1991 Multiplexing fiber Bragg grating sensors英文电子资料.pdf

Invited Paper Multiplexing fiber bragg grating sensors ww. Morey, J.R. Dunphy, and G. Meltz United Technologies Research Center East Hartford, CT 06108 ABSTRACT Bragg reflection gratings and out—coupling taps for sensors can be written holographically within the core of many commercial fil,ers available today. The gratings appear tobe permanent and have been tested to temperatures in excess of 500°C. Quasi-distributed temperature, strain, pressure, chemical, and interferometric type sensors can be made with the wavelength selective, reflection gratings and taps. The fiber gratings, and the different types of sensors they can make, conveniently lend themselves to WDM, 1DM, and FDM types of multiplexing schemes. Instrumentation to detect the multiple sensors and measure their spectral shift for localized and quasi-distributed sensing is currently under develop- ment. 1. INTRODUCTION Permanent holographic grátmgs have been written in many commercial optical fiber types that have germania doped cores. These include the standard telecommunications fibers, polarization maintaining fibers, bend insensitive or pay out fibers, and rare earth doped amplifier or laser fibers. The gratings are made with a technique using interfering beams of Uv laser illumination on the side of the fiber12. A periodic modulation of the index of refraction is produced in the ger- mania do