Stochastic Approximation Aided Adaptive Thresholding for Optical Detection in PAM4 Based FSO Transmission

Jae Young Choi, Joon Woo Lee, Sang Kook Han

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1 Citation (Scopus)


This study proposes an adaptive thresholding optical detection technique using a stochastic approximation (SA) to enhance receiver performance in multi-level pulse amplitude modulation (PAM) based free-space optical (FSO) transmission. When the receiver detects the symbol by fixed threshold decision (FTD) scheme, the detection performance of high order modulation, including PAM4, becomes degraded due to a random fluctuation of the received signal. Owing to the slow varying characteristic of atmospheric turbulence, we used an adaptive linear prediction (ALP) filter to predict the decision threshold of the upcoming frame. The experiment was conducted on various degrees of turbulence channels. A Mach-Zehnder modulator (MZM) based turbulence channel emulator was used to experimentally investigate the turbulence-induced scintillation effect. The experiment results confirmed that the proposed technique yielded improved receiver performance compared to FTD. In the case of considering the amplified spontaneous emission (ASE) noise of erbium-doped fiber amplifier (EDFA), the adaptive threshold decision (ATD) scheme obtained about 3dB gain compared with an even-valued threshold (EVT) decision scheme when the average EDFA input optical power was below-16dBm.

Original languageEnglish
Article number9500214
Pages (from-to)106451-106458
Number of pages8
JournalIEEE Access
Publication statusPublished - 2021

Bibliographical note

Funding Information:
This work was supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT; Ministry of Science and ICT) (No. 2019-0-00685, Free-space-optical-communication-based vertical mobile network).

Publisher Copyright:
© 2013 IEEE.

All Science Journal Classification (ASJC) codes

  • Computer Science(all)
  • Materials Science(all)
  • Engineering(all)


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