无源光网络(PON)通常采用二进制非归零码(NRZ)调制技术，该技术存在如下缺点：系统的频谱效率最低，对无源光网络中相邻射频(RF)电视信道产生拉曼串扰影响，以及高速传输时光纤色散代价大。为了克服上述问题，采用了将正交频分复用(OFDM)调制技术应用于PON系统的解决方法。对基于强度调制和雪崩光电二极管(APD)直接检测的10 Gb/s 16位正交幅度调制(16QAM)OFDM-PON系统进行了100 km的下行方向传输实验。实验结果表明，在误码率（BER）水平为1×10-3的条件下，系统接收灵敏度可以达到-26 dBm。在1556 nm波段，传输距离小于100 km的情况下，标准单模光纤的色度色散对该系统传输性能的影响可以忽略。

Traditional passive optical network (PON) systems are based on binary non-return-to-zero (NRZ) modulation format, which results in some disadvantages, such as the lowest system spectral efficiency, Raman crosstalk against radio-frequency (RF) video channels and large fiber dispersion penalty. In order to avoid the above problems, applying orthogonal frequency division multiplexing (OFDM) modulation format in PON systems could be a feasible technique. So a 10 Gb/s intensity modulation and direct detection (IM-DD) 16 quadrature amplitude modulation (16QAM) OFDM-PON downstream transmission over 100 km standard single-mode fiber (SSMF) is experimentally demonstrated. The recorded downstream receiving sensitivity is -26 dBm at the bit error rate (BER) level of 1×10-3 using avalanche photodiode (APD) direct detection. The dispersion penalty can be ignored at 1556 nm wavelength when the transmission distance is less than 100 km.