Method and apparatus for optical sensing

摘要

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fiber. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fiber while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

主权项

1. An optical sensor system comprising:
a light source generating a pulsed optical signal; an optical modulator arranged to modulate the pulsed optical signal with a first modulation frequency (f1) and a second modulation frequency (f2) within an optical pulse modulation envelope, the modulation thereby generating frequency sidebands in the pulsed optical signal; an optical filter configured to controllably select a plurality of the frequency sidebands, and, thereby vary the frequency of the light output therefrom, wherein the frequency sidebands selected by the optical filter include at least a first first order sideband and a second first order sideband, respectively generated for the first modulation frequency (f1) and for the second modulation frequency (f2); and an optical sensing fibre configured to receive light of a frequency corresponding to the selected plurality of frequency sidebands.