| 摘要 |
A fibre optic cable 20 for distributed acoustic sensing has an optical fibre 100 (e.g. fibre-in-metal-tube) concentrically surrounded by an outer layer 101. Discrete acoustic sensing points are achieved by selectively enhancing the acoustic coupling between the outer layer 101 and the optical fibre 100, such that acoustic energy may be transmitted selectively from the outer layer to the optical fibre. The region between the outer layer and the optical fibre contains material 201 which is acoustically insulating (e.g. air). Regions 202 of acoustic coupling between the fibre 100 and the outer layer 101 may be provided by built up regions of filler 102 interspersed along the length of the fibre, or by crimping the outer layer to form narrowed points (103, fig. 5). By providing a plurality of discrete acoustic sensors along a cable acoustic signals may be measured in situations where the fibre optic cable has not been secured to a structure or area by a series of clamps. This may reduce aliasing. |
