Design and optimization of bidirectional and optical logic systems in the presence of noise

The work in this thesis covers the critical aspects of optical noise in bidirectional and optical logic systems. With applications ranging from ultra-dense transmission and fiber-to-the-home to all-optically routed networks and optical computing, bidirectional fiber optic links and optical digital logic play an important role in future photonics systems. As with any communication systems, the fundamental performance of bidirectional and optical logic systems is ultimately limited by noise. In this thesis, the impact of optical noise in bidirectional and optical logic systems is investigated with the goal of determining the optimal design and performance requirements of future systems. Two types of bidirectional optical systems are analyzed: interleaved bidirectional systems and passive optical networks. It is demonstrated, both theoretically and experimentally, that Rayleigh backscattering noise is a fundamental limitation in bidirectional systems. Owing to its absence in conventional unidirectional systems, Rayleigh backscattering noise is an oft neglected noise mechanism in optical fiber systems and few design rules exist which seek to minimize its impact. It is shown that in bidirectional fiber systems, Rayleigh backscattering places markedly unique constraints on optical link design with respect to receiver design, system power budget, capacity and choice of modulation format. New design rules are offered which rigorously account for the deleterious impact of Rayleigh backscattering noise in fiber optic systems. This thesis also addresses the role of noise in future optical logic systems. In particular, experimental work characterizes the progress of optical Boolean logic functionality in bistable 1550 nm Vertical Cavity Surface Emitting Lasers. Record bistable switching powers in 1550 nm Vertical Cavity Semiconductor Optical Amplifiers are observed and a novel, cascadable 1550 nm optical inverter is demonstrated up to 2.5 Gb/s. Positive noise margins and signal regeneration is achieved representing an important step towards the realization of robust, noise immune optical information processing system