Surpassing the detection limits of current distributed acoustic sensing systems (Conference Presentation)

Enhanced Distributed Fiber Optic Vibration Sensing and Simultaneous Temperature Gradient Sensing Using Traditional C-OTDR and Structured Fiber with Scattering Dots

“…In previous work, our group outlined that inscribing simple strongly scattering dots (reflectors) via femtosecond laser pulses into the sensing fiber core (as was before demonstrated for polymer optical fiber [49,50]) also results in significant improvements of DVS with regard to sensitivity, fading and strain transfer regularization [51], which was also shown analogously for discrete UV-enhanced strong scattering segments [52]. Very recently Donko et al proposed a similar technique with fs-inscribed discrete reflectors to enhance distributed sensing performance [53,54,55]. Fiber structuring based on scattering dots can be considered as simpler and has fewer demands than an FBG-based approach.…”

“…Nevertheless, until recently investigations regarding quasi-distributed interferometric DAS/DVS focused almost exclusively on FBGs. However, recently another group has described the method of femtosecond laser inscription of backscatter enhanced dots and outline the benefits [53,54,55], though so far no in-depth sensing performance analysis has been published.…”

“…This test object was chosen because our motivation is the application of our method for vibration (and temperature) monitoring of extended power cable installations, e.g., subsea power cables connecting offshore wind farms with the shore [61]. For this application, a long sensing range is key [55,62,64], but also the ability to demodulate and localize low frequency vibrations, e.g., from anchors being dragged over the seabed close to and/or towards the submarine cable, is highly desirable for transmission system operators (TSO) to avert damages or failures [62]. Furthermore, determining dynamic or transient strain values in the power cable for conditions monitoring during the power cable installation process via DVS [63] is an attractive application that could allow for a early detection of damages to the cable sustained during laying thus saving costs and preventing later occuring secondary damages.…”

“…In DAS/DVS an increased sensing range is highly desired for many applications, e.g., for subsea power cable monitoring [55,61,62,69]. At large distances sensitivity may be raised by increasing backscatter intensity.…”

“…Also experiments with range-optimized fiber configurations combining low-loss fiber with high scattering fiber have recently been published [69]. Very recently, the approach to use of fs-inscribed reflectors in ULL fiber to attain large sensing ranges via localized enhanced backscatter has been described [55]. However, DVS performance results are lacking.…”