Building a low-cost strain sensor prototype using fiber Bragg gratings with resonant cavity light emitting diodes

Abstract

This project demonstrates the prototype of a low-cost strain sensor by directly coupling light from a resonant cavity light emitting diode into a single mode fiber with a fiber Bragg grating and detecting the transmitted light using a fiber-coupled photodiode. While most strain sensors use expensive techniques for measuring the spectral shift in the reflected or transmitted light from the fiber Bragg grating, such as optical spectrum analyzers or spectrometers, this project demonstrates the use of a silicon photodiode for detection. We measure the coupling efficiency between the resonant cavity light emitting diode and single mode fiber, showing that it is more efficient than coupling between a surface emitting light emitting diode and a single mode fiber. We demonstrate a proof-of-concept strain sensor using these low-cost components that has a detection limit of approximately 100 µε. This work could help enable a new application space for fiber-based sensors where many inexpensive sensors are needed, such as distributed sensing networks.