Multidimensional Constellation Shaping for Coherent Optical Communication Systems
Doctoral thesis, 2022

To overcome the increasing demands for Internet traffic, exploiting the available degrees of freedom in optical communication systems is necessary. In this thesis, we study how constellation shaping can be achieved in various dimensions and how various shaping schemes affect the whole performance in real systems. This thesis investigates the performance of constellation shaping methods including geometric shaping and probabilistic shaping in coherent fiber-optic systems.
To study geometric shaping, we explore multidimensional lattice-based constellations. These constellations provide a regular structure with fast and low-complexity encoding and decoding. We show the possibility of transmitting and detecting constellations with a size of more than 10^{28} points, which can be done without a look-up table to store the constellation points. Moreover, we experimentally realize our proposed multidimensional modulation formats in long-haul optical communication systems.
Finally, we investigate the performance of probabilistically shaped quadrature amplitude modulation and compare it with uniform cross quadrature amplitude modulation in the presence of transmitter impairments, and with uniform quadrature amplitude modulation in links where higher-order modulation formats co-propagate with on-off keying wavelength channels.

lattice-based constellations

geometric shaping

probabilistic shaping

multidimensional modulation format

Voronoi constellation

constellation shaping

optical communications

coherent receiver

Kollektorn, MC2 department, Kemivägen 9, Chalmers
Opponent: David Millar, Infinera corp., Canada


Ali Mirani

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Lattice-based geometric shaping

European Conference on Optical Communication, ECOC,; (2020)

Paper in proceeding

Low-complexity geometric shaping

Journal of Lightwave Technology,; Vol. 39(2021)p. 363-371

Journal article

Physical Realizations of Multidimensional Voronoi Constellations in Optical Communication Systems

Journal of Lightwave Technology,; Vol. In Press(2023)

Journal article

Capacity of phase-sensitively preamplified optical links at low signal-to-noise ratio

2022 European Conference on Optical Communication, ECOC 2022,; (2022)

Paper in proceeding

Performance of Probabilistic Shaping Coherent Channels in Hybrid Systems

International Conference on Transparent Optical Networks,; Vol. 2020-July(2020)p. 1-3

Paper in proceeding

Have you ever encountered the problem of finding the best structure to pack objects inside a limited space? In mathematics, this problem is known as sphere packing and has been studied in dimensions higher than what we can visualize, i.e., more than three. This concept is closely related to communication theory via coding and modulation.
Usually, in communication theory, the transmitted information is represented with discrete points known as symbols. When the symbols are transmitted over the channel, different noise sources distort the signal, and what we receive is different than what we transmitted. Because of these noise sources, the received samples appear as spherical clouds on the receiver side which can overlap with each other. The purpose of coding and modulation is to reduce the error probability because of this overlap and to increase the information rate that can be transmitted over the channel.
The goal of this thesis is to propose energy-efficient modulations that can outperform the conventional modulations already used in optical communication systems. We show that by increasing the dimension of the symbols, an improved sensitivity can be achieved to tolerate the channel noise. Therefore, the optical signal can propagate for a longer distance over the fiber link.

Communications over bursty optical channels

Swedish Research Council (VR) (2021-03709), 2022-01-01 -- 2025-12-31.

Polarization-aware fiber optic transmisson

Swedish Research Council (VR) (2015-04239), 2016-01-01 -- 2019-12-31.

Signal shaping in optical communications—Beyond the Gaussian channel

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

Noiseless phase-sensitive optical amplifiers and their applications

Swedish Research Council (VR) (2015-00535), 2016-01-01 -- 2025-12-31.

Unlocking the Full-dimensional Fiber Capacity

Knut and Alice Wallenberg Foundation (KAW 2018.0090), 2019-07-01 -- 2024-06-30.

Coupled fiber optic channels

Swedish Research Council (VR) (2019-04078), 2019-12-01 -- 2023-11-30.

Areas of Advance

Information and Communication Technology

Driving Forces

Sustainable development

Innovation and entrepreneurship

Subject Categories


Atom and Molecular Physics and Optics

Communication Systems

Electrical Engineering, Electronic Engineering, Information Engineering


Basic sciences


C3SE (Chalmers Centre for Computational Science and Engineering)

Learning and teaching

Pedagogical work



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5241



Kollektorn, MC2 department, Kemivägen 9, Chalmers

Opponent: David Millar, Infinera corp., Canada

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