Nonlinear optics enables the manipulation of spectral and temporal characteristics of optical pulses interacting with a dielectric medium. Optical fibres, as a uniquely practical medium, provide an environment for effectively exploiting the nonlinear effects. This has facilitated the rapid growing interest in this field focused on the investigation of fibrebased sources incorporated with various novel saturable absorber devices for ultrashort pulse generation.This thesis reports a series of experiments exploring the ongoing research in the field of nonlinear optics, including the development of ultrafast mode-locked fibre sources and their applications in supercontinumm generation and third order parametric interactions in new carbon materials.Firstly, the integration of carbon-based materials with rare-earth doped media allows the demonstration of ultrafast mode-locked laser sources operating at wavelengths across the near-infrared region in a compact, low cost and environmentally robust scheme.Power scaling of such sources can be achieved by operating in the all-normal dispersion regime making use of a glass-substrate saturable absorber device that exhibits a higher damage threshold.Supercontinuum generation has been used as an effective method for spectral broadening. Pumping with a conceptually simple and reliable fibre-based system, a continuum covering from 2 to 3 µm is generated in a highly nonlinear GeO 2 fibre. This experiment demonstrates a robust and long-term stable source of radiation in an important band, coincident with a portion of the atmospheric transmission window.Finally, the demonstration of a simple and compact nano-material based dual-wavelength system shows the performance of such devices as a simultaneous saturable absorber and passive synchroniser. An experimental study of coherent frequency mixing at large frequency shifts in a graphene sample, pumped by a two-colour fibre-integrated source, proves the strong nonlinear response of this new carbon material. Woodward who not only provided company inside and outside of the lab, but were also happy to discuss and help all matters of my work and life in UK. In particular, I would like to thank Ed for providing me with much needed support, interesting discussions (especially on food and culture) and continued collaboration since I joined the group. Tim, for making couplers for the Tm-system. Thanks to Tim, Robbie (shared the same office over the past three years!), Ed, and Rob for endless support, spending hours and hours proof reading chapters of this thesis and cheering me up all the time. Thanks to the visitor from A*STAR (Singapore), Dr. Dora Hu (more like a sister), for proof reading and encouraging me to relax during the thesis writing.