Multichannel photonic networks.

Abstract

This thesis presents several alternatives for fibre-optic local and metropolitan area networks. The issues considered are mainly related to the physical layer of the networks, i.e., the topology and the optical communications problems. The following approaches were considered in more detail: photonic switching using spatial light modulators; subcarrier-multiplexing techniques using direct optical detection, and in particular the transmission of 64-QAM signals by optical fibre; and subcarrier-multiplexing techniques combined with coherent optical detection. The spatial light modulator appears to be one of the most promising means for building a large-size (e.g., 1000 $\times$ 1000) optical space switch. The main constraints are the attenuation of the optical signal and the crosstalk between the channels. Other problems such as fan-in and fan-out are also addressed. Theoretical and experimental results are presented on the fibre-optic transmission of microwave 64-QAM signals at 90 Mb/s rate. Two important methods of improving the system performance are discussed and demonstrated: laser reflection-induced intensity noise minimization, and error-correction coding using a self-orthogonal convolutional code. The applicability of this transmission technique to the distribution of digital video services is assessed. The concept of photonic networks which use subcarrier-multiplexing techniques together with coherent optical detection is presented. The different radio and optical modulation formats that can be used are investigated and compared for several system modes of operation. The effects of laser phase noise on the system performance are also addressed. An 8-port homodyne phase-diversity receiver is analyzed theoretically.