This paper describes the fabrication of a wide-temperature and low-loss fused single-mode optioalfibre coupler. The device is fabricated from standard communication fibre. The specifications of the packaga device at 1.52μm are as follows: splitting at 0(?)50%,splitting ratio tolerance <±5%, operating temperature range from -30 to +70℃, insertion loss <0.2dB, directivity >40 dB. The splitting ratio is highly sensitive to operating wavelength, but insensitive to polarization of input light.