Scintillation Robust Adaptive Optical Signal Detection in Free Space Optical Communications using CSI Prediction

J. Y. Choi, S. K. Han

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Adaptive multi-level symbol detection technique in free-space optical communication (FSOC) is presented in this paper. Generally, the on-off keying (OOK) format is used in intensity modulation/direct detection (IM/DD) based free-space optical (FSO) system. For OOK symbol detection in FSOC, the maximum likelihood (ML) based optimal detection scheme is adopted. The ML detection techniques need the accurate marginal distribution of the turbulence-induced fading. However, it is non-attainable in practical system, and the distribution model is also not fixed in the FSO link. The response of intensity fluctuation in turbulence is relatively slow compared with that of the data rate with a cutoff frequency of 1 kHz. For this reason, there is a variation in time about the optimal threshold, causing significant burst errors when a fixed threshold is used. Applying a DC block or AC coupling of PD can stabilize symbol detection in OOK symbol. However, when it comes to multi-level pulse amplitude modulation (PAM) format in FSO system, the symbol detection problem cannot be solved with previous detection techniques. In this paper, the channel state information (CSI) prediction technique for adaptive multi-level optical symbol detection is proposed. Considering the slow varying characteristic of scintillation channel, we used an adaptive linear prediction (ALP) filter to predict the CSI of the upcoming frame. The proof-of-concept experiments were conducted with a Mach-Zehnder modulator (MZM) based channel emulator. The validity of the proposed symbol detection technique was experimentally demonstrated by comparing with the fixed threshold decision (FTD) and adaptive threshold decision (ATD) scheme.

Original languageEnglish
Title of host publicationNext-Generation Optical Communication
Subtitle of host publicationComponents, Sub-Systems, and Systems XI
EditorsGuifang Li, Kazuhide Nakajima
ISBN (Electronic)9781510649279
Publication statusPublished - 2022
EventNext-Generation Optical Communication: Components, Sub-Systems, and Systems XI 2022 - San Francisco, United States
Duration: 2022 Jan 222022 Jan 27

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceNext-Generation Optical Communication: Components, Sub-Systems, and Systems XI 2022
Country/TerritoryUnited States
CitySan Francisco

Bibliographical note

Publisher Copyright:
© 2022 SPIE

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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