Avoiding Aliasing in Allan Variance: An Application to Fiber Link Data Analysis

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 63; no. 4; pp. 646 - 655
• Main Authors: Calosso, Claudio E., Clivati, Cecilia, Micalizio, Salvatore
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-04-2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: aliasing; Allan variance; atomic clock comparison; Bandwidth; Bandwidths; Frequency estimation; Frequency-domain analysis; modified Allan variance; Optical fiber communication; Optical fiber link; Optical fibers; Phase noise; modified Allan variance (MVAR); Allan variance (AVAR); optical fiber link; Aliasing; atomic clock comparison
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2016.2519265

Optical fiber links are known as the most performing tools to transfer ultrastable frequency reference signals. However, these signals are affected by phase noise up to bandwidths of several kilohertz and a careful data processing strategy is required to properly estimate the uncertainty. This aspect is often overlooked and a number of approaches have been proposed to implicitly deal with it. Here, we face this issue in terms of aliasing and show how typical tools of signal analysis can be adapted to the evaluation of optical fiber links performance. In this way, it is possible to use the Allan variance (AVAR) as estimator of stability and there is no need to introduce other estimators. The general rules we derive can be extended to all optical links. As an example, we apply this method to the experimental data we obtained on a 1284-km coherent optical link for frequency dissemination, which we realized in Italy.