<title>Advances In Optical Fiber Sensors</title>

Abstract

AbstractOver the past several years, a new non -communication optical fiber application hasemerged. This application utilizes optical fibers for sensing. Initial interest centeredaround rate rotation sensing. Since that time, however, acoustic, magnetic, and tempera-ture sensing utilizing optical fibers has evolved into a viable research effort with sig-nificant potential payoff. As an example, laboratory fiber optic acoustic sensors nowrival the best sensitivity obtained with piezoelectric ceramics. These sensors possess aunique geometric versatility previously unavailable. In conjunction with the DefenseAdvanced Research Projects Agency (DARPA), the Navy has begun a Fiber Optic Sensor System(FOSS) program to develop associated technology necessary to realize these sensors.Substantial effort is ongoing at the Naval Research Laboratory (NRL) and other Navylaboratories with considerable contractual effort from universities and industry. Thispaper reviews the status of the FOSS program.IntroductionInitial fiber sensor efforts concentrated on rotation rate sensing.' Acoustic,2magnetic,3 and temperature field sensors utilizing optical fibers are now under intenseinvestigation. Threshold detectabilities of laboratory optical- fiber -acoustic sensorsrival the best piezoelectric devices. For magnetic field sensing the potential fordetecting on the order of 10 -11 to 10-12 G appears possible. That detectability rivalsthe best conventional magnetometers. Optical fiber accelerometers with sensitivities inthe sub pg range also appear feasible.4 Thus fiber optic sensors appear to be extremelycompetitive with conventional devices.Fiber interferometerConsider a typical Mach -Zehnder configuration for an optical fiber sensor (Fig. 1).