The development of a fluoride fibre laser for hydrocarbon gas sensing is discussed. The use of a fibre laser as a source for optical sensing has many advantages including small size and ease of adaptability into industrial systems. The fibre laser constructed in this work has an operating wavelength of X = 2.3 n.m, which corresponds to an absorption band of many hydrocarbon gases. The thulium-doped fibre has been fully characterised in terms of absorption, fluorescence and fluorescence lifetimes. These data were then used to choose a pump laser diode and appropriate laser mirrors. The operational fibre laser was fully characterised in terms of output power and slope efficiency. Two fibre laser configurations were demonstrated. The first fibre laser exhibited a dual laser emission simultaneously at 1.92 p.m and 2.31 urn, with output powers of 7 mW and 1.2 mW, respectively. A second fibre laser was also demonstrated; this device was optically pumped with a low power laser diode. The output from the fibre laser pumped by the low power laser diode was utilised as a unique source for detection of methane. A detection limit of 1000 ppm metres was routinely demonstrated with this unoptimised system.