Abstract: A low temperature fluorophosphate glass useful for joining single-mode fluoride and silica optical fibers includes 5 to 7 mol % InF3, 20 to 35 mol % PbF2 and 57.5 to 75 mol % P2O5. An alkali for maintaining a low glass transition temperature can be included. Up to 25% (glass molar basis) of the P2O5 can be replaced by PbO.

Abstract: A current sensor which makes use of the Faraday effect, which is patterned on a Sagnac interferometer and which employs a coil of spun birefringent optical fibre for sensing the magnitude of current flowing through a conductor about which the sensor is, in use, located. The sensor in its preferred form comprises a coil (1) of spun single mode birefringent optical fibre (11), the coil being arranged to locate about a conductor (12) through which current flow occurs. A beam splitting device (22) in the form of a 3*3 coupler is coupled with the ends of the coil fibre and is arranged to launch counter-propagating light beams into the respective ends of the coil fibre. A lasing light source (16) is optically coupled to the beam splitting device by way of a 2*2 coupler (21), and detectors (18) which are arranged to detect a phase shift between the polarisation modes of the counter-propagated light beams are optically coupled to the ends of the coil fibre by way of the beam splitting device.