Coherent Optical SIgnals for extremely high-capacity NEtworks (COSINE)

高速光纤电缆连接着地球仪上的城市、国家和各大洲，支撑着互联网以及固定和移动的电话网络，使我们今天的生活得以实现和丰富。从历史上看，增加在单根光纤上传输的总数据速率已经显著降低了数据传输的成本，并且这是使得高数据速率连接能够以合理的成本对最终用户可用的一个因素。随着社交网络、音乐下载和视频点播等服务吸引了公众的注意力，它们反过来又创造了对这些网络上大幅增加容量的需求。随着已安装的光纤容量达到极限，我们可以预计这个周期将继续下去。为了在单根光纤上实现高传输容量，数据在多个波长通道（波分复用，WDM）上传输。为了与现有系统中使用的组件兼容，并且为了避免必须管理大量的波长，优选的是通过增加每个信道的数据速率来增加所传输的数据量，而不是通过将波长信道越来越紧密地打包在一起。现在正在部署具有40 Gb/s线路速率的WDM网络，并且当前有相当多的活动针对在单波长上的100 Gb/s以太网（100 GE）的研究和标准化。通过使用类似于在无线通信中使用的那些高级调制方案来扩展针对100 GE提出的方法，在每个波长上压缩几百Gb/s的数据传输速率是可能的，但所提出的技术挑战将是巨大的。要超越这一点--达到每波长1 Tb/s（1，000 Gb/s）--需要新的技术。在这项工作中，我们将研究一种实现这一目标的方法，这种方法还可以减轻当前方法对光发射机和接收机的一些严格要求。每个波长信道将被划分为多个子信道，并且高级调制格式用于在每个子信道的窄谱带中以高速率传输数据。将需要在发射器处高效且成本有效地生成限定子信道的光信号，并且在接收器处产生同步的光信号以恢复数据。为此，我们将在发射机处从定义整个信道的频率的单个激光器生成所有子信道，并且我们将使用一个子信道来传输信息，以允许在接收机处创建用于信道解调的相同的光信号集合。以这种方式，子信道在整个信道内彼此同步（锁相），发射机和接收机也是如此。这意味着子信道可以尽可能紧密地封装在一起，并且表现为单个单元，同时简化了接收器处的数据恢复。通过这种方式，我们期望将总光纤传输容量增加到135 Tb/s，比商业长距离传输系统的当前技术水平大一个数量级以上。这项工作将主要以实验方式进行，在将它们结合起来之前，分阶段调查提案的关键技术要素，以表明如果全面实施，整个方案可以实现预期的传输容量增加。将被检查的领域包括在发射机生成锁相子信道的新方法;在接收机生成和同步相应的光信号的方法;以及在窄谱带中提供高数据速率传输的调制和解调技术。实验演示将得到系统的计算机模拟的支持，这也将允许研究由该方法实现的新应用-太先进了，无法在现阶段进行实验演示。

High-speed fibre-optic cables link cities, countries and continents across the globe, underpinning the Internet and the fixed and mobile phone networks that enable and enrich our lives today. Historically, increasing the overall data rate transmitted on a single optical fibre has dramatically reduced the cost of data transmission, and this is one factor that has enabled high data rate connections to be available at reasonable cost to end users. As services like social networking, music downloads, and video-on-demand capture the public's attention, they in turn create demand for greatly increased capacity on these networks. We can expect this cycle to continue as the installed fibre capacity is pushed to its limit.To achieve high transmission capacity on a single fibre, data is transmitted on several wavelength channels (wavelength division multiplexing, WDM). For compatibility with the components used in existing systems, and to avoid having to manage a huge number of wavelengths, it is preferable to increase the amount of data transmitted by increasing the data rate per channel, rather than by packing the wavelength channels closer and closer together. WDM networks with 40 Gb/s line rate are now being deployed, and there is currently considerable activity directed towards research and standardisation of 100 Gb/s Ethernet (100 GE) on a single wavelength.By extending the approach proposed for 100 GE by using advanced modulation schemes like those used in wireless communications, it may be possible to squeeze data transmission rates of several hundred Gb/s onto each wavelength, but the technological challenges posed will be significant. To move beyond this - towards 1 Tb/s (1,000 Gb/s) per wavelength - will require new techniques.In this work, we will investigate one approach to achieving this, which also eases some of the stringent demands on the optical transmitters and receivers imposed by current methods. Each wavelength channel will be divided into a number of sub-channels, and advanced modulation formats used to transmit data at a high rate in the narrow spectral band of each sub-channel. It will be necessary to generate the optical signals that define the sub-channels at the transmitter efficiently and cost-effectively, and to produce synchronised optical signals at the receiver to recover the data. To do so, we will generate all the sub-channels at the transmitter from a single laser that defines the frequency of the overall channel, and we will use one sub-channel to transmit information to allow an identical set of optical signals for channel demodulation to be created at the receiver. In this way, the sub-channels are synchronised (phase locked) to each other within the overall channel, as are the transmitter and receiver. This means that the sub-channels can be packed as closely together as possible and behave as a single unit, while recovering the data at the receiver is simplified.By this means we expect to increase the overall fibre transmission capacity to 135 Tb/s, more than an order of magnitude greater than the current state of the art for commercial long haul transmission systems. The work will mainly be carried out experimentally, investigating the key technical elements of the proposal in stages before combining them to show that the full scheme could deliver the anticipated increase in transmission capacity if fully implemented. Areas that will be examined include new ways of generating phase-locked sub-channels at the transmitter; methods for generating and synchronising the corresponding optical signals at the receiver; and modulation and de-modulation techniques giving high data rate transmission in a narrow spectral band. The experimental demonstration will be supported by computer simulations of the system, which will also allow new applications enabled by the approach - too advanced to be demonstrated experimentally at this stage - to be investigated.