Optical Communication Using Subcarrier PSK Intensity Modulation Through Atmospheric Turbulence Channels

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper studies optical communications using subcarrier phase shift keying (PSK) intensity modulation through atmospheric turbulence channels. The bit error rate (BER) is derived for optical communication systems employing either on/off key (OOK) or subcarrier PSK intensity modulation. It is shown that at <formula formulatype="inline"><tex>${\hbox{BER}} =10^{-6}$</tex></formula> and a scintillation level of <formula formulatype="inline"><tex>$\sigma = 0.1$</tex></formula>, an optical communication system employing subcarrier BPSK is 3 dB better than a comparable system using fixed-threshold OOK. When <formula formulatype="inline"><tex> $\sigma =0.2$</tex></formula>, an optical communication system employing subcarrier BPSK achieves a <formula formulatype="inline"><tex>${\hbox{BER}} = 10^{-6}$</tex></formula> at <formula formulatype="inline"><tex> ${\hbox{SNR}} = 13.7$</tex></formula> dB, while the BER of a comparable system employing OOK can never be less than <formula formulatype="inline"><tex>$10^{-4}$</tex></formula>. Convolutional codes are discussed for optical communication through atmospheric turbulence channels. Interleaving is employed to overcome memory effect in atmospheric turbulence channels. An upper bound on BER is derived for optical communication systems employing convolutional codes and subcarrier BPSK modulation. </para>