Waveguide-assisted Single-mode Fiber Bragg Gratings in a Highly Multimode Coreless Fiber Via Femtosecond Laser Inscription for Extreme Temperature Quasi-Distributed Thermal Sensing

Abstract

This research reports a potential quasi-distributed thermal mapping optical sensing system for extreme temperatures, leveraging femtosecond (fs) laser inscribed single-mode fiber Bragg gratings (FBGs) and a waveguide within coreless, highly multimode optical fiber, resulting in a single-mode structure. Unlike doped single-mode fibers, coreless fibers composed of silica rods prevent issues associated with dopant migration and ensure data accuracy. The strategic placement of point-by-point FBGs in a cascaded formation on the fs-laser inscribed waveguide facilitates localized multipoint sensing. The long-term stability of the proposed waveguide-assisted FBG system was assessed over 24 hours at elevated temperatures (1000°C), showing no hysteresis during heating and cooling cycles. This approach promotes the use of single-mode waveguide-assisted cascaded FBG systems in extreme temperature environments. The point-by-point FBG writing technique via fs-laser enables rapid inscription compared to the conventional line-by-line method, providing fine control over the grating configuration and ensuring fast bulk production. The proposed device offers comprehensive temperature monitoring suitable for challenging multipoint sensing applications, such as industrial processes operating in extreme conditions.

Department(s)

Electrical and Computer Engineering

Second Department

Materials Science and Engineering

Publication Status

Early Access

Keywords and Phrases

coreless fiber; Femto-laser writing; high temperature sensing; Quasi-distributed thermal mapping; single mode fiber; Waveguide assisted FBG

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

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