LAUSR

Free Space Optical (FSO) communication has been widely studied because of its advantages such as rich spectrum resource, high transmission capacity, high security, low power consumption and flexible installation. However, FSO link is sensitive to weather conditions and atmospheric turbulence, which poses a great challenge on signal transmission quality. Differential Phase Shift Keying (DPSK) modulation is well recognized as a promising technique to deal with the inter-symbol interference due to channel fading. Nevertheless, the existing system structure for high-order DPSK modulation technology is too complex to be used in practice for FSO system. Therefore, this letter proposes a simplified DPSK modulation scheme. In order to alleviate signal transmission performance degradation caused by simplification, a constellation remapping method is employed in the proposed scheme to achieve flexible signal transmission and improve the Bit Error Rate (BER) performance. It is demonstrated that compared with the traditional DPSK system, the proposed scheme significantly reduces the system complexity and has better BER performance under low to moderate atmospheric turbulence.