Interrogation strategies for distributed and multipoint fiber optic sensors

Abstract

Fiber optic sensors have matured to allow the detection of chemical and physical parameters at multiple points, or in a distributed fashion, along the length of a single optical fiber strand. The electro-optic readout unit connected to the fiber needs to be tailored to the specific sensor application to balance the requirements for spatial and frequency resolution, interrogation intervals, readout time, noise suppression, system size and cost, and other parameters. This paper will discuss different fiber optic sensor configurations and suitable readout strategies to meet the requirements of the sensing application.

Disbond detection in a composite honeycomb structure of an aircraft vertical stabilizer by fiber Bragg gratings detecting guided ultrasound waves

“…The next stage builds on the measured PZT responses by substituting the PZT receivers with a fixed array of fiber optic transducers, and instead of moving the receiver along the surface to different points, several fiber transducer locations in a single strand of fiber, when in contact with the test surface, acquire position-sensitive responses covering the entire area to be investigated. Fiber optical Bragg grating transducers [16][17][18][19][20][21][22] are well-known spectrally selective optical elements intrinsic to optical fiber, (spectral plot of 19 shown in Figure 4) that are extremely sensitive to physical changes such as temperature and strain. However, this extreme strain sensitivity is also challenging when dynamic ultrasound displacements four orders of magnitude smaller than large static effects are to be measured.…”