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 with 00K or subcarrier PSK intensity modulation. It is shown that a${\rm BER}=10^{-6}$and a scintillion level$\sigma=0.1$, an optical communication system employing subcarrier BPSK is 3 dB better than a comparable system using fixed threshold 00K. When$\sigma=0.2$, an optical communication system employing subcarrier BPSK achieves a${\rm BER}=10^{-6}$at SNR 13.7 dB, while the BER of a comparable system employing 00K can never be less than${\hbox{10}}^{-4}$. 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 convolution codes and subcarrier BPSK modulation.