Laser Focus World Magazine has published a feature article on downhole optical sensing applications and technologies. Gail Overton, Senior Editor, spoke also with LIOS Technology about downhole deployments.
"Our Raman-OFDR [ optical frequency-domain reflectometer ]—with an installed base of 2200-plus systems and the only frequency-domain-based DTS system on the market—is the most cost-effective system available today," says Daan Van Laar, LIOS (Cologne, Germany) key account manager for the oil and gas upstream sector.
The Raman OFDR uses a continuous-wave (CW) laser modulated at different frequencies instead of a pulsed laser as in Raman-OTDR technology. Frequency profiles are generated by measuring amplitude and phase of anti-Stokes and Stokes Raman signals at a range of frequencies, with time- and thus distance-dependent Raman signals obtained after inverse Fourier transform of the frequency profiles. These signals are then used in the calculation of spatially resolved temperature profiles along optical fibers. "Major advantages of Raman-OFDR are CW laser operation for high signal levels at moderate laser peak powers for extended laser lifetimes, as well as economic detection schemes based on the heterodyne concept," adds Van Laar.Read the full feature article here: