All-optical signal processing in novel highly nonlinear fibres and waveguides

All-optical signal processing has recently become an attractive research field, a result of nonlinear optical systems making major advances in terms of cost, compactness, energy consumption, integrability and reliability. This technology has impacted several areas ranging from telecommunications and biomolecular sensing to military and quantum communications, and spanning a vast range of frequencies from the near to mid-infrared. This PhD research project was aimed at investigating the features and feasibility of two state-of-the-art all-optical signal processing technologies: highly nonlinear soft glass fibres and silicon-based waveguides.Of the various soft glasses available, lead silicate and tellurite are considered within this thesis. The optical properties of a highly nonlinear lead silicate W-type fibre are studied and the design process of such fibres is explained in detail. A number of telecommunications-based all-optical processing applications are also demonstrated in this fibre technology. Phase sensitive amplification is demonstrated in the W-type fibre and the process is used to regenerate the phase of 40 Gbit/s differential phase shift keying (DPSK) signals.The optical characteristics of a highly nonlinear tellurite fibre are also studied both at 1.55 and 2 µm. Efficient four wave mixing (FMW)-based wavelength conversion of 1.55 µm signals is demonstrated in the fibre and a detailed numerical study into the potential of the fibre in realizing phase-matched mid-infrared (MIR) to near-infrared (NIR) spectral translation is conducted.The second all-optical signal processing platform investigated in this project is silicon germanium (SiGe) waveguides. A detailed account of the linear and nonlinear optical properties of this newly emerging silicon-based technology is reported for the first time and the potential of this platform is highlighted by demonstrating wavelength conversion of 40 Gbaud DPSK and QPSK signals. Broadband spectral translation is also demonstrated in the SiGe waveguides with record FWM bandwidths