Approaching optimum phase measurement in the presence of amplifier noise

Darko Zibar*, Jens E. Pedersen, Poul Varming, Giovanni Brajato, Francesco Da Ros

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

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Abstract

In fundamental papers from 1962, Heffener and Haus showed that it is not possible to construct a linear noiseless amplifier [Proc. IRE 50, 1604 (1962); Phys. Rev. Lett. 128, 2407 (1962)]. This implies that amplifier intrinsic noise sources induce random perturbations on the phase of the incoming optical signal, which translates into spectral broadening. Achieving the minimum induced phase fluctuation requires a phase measurement method that introduces minimum uncertainty, i.e., optimum phase measurement. We demonstrate that a measurement method based on heterodyne detection and extended Kalman filtering approaches optimum phase measurement in the presence of amplifier noise. A penalty of 5 dB (numerical) and 15 dB (experimental) compared to quantum limited spectral broadening is achieved. Spectral broadening reduction of 44 dB is achieved, compared to when using the widely employed phase measurement method, based purely on the argument of the signal field. Our results reveal new scientific insights by demonstrating a phase measurement method that enables to approach minimum phase fluctuation, induced by amplifier noise. An impact is envisioned for phase-based optical sensing systems, as optical amplification could increase sensing distance with minimum impact on the phase.

Original languageEnglish
JournalOptica
Volume8
Issue number10
Pages (from-to)1262-1267
ISSN2334-2536
DOIs
Publication statusPublished - Oct 2021

Bibliographical note

Funding Information:
Villum Fonden, VYI OPTIC-AI (29344); European Research Council, H2020-EU CoG FRECOM (771878).

Publisher Copyright:
© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

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