The input broadband, flat spectrum in a multimode fiber becomes multiresonant on output (bottom), enabling the extraction of multiple parameters from wavelength-shift measurements of many resonances (top).
Optical-fiber sensors have become hugely successful for measuring temperature and strain—in both distributed and quasi-distributed applications, continually and over long distances. Today, Rayleigh, Raman, Brillouin and Bragg refer not only to eminent scientists but to the physical principles on which most sensing modalities are based. These, in turn, form the core business of small and large companies worldwide. Tall buildings, bridges, ships and airplanes—as well as volcanoes, ocean floors and pipelines—are now wired optically to monitor important safety, maintenance and operating parameters. Medical applications have also increased in recent years, mainly for localized pressure and temperature measurements of bodily fluids.