Novel Dispersion-Division-Multiplexing Technique for Enabling Double the Spectral Efficiency in Transmission and Routing of Photonic and Microwave Networks

长期以来，光纤具有无限带宽，因此我们有带宽可以燃烧，这是一个令人舒服的谬论。随着波分复用（WDM）技术在多信道通信中的应用，可用带宽成为了人们关注的焦点。当将光通信与其他类型的通信进行比较时，我们在频谱效率方面远远落后（即，比特/赫兹），我们甚至没有接近香农容量限制。事实上，更高的频谱效率可能是该领域中创造性活动最少的领域，但它为未来系统容量的革命性增长带来了希望。 在光通信中，一个最浪费带宽的技术领域是在一个波长载波上实现多个低速信道的副载波复用（SCM）。在SCM中，一半的数据带宽被浪费，因为：（i）传输双边带信号本质上将复制正在发送的数据，假定每个边带携带接收所需的全部信息，或者（ii）传输单边带信号要求载波另一侧的镜像频率（即，第二边带将位于何处）保持未被任何其它数据信号占用。 副载波多路复用对未来的光通信系统有许多优点，包括：（a）在单个高容量波长上传输许多低速数字数据信号，（B）传输许多模拟调制信号，（c）网络的传输介质，以适应基于无线微波的光信号，以及（d）在分组交换网络中传输用于有效路由的数字标签。 我们提出了一种新的复用方案，使使用副载波复用的光学系统的频谱效率加倍。该方案被称为色散分多路复用（DDM），它依赖于将两个数据信道同时放置在远离光载波的相同频率空间中。例如，一个双边带数据通道按常规方式传输，第二个双边带通道在第一个通道的阴影下传输。由于光纤的色散而发生遮蔽。由于色散，单个信道的两个双边带中的每一个都将以略微不同的速度传播。这些边带将相对于光载波周期性地彼此异相，从而彼此抵消并引起RF功率衰落（即，在接收机处给定信道的功率几乎完全消失）。当一个通道同相且满功率时，另一个通道将衰落。通过使用可调谐色散诱导元件，接收机可以改变每个信道的两个边带之间的相对相位，从而恢复两个频率共置信道中的任何一个。 我们的研究计划将调查独特的功能，机会和局限性，当使用频谱效率的色散-分割-复用，可以在5- 10年的时间框架内取得重大成果。我们的系统和网络研究计划的主要基本特征如下。我们将：（a）演示许多WDM信道的高频谱效率DDM，（B）演示DDM在基于无线的光子网络中用于互连节点的实用性，（c）演示WDM光子网络中的SCM标签交换和路由，以及（d）研究在考虑SNR、消光比和数据带宽时生成、发送和接收DDM信道的基本限制。目录

It has long been a comfortable fallacy that the optical fiber has infinite bandwidth, and, therefore,we have bandwidth to burn. With the explosion of multiple-channel communications through the usewavelength-division-multiplexing (WDM), available bandwidth now takes center stage. Whencomparing optical communications with other types of communications, we lag far behind in terms ofspectral efficiency (i.e., bits/Hz) and we are not even close to the Shannon capacity limit. In fact, higherspectral efficiency is probably the area of least creative activity within the field, and yet it holds thepromise for revolutionary increases in future systems capacity. One of the technical areas within optical communications that has shown the most bandwidthwaste and has many future potential applications is subcarrier multiplexing (SCM) of many lower-speedchannels on a single wavelength carrier. In SCM, half the data bandwidth is wasted since either:(i) transmitting double-sideband signals will, in essence, duplicate the data being sent given that eachsideband carries the full information needed for reception, or (ii) transmitting single-sideband signalsrequires that the mirror frequencies on the other side of the carrier wave (i.e., where the second sidebandwould have been located) remain unoccupied by any other data signals. Subcarrier multiplexing has many advantages for future optical communications systems,including: (a) the transmission of many lower-speed digital data signals on a single high-capacitywavelength, (b) the transmission of many analog-modulated signals, (c) the transmission medium fornetworks that accommodate wireless microwave-based optical signals, and (d) the transmission of controllabels for efficient routing in packet-switched networks. We propose implementing a new multiplexing scheme that enables double the spectral efficiencyfor optical systems that use subcarrier multiplexing. The scheme is called dispersion-division-multiplexing(DDM) and relies on placing two data channels simultaneously in the same frequency spaceaway from an optical carrrier. For example, one double-sideband data channel is transmittedconventionally, and a second double-sideband channel is transmitted in the shadow of the firstchannel. Shadowing occurs due to the chromatic dispersion of the optical fiber. Due to dispersion, eachof the two double sidebands of a single channel will travel at slightly different speeds. These sidebandswill periodically be out-of-phase will each other relative to the optical carrier wave, thereby cancelingeach other and inducing RF power fading (i.e., a nearly complete disappearing of the given channel'spower at a receiver). One channel would be faded when the other channel would be in-phase and havefull power. By using a tunable dispersion-inducing element, a receiver can change the relative phasebetween each cannel's two sidebands and thus recover either of the two frequency-co-located channels. Our research program will investigate unique functionalities, opportunities, and limitations whenusing spectrally-efficient dispersion-division-multiplexing that could bear significant fruit in the 5-10year time frame. The key fundamental features of our systems and networking research program are asfollows. We will:(a) demonstrate highly-spectrally-efficient DDM for many WDM channels,(b) demonstrate the utility of DDM for interconnecting nodes in a wireless-based photonicnetwork,(c) demonstrate SCM label swapping and routing in a WDM photonic network, and(d) investigate the fundamental limitations of generating, transmitting, and receiving DDMchannels when considering SNR, extinction ratio, and data bandwidth.TABLE OF CONTENTS