Soa-based multilevel polarization shift on–off keying transmission for free-space optical communication

Yan Qing Hong, Do Hoon Kwon, Jae Young Choi, In Ho Ha, Won Ho Shin, Sang Kook Han

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


This paper proposes a semiconductor optical amplifier (SOA)-based multilevel polarization shift on–off keying (MPS-OOK) transmission for free-space optical (FSO) communication. At the transmitter end, the MPS-OOK signal is modulated with a constant linear state of polarization (SOP) at the high-intensity level and various SOPs at the low-intensity level in order to improve the spectral efficiency (SE) with the transmitted power efficiency. At the receiver end, first, a polarization-independent SOA was introduced to optically suppress the turbulence-induced scintillation effect and equalize the intensities of the various SOPs in the deep gain saturation state without polarization distortion. Then, a linear polarizer (LP) with a high extinction ratio (ER) was deployed to convert the equalized SOPs into a known intensity. Finally, the converted MPS-OOK signal was detected using a single photodiode (PD) and distinguished using a multilevel fixed-threshold decision (M-FTD). The proposed technique was evaluated using experiments. A Mach–Zehnder modulator (MZM)-based fading simulator was introduced to emulate the turbulence-induced scintillation effect. The experimental results demonstrated that the scintillation effect was effectively mitigated and the SE was improved by up to 2 bit/s/Hz using the proposed four-level polarization shift on–off keying (4PS-OOK) transmission.

Original languageEnglish
Article number100
Issue number4
Publication statusPublished - 2021 Apr

Bibliographical note

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

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Radiology Nuclear Medicine and imaging


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