Optoplan has been awarded the world's first commercial contract for a fibre optic Ocean Bottom
Seismic Cable (OBC) system [1] for permanent reservoir monitoring at the Ekofisk field in the North
Sea. An area of 60 sq. km of the seabed will be covered by four component (4C) sensors in 2010. The
system consists of i) a top-side (platform) laser interrogation and recording system, and ii) a wet-end
system including 200 km of seismic cable with 4000 sensor stations, each containing 4 FBG-based
interferometric sensors (three accelerometers and one hydrophone). The wet-end system includes
24000 FBGs and more than 3500km of optical fibres, and will probably be the largest single fibre optic
sensor network ever made.
The completely passive wet-end part of the system is designed to operate with ultra-high reliability
subsea over more than 25 years. The system is expected to significantly enhance the oil and gas
recovery of the field.
This commercial success is a result of i) Optoplan's long experience and credibility in the field of fibreoptic
sensors for the oil and gas industry [2], [3], ii) close collaboration with oil companies and
qualification through extensive field testing [4], [5], iii) the establishment of a high capacity supply
chain and manufacturing system with innovative automated processes, iv) sensor/manufacturing
design for high reliability and good manufacturability with high yield, v) innovative sensor fibre network
and instrumentation design [1], [6], [7], [
Optoplan has developed a novel, high-performance large-scale fibre optic Ocean Bottom seismic Cable (OBC)
system, which has successfully been qualified through field installations. This OBC system is based on
combined wavelength- and time-multiplexing of fibre Bragg grating (FBG) based interferometric sensors. A
large-scale manufacturing system has been developed to handle the manufacturing of several system per year -
each system having at least 2000 sensor stations. The first full scale OBC system will be ready for installation
early 2009.
Characterization of the complex relection spectrum and the spatial profile of fiber Bragg gratings using optical frequency domain reflectometry and the layer peeling algorithm is presented. The importance of correct scaling and polarization effects are discussed. The method gives accurate measurement of the spatial profile for grating with reflectivity < 98-99 %. Immunity to spurious reflections and high dynamic range in spectral measurements are achieved.
Fiber distributed feedback (F-DFB) lasers have proven to be attractive devices for interrogation of optical sensors with high frequency resolution, due to their very low frequency noise/narrow linewidth, low relative intensity noise (RIN), robust mode-hop free tunability, compact size, and flexible and accurate wavelength setting. It has also been demonstrated that F-DFB lasers can act as sensor elements for high resolution measurements of physical quantities causing strain, refractive index, or birefringence changes in the laser fiber. It has been demonstrated that F-DFB lasers can be used as fast tunable sources for high resolution and high accuracy spectral component characterization. They may also find applications in dense WDM transmission systems utilizing their potentials for accurate wavelength setting, easy wavelength tuning, semiconductor pump redundancy, or multiple wavelength operation. In this paper properties and applications of F-DFB lasers will be discussed, with emphasis on modeling, design and characterization of the devices. In particular, RIN and frequency noise properties, requirements on grating and gain medium quality, the design requirements for achieving singlemoded or (intentionally) multimoded laser operation, and the output characteristics of single- versus multimoded F-DFB laser devices will be treated.
Our aim is to investigate the use of distributed feedback (DFB) fiber lasers [1] as acoustic sensors. In this paper we will discuss the various contributions to the frequency shifts that make such sensing possible, and compare the theoretical results with preliminary experimental results.
Conference Committee Involvement (1)
Fiber-Based Component Fabrication, Testing and Connectorization
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