Silicon photonics is an advanced platform for the development of compact integrated optical devices. Major breakthroughs such as light generation, signal amplification and high-speed modulation have been demonstrated in silicon waveguides due to their large nonlinear effects. Recent fabrication methods have enabled the infiltration of crystalline and amorphous semiconductor materials inside silica capillaries to combine the excellent optoelectronic properties of silicon with the waveguiding capabilities of fibres. This new class of waveguide maintains many of the advantageous properties of commercial silica glass fibres such as robustness and flexibility, as well as offering the potential for seamless integration within existing networks. Furthermore, the silicon fibre platform can also be post-processed to fabricate novel micron-scale devices, beyond what is achievable in their planar counterparts. In this thesis, two forms of fibre-based semiconductor devices have been investigated; tapered silicon core waveguides and whispering gallery mode microresonators. These devices were fabricated as a unique approach to enhance the light-matter interactions for the development of all-optical signal processing devices. Improvements in the crystallinity and the optical transmission properties of polysilicon core fibres were achieved via fibre tapering, enabling the first demonstration of nonlinear propagation in this material. Moreover, different forms of resonators were fabricated from amorphous and polycrystalline silicon core fibres. Ultrafast all-optical modulation via the Kerr nonlinearity is demonstrated at picoseconds switching speeds using pure amorphous silicon resonators and in hybrid silica glass and polysilicon core resonators.