Schlumberger Technology Corporation

Peter C Wait

Arthur H Hartog

Gareth P Lees

Colin Allan Wilson

Paul Frederick Cilgrim Dickenson

Jakub Szypicyn

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.

Simultaneous distributed measurements on optical fiber

An improved laser source for use in a distributed temperature sensing (DTS) system (and DTS systems employing the same) includes a laser device and drive circuitry that cooperate to emit an optical pulse train at a characteristic wavelength between 1050 nm and 1090 nm. An optical amplifier, which is operably coupled to the laser device, is adapted to amplify the optical pulse train for output over the optical fiber sensor of the DTS system. In the preferred embodiment, the laser device operates at 1064 nm and outputs the optical pulse train via an optical fiber pigtail that is integral to its housing. The optical power of the optical pulse train generated by the laser source is greater than 100 mW, and preferably greater than 1 W, at a preferred pulse repetition frequency range between 1 and 50 kHz, and at a preferred pulse width range between 2 and 100 ns.

Optical pulse generator for distributed temperature sensing operating at a characteristic wavelength in a range between 1050 nm and 1090 nm

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.

Optical time domain reflectometry for two segment fiber optic systems having an optical amplifier therebetween

Optical time domain reflectometry

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.

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Salisbury, United Kingdom

Peter C Wait