Single-mode fibres containing several different rare-earth dopants have been fabricated. Characteristics of the fibres, including absorption and fluorescence spectra, fluorescence lifetimes and uniformity of dopant incorporation have been measured and the results obtained and their influence upon the performance of these fibres as fibre-lasers and amplifiers will be discussed. Use of these fibres as tunable CW lasers centred an 1.088µm (Nd3+-doped fibres) and 1.54µm (Er3+-doped) with tuning ranges of 80nm and 25nm respectively are described. High peak-power output pulses have also been obtained by operating fibre-lasers in a Q-switched mode, with maximum peak-power of 2W in a 1µs pulse for a 200Hz pulse repetition rate