Optical fiber bragg sensors

Fiber Bragg gratings (FBGs) are increasingly used as wavelength selective sensors for the measurement of temperature and strain. Nowadays, readout concepts for distributed fiber Bragg grating sensors suffer from restrictions concerning accuracy, bandwidth, response time and multiplexibility. This thesis intends to provide a contribution to extenuate these insufficiencies. The work includes the fields optical and electronic system design, signal processing and algorithm investigations. The spectrometric readout concept for the temperature and strain response of fiber Bragg gratings was studied and refined with the objective of extending system bandwidth and accuracy for demanding applications in the area of vibration control of lightweight structures and health monitoring. Subpixel approximation techniques enhance the measurement resolution of the system. Besides the extensive study of reported algorithms, the performance of a novel linear phase operator technique LPO is presented by means of simulations and measurements. The LPO technique ensures a significant resolution enhancement under extreme noisy conditions and is efficient in its implementation. A convenient solution for the signal processing of recording CCDs with high frame rates has been developed by the use of digital signal processors and field programmable gate arrays. Furthermore, the thesis exposes a novel, high bandwidth readout concept based on lateral photodiodes. Here, the system bandwidth was significantly increased up to the range of tens of kilohertz, whereas the time delay was decreased compared to CCD-based concepts. With the high bandwidth capability, the lateral diode concept invades the domain of tunable filter interrogation concepts while providing a higher wavelength accuracy and multiplexibility. This enables future applications in the field of structural monitoring, e. g., for safety-relevant aircraft components. The systems and algorithms presented in this work have demonstrated their performance during numerous cycles on test benches.