有限层信息流叠加时频谱能量有效正交频分复用(SEE-OFDM)技术与直流偏置光正交频分复用(DCO-OFDM)技术的频谱效率存在差距.针对该问题,提出一种基于SEE-OFDM的叠加非对称限幅光正交频分复用(ACO-OFDM)调制技术.通过改变不同层信息流的调制阶数,使得叠加ACO-OFDM的频谱效率与DCO-OFDM相等.对系统误比特率(BER)进行理论分析,确定系统BER最小时的调制阶数组合算法,并提取每层信息流在解调时的子载波.实验结果表明,当频谱效率为1.5时,在线性AWGN信道下叠加ACO-OFDM技术的BER性能要优于DCO-OFDM技术与ACO-OFDM技术.%When limited information streams superpose,Spectral and Energy Efficient Orthogonal Frequency Division Multiplexing(SEE-OFDM) and Direct Current-biased Optical OFDM (DCO-OFDM) have different spectral efficiency.Aiming at this problem,a superposition Asymmetrically Clipped Optical OFDM (ACO-OFDM) tecnique based on SEEOFDM is proposed.By changing the modulation order of information stream in different layers,the spectral efficiency of superposition ACO-OFDM can be equal to that of DCO-OFDM.After theoretical analysis of the Bit Error Rate(BER) for the system,an algorithm is given to find the modulation order with the least BER.And subcarrier is extracted for information stream in each layer in the demodulation process.Experimetual results show that the superposition ACOOFDM is superior to DCO-OFDM and ACO-OFDM in the BER performance under the linear Additive White Gaussian Noise(AWGN) channel when the spectral efficiency is 1.5.
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