Frontiers of optical networking technologies: Millimeter-wave radio-over-fiber and 100g transport system for next-generation high-data-rate applications.

摘要

The ongoing growth of Internet traffic being driven by data storage and video file-sharing traffic have placed huge bandwidth and capacity requirements not only for the long-haul networks but also for the last mile access networks. In response to the remarkable development, the line rate in the metro core networks based on fiber-optic technology has to be upgraded from 10 Gb/s to 100 Gb/s, while a millimeter-wave radio-over- fiber technology has been considered the most practical and efficient solution for future super-broadband wireless access networks. The Ph.D. work then focuses on investigating both wired and wireless communications over optical systems for the provision of high-data-rate applications in next-generation telecommunications network.;The radio-over-fiber system at millimeter wave, especially 60-GHz band with 7-GHz unlicensed bandwidth, has unique potential to deliver multi-gigabit services to remote base stations. Therefore, one major objective of this work is to develop a simple and cost-effective millimeter-wave optical-wireless system through the all-round research on the technical challenges of optical millimeter-wave generation, full-duplex transmission, transmission impairments compensation, and multi-band generation. The general methods of optical millimeter-wave generation were reviewed concerning the system flexibility, structure complexity, and power efficiency. Then two novel optical frequency-doubled millimeter-wave generation schemes based on external phase modulation were proposed and experimentally demonstrated their simplicity, reliability, and cost-efficiency compared with the existing schemes. For successful full-duplex transmission, two methods for eliminating the requirements of light sources and wavelength management at the base station were shown here: downlink wavelength reuse and remote-carrier delivery for uplink. Moreover, the penalties due to backscattering signals for bi-directional transmission over a single fiber can be mitigated by different wavelength assignments for downlink and uplink. The transmission distance limited by fiber chromatic dispersion is also a key challenge for cost-efficient millimeter-wave radio-over-fiber implementations with less central offices. The numerical analysis and experimental demonstration suggested that a radio-over-fiber system with the optical single-sideband-plus-carrier format or remote optical-carrier-suppression is more resistant to this transmission impairment and then achieve longer transmission distance. Additionally, several radio-over-fiber systems were designed to simultaneously deliver multi-band wireless services on a single optical infrastructure, enabling converged system control and quality maintenance in central office. Some proposed schemes efficiently integrated the new 60-GHz band with commercial wireless services at low RF regions, allowing a system not only providing multi-gigabit data and video distributions but also has backward compatibility to legacy wireless services. The lightwave centralization, frequency doubling/tripling, long transmission distance, high-level modulation format were also realized in these novel multi-band RoF architectures.;For the long-haul core network, moving from 10G to 100G line speeds comes with technical challenges. The Ph.D work explored the issues related to successful implementations of transmitter, transmission link, and receiver of a serial 112-Gb/s polarization-division multiplexing-quadrature phase shift keying (PDM-QPSK) optical transport. The experimental results based on our constructed 112-Gb/s testbed indicated that careful dispersion management can effectively increase QPSK channel tolerance to nonlinear transmission impairments. Moreover, 100G dense wavelength-division multiplexing networks with reconfigurable optical add-drop multiplexers (ROADMs) enable dynamically reconfigurable networks and are therefore part of the solution needed to meet increasing bandwidth and routing flexibility requirements for future metro core networks. Thus, the special emphasis on the two impairments in a 100G ROADM-enabled network, passband and in-band crosstalk effects, was studied in this thesis. The experimental results showed the penalties contributed by passband narrowing and frequency detuning are pulse format dependent; return-to-zero pulse shape offers better tolerance to filtering and fiber nonlinearity compared to non-return-to-zero. A weighting method was also demonstrated to quantify the penalty of in-band crosstalk that accounts for the varying spectral content. Lastly, a nonlinearity-enhanced crosstalk penalty were experimentally and numerically demonstrated that results from the nonlinear interaction between crosstalk and signals over long-distance transmission. It is another critical transmission limitation except for the nonlinear interactions between signal and ASE noise. Therefore, the research results related to the dispersion management, fiber nonlinearity penalties, and ROADM-induced impairments can be effectively applied to the deployment and performance estimation of future 100G optical transport networks.