Free-space optical communication employing subcarrier modulation and spatial diversity in atmospheric turbulence channel

W. O. Popoola, Z. Ghassernlooy, J. I. H. Allen, E. Leitgeb, S. Gao

Research output: Contribution to journalArticlepeer-review


An expression for the bit error rate of a multiple subcarrier intensity-modulated atmospheric optical communication system employing spatial diversity is derived. Spatial diversity is used to mitigate scintillation caused by atmospheric turbulence, which is assumed to obey log-normal distribution. Optimal but complex maximum ratio, equal gain combining (EGC) and relatively simple selection combining spatial diversity techniques in a clear atmosphere are considered. Each subcarrier is modulated using binary phase shift keying. Laser irradiance is subsequently modulated by a subcarrier signal, and a direct detection PIN receiver is employed (i.e. intensity modulation/direction detection). At a subcarrier level, coherent demodulation is used to extract the transmitted data/information. The performance of on-off-keying is also presented and compared with the subcarrier intensity modulation under the same atmospheric conditions.

Original languageEnglish
Pages (from-to)16-23
Number of pages8
JournalIET Optoelectronics
Issue number1
Publication statusPublished - Feb 2008

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