Abstract
Sapphire fiber Bragg gratings (SFBGs) have attracted growing interest for high temperature sensing in harsh environments, yet their interrogation typically relies on optical spectrum measurements, demanding a high-resolution optical spectrum analyzer (OSA) that is bulky, expensive, and constrained in acquisition speed. Moreover, the inherently multimode nature of sapphire fiber further complicates spectrum-based demodulation, thereby limiting the achievable sensing resolution. In this paper, we propose and experimentally demonstrate a microwave-photonic interrogation approach for SFBG sensors. Instead of measuring the optical reflection spectrum, the complex frequency response in the microwave domain of an SFBG is acquired using a vector network analyzer (VNA) via a dispersive wavelength-to-delay mapping framework, followed by time-domain analysis to retrieve the sensing information. By applying an inverse Fourier transform and an energy-quantile delay estimator, temperature-induced Bragg wavelength shifts are robustly converted into measurable time shifts, even in the presence of multimode-induced spectral distortions. Temperature sensing from room temperature to 1050°C is experimentally validated, yielding a sensitivity of −0.0208 ns/°C at room temperature and a resolution of 0.02°C, corresponding to an approximately 20-fold improvement relative to a typical OSA-based interrogation. The proposed technique enables accurate frequency-time-domain demodulation without high-resolution optical spectrum acquisition and offers a practical route toward high-performance SFBG sensing systems.
Recommended Citation
R. Jie et al., "Sapphire Optical Fiber Bragg Grating Sensors Based on Dispersive Microwave-photonic Frequency-Time Domain Analysis," Journal of Lightwave Technology, Institute of Electrical and Electronics Engineers; Optica Publishing Group, Jan 2026.
The definitive version is available at https://doi.org/10.1109/JLT.2026.3686929
Department(s)
Electrical and Computer Engineering
Publication Status
Early Access
Keywords and Phrases
fiber Bragg grating; microwave photonics; Optical fiber sensing; sapphire fiber
International Standard Serial Number (ISSN)
1558-2213; 0733-8724
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2026 Institute of Electrical and Electronics Engineers; Optica Publishing Group, All rights reserved.
Publication Date
01 Jan 2026
