Modeling, design, fabrication, and testing of a fiber Bragg grating strain sensor array.

Area of Science:

• Fiber optics
• Optical sensing technologies
• Strain measurement systems

Background:

• Traditional strain measurement methods can be limited in scope and accuracy.
• Fiber Bragg Gratings (FBGs) offer a promising alternative for precise strain detection.
• Coherent Optical Frequency Domain Reflectometry (C-OFDR) provides high-resolution interrogation capabilities.

Purpose of the Study:

• To model, design, simulate, fabricate, calibrate, and test a three-element fiber Bragg grating array (FBGA) using C-OFDR.
• To validate the system's performance against established electric strain gauges (ESGs).
• To demonstrate the efficacy of the transfer matrix method for system-wide FBGA-C-OFDR modeling.

Main Methods:

• Utilized in-house software with transfer matrices for FBGA-C-OFDR system simulation.
• Fabricated the FBGA by imprinting the design into photosensitive fiber using the phase mask technique.
• Employed a fiber optic Fabry-Perot interferometric (FPI) strain gauge calibrator for nondestructive FBG calibration.
• Tested the FBGA on a cantilever beam, interrogating with a tunable laser and verifying with ESGs.

Main Results:

• Achieved a peak strain error of 18% when comparing FBGA measurements to ESG data.
• Demonstrated good agreement between simulation predictions and experimental outcomes.
• Successfully calibrated the FBGA using a nondestructive FPI method.

Conclusions:

• The developed FBGA system interrogated with C-OFDR is a viable method for strain measurement.
• The transfer matrix method provides an effective system-wide approach for modeling such optical sensing systems.
• Further validation and refinement can enhance the accuracy and applicability of this FBGA-C-OFDR technology.