Optical fibre with enhanced security against signal tapping

Abstract From the Canadian patent

Abstract of the Disclosure, An optical fibre has a light conducting core surrounded by a cladding layer of lower refractive index than the core. A light conducting layer is around the cladding layer and has a refractive index higher than that of the cladding layer and a second cladding layer surrounds the light conducting layer the second cladding layer having a lower refractive index than that of the light conducting layer. A data carrying signal can be propagated in the core and a monitoring signal can be propagated in the light conducting layer. Any attempt to tap the fibre to abstract data information results in aberration of the monitor signal, which can be detected. The monitor signal …