Femtosecond laser-inscribed fiber Bragg gratings for strain monitoring in power cables of offshore wind turbines

Abstract

A fiber Bragg grating sensor system used for monitoring the effects of strain on the power cable of an offshore wind turbine is presented. The Bragg grating structure was inscribed into coated nonphotosensitive standard telecommunication fibers using an IR femtosecond laser and the point-by-point writing technique. Because of the presence of the protective coating of the fiber, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a bare fiber. A system containing this sensing element was to our knowledge for the first time successfully installed and tested in an offshore wind turbine prototype (REpower 6M, REpower Systems, AG, Germany) in February 2010, near Ellhöft (Germany). The fabrication process of the fiber Bragg gratings, measurement results of the online monitoring, and a comparison between the sensor signal and commonly used sensing techniques are presented.

Structural Health Monitoring of Civil Infrastructure Using Optical Fiber Sensing Technology: A Comprehensive Review

“…Kim et al [121] conducted experimental investigations on deflection estimation of wind turbine blades using embedded FBG sensors. Burgmeier et al [122] developed and tested an FBG-based sensor system for remote measurement of strain that affects the power cable in an offshore wind turbine.…”

Fiber Bragg grating sensors for steel wire monitoring in real-time

“…The FBGs are processed within a bend-insensitive, single mode glass fiber (Bendbright Elite glass fiber, Draka, Prysmian Group) by applying the femtosecond laser point-by-point inscription method through the glass fiber acrylate 7,8 . The glass fiber has a total diameter of 242 µm and a core diameter of 9 µm.…”

Arrayed waveguide grating interrogator for fiber Bragg grating sensors: measurement and simulation

“…2, consists of an Exalos EXS1520-2111 SLED with an optical power of 20 mW at a central wavelength of 1550 nm and a spectral 3 dB half-width of 60 nm, an Agilecom AAWG-C321C55G23-01 athermal 100 GHz AWG with Gaussian profile and corresponding electronics for data evaluation, an Ocean Optics NIRquest512 spectrometer with a spectral resolution of 150 pm, two 3 dB single-mode fiber couplers, and a nonapodized FBG sensor (Fig. 3, inset), which is processed within the bend-insensitive Draka Bendbright Elite glass fiber by point-by-point femtosecond-laser writing [10]. The broadband light is emitted by the SLED; light, which corresponds to the Bragg wavelength, is reflected back by the FBG and simultaneously analyzed by the spectrometer and the AWG module.…”