Minimizing the effects of distortion and noise in fiber-optic communications and interferometric imaging through digital signal processing
- In this dissertation we will study the effects of distortion and noise in fiber-optic communications and interferometric imaging and methods to reduce their impact. In the area of fiber-optic communications, we will explore the two most economically significant applications: intra-data center links and optical access networks. The motivation for this study is the imminent need for optical links to undergo a large-scale upgrade in capacity to meet the needs of exponentially-growing Internet traffic. As these markets are high-volume and low-cost, we favor techniques which emphasize digital signal processing (DSP) over optical signal processing. The ability to transition to heavily DSP-based architectures is now possible due to recent development of commercial CMOS digital-to-analog and analog-to-digital converters with up to 65 Gsample/s conversion rates. However, such ultra-high-speed converters have limitations in resolution, and so we will investigate methods to compensate for this deficiency. In particular, we will introduce a new method of spectral reshaping to greatly increase a transmitter's signal-to-noise ratio when limited by a low-resolution digital-to-analog converter. Next we will discuss a novel architecture which enables electronic dispersion compensation in optical access networks using minimal opto-electronic components. We will present simulation and experimental measurement of record bit rates in a single polarization and wavelength using a receiver based on single-photodiode detection. The third topic within fiber-optic communications relates to intra-data center communications. For this application, chromatic dispersion is minimal and thus direct modulation of distributed feedback lasers is preferred, as it eliminates the need for both a laser and a separate high-speed modulator. However, direct modulation is characterized by significant nonlinearity in the conversion of drive current to optical intensity. We will show how this effect can be mitigated through the use of novel quadrature amplitude modulation constellations in a fully-digital implementation. Finally, we will discuss the impacts of noise and non-ideal detection in an interferometric imaging system based on the concept of phase-sensitive spectral-domain optical coherence tomography. We will analyze the impacts of noise and digital processing on the sensitivity of such a system in measuring sub-nanometer features.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Ling, William A
|Stanford University, Department of Electrical Engineering.
|Statement of responsibility
|William A. Ling.
|Submitted to the Department of Electrical Engineering.
|Ph.D. Stanford University 2014
- © 2014 by William Ling
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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