Multi-Channel Optical 3R Regeneration and Buffering for Networking Applications

可能阻碍使用现有技术大规模部署光网络的关键特征之一是它们不能执行光IP路由功能。光缓存是高效实现光/光分组交换器或IP路由器的关键技术之一。需要缓冲器在接入节点处对分组进行排队，以便弥合光-电速度差距，使接收器能够以比可以处理的速度更快的速率处理数据，以及结合光开关进行速率转换。初步分析表明，环路类型的动态存储技术对于实际实现光缓冲是最有效的，但这种设备的可积性问题仍然需要解决。如果可能，希望具有长达数十秒的存储时间。考虑到在光纤存储环路中信号是动态存储的，这相当于存储的信号传输了几百万公里的距离。因此，光3R再生(重定时、整形和重传)是一项关键的使能技术。需要防止被放大的自发辐射噪声、色散和偏振模色散以及缓冲器组件中的光学非线性所损害的数据信号的失真。此外，现有的光缓冲技术仅允许在单个通道上存储数据。另一方面，很明显，下一代光网络将使用大规模的波分复用。从这一观点来看，非常希望具有能够在单个设备中存储多通道数据的缓冲器，而不是其中必须为每个通道专用单独的缓冲器的传统方法。多通道缓冲方法在占用空间更小、功耗更低、处理相同数量的包所需的组件数量更少方面提供了更高效、更经济的解决方案。此外，对于网络应用，在缓冲器中具有光纤分插复用器(OADM)功能非常重要。据PI所知，到目前为止，OADM功能还没有在现有的和建议的光缓冲器中得到演示。在本项目中，提出了一种使用非线性非对称环镜和同步电吸收调制器的4通道光缓存器，每通道的数据速率为20 Gb/S。将演示OADM功能，即，在不影响已经存储的分组的情况下将附加分组(在附加波长)添加到缓冲器，并且从缓冲器丢弃存储的分组，使其他信道上的分组保持不变。多通道光缓冲器将对所有通道同时具有3R再生功能，允许数十秒的存储时间。将对所提出的多通道缓冲系统进行详细而准确的数值模拟和参数研究。建模的目标包括：1)最大分组存储时间及其限制因素，2)信噪比随存储时间的降低，3)在每通道数据速率和通道数量方面限制系统可伸缩性。拟议活动的智力优势：拟议活动将解决广泛部署分组交换光网络的两个基本障碍，即3R再生和光缓冲。理论和实践需要齐头并进，才能取得成功。PI和共同PI带来了理论和实验专业知识和技能的独特组合来解决问题。拟议活动的更广泛影响：学生将参与跨学科的工作。除了通常的电物理和光子学课程外，他们还将接受网络工程概念方面的培训。西北大学的欧洲经委会系在通信网络方面有一个强大的团队。因此，学生可以使用完整的课程菜单进行正式学习，并存在用于点对点学习的多样化学生群体。将通过西北大学光子通信和计算中心开展外联活动，以便对整个社区产生更广泛的影响。将通过大学现有的所有资源作出全面努力，使代表人数不足的学生参与这一项目。有关更多详细信息，请参阅项目说明。

0401251KUMAROne of the critical features that are likely to hinder massive deployment of optical networks using already existing technologies is their inability to perform optical IP routing functions. Optical buffering is one of the key techniques for efficiently implementing optical/photonic packet switchers or IP routers. Buffers are needed for queuing packets at the access nodes in order to bridge the photonic-electric speed gap, for enabling receivers to handle data at rates faster than can be processed, and for rate conversion in conjunction with optical switches. A preliminary analysis shows that the loop-type dynamic storage techniques are the most efficient for practical implementation of optical buffering, although the issue of integrability of such devices still needs to be addressed. It is desirable to have a long storage time, extending to tens of seconds, if possible. Given the fact that in fiber storage loops the signals are stored dynamically, it is equivalent of several million kilometers of distance traveled by the stored signals. For this reason optical 3R regeneration (retiming, reshaping, and retransmitting) is a key enabling technology. It is needed to prevent distortion of the data signals that get impaired by the amplified spontaneous emission noise, chromatic and polarization-mode dispersion, and optical nonlinearity in the buffer components. Furthermore, the existing optical buffering technologies allow data storage only at a single channel. On the other hand, it is clear that the next generation optical networks will use massive wavelength-division-multiplexing. From this standpoint it is highly desirable to have a buffer that is capable of storing multi-channel data in a single device versus the conventional approach in which a separate buffer has to be dedicated to each channel. The multi-channel buffering approach provides more efficient and economic solution in terms of smaller footprint, lower power consumption, and smaller number of components needed for handling the same number of packets. In addition, for networking applications it is important to have optical add-drop multiplexer (OADM) functionality in the buffer. To the best of the PI's knowledge, thus far, OADM functionality has not been demonstrated in existing and proposed optical buffers. In this project a 4-channel optical buffer using a nonlinear asymmetric loop mirror (NALM) and a synchronous electro-absorption modulator (EAM) operating at 20 Gb/s data rate per channel is proposed. The OADM functionality will be demonstrated, i.e., adding additional packets (at additional wavelengths) to the buffer without affecting the packets already stored and dropping from the buffer stored packets leaving the packets at other channels intact. The multi-channel optical buffer will have simultaneous 3R regeneration feature for all channels, allowing tens of seconds of storage time. Detailed and accurate numerical simulation and parameter studies of the proposed multi-channel buffering system will be performed. The goals of the modeling include: 1) maximum packet storage time and its limiting factors, 2) degradation of the signal-to-noise ratio versus storage time, 3) limits to system scalability in terms of data rate per channel and the number of channels. Intellectual merit of the proposed activity: The proposed activity will address two of the fundamental roadblocks to widespread deployment of packet-switched optical networking, namely, 3R regeneration and optical buffering. Theory and practice will need to go hand-in-hand for a successful outcome. The PI and co-PI bring a unique combination of theoretical and experimental expertise and skills to bear upon the problem. Broader impacts of the proposed activity: The students will get involved in cross-disciplinary work. They will be trained in the network engineering concepts in addition to the usual curriculum in electro-physics and photonics. The ECE department at Northwestern University has a strong group in communications networks. Consequently, a full menu of courses is available to the students for formal learning and a diverse student body exists for peer-to-peer learning. Outreach activities through the Center for Photonic Communication and Computing at Northwestern will be undertaken to have a much wider impact on the community at large. Full scale efforts will be made through all resources available at the University to engage underrepresented students in this project. See the Project Description for further details.