为了减少直接检测的光正交频分复用(DD-OOFDM)传输系统中色散对系统的影响，传输系统使用了基于频域的最小均方(LMS)自适应均衡技术，由于基于频域的LMS估计方法计算复杂度低且便于信号块处理，相比最小平方(LS)估计方法，可更有效地追踪信道变化，减小相位噪声对传输系统的影响。实验结果表明，经背靠背(BTB)和100 km标准单模光纤(SSMF)传输后，使用频域LMS估计方法的信号比使用频域LS估计方法的信号系统接收功率代价在误码率为10×10-2.5和10×10-2.0时分别降低了2 dB及2.5 dB， 频域LMS估计方法比频域LS估计方法对传输系统具有更好的色散补偿效果。

In order to overcome the defects of least squares (LS) estimator used to defend chromatic dispersion in the direct-detection (DD) optical orthogonal frequency division multiplexing (OOFDM) transmission system, an adaptive least mean square (LMS) estimator is presented owing to its brief calculation and easy signal block processing. The performance of the proposed estimator is evaluated in an experimental system with 2.5 Gb/s DD-OOFDM signal at back-to-back (BTB) and transmitting over 100 km standard single mode fiber (SSMF). The experimental results show that the power penalty of system using LMS equalizer is 2 dB less at 10×10-2.5 bit error rate (BER) and 2.5 dB less at 10×10-2.0 BER than using LS equalizer when the OFDM signals transmitted by BTB and 100 km SSMF. It is proved that the system using LMS equalizer has a better performance to restore signals than using LS equalizer.