:26:54Z
• Authors: Won-Kyu Lee; Fabio Stefani; Anthony Bercy; Olivier Lopez; Anne Amy-Klein; Paul-Eric Pottie
• Keywords: Laser stabilization; [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]; Quantum Physics; Frequency transfer; Phase noise; FOS: Physical sciences; Time and frequency metrology; Physics and Astronomy (miscellaneous); Physics and Astronomy (all); 530; 620; [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph]; Optical link; 11. Sustainability; [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Quantum Physics (quant-ph); [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing; Physics - Optics; Optics (physics.optics)

We present the first experimental demonstration over a 43-km-long urban fiber network of a local two-way optical frequency comparison, which does not require any synchronization of the measurements. It was combined with a regular active-noise compensation on another parallel fiber leading to a very reliable and robust frequency transfer. This hybrid scheme enables us to investigate the major limiting factors of the local two-way comparison. We analyze the contribution to the phase noise of the recovered signal by the interferometers at local and remote places. By using the ability of this set up to be injected by a single laser or two independent lasers, we measure the contribution to the long-term instability by the demodulated laser instabilities. We show that a fractional frequency instability level of $1\times10^{-20}$ at 10 000 s can be obtained with this simple setup after 43-km-long propagation in an urban area.