针对大气光通信中常规多脉冲位置调制(MPPM)的光调制方式，提出了一种由二进制相移键控(BPSK)改进的混合多脉冲调制方案。本方案中，BPSK 调制后的光脉冲在BPSK-MPPM 混合帧中传输，信息被携带在所发送光脉冲的位置与相位中，利用光脉冲位置变化来传输更多的比特。研究了改进的系统模型、传输信道、带宽利用率、传输效率和信道容量，并与常规方案性能指标做了比较。仿真结果表明，改进方案的带宽利用率和传输效率高于常规方案，并且在有保护时隙的混合MPPM 帧结构中，信道容量也会提高。

Considering the conventional multi-pulse position modulation (MPPM) in free atmosphere optical communication, a hybrid MPPM modulation scheme based on modified binary phase shift keying (BPSK) is proposed. In the scheme, BPSK-modulated optical pulses are transmitted in a BPSK-MPPM hybrid frame and as the transmitted information is carried by both position and phase of the transmitted pulse, the change of optical pulse position is used to transmit more bits. The modified system model, channel transmission characteristics, bandwidth utilization, transmission efficiency and channel capacity are researched and measured, which are also compared with those of traditional schemes. Simulation results show that bandwidth utilization and transmission efficiency of the proposed scheme are higher than those of the ordinary schemes. In addition, the channel capacity in the hybrid MPPM frame construction including protected slots is also higher than that of the ordinary schemes.