Free Space Optical Coupling to Embedded Fiber Bragg Grating Sensors through Panel Surfaces

摘要

In recent decades, optical fiber has proven useful for many sensor applications. Specifically, fiber Bragg grating (FBG) sensors have shown great utility for integrity management and environmental sensing of composite structures. One major drawback of the application of FBG sensors, however, is the lack of a robust, non-"pigtail" technique for coupling the embedded FBG sensor to an external optical interrogation device. In this paper, a novel method of free space passive coupling of light into FBG sensors has been investigated. Angled 45-degree mirrors integrated directly into fibers were used as input coupling technique. Due to the difficulty of directly coupling to single mode fiber, we have explored a novel method of coupling to the sensor via splicing and fusing an angle-polished multimode fiber to a single mode FBG. Finally, we employed this coupling method in a strain test of an embedded FBG sensor.