Fiber Bragg grating characterization using factorial design.

Area of Science:

• Optical Engineering
• Materials Science
• Experimental Design

Background:

• Fiber Bragg gratings (FBGs) are crucial optical sensors.
• Characterizing FBG responses to multiple environmental stimuli is complex.
• Efficient experimental designs are needed to minimize resource use.

Purpose of the Study:

• To apply a three-variable, two-level factorial design for FBG characterization.
• To assess FBG sensitivities to simultaneous temperature, humidity, and strain.
• To quantify cross-sensitivities between these stimuli for different FBG coatings.

Main Methods:

• Inscribed three uniform FBGs in single-mode optical fiber via interferometric technique.
• Recoated two FBGs with acrylate and polyimide, leaving one bare.
• Utilized a factorial design with eight measurement points to determine sensitivities.

Main Results:

• Computed temperature, strain, and humidity sensitivities with high accuracy.
• Quantified cross-sensitivities between all tested stimuli.
• Achieved temperature sensitivity of ~10 pm/°C and strain sensitivity of ~1.1 pm/µε.
• Determined humidity sensitivity for polyimide-coated FBGs at ~4.47 pm/%RH.

Conclusions:

• The factorial design provides a highly efficient method for FBG characterization.
• Results are comparable to traditional methods, demonstrating design validity.
• This approach enables precise quantification of multi-stimuli responses and cross-sensitivities.