A couple of presentations at the 2015 OFS24 in Brazil highlight FBGS’s DTG® sensors in conjunction with new interrogation. They shed light on how these sensors can jointly advance the overall performance of a quasi-distributed sensing system for a wide range of key current and future applications. The following are the highlights of each article:
1. High DTG® Sensor Count
- FBGS demonstrates a high spatial-density quasi-distributed sensing system that can accommodate over 1000 DTG® sensors over a single optical fiber of more than 2 km long.
- The individual FBG sensors are of low reflectivity (0.1%), which helps stack a higher number of sensors in a more cost-effective approach that takes advantage of the established automated draw-tower process.
- A high-speed and high-precision interrogation platform introduced by Insight Photonic Solutions combines WDM/TDM schemes (dubbed as wavelength-to-time-domain reflectometry (WTDR)), which overcomes the status quo limitation of WDM and TDM measurement systems.
- The new approach opens up the door for the next generation applications (oil & gas, structural monitoring, perimeter monitoring, transportation networks, civil engineering, geotextile, etc.) that demand fast interrogation of high numbers of sensing points over long sensing lengths..
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2. Decoupling of T & ε Cross-sensitivity with a Single PM-DTG® Optical Fiber
- At the heart of the innovation is the fabrication of a special polarization-maintaining (PM) optical fiber inscribed with fiber Bragg grating (FBG) sensors using the draw-tower (PM-DTG®s).
- The induced birefringence of this fiber is generating two narrowly-separated wavelength peaks (~ 0.5 nm) with orthogonal polarizations for each PM-DTG. In response to an external physical stimuli (T and/or ε), both peaks respond with different responsivities to T & ε. However, the peaks separation responds more predominately by T variations. Analytically, one can extract the decoupled signals and simultaneously monitor them independently.
- A new option for an interrogation scheme based on I4-platform (no moving parts) by FAZ Technology demonstrated a high reliability and high-accuracy approach in decoupling the inherited cross-sensitivity in measuring temperature (T) and strain (ε).
- The platform provides higher stability performance (< 50 fm), which translates to a temperature stability of +/- 0.2 °C. For the strain measurements, the orthogonal components show almost identical sensitivities of 1.176 pm/με and 1.191 pm/με.
- The exhibited performance will have a high impact for any application in distributed temperature measurement, where the optical fiber is under strain. Examples range from small size flexible minimally-invasive medical devices (catheters, needles, etc.) to remote monitoring of reactors and various industrial processing facilities.
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