Abstract: A system and technique for obtaining two or more distributed measurements from an optical sensing fiber deployed along a desired measuring path are disclosed. Interrogating probes from two or more different distributed measuring systems are combined and launched into the sensing fiber. Backscattered light generated in response to the combined interrogating probes is separated into portions and each portion is provided to a respective distributed measuring instrument. In this manner, distributed measurements corresponding to different parameters of interest, such as temperature and pressure, along the measuring path can be measured simultaneously using the same sensing fiber.

Abstract: A system and technique for obtaining two or more distributed measurements from an optical sensing fiber deployed along a desired measuring path are disclosed. Interrogating probes from two or more different distributed measuring systems are combined and launched into the sensing fiber. Backscattered light generated in response to the combined interrogating probes is separated into portions and each portion is provided to a respective distributed measuring instrument. In this manner, distributed measurements corresponding to different parameters of interest, such as temperature and pressure, along the measuring path can be measured simultaneously using the same sensing fiber.

Abstract: An optical time domain reflectometry apparatus for sensing a parameter in a region of interest is characterized in that the optical fiber includes a first section into which optical radiation at the probe wavelength is launched and a second section deployed in the region of interest. The first section has a higher intensity threshold for the onset of non-linear effects than the second section. The source launches the optical radiation into the first section at an intensity lower than the non-linear effects intensity threshold of the first section but higher than the non-linear effects intensity threshold of the second section. The attenuation characteristics of the first section are chosen such that the intensity of the optical radiation at the probe wavelength that reaches the second section is below the threshold for the onset of non-linear effects of the second section.

Abstract: The present invention comprises the use of a fiber in a sensing optical fiber system operated in a region of negative chromatic dispersion to minimize modulation instability thereby enabling the identification and measurement of the information-carrying signals. The present invention may be used in a variety of sensing environments.

Abstract: 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.