Ph.D Thesis

Ph.D StudentAgmon Amos
SubjectArchitecture and Algorithms for Broadband Optical Access
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Moshe Nazarathy


This work addresses the challenging task of improving optical access networks technology, increasing data throughputs while maintaining low complexity. The work begins with an experimental validation of a polarization multiplexing scheme (theoretically developed in our previous work), comparing the relative performance of a traditional 1:16 passive split network with a polarization multiplexing based network. The results validate the concept, showing good agreement with theory, and suggesting that data rates may be doubled in future generation Passive Optical Networks (PON) while keeping baud rate unchanged, using this technique.

Considering next generation PON, we note that it is challenging to increase Time Division Multiplexing (TDM) symbol rates beyond 10 GBaud, therefore, improved schemes attaining higher spectral efficiency are called for. We conceived and investigated a new top down optical network architecture, based on self-coherent optical detection in the downstream direction and reflective modulation in the upstream direction. This PON architecture balances contradicting system requirements such as higher data rates; longer reach, laserless, colorless & low digital-rate end-user terminals. The scheme allows for low complexity optical network units (ONU) end-user terminals and relatively simple central-office equipment to satisfy network requirements. High spectral efficiency and low digital signal processing rates are attained by virtue of the PON spectral design, based on a variant of Orthogonal Frequency Division Multiplexing (OFDM).

Next we elucidate the degradation caused when polarization multiplexing is attempted in a self-coherent heterodyne receiver, revealing the effect of random polarization fading. To address this impairment, we propose, analyze and simulate a novel method to mitigate polarization fading by means of a low-complexity optical receiver, comprising a simple electro-optical front-end and Multiple Input Multiple Output (MIMO) digital signal processing.

The work concludes with a presentation and analysis of self-coherent detection, deriving its Signal to Noise Ratio (SNR) performance, accounting for major channel impairments.