The primary aim of this issue of MRS Bulletin is to present an overview of the deployment of optical-fiber sensors in a selected range of applications. The topics covered include a general introduction to optical fibers; a review of the sensing mechanisms that are available to monitor strain, temperature, pressure, chemical species, damage, and acoustic emission; and the use of optical-fiber sensors in medical applications. This introductory article presents a brief discussion of the advantages and disadvantages of optical-fiber sensors.

Optical-fiber sensors based on fiber Bragg gratings (FBGs) provide accurate, nonintrusive, and reliable remote measurements of temperature, strain, and pressure, and they are immune to electromagnetic interference. FBGs are extensively used in telecommunications, and their manufacture is now cost-effective. As sensors, FBGs find many industrial applications in composite structures used in the civil engineering, aeronautics, train transportation, space, and naval sectors. Tiny FBG sensors embedded in a composite material can provide in situ information about polymer curing (strain, temperature, refractive index) in an elegant and nonintrusive way. Great improvements in composite manufacturing processes such as resin transfer molding (RTM) and resin film infusion (RFI) have been obtained through the use of these sensors. They can also be used in monitoring the “health” of a composite structure and in impact detection to evaluate, for example, the airworthiness of aircraft. Finally, FBGs may be used in instrumentation as composite extensometers or strain rosettes, primarily in civil engineering applications.

Acoustic emission (AE) is used as a means to anticipate the mechanical failure of critical materials and structures by detecting the release of energy caused by material rearrangement at the microlevel. Optical-fiber sensors have potential advantages over conventional tuned piezoelectric transducers and signal-processing methods for the detection of such types of ultrasonic acoustic wave events. A number of fiber Bragg grating techniques are presented, which in particular offer the potential to provide the high-speed signal processing and ability to multiplex numbers of AE sensors necessary to detect, quantify, and locate AE sources and thereby determine material properties and damage.

This article provides an overview of the field of optical-fiber sensing, including a brief introduction to the properties of optical fibers that make them suitable for material characterization and monitoring. Some of the recent developments in the field are described, with an emphasis on Bragg grating sensors, multiplexed systems, and chemical sensing, as well as the new field of microstructured fiber.

Optical-fiber sensors can be placed on the skin or inside the human body for the direct measurement of biomedical parameters. This article presents an overview of the most recent applications of optical-fiber sensors for biomedical purposes and those currently under development.

This article gives a brief review of advances in optical-fiber temperature and pressure sensors. Developments over the last two decades have seen enhancements in utility and performance, as more advanced techniques are applied. Applications to industrial problems are highlighted.

This article presents a review of optical-fiber-based process-monitoring techniques that can be used to track the chemical reactions that take place during the processing of materials, with specific reference to thermosetting resins. The techniques covered include quantitative process-monitoring methods based on near and mid-infrared, Raman, UV–visible, evanescent wave, and fluorescence spectroscopy. The basis for refractive-index-based process monitoring using optical fibers is also presented. The techniques described here can be readily applied to other classes of materials and other areas of interest such as aging and degradation. Recent advances in noncontact process monitoring are also presented.