Directional control of weakly localized Raman from a random network of fractal nanowires

Disordered optical media are an emerging class of materials capable of strongly scattering light. Their study is relevant to investigate transport phenomena and for applications in imaging, sensing and energy storage. While such materials can be used to generate coherent light, their directional emission is typically hampered by their very multiple scattering nature. Here, we tune the out-of-plane directionality of coherent Raman light scattered by a fractal network of silicon nanowires. By visualizing Rayleigh scattering, photoluminescence and weakly localized Raman light from the random network of nanowires via real-space microscopy and Fourier imaging, we gain insight on the light transport mechanisms responsible for the material's inelastic coherent signal and for its directionality. The possibility of visualizing and manipulating directional coherent light in such networks of nanowires opens venues for fundamental studies of light propagation in disordered media as well as for the development of next generation optical devices based on disordered structures, inclusive of sensors, light sources and optical switches

Metasurface-based Spectral Convolutional Neural Network for Matter Meta-imaging

Convolutional neural networks (CNNs) are representative models of artificial neural networks (ANNs), that form the backbone of modern computer vision. However, the considerable power consumption and limited computing speed of electrical computing platforms restrict further development of CNNs. Optical neural networks are considered the next-generation physical implementations of ANNs to break the bottleneck. This study proposes a spectral convolutional neural network (SCNN) with the function of matter meta-imaging, namely identifying the composition of matter and mapping its distribution in space. This SCNN includes an optical convolutional layer (OCL) and a reconfigurable electrical backend. The OCL is implemented by integrating very large-scale, pixel-aligned metasurfaces on a CMOS image sensor, which accepts 3D raw datacubes of natural images, containing two-spatial and one-spectral dimensions, at megapixels directly as input to realize the matter meta-imaging. This unique optoelectronic framework empowers in-sensor optical analog computing at extremely high energy efficiency eliminating the need for coherent light sources and greatly reducing the computing load of the electrical backend. We employed the SCNN framework on several real-world complex tasks. It achieved accuracies of 96.4% and 100% for pathological diagnosis and real-time face anti-spoofing at video rate, respectively. The SCNN framework, with an unprecedented new function of substance identification, provides a feasible optoelectronic and integrated optical CNN implementation for edge devices or cellphones with limited computing capabilities, facilitating diverse applications, such as intelligent robotics, industrial automation, medical diagnosis, and astronomy

Electronic/photonic interfaces for ultrafast data processing.

This report summarizes a 3-month program that explored the potential areas of impact for electronic/photonic integration technologies, as applied to next-generation data processing systems operating within 100+ Gb/s optical networks. The study included a technology review that targeted three key functions of data processing systems, namely receive/demultiplexing/clock recovery, data processing, and transmit/multiplexing. Various technical approaches were described and evaluated. In addition, we initiated the development of high-speed photodetectors and hybrid integration processes, two key elements of an ultrafast data processor. Relevant experimental results are described herein

Future development trends of optical transport network infrastructure: an infrastructual framework for metropolitan-based optical transport networks - a field test of a Chinese ISP and a case study of a Chinese Electric Power Company

Optical Transport Networks (OTNs) play a foundational role in current and future telecommunication infrastructure. However, the development and implementation of OTNs have been restrained since the bursting of the dot-com bubble. Many service providers and large companies are confused in the development directions of future OTN infrastructure, as there are several standards organisations with differing positions. On the other hand, there is a lack of large scale testing, as well as practical implementation cases due to the emerging nature of the OTN. Therefore, this thesis develops a framework demonstrating a landscape of current and future development steps of OTN infrastructure from both theoretical and commercial standpoints. The key concept of the framework is the integration of the IP-oriented data transmission layer and the WDM-based optical transport layer. Traditional telecommunication infrastructure focuses on long-haul, point-to-point optical transmission with ultra broadband carrier capacity. Nevertheless, the next generation OTN systems will emphasis the delivery of IP-oriented multifunctional data services, instead of legacy simplex TDM-based services across a metropolitan span with sufficient reliability and efficiency. Thus, this thesis gives a systematic validation of the proposed framework from two angles. Firstly, it provides in-depth research on the evolution of protection technologies in metro core optical networks, along with a MPLS-based network fast recovery field test to validate the framework from the network reliability aspect. The field test was conducted using a large Chinese ISP test bed and demonstrated the practical performance of the advanced OTN protection technology from the perspective of a service provider. Secondly, this research presents a comprehensive case study based on a large commercial metro OTN upgrade project of Shanghai Municipal Electric Power Company (SMEPC). The outcome of the case study is an evolutional roadmap, which illustrates the infrastructural development trends of this ongoing project. The roadmap can be considered as another evaluation of the framework in terms of network efficiency from an industrial-based dimension. The outcome of this research is to clarify future development trends in OTN infrastructure for the purpose of informing the design and implementation of commercial OTN applications

Broadband : towards a national plan for Scotland

The development of national broadband plans has been used by many countries to join up different areas of governmental and regulatory activities and to set ambitious targets for ubiquitous access to and use of the latest fixed and wireless networks and services. For Scotland this requires working within EU and UK legislative frameworks, which have also provided the bulk of the finance for interventions. It also requires an understanding of the significant weaknesses of urban broadband adoption compared to other UK and EU nations and of its e-commerce supply and demand. While resources are being targeted at rural and remote areas, more are needed to close the social digital divide, which is unavoidable if the stated ambition of being world class is to be achieved

Current optical technologies for wireless access

The objective of this paper is to describe recent activities and investigations on free-space optics (FSO) or optical wireless and the excellent results achieved within SatNEx an EU-framework 6th programme and IC 0802 a COST action. In a first part, the FSO technology is briefly discussed. In a second part, we mention some performance evaluation criterions for the FSO. In third part, we briefly discuss some optical signal propagation experiments through the atmosphere by mentioning network architectures for FSO and then discuss the recent investigations in airborne and satellite application experiments for FSO. In part four, we mention some recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented

Exploring the benefit of rerouting multi-period traffic to multi-site data centers

In cloud-like scenarios, demand is served at one of multiple possible data center (DC) destinations. Usually, the exact DC that is used can be freely chosen, which leads to an anycast routing problem. Furthermore, the demand volume is expected to change over time, e.g., following a diurnal pattern. Given that virtually all application domains today rely heavily on cloud-like services, it is important that the backbone networks connecting users to the DCs are resilient against failures. In this paper, we consider the problem of resiliently routing multi-period traffic: we need to find routes to both a primary DC and a backup DC (to be used in the case of failure of the primary one, or of the network connection to it), and also account for synchronization traffic between the primary and backup DCs. We formulate this as an optimization problem and adopt column generation, using a path formulation in two sub-problems: the (restricted) master problem selects "configurations" to use for each demand in each of the time epochs it lasts, while the pricing problem (PP) constructs a new "configuration" that can lead to lower overall costs (which we express as the number of network resources, i.e., bandwidth, required to serve the demand). Here, a "configuration" is defined by the network paths followed from the demand source to each of the two selected DCs, as well as that of the synchronization traffic in between the DCs. Our decomposition allows for PPs to be solved in parallel, for which we quantitatively explore the reduction in the time required to solve the overall routing problem. The key question that we address with our model is an exploration of the potential benefits of rerouting traffic from one time epoch to the next: we compare several (re) routing strategies, allowing traffic that spans multiple time periods to i) not be rerouted in different periods, ii) only change the backup DC and routes, or iii) freely change both primary and backup DC choices and the routes toward them