Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

Quantum Dash Multi-Wavelength Lasers for Next Generation High Capacity Multi-Gb/s Millimeter-Wave Radio-over-Fiber Wireless Communication Networks

The ever-increasing proliferation of mobile users and new technologies with different applications and features, and the demand for reliable high-speed high capacity, pervasive connectivity and low latency have initiated a roadmap for the next generation wireless networks, fifth generation (5G), which is set to revolutionize the existing wireless communications. 5G will use heterogeneous higher carrier frequencies from the plentifully available spectra in the higher microwave and millimeter-wave (MMW) bands, including licensed and unlicensed spectra, for achieving multi-Gb/s wireless connectivity and overcoming the existing wireless spectrum crunch in the sub-6 GHz bands, resulting from the tremendous growth of data-intensive technologies and applications. The use of MMW when complemented by multiple-input-multiple-output (MIMO) technology can significantly increase data capacity through spatial multiplexing, and improve coverage and system reliability through spatial diversity. However, high-frequency MMW signals are prone to extreme propagation path loss and are challenging to generate and process with conventional bandwidth-limiting electronics. In addition, the existing digitized fronthaul for centralized radio access network (C-RAN) architecture is considered inefficient for 5G and beyond. Thus, to fully exploit the promising MMW 5G new radio (NR) resource and to alleviate the electronics and fronthaul bottleneck, microwave photonics with analog radio-over-fiber (A-RoF) technology becomes instrumental for optically synthesizing and processing broadband RF MMW wireless signals over optical links. The generation and distribution of high-frequency MMW signals in the optical domain over A-RoF links facilitate the seamless integration of high-capacity, reliable and transparent optical networks with flexible, mobile and pervasive wireless networks, extending the reach and coverage of high-speed broadband MMW wireless communications. Consequently, this fiber-wireless integration not only overcomes the problem of high bandwidth requirements, transmission capacity and span limitation but also significantly reduces system complexity considering the deployment of ultra-dense small cells with large numbers of 5G remote radio units (RRUs) having massive MIMO antennas with beamforming capabilities connected to the baseband units (BBU) in a C-RAN environment through an optical fiber-based fronthaul network. Nevertheless, photonic generation of spectrally pure RF MMW signals either involves complex circuitry or suffers from frequency fluctuation and phase noise due to uncorrelated optical sources, which can degrade system performance. Thus simple highly integrated and cost-efficient low-noise optical sources are required for next-generation MMW RoF wireless transmission systems. More recently, well-designed quantum confined nanostructures such as semiconductor quantum dash/dot multi-wavelength lasers (QD-MWLs) have attracted more interest in the photonic generation of RF MMW signals due to their simple compact and integrated design with highly coherent and correlated optical signals having a very low phase and intensity noise attributed to the inherent properties of QD materials. The main theme of this thesis revolves around the experimental investigation of such nanostructures on the device and system level for applications in high-speed high-capacity broadband MMW RoF-based fronthaul and wireless access networks. Several photonic-aided high-capacity long-reach MMW RoF wireless transmission systems are proposed and experimentally demonstrated based on QD-MWLs with the remote distribution and photonic generation of broadband multi-Gb/s MMW wireless signals at 5G NR (FR2) in the K-band, Ka-band and V-band in simplex, full-duplex and MIMO configurations over 10 to 50 km optical fiber and subsequent wireless transmission and detection. The QD-MWLs-based photonic MMW RoF wireless transmission systems’ designs and experimental demonstrations could usher in a new era of ultra-high-speed broadband multi-Gb/s wireless communications at the MMW frequency bands for next-generation wireless networks. The QD-MWLs investigated in this thesis include a simple monolithically integrated and highly coherent low-noise single-section semiconductor InAs/InP QD buried heterostructure passively mode-locked (PML) laser-based optical coherent frequency comb (CFC) and a novel monolithic highly correlated low-noise semiconductor InAs/InP buried heterostructure common-cavity QD dual-wavelength distributed feedback laser (QD-DW-DFBL). The performance of each device is thoroughly characterized experimentally in terms of optical phase noise, relative intensity noise (RIN), timing jitter and RF phase noise exhibiting promising results. Based on these devices, different long-reach photonic MMW RoF wireless transmission systems, including simplex single-input-single-output (SISO) and multiple-input-multiple-output (MIMO) and bidirectional configurations, are proposed and experimentally demonstrated with real-time remote electrical RF synthesizer-free all-optical frequency up-conversion, wireless transmission and successful reception of wide-bandwidth multi-level quadrature amplitude modulated (M-QAM) RF MMW wireless signals having bit rates ranging from 4 Gb/s to 36 Gb/s over different hybrid fiber-wireless links comprising of standard single mode fiber (SSMF) and indoor wireless channel. The end-to-end links are thoroughly investigated in terms of error-vector-magnitude (EVM), bit-error-rat (BER), constellations and eye diagrams, realizing successful error-free transmission. Finally, novel high-capacity spectrally efficient MIMO and optical beamforming enabled photonic MMW RoF wireless transceivers design and methods based on QD-MWLs with wavelength division multiplexing (WDM) and space division multiplexing (SDM) are proposed and discussed. A proof-of-concept implementation of the proposed photonic MMW RoF wireless transmission system is also simulated in a simple WDM-based configuration with bidirectional 4×4 MIMO MMW carrier streams

RoF data transmission using four linearly polarized vector Modes of a polarization maintaining elliptical ring core fiber

We experimentally investigate the feasibility of transmission of radio frequency (RF) signals over a 900 m polarization-maintaining, elliptical ring core fiber. No multiple-input multiple output (MIMO) processing is used to recover the RF signals carried by different modes; we recover the 16QAM, orthogonal frequency division multiplexing (OFDM) RF signals with the same techniques used for single mode fibers. For the first time, we report transmission of four RF streams over four channels in a few mode fiber. Also, for the first time, we transmit RF signals over two polarizations of a mode in few mode fibers and successfully recover data in both polarizations without polarization tracking or digital signal processing to separate polarizations. Furthermore, we examine the impact of fiber bending on crosstalk among channels. We show that even under severe bending, the polarization states remain separated and the RF streams transmitted on polarization states of a mode could be recovered with low power penalty

Mode division multiplexing in radio-over-free-space-optical system incorporating orthogonal frequency division multiplexing and photonic crystal fiber equalization

Radio over free space optics (Ro-FSO) is a revolutionary technology for seamlessly integrating radio and optical networks without expensive optical fiber cabling. RoFSO technology plays a crucial role in supporting broadband connectivity in rural and remote areas where current broadband infrastructure is not feasible due to geographical and economic inconvenience. Although the capacity of Ro-FSO can be increased by mode division multiplexing (MDM), the transmission distance and capacity is still limited by multipath fading and mode coupling losses due to atmospheric turbulences such as light fog, thin fog and heavy fog. The main intention of this thesis is to design MDM system for Ro-FSO for long and short haul communication. Orthogonal frequency division multiplexing (OFDM) is proposed for long haul communication to mitigate multipath fading and Photonic Crystal Fiber (PCF) is proposed for short haul communication to reduce mode coupling losses. The reported results of the proposed scheme for long haul communication show a significant 47% power improvement in deep fades from multipath propagation with the use of OFDM in MDM-Ro-FSO systems as compared to without OFDM. The results of the proposed scheme for short haul communication show 90.6% improvement in power in the dominant mode with the use of PCF in MDM-Ro-FSO as compared to without PCF. The reported results in the thesis show significant improvement in Ro-FSO systems as compared to previous systems in terms of capacity and transmission distance under clear weather conditions as well as under varying levels of fog. The contributions of this thesis are expected to provide seamless broadband services in remote areas

Convergence of millimeter-wave and photonic interconnect systems for very-high-throughput digital communication applications

In the past, radio-frequency signals were commonly used for low-speed wireless electronic systems, and optical signals were used for multi-gigabit wired communication systems. However, as the emergence of new millimeter-wave technology introduces multi-gigabit transmission over a wireless radio-frequency channel, the borderline between radio-frequency and optical systems becomes blurred. As a result, there come ample opportunities to design and develop next-generation broadband systems to combine the advantages of these two technologies to overcome inherent limitations of various broadband end-to-end interconnect systems in signal generation, recovery, synchronization, and so on. For the transmission distances of a few centimeters to thousands of kilometers, the convergence of radio-frequency electronics and optics to build radio-over-fiber systems ushers in a new era of research for the upcoming very-high-throughput broadband services. Radio-over-fiber systems are believed to be the most promising solution to the backhaul transmission of the millimeter-wave wireless access networks, especially for the license-free, very-high-throughput 60-GHz band. Adopting radio-over-fiber systems in access or in-building networks can greatly extend the 60-GHz signal reach by using ultra-low loss optical fibers. However, such high frequency is difficult to generate in a straightforward way. In this dissertation, the novel techniques of homodyne and heterodyne optical-carrier suppressions for radio-over-fiber systems are investigated and various system architectures are designed to overcome these limitations of 60-GHz wireless access networks, bringing the popularization of multi-gigabit wireless networks to become closer to the reality. In addition to the advantages for the access networks, extremely high spectral efficiency, which is the most important parameter for long-haul networks, can be achieved by radio-over-fiber signal generation. As a result, the transmission performance of spectrally efficient radio-over-fiber signaling, including orthogonal frequency division multiplexing and orthogonal wavelength division multiplexing, is broadly and deeply investigated. On the other hand, radio-over-fiber is also used for the frequency synchronization that can resolve the performance limitation of wireless interconnect systems. A novel wireless interconnects assisted by radio-over-fiber subsystems is proposed in this dissertation. In conclusion, multiple advantageous facets of radio-over-fiber systems can be found in various levels of end-to-end interconnect systems. The rapid development of radio-over-fiber systems will quickly change the conventional appearance of modern communications.PhDCommittee Chair: Gee-Kung Chang; Committee Member: Bernard Kippelen; Committee Member: Shyh-Chiang Shen; Committee Member: Thomas K. Gaylord; Committee Member: Umakishore Ramachandra