SELF-POWERED FIBER BRAGG GRATING SENSORS

Fiber Bragg gratings (FBGs) are key components for optical sensing and communication. Traditionally, fiber grating sensors were purely passive, but recent developments have been made to allow active tuning of these sensors. These tuning methods, though effective, are often bulky, cumbersome, and expensive to package. This thesis demonstrates an approach for tuning in-fiber Bragg grating sensors by optical energy carried by the same optical fiber. Optical energy carried by optical fiber was used to heat in-fiber Bragg gratings to alter grating response to surrounding media. This tuning technique requires no external actuation or expensive packaging. Through the use of a simple metallic film and the delivery of high power laser light to the grating, 'active' tuning is obtained.</br>Two applications are demonstrated where self-powered FBG technology is applied to a level sensor capable of measuring discrete liquid levels as well as a vacuum sensor, with sensitivity into the milli-torr range. These sensors are also a demonstration of the networkability of FBG sensor arrays, allowing for large multipoint sensor networks. In addition, both sensors have dual functionality, being capable of sensing local temperature in addition to vacuum and liquid levels. These sensors are comparable or better than most MEMS and fiber based technology. Optical fiber in both these applications serves as a conduit for both signal-carrying light as well as power light, used to tune the gratings. This new self-powered FBG-based technology provides an innovative solution to fiber sensing, allowing design of versatile sensors without compromising their intrinsic benefits. Not only does the one-fiber solution provide lower design costs by utilizing a single feed through, but it also boasts simple packaging, long lifetime, reliable operation in harsh environments, and immunity to electromagnetic fields