Atmospheric turbulence in free space optical satellite downlinks negatively impacts link availability and bit error rate. These effects can be mitigated using a compensation system capable of measuring the incoming wavefront distortion and applying a suitable correction to the received signal. The traditional solution based on adaptive optics and the Shack-Hartmann wavefront sensor has limitations in bandwidth, system complexity, size, weight, and power consumption. Signal correction can also be accomplished using a novel single-chip silicon photonic solution. This work introduces a four-arm grating coupler structure acting as a wavefront sensing element that emulates the performance of the Shack-Hartmann wavefront sensor by giving local tip and tilt estimation. FDTD simulations and measurements have confirmed the presence of a monotonic relationship between incident angle, polarization, and coupler output which can be converted to phase estimation through a reconstruction algorithm. An array of four-arm couplers on a silicon photonic chip provides enough sampling to fully reconstruct the wavefront, providing benefits over traditional solutions such as higher bandwidth, reduced size and weight, and reduced cost. Scaling up the results of this work to a full device could provide a solution for free space optical satellite to ground links in remote and rural communities across Canada and around the world. / Thesis / Master of Applied Science (MASc)

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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / We present a novel communications link concept. This system offers the potential of low data rate full-duplex communications between earth and LEO. We will present a detailed link model for this system.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

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by Eddie Ting Pong Kong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 61-68). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Optical Network Architecture --- p.1 / Chapter 1.2 --- High-Speed All-Optical Tunable-Channel Multi-Access Networks --- p.3 / Chapter 1.3 --- Fault Surveillance of Optical Cross-Connects in Wavelength Routing Network --- p.3 / Chapter 1.4 --- Outline of the Thesis --- p.5 / Chapter 2 --- Optical Multi-Access Networks --- p.6 / Chapter 2.1 --- All-Optical Networks --- p.6 / Chapter 2.2 --- Optical Multi-Access Schemes --- p.8 / Chapter 2.2.1 --- Wavelength-Division Multi-Access (WDMA) --- p.9 / Chapter 2.2.2 --- Time-Division Multi-Access (TDMA) --- p.12 / Chapter 2.2.3 --- Subcarrier Multi-Access (SCMA) --- p.14 / Chapter 2.3 --- Design Considerations --- p.14 / Chapter 3 --- All-Optical Tunable-Channel Multi-Access Networks --- p.18 / Chapter 3.1 --- Tunable-Channel Multi-Access Networks --- p.19 / Chapter 3.2 --- Protocols for TCMA Networks --- p.20 / Chapter 3.3 --- Photonic Implementation of a Wavelength Division TCMA Network with Time- Slot Access --- p.23 / Chapter 3.3.1 --- Proposed Network Architecture --- p.25 / Chapter 3.3.2 --- Experimental Results --- p.30 / Chapter 3.3.3 --- Discussion --- p.34 / Chapter 3.3.4 --- Summary --- p.35 / Chapter 4 --- Fault Surveillance for Optical Cross-Connects in Wavelength Routing Networks --- p.36 / Chapter 4.1 --- Wavelength Routing Networks --- p.37 / Chapter 4.2 --- Options in Fault Surveillance --- p.39 / Chapter 4.3 --- Optical Path Surveillance of Optical Cross-Connects in Wavelength Routing Networks --- p.41 / Chapter 4.3.1 --- Scanning Amplified Spontaneous Emission Identification Surveillance Scheme --- p.43 / Chapter 4.3.2 --- Pilot-Tone Based Surveillance and Removal Scheme --- p.49 / Chapter 4.4 --- Summary --- p.55 / Chapter 5 --- Conclusion --- p.57 / Chapter 5.1 --- Summary of the Thesis --- p.57 / Chapter 5.2 --- Future Work --- p.60 / Bibliography --- p.61 / Publication List --- p.59