Channel capacity of IM/DD optical communication systems and of ACO-OFDM

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In this paper we investigate the channel capacity of intensity modulated direct detection (IM/DD) wireless optical communication systems for an AWGN channel with a limit on the average transmitted optical power. It has recently been shown that asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) is more efficient in terms of optical power than conventional optical modulation techniques such as pulse position modulation (PPM). When ACO-OFDM is used, the transmitted signal has a clipped Gaussian probability distribution. We calculate the channel capacity for systems using transmitted signals with exponential and clipped Gaussian distributions, and for an ACO-OFDM system. For practical signal to noise ratios, ACO-OFDM has a slightly lower capacity than the other distributions, due to the correlation between samples caused by the ACO-OFDM modulation process. ACO-OFDM has many practical advantages including its tolerance to multipath distortion. This paper shows that it also makes efficient use of the available power and bandwidth.

Original languageEnglish
Title of host publication2007 IEEE International Conference on Communications, ICC'07
Number of pages6
Publication statusPublished - 1 Dec 2007
Event2007 IEEE International Conference on Communications, ICC'07 - Glasgow, Scotland, United Kingdom
Duration: 24 Jun 200728 Jun 2007


Conference2007 IEEE International Conference on Communications, ICC'07
CountryUnited Kingdom
CityGlasgow, Scotland


  • Asymmetrically clipped optical OFDM
  • Channel capacity
  • IM/DD
  • Intensity modulated direct detection
  • OFDM
  • Optical communications

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