A Silicon Photonic 32-Input Coherent Combiner for Turbulence Mitigation in Free Space Optics Links

Lorenzo De Marinis; Peter Seigo Kincaid; Yann Lucas; Lea Krafft; Vincent Michau; Matteo Cherchi; Mikko Karppinen; Giampiero Contestabile

doi:10.1109/ACCESS.2025.3541870

A Silicon Photonic 32-Input Coherent Combiner for Turbulence Mitigation in Free Space Optics Links

Lorenzo De Marinis^*
, Peter Seigo Kincaid
, Yann Lucas
, Lea Krafft
, Vincent Michau
, Matteo Cherchi
, Mikko Karppinen
, Giampiero Contestabile

^*Corresponding author for this work

Sant'Anna School of Advanced Studies
University of Paris-Saclay
Xanadu Quantum Technologies

Research output: Contribution to journal › Article › Scientific › peer-review

5 Citations (Scopus)

Abstract

Free space optical links promise high data rates for future wireless communications systems, but performance is degraded by turbulence, limiting the potential use cases. A photonic integrated circuit (PIC) for turbulence mitigation is reported and characterized, which coherently combines 32 input optical signals into a single output fiber. The PIC was fabricated using a low-loss, and high integration density, thick silicon-on-insulator (SOI) process and packaged with 32 input fibers and 1 output fiber. The basic building block is a 2x2 Mach-Zehnder interferometer (MZI) with an external (to the MZI branches) and an internal thermal phase shifter, and a bandwidth in excess of 80 kHz. The PIC monolithically integrates 31 MZIs and 31 germanium photodetectors and is suitable in principle for turbulence mitigation in LEO-ground and horizontal free space optics links. Improvements to the device for the coherent combination of 64 inputs and for the reduction of insertion losses are also discussed.

Original language	English
Pages (from-to)	31718-31728
Number of pages	11
Journal	IEEE Access
Volume	13
DOIs	https://doi.org/10.1109/ACCESS.2025.3541870
Publication status	Published - Feb 2025
MoE publication type	A1 Journal article-refereed

Funding

This work was supported in part by the European Union (EU) Horizon 2020 Programme through the Actphast 4R Project under Grant 779472; and in part by Valtion Teknillinen Tutkimuskeskus ( VTT’s) Si photonics activities are part of the Research Council of Finland Flagship Programme, Photonics Research and Innovation (PREIN) under Grant 346545.

Keywords

Adaptive optics
coherent combiner
free space optics
silicon photonics
turbulence mitigation

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10.1109/ACCESS.2025.3541870Licence: CC BY

Cite this

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title = "A Silicon Photonic 32-Input Coherent Combiner for Turbulence Mitigation in Free Space Optics Links",

abstract = "Free space optical links promise high data rates for future wireless communications systems, but performance is degraded by turbulence, limiting the potential use cases. A photonic integrated circuit (PIC) for turbulence mitigation is reported and characterized, which coherently combines 32 input optical signals into a single output fiber. The PIC was fabricated using a low-loss, and high integration density, thick silicon-on-insulator (SOI) process and packaged with 32 input fibers and 1 output fiber. The basic building block is a 2x2 Mach-Zehnder interferometer (MZI) with an external (to the MZI branches) and an internal thermal phase shifter, and a bandwidth in excess of 80 kHz. The PIC monolithically integrates 31 MZIs and 31 germanium photodetectors and is suitable in principle for turbulence mitigation in LEO-ground and horizontal free space optics links. Improvements to the device for the coherent combination of 64 inputs and for the reduction of insertion losses are also discussed.",

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AU - De Marinis, Lorenzo

AU - Kincaid, Peter Seigo

AU - Lucas, Yann

AU - Krafft, Lea

AU - Michau, Vincent

AU - Cherchi, Matteo

AU - Karppinen, Mikko

AU - Contestabile, Giampiero

PY - 2025/2

Y1 - 2025/2

N2 - Free space optical links promise high data rates for future wireless communications systems, but performance is degraded by turbulence, limiting the potential use cases. A photonic integrated circuit (PIC) for turbulence mitigation is reported and characterized, which coherently combines 32 input optical signals into a single output fiber. The PIC was fabricated using a low-loss, and high integration density, thick silicon-on-insulator (SOI) process and packaged with 32 input fibers and 1 output fiber. The basic building block is a 2x2 Mach-Zehnder interferometer (MZI) with an external (to the MZI branches) and an internal thermal phase shifter, and a bandwidth in excess of 80 kHz. The PIC monolithically integrates 31 MZIs and 31 germanium photodetectors and is suitable in principle for turbulence mitigation in LEO-ground and horizontal free space optics links. Improvements to the device for the coherent combination of 64 inputs and for the reduction of insertion losses are also discussed.

AB - Free space optical links promise high data rates for future wireless communications systems, but performance is degraded by turbulence, limiting the potential use cases. A photonic integrated circuit (PIC) for turbulence mitigation is reported and characterized, which coherently combines 32 input optical signals into a single output fiber. The PIC was fabricated using a low-loss, and high integration density, thick silicon-on-insulator (SOI) process and packaged with 32 input fibers and 1 output fiber. The basic building block is a 2x2 Mach-Zehnder interferometer (MZI) with an external (to the MZI branches) and an internal thermal phase shifter, and a bandwidth in excess of 80 kHz. The PIC monolithically integrates 31 MZIs and 31 germanium photodetectors and is suitable in principle for turbulence mitigation in LEO-ground and horizontal free space optics links. Improvements to the device for the coherent combination of 64 inputs and for the reduction of insertion losses are also discussed.

KW - Adaptive optics

KW - coherent combiner

KW - free space optics

KW - silicon photonics

KW - turbulence mitigation

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DO - 10.1109/ACCESS.2025.3541870

M3 - Article

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JO - IEEE Access

JF - IEEE Access

ER -

A Silicon Photonic 32-Input Coherent Combiner for Turbulence Mitigation in Free Space Optics Links

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