Opto-VLSI processing for reconfigurable optical devices

The implementation of Wavelength Division Multiplexing system (WDM) optical fibre transmission systems has the potential to realise this high capacity data rate exceeding 10 Tb/s. The ability to reconfigure optical networks is a desirable attribute for future metro applications where light paths can be set up or taken down dynamically as required in the network. The use of microelectronics in conjunction with photonics enables intelligence to be added to the high-speed capability of photonics, thus realising reconfigurable optical devices which can revolutionise optical telecommunications and many more application areas. In this thesis, we investigate and demonstrate the capability of Opto-VLSI processors to realise a reconfigurable WDM optical device of many functions, namely, optical multiband filtering, optical notch filtering, and reconfigurable-Optical-Add-Drop Multiplexing (ROADM). We review the potential technologies available for tunable WDM components, and discuss their advantages and disadvantages. We also develop a simple yet effective algorithm that optimises the performance of Opto-VLSI processors, and demonstrate experimentally the multi-function WDM devices employing Opto-VLSI processors. Finally, the feasibility of Opto-VLSI-based WDM devices in meeting the stringent requirements of the optical communications industry is discussed

XR-RF Imaging Enabled by Software-Defined Metasurfaces and Machine Learning: Foundational Vision, Technologies and Challenges

We present a new approach to Extended Reality (XR), denoted as iCOPYWAVES, which seeks to offer naturally low-latency operation and cost-effectiveness, overcoming the critical scalability issues faced by existing solutions. iCOPYWAVES is enabled by emerging PWEs, a recently proposed technology in wireless communications. Empowered by intelligent (meta)surfaces, PWEs transform the wave propagation phenomenon into a software-defined process. We leverage PWEs to i) create, and then ii) selectively copy the scattered RF wavefront of an object from one location in space to another, where a machine learning module, accelerated by FPGAs, translates it to visual input for an XR headset using PWEdriven, RF imaging principles (XR-RF). This makes for an XR system whose operation is bounded in the physical layer and, hence, has the prospects for minimal end-to-end latency. Over large distances, RF-to-fiber/fiber-to-RF is employed to provide intermediate connectivity. The paper provides a tutorial on the iCOPYWAVES system architecture and workflow. A proof-of-concept implementation via simulations is provided, demonstrating the reconstruction of challenging objects in iCOPYWAVES produced computer graphics

Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays

Massive MIMO (multiple-input multiple-output) is no longer a "wild" or "promising" concept for future cellular networks - in 2018 it became a reality. Base stations (BSs) with 64 fully digital transceiver chains were commercially deployed in several countries, the key ingredients of Massive MIMO have made it into the 5G standard, the signal processing methods required to achieve unprecedented spectral efficiency have been developed, and the limitation due to pilot contamination has been resolved. Even the development of fully digital Massive MIMO arrays for mmWave frequencies - once viewed prohibitively complicated and costly - is well underway. In a few years, Massive MIMO with fully digital transceivers will be a mainstream feature at both sub-6 GHz and mmWave frequencies. In this paper, we explain how the first chapter of the Massive MIMO research saga has come to an end, while the story has just begun. The coming wide-scale deployment of BSs with massive antenna arrays opens the door to a brand new world where spatial processing capabilities are omnipresent. In addition to mobile broadband services, the antennas can be used for other communication applications, such as low-power machine-type or ultra-reliable communications, as well as non-communication applications such as radar, sensing and positioning. We outline five new Massive MIMO related research directions: Extremely large aperture arrays, Holographic Massive MIMO, Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin

Adaptive applications of OPTO-VLSI processors in WDM networks

Communication is an inseparable part of human life and its nature continues to evolve and improve. The advent of laser was a herald to the new possibilities in the communication world. In recent years technologies such as Wavelength Division Multiplexing (WDM) and Erbium Doped Fiber Amplifiers (EDFA) have afforded significant boost to the practice of optical communication. At the heart of this brave new world is the need to dynamically/ adaptively steer/route beams of light carrying very large amounts of data. In recent years many techniques have been proposed for this purpose by various researchers. In this study we have elected to utilise the beam-steering capabilities of Opto-VLSI processors to investigate band-pass filtering and channel equalisation as two possible and practical applications in WDM networks

Parallel computing 2011, ParCo 2011: book of abstracts

This book contains the abstracts of the presentations at the conference Parallel Computing 2011, 30 August - 2 September 2011, Ghent, Belgiu

Optimizing Sparse Linear Algebra on Reconfigurable Architecture

The rise of cloud computing and deep machine learning in recent years have led to a tremendous growth of workloads that are not only large, but also have highly sparse representations. A large fraction of machine learning problems are formulated as sparse linear algebra problems in which the entries in the matrices are mostly zeros. Not surprisingly, optimizing linear algebra algorithms to take advantage of this sparseness is critical for efficient computation on these large datasets. This thesis presents a detailed analysis of several approaches to sparse matrix-matrix multiplication, a core computation of linear algebra kernels. While the arithmetic count of operations for the nonzero elements of the matrices are the same regardless of the algorithm used to perform matrix-matrix multiplication, there is significant variation in the overhead of navigating the sparse data structures to match the nonzero elements with the correct indices. This work explores approaches to minimize these overheads as well as the number of memory accesses for sparse matrices. To provide concrete numbers, the thesis examines inner product, outer product and row-wise algorithms on Transmuter, a flexible accelerator that can reconfigure its cache and crossbars at runtime to meet the demands of the program. This thesis shows how the reconfigurability of Transmuter can improve complex workloads that contain multiple kernels with varying compute and memory requirements, such as the Graphsage deep neural network and the Sinkhorn algorithm for optimal transport distance. Finally, we examine a novel Transmuter feature: register-to-register queues for efficient communication between its processing elements, enabling systolic array style computation for signal processing algorithms.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169877/1/dohypark_1.pd

Reconfigurable phase-change optical metasurfaces: novel design concepts to practicable devices

Optical metasurfaces have been proven to be capable of controlling amplitude, phase and polarization of optical beams without the need of bulky geometries, making them really attractive for the development of compact photonic devices. Recently, their combination with chalcogenide phase-change materials (traditionally employed in non-volatile optical and electrical memories), whose refractive index can be reversibly and repeatedly controlled, has been proposed to yield low power consumption tunable metasurfaces having several functionalities in a single device. However, despite phase-change memories are commercially available since various decades now, the unification of phase-change materials with metasurfaces towards real life applications is becoming a formidable task, mainly due to the several engineering branches involved in this technology, which sometimes compromise each other in a non-trivial way. This includes thermo/optical, thermo/electric, and chemical incompatibilities which are typically not taken into account by researchers working in the field, resulting in devices having exciting reconfigurable properties, but at the same time, lack of practicability. This thesis is therefore dedicated to the development of novel phase-change metasurface architectures which could partially or totally address such engineering problems. Particular emphasis has been put in the realization of reconfigurable metasurfaces for active wavefront control, as such a functionality remains relatively unexplored. The first part of this thesis focuses in the first experimental demonstration of active, reconfigurable non-mechanical beam steering devices working the near-infrared. This was achieved via integration of ultra-thin films of chalcogenide phase-change materials (in this case, the widely employed alloy Ge2Sb2Te5) within the body of a dielectric spacer in a plasmonic metal/insulator/metal metasurface architecture. Active, and optically reversible beam steering between two different angles with efficiencies up to 40% were demonstrated. The second part of this work shows the work carried out in metal-free metasurfaces as a way to manipulate optical beams with high efficiency in both transmission and/or reflection. This was achieved via combination of all-dielectric silicon nanocylinders with deeply-subwavelenght sized Ge2Sb2Te5 inclusions. By strategic placement of the phase-change inclusions in the regions of high electric field density, independent and active control of the metasuface resonances is demonstrated, with modulations depths as high as 70% and 65% in reflection and transmission respectively. Multilevel, and fully reversible optically-induced switching of the phasechange layer is also reported, with up to 11 levels of tunability over 8 switching cycles. Finally, the last section of this thesis introduces the concept of hybrid dielectric/plasmonic phase-change metasurfaces having key functional benefits when compared to both purely dielectric and plasmonic approaches. The proposed architectures showed great versatility in terms of both active amplitude and phase control, offering the possibility of designing devices for different purposes (i.e. such as active absorbers/modulators or beam steerers with enhanced efficiency) employing the same unit-cell configuration with minor geometry re-optimizations. Initial device experimental demonstrations of such an approach are discussed, as well as their potential in terms of delivering in-situ electrical switching capabilities using a metallic ground plane as a resistive heater.Engineering and Physical Sciences Research Council (EPSRC