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为了提升非对称限幅光正交频分复用(ACO-OFDM)的频谱效率,提出了一种单极性非对称限幅光OFDM(UACO-OFDM)调制技术。UACO-OFDM是由ACO-OFDM和单极性OFDM(UOFDM)两种光OFDM信号组成,不同长度的信号在发送端按照一定规则进行叠加。然后通过发光二极管(LED)进行传输,在接收端只用1个光电检测器(PD)接收光信号,采用干扰消除方法依次对不同信号进行解调。当调制阶数相同时,UACO-OFDM的频谱效率要高于ACO-OFDM。在频谱效率相等的情况下,对UACO-OFDM和其他传统光OFDM调制方式的误比特率(BER)和峰均比(PAPR)性能进行对比分析。仿真结果表明,UACO-OFDM的BER性能更优。与频谱能量有效OFDM(SEE-OFDM)相比,当子载波数为64时,两者的PAPR性能比较接近;当子载波数为256和1 024时,UACO-OFDM比SEE-OFDM的PAPR分别低2dB和5dB以上。
In order to improve the spectral efficiency of asymmetric limiting optical orthogonal frequency division multiplexing (ACO-OFDM), a unipolar asymmetric limiting optical OFDM (UACO-OFDM) modulation technique is proposed. UACO-OFDM is composed of two types of optical OFDM signals, such as ACO-OFDM and unipolar OFDM (UOFDM). Signals of different lengths are superimposed on the transmitting end according to certain rules. Then it is transmitted through the light-emitting diode (LED), only one photodetector (PD) is used to receive the optical signal at the receiving end, and the different signals are sequentially demodulated by the interference elimination method. When the modulation order is the same, the spectral efficiency of UACO-OFDM is higher than that of ACO-OFDM. When the spectral efficiency is equal, the bit error rate (BER) and peak-to-average ratio (PAPR) performance of UACO-OFDM and other conventional optical OFDM modulation schemes are compared and analyzed. Simulation results show that the BER performance of UACO-OFDM is better. Compared with SEE-OFDM, the PAPR performance of the two is close when the number of subcarriers is 64. When the number of subcarriers is 256 and 1 024, PAPR of UACO-OFDM is higher than that of SEE-OFDM Low 2dB and 5dB above.