Abstract
Frequency dissemination over optical fiber links relies on measuring the phase of fiber-delivered lasers. Phase is extracted from optical beatnotes and the detection fails in case of beatnotes fading due to polarization changes, which strongly limit the reliability and robustness of the dissemination chain. We propose a new method that overcomes this issue, based on a dual-polarization coherent receiver and a dedicated signal processing that we developed on a field programmable gated array. Our method allowed analysis of polarization-induced phase noise from a theoretical and experimental point of view and endless tracking of the optical phase. This removes a major obstacle in the use of optical links for those physics experiments where long measurement times and high reliability are required.
Highlights
In recent years, the dissemination of frequency references over phase-stabilised optical fibers has become a key tool in a number of physics areas
Phase-stabilised optical links have been used in high-resolution atomic and molecular spectroscopy [5,6,7], radioastronomy and space geodesy based on Very Long Baseline Interferometry (VLBI) [8,9,10], and to detect seismic noise in seas and oceans, one of the most challenging tasks of modern seismology [11]
We used an optical hybrid to detect the phase difference between the signal received from a phase-stabilised optical link and a local oscillator and phase lock the two, and compare its performance with a standard detection scheme based on a single photodiode
Summary
The dissemination of frequency references over phase-stabilised optical fibers has become a key tool in a number of physics areas. Far from being a mere operational requirement, the latter is a key step to enable a new class of physics experiments, where the high measurement precision allowed by frequency dissemination over fiber can be combined with averaging times of several hours or days This could open new possibilities, for instance, in fundamental physics experiments: nowadays the most advanced tests of special relativity [2] and the search for dark matter [16] rely on fiber-based. Our results show that the proposed detection scheme is a viable solution in fiber-based frequency dissemination, allowing long-term operation of optical links while preserving the metrological requirements in terms of resolution. This allows an improvement in the reliability and reduces the risk of unexpected losses of coherence. The paper is organised as follows: Sec. 2 explains the model we developed to describe fiber birefringence in the metrological context; Sec. 3 shows the optical hybrid principle of operation and Sec. 4 reports on the obtained experimental results
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
