Abstract
In this study, two co-incident sapphire fiber Bragg gratings (SFBGs) were successfully inscribed utilizing a femtosecond (fs) laser to achieve a high fringe contrast interferogram. These two SFBGs employ a unique configuration, one parallel to the center axis, called p-SFBG, and the other forming an angle from the center-axis, called a-SFBG, allowing for simultaneous strain and temperature measurements with low crosstalk. As a proof of concept, p-SFBG and a-SFBG using line-by-line method are characterized, which are shorter in length (i.e., 1.5 mm), producing reflectivity of ~3dB. This effort demonstrates the use of two coincident SFBGs forming an angle of 2.29° between them within an extremely highly multimode sapphire fiber. The p-SFBG exhibits superior strain sensitivity (1.8 pm/μϵ) in contrast to the a-SFBG (0.4 pm/μϵ). Their efficacy was evaluated under applied strains reaching up to 1000 μϵ. Both SFBGs underwent thorough characterization for long-term stability at elevated temperatures, enduring exposure at 1600°C for 24 hours. The novelty of the sensor lies in the fact that a-SFBG exhibits extremely low sensitivity compared to p-SFBG, which plays an important role in eliminating the crosstalk between co-incident SFBGs. This configuration addresses challenges related to temperature and strain crosstalk, facilitating simultaneous measurements via sensitivity matrix in harsh environmental conditions. This achievement represents a significant advancement in the field of optical sensing, paving new avenues for simultaneous temperature and strain measurement, particularly for applications in harsh environments.
Recommended Citation
F. Mumtaz et al., "Discrimination of Temperature and Strain by Characterizing Two Femtosecond Laser-Written Coincident Sapphire Fiber Bragg Gratings for Harsh Environment Applications," IEEE Transactions on Instrumentation and Measurement, Institute of Electrical and Electronics Engineers, Jan 2025.
The definitive version is available at https://doi.org/10.1109/TIM.2025.3548203
Department(s)
Electrical and Computer Engineering
Second Department
Materials Science and Engineering
Keywords and Phrases
Coincident sapphire fiber Bragg gratings; dual parameter sensor; femto-laser inscription; highly multimode waveguide; line-by-line method
International Standard Serial Number (ISSN)
1557-9662; 0018-9456
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 Institute of Electrical and Electronics Engineers, All rights reserved.
Publication Date
01 Jan 2025
