When to Use Optical Amplification in Noncoherent Transmission: An Information-Theoretic Approach
Journal article, 2020

The standard solution for short-haul fiber-optic communications is to deploy noncoherent systems, i.e., to modulate and detect only the light intensity. In such systems, the signal is corrupted with optical noise from amplifiers and with thermal (electrical) noise. The capacity of noncoherent optical links has been studied extensively in the presence of either optical noise or thermal noise. In this paper, for the first time, we characterize the capacity under an average power constraint with both noise sources by establishing upper and lower bounds. In the two extreme cases of zero optical noise or zero thermal noise, we assess our bounds against some well-known results in the literature; improvements in both cases are observed. Next, for amplified fiber-optic systems, we study the trade-off between boosting signal energy (mitigating the effects of thermal noise) and adding optical noise. For a wide spectrum of system parameters and received power levels, we determine the optimal amplification gain. While mostly either no amplification or high-gain amplification is optimal, the best performance is for some parameter intervals achieved at finite gains.

phase-noise channel

Channel capacity

noncoherent optics

optical amplification

passive optical network


Kamran Keykhosravi

Chalmers, Electrical Engineering, Communication, Antennas and Optical Networks

Erik Agrell

Chalmers, Electrical Engineering, Communication, Antennas and Optical Networks

Marco Secondini

Sant'Anna School of Advanced Studies (SSSUP)

Magnus Karlsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

IEEE Transactions on Communications

0090-6778 (ISSN) 15580857 (eISSN)

Vol. 68 4 2438-2445 8966942

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Swedish Research Council (VR) (2013-5271), 2014-01-01 -- 2017-12-31.

Signal shaping in optical communications—Beyond the Gaussian channel

Swedish Research Council (VR) (2017-03702), 2018-01-01 -- 2021-12-31.

Subject Categories


Communication Systems

Signal Processing



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