| 摘要 |
<p>An optical time domain reflectometry method of sensing a parameter to be measured in a region of interest comprises launching optical radiation (4) at a probe wavelength into an-optical fibre (5, 6) and producing electrical output signals in response to optical radiation backscattered from the optical fibre (5, 6). In one aspect of the invention the optical fibre comprises first and second sections (5, 6), the second section (6) having a lower intensity threshold for the onset of non-linear effects than the first section (5) and being deployed in the region of interest. Optical radiation (4) at the probe wavelength is launched into the said first section (5) at an intensity lower than the non-linear effects intensity threshold of the first section (5) but higher than the non-linear effects intensity threshold of the second section (6), the attenuation characteristics of the said first section (5) being chosen so that the intensity of the optical radiation (4) at the probe wavelength reaching the second section (6) is below that of the non-linear effects intensity threshold of the said second section (6). In another aspect of the invention the optical fibre comprises first and second sections connected together by a remote amplifier, the gain of the amplifier being selected so as to compensate for attenuation losses in the probe wavelength in the first section.</p> |
