This thesis reports work in high repetition rate femtosecond fiber lasers. Driven by the applications including optical arbitrary waveform generation, high speed optical sampling, frequency metrology, and timing and frequency distribution via fiber links, low noise fiber laser sources operating at multi-gigahertz repetition rates are developed systematically. A 200 MHz fundamentally mode-locked soliton laser and a 200 MHz fundamentally mode-locked similariton laser are first developed. Intra-cavity soliton formation is recognized as the optimum route towards achieving high fundamental repetition rates compact lasers, under the limitation of realistically available pump power. A 3 GHz fundamentally mode-locked femtosecond fiber laser is developed and verifies the soliton formation theory. Techniques in external cavity repetition rate multiplications are also discussed. A theoretical model that relates the repetition rate of the soliton laser and its other physical measurable parameters is developed to guide further high repetition rate laser development.