| 摘要 |
Distributed fibre optic sensing system comprising: an optical sensing fibre 712 which receives optical signals; a means for receiving backscattered and/or reflected light from along the fibre and a means for processing the received light to measure phase, frequency and amplitude data which is synchronised to enhance signal sensitivity. The processing means may be arranged to detect acoustic perturbations incident along the fibre and possibly further arranged to measure phase modulation of the received light. The fibre may receive a pulsed optical signal. The fibre may be a standard telecommunications fibre optic cable. The system may further comprise: a means of calibration; and possibly an optical modulator 703 generating sidebands in the optical-signal with an optical filter 708 for sideband selection to vary the optical-signal frequency. The fibre may be arranged along a structure or in an area to be monitored. The optical-signal frequency may be changed to improve the sensitivity of the backscattered and/or reflected light from along the fibre. The receiving means may comprise an interferometer comprising at least two optical paths of differing length, a plurality of photodetectors and means of determining phase angle. Also methods, where a preferable combination of the data provides coherent field images. |
