Advanced DSP Techniques for High-Capacity and Energy-Efficient Optical Fiber Communications

The rapid proliferation of the Internet has been driving communication networks closer and closer to their limits, while available bandwidth is disappearing due to an ever-increasing network load. Over the past decade, optical fiber communication technology has increased per fiber data rate from 10 Tb/s to exceeding 10 Pb/s. The major explosion came after the maturity of coherent detection and advanced digital signal processing (DSP). DSP has played a critical role in accommodating channel impairments mitigation, enabling advanced modulation formats for spectral efficiency transmission and realizing flexible bandwidth. This book aims to explore novel, advanced DSP techniques to enable multi-Tb/s/channel optical transmission to address pressing bandwidth and power-efficiency demands. It provides state-of-the-art advances and future perspectives of DSP as well

Next-generation High-Capacity Communications with High Flexibility, Efficiency, and Reliability

The objective of this dissertation is to address the flexibility, efficiency and reliability in high-capacity heterogeneous communication systems. We will experimentally investigate the shaping techniques, and further extend them to more diverse and complicated scenarios, which result in more flexible systems. The scenarios include 1) entropy allocation scheme under uneven frequency response for multi-carrier system, 2) fiber-free space optics link using unipolar pairwise distribution, and 3) flexible rate passive optical network with a wide range of received optical powers. Next, we perform efficiency analysis in inter-data center and long-haul communications. We will characterize the impact of the laser linewidth, jitter tones, and the flicker noise on coherent systems with different baud rates and fiber lengths through theoretical analysis, simulation, and experimental validation. The trade-off analysis indicates the importance of setting up frequency noise power spectral density masks to qualify the transceiver laser design. Besides efficiency analysis, we will also work on efficient system architecture and algorithm design. We investigate the combined impact of various hardware impairments using proposed simplified DSP schemes in beyond 800G self-homodyne coherent system. The proposed scheme is very promising for next-generation intra-data center applications. On the other hand, to improve the data efficiency of the nonlinearity correction algorithm in broadband communication systems, we leverage the semi-supervised method and Lasso. Experimental results validate that Lasso can reduce the required pilot symbol number by exploiting the sparsity of the tap coefficients. Semi-supervised method can further enhance the system performance without introducing additional overhead. Last but not least, regarding reliability, we propose and experimentally demonstrate an ultra-reliable integrated millimeter wave and free space optics analog radio over fiber system with algorithm design. The multiple-spectra operation shows superior performance in reliability and sensitivity compared to the conventional systems, even in extreme weather conditions and strong burst interference.Ph.D

Surface Micromachined Widely Tunable VCSEL and OAM-Filter for Optical Data Transmission

The implication of wavelength division multiplexed passive optical network (WDM PON) is becoming more evident as the traffic demands of the mobile network operators keep increasing. It offers a cost-efficient solution to handle the bandwidth and latency requirements of the mobile fronthaul. The key component of such a WDM-PON system is a centralized wavelength-controlled tunable laser. The biggest challenge up to now is the lack of low-cost wideband 1550 nm tunable lasers with 10 Gbit/s transmission capacity. In the first part of this work, a widely-tunable microelectromechanical system vertical-cavity surface-emitting laser (MEMS VCSEL) is developed. The cost-efficient, directly-modulated laser can be utilized for 10Gbit/s transmission over relevant reach. It also offers simplicity for wideband autonomous tuning. The device is suitable for applications including hot backup and fixed wavelength laser replacement for inventory reduction. Within the framework of this work, a PECVD-deposited MEMS distributed Bragg reflector (DBR) mirror is surface-micromachined on top of a short-cavity active VCSEL structure. The MEMS-DBR consisting of SiNx/SiOy dielectric materials has a very high reflectivity with wide stopband. Wavelength tuning is realized by the electrothermal actuation of the MEMS electrode. The fabrication steps of the MEMS aiming for large volume production is discussed in detail. A comprehensive static and dynamic characterizations of MEMS VCSEL including far-field, linewidth, polarization behavior, modulation capacity and relative intensity noise is presented. The effect of the temperature change on its tuning behavior as well as on the static and dynamic performance is investigated. The obtained wavelength tuning range of more than 100 nm covers the complete telecom C-band (1530–1565 nm) and part of L-band (1565–1625 nm). A small-signal amplitude modulation bandwidth of up to 8.35GHz is demonstrated for the center emission wavelength around 1550 nm. This enables to implement a directly-modulated MEMS VCSEL based back-to-back link at 10Gbit/s data transmission for 76 nm tuning range. Also, quasi error-free 10Gbit/s transmission over 40 km standard single-mode fiber for a tuning range of more than 60 nm validates its potential for the above mentioned novel WDM-PON system. Apart from optical communication, the scope of this tunable source is investigated in applications such as dispersion spectroscopy and tunable terahertz (THz) signal generation. Experimental validation of multi-species dispersion spectroscopy using MEMS VCSEL is presented for the first time in this work, where concurrent detection of acetylene (C2H2), hydrogen cyanide (HCN), and carbon monoxide (CO) is demonstrated. The second part of the work constitutes demonstration and experimental validation of a novel optical component called MEMS orbital angular momentum (OAM) filter. The filter consists of a micro-sized spiral phase plate (SPP) which is integrated to the MEMS-DBR of a Fabry-Perot optical filter by means of direct laser writing. The onchip devices are suitable for distinguishing different OAM modes for a broad tuning range around 1550 nm emission and considered as a compact, robust and cost-effective solution for simultaneous OAM- and WDM optical communications. The utilization of the OAM modes as an additional orthogonal basis of information carriers in both free space and optical fiber communication systems potentially enhances the transmission capacity tremendously. Four devices with OAM orders of 0 (i.e., no SPP on MEMS), 1, 2 and 3 have been investigated. They are capable of generating/receiving the OAM beam of corresponding order over a continuous tuning range of more than 30 nm, for which the designed SPPs work with high mode purity. The system performance is evaluated by multiplexing two wavelength- and two OAM channels. Error-free free-space transmission at 10Gbit/s suggests that OAM-filters functioning over a wide wavelength range could be employed as an additional degree of freedom for increasing the capacity of free-space communication to a great extent

The Fifteenth Marcel Grossmann Meeting

The three volumes of the proceedings of MG15 give a broad view of all aspects of gravitational physics and astrophysics, from mathematical issues to recent observations and experiments. The scientific program of the meeting included 40 morning plenary talks over 6 days, 5 evening popular talks and nearly 100 parallel sessions on 71 topics spread over 4 afternoons. These proceedings are a representative sample of the very many oral and poster presentations made at the meeting.Part A contains plenary and review articles and the contributions from some parallel sessions, while Parts B and C consist of those from the remaining parallel sessions. The contents range from the mathematical foundations of classical and quantum gravitational theories including recent developments in string theory, to precision tests of general relativity including progress towards the detection of gravitational waves, and from supernova cosmology to relativistic astrophysics, including topics such as gamma ray bursts, black hole physics both in our galaxy and in active galactic nuclei in other galaxies, and neutron star, pulsar and white dwarf astrophysics. Parallel sessions touch on dark matter, neutrinos, X-ray sources, astrophysical black holes, neutron stars, white dwarfs, binary systems, radiative transfer, accretion disks, quasars, gamma ray bursts, supernovas, alternative gravitational theories, perturbations of collapsed objects, analog models, black hole thermodynamics, numerical relativity, gravitational lensing, large scale structure, observational cosmology, early universe models and cosmic microwave background anisotropies, inhomogeneous cosmology, inflation, global structure, singularities, chaos, Einstein-Maxwell systems, wormholes, exact solutions of Einstein's equations, gravitational waves, gravitational wave detectors and data analysis, precision gravitational measurements, quantum gravity and loop quantum gravity, quantum cosmology, strings and branes, self-gravitating systems, gamma ray astronomy, cosmic rays and the history of general relativity

The Fifteenth Marcel Grossmann Meeting

The three volumes of the proceedings of MG15 give a broad view of all aspects of gravitational physics and astrophysics, from mathematical issues to recent observations and experiments. The scientific program of the meeting included 40 morning plenary talks over 6 days, 5 evening popular talks and nearly 100 parallel sessions on 71 topics spread over 4 afternoons. These proceedings are a representative sample of the very many oral and poster presentations made at the meeting.Part A contains plenary and review articles and the contributions from some parallel sessions, while Parts B and C consist of those from the remaining parallel sessions. The contents range from the mathematical foundations of classical and quantum gravitational theories including recent developments in string theory, to precision tests of general relativity including progress towards the detection of gravitational waves, and from supernova cosmology to relativistic astrophysics, including topics such as gamma ray bursts, black hole physics both in our galaxy and in active galactic nuclei in other galaxies, and neutron star, pulsar and white dwarf astrophysics. Parallel sessions touch on dark matter, neutrinos, X-ray sources, astrophysical black holes, neutron stars, white dwarfs, binary systems, radiative transfer, accretion disks, quasars, gamma ray bursts, supernovas, alternative gravitational theories, perturbations of collapsed objects, analog models, black hole thermodynamics, numerical relativity, gravitational lensing, large scale structure, observational cosmology, early universe models and cosmic microwave background anisotropies, inhomogeneous cosmology, inflation, global structure, singularities, chaos, Einstein-Maxwell systems, wormholes, exact solutions of Einstein's equations, gravitational waves, gravitational wave detectors and data analysis, precision gravitational measurements, quantum gravity and loop quantum gravity, quantum cosmology, strings and branes, self-gravitating systems, gamma ray astronomy, cosmic rays and the history of general relativity