The generation of coherent optical subcarriers based on a concatenated dual-drive Mach-Zehnder intensity modulator (IM) and two phase modulators (PMs) is proposed and experimentally demonstrated. The modulation index and DC bias of PM+IM modulation are theoretically investigated. Theoretical analysis and numerical study are also carried out to examine the proposed scheme. We use 25-GHz RF synchronous sinusoidal signals to drive cascaded two-stage PMs and IM, through which we generate 28 subcarriers with peak power fluctuations less than 4 dB. The measured tone-to-noise ratio of the subcarrier is higher than 40 dB. The experimental results show that for 100-Gb/s polarization multiplexing QPSK signal, the receiver sensitivity of the back-to-back signal is -28.6 dBm, and the power penalty is lower than 1 dB after 100-km transmission at the BER of 1 \times 10^{-9}.

研究了基于双臂马赫曾德尔调制器（MZM）产生全光正交频分复用信号的原理，讨论了正交光子载波的产生由MZM的射频驱动和直流偏置电压决定的特性；并对基于载波抖动对系统的损伤定义了一个新的参数载波均衡，以准确地描述产生全光正交频分复用载波的传输性能。根据选择的载波均衡参数，得到了产生2,3,4和5条正交光载波的最佳工作点；在接收端采用改进的马赫曾德尔延时干涉仪和光门实现全光离散傅里叶变换，并测得了光门的相位取值和接收端滤波器带宽对接收信号误码性能的影响；最后研究了基于5条正交光边带100 Gb/s全光正交频分复用的传输系统性能。

提出并证明了一种基于副载波单边带分插复用的正交频分复用无源光网络(OFDM-PON)系统的新型结构。该结构的下行传输是基于单边带的OFDM-4-正交幅度调制(QAM)，传输速率为10 Gbit/s；而上行传输则是利用下行信号中保留的另一条边带进行2.5 Gbit/s速率的幅移键控(ASK)调制，采用时分多路接入方式。该方案可以较好地避免双向传输中的后向瑞利散射，考虑后向散射情况下，下行信号功率代价＜0.8 dB，上行信号功率代价＜1.8 dB。

随着接入网带宽需求和业务支持需求的快速发展，环形结构的无源光网络(PON)的应用越来越重要，更长距离、支持更多光网络单元、与环形网络无缝融合已经成为PON在城域网中继续发展的3大要求。文章详细论述了新型环树融合拓扑结构的PON的原理及关键技术，讨论了这种新型结构的典型应用，总结了不同方案的优缺点，为未来接入网与城域网更深层次的融合发展的研究提供参考。

文章提出了一种新型的基于正交频移键控(FSK)/幅移键控(ASK)再调制的波分复用-无源光网络(WDM-PON)结构，在下行方向，采用一种新型的基于相位-强度调制转换的FSK调制技术，实现了40 GHz的高速FSK信号；在上行方向，直接将10 GHz的ASK信号调制到FSK信号上，实现正交调制。文章研究了整个系统的性能，仿真结果显示，这种WDM-PON结构能满足接入网的传输要求，为未来的高速接入网提供了一种选择。

Optical frequency shift keying (FSK) homodyne detection utilizing image rejection in FSK/amplitude shift keying (ASK) re-modulation wavelength-division-multiplexed passive optical network (WDM-PON) is proposed and demonstrated. Image rejection is adopted to achieve better performance. We show the result in back-to-back and 40-km distance respectively and apparent improvement is obtained in the latter situation by using image rejection. Several factors which affect the image rejection receiver are analyzed in order to find out the optimum parameters. Result shows that the presented scheme is suitable for super long reach access network, especially for future metro access network.

A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing (OFDM) continuous phase modulation (CPM) signal, which is combining minimum shift keying (MSK) coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing (WDM) passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying (OOK) data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.