High-density fiber Bragg grating array enabling fully distributed sensing with sub-millimeter spatial resolution

Distributed, cost-effective sensing with sub-millimeter spatial resolution remains critical and yet challenging for a wide range of industries, including aerospace, biomedical engineering, and additive manufacturing. In this Letter, we propose and experimentally demonstrate a novel staggered contiguous cladding fiber Bragg grating (SC-CLFBGs)-array-based fully distributed sensing configuration. As a proof of concept, a spatial resolution of 800 μm over a total sensing length of 1.04 cm is realized based on an FBG array fabricated by femtosecond (fs) laser direct inscription. To the best of our knowledge, this marks the first demonstration of fully distributed FBG sensing with sub-millimeter resolution by eliminating the dark zones in conventional FBG array compatible with standard spectral interrogators. The experimental validation confirms the excellent performance and thermal resilience of the proposed FBG array at temperatures up to 710°C without any observed hysteresis, establishing its suitability for high-temperature environments. A maximum temperature sensitivity of 15.17 pm/°C was recorded. This approach opens up a cost-effective and straightforward route for realizing sub-millimeter spatial resolution with enhanced signal fidelity, making it highly promising for advanced sensing applications in demanding fields.