Equivalent Broadband Optical Frequency Domain Reflectometry via Multiband Laser Injection and Signal Stitching for Distributed Fiber Sensing

Optical frequency domain reflectometry (OFDR) distributed optical fiber sensing technology has become a critical technique for structural health monitoring due to its exceptional spatial sensing resolution. Current state-of-the-art OFDR sensing systems predominantly use external-cavity tunable lasers (ECTLs) as their light sources to detect the Rayleigh backscattering spectra (RBS) over wavelength ranges spanning several tens of nanometers. However, the significant challenges posed by ECTLs in terms of size, weight, power consumption, and cost (SWaP-C) have constrained the large-scale industrial deployment of OFDR sensing technology. This study introduces a novel multiband multiplexed OFDR distributed optical fiber sensing approach that replaces the conventional single-shot optical frequency modulation light injection detection strategy with time-division segmented spectral detection. Both theoretical analyses and experimental validations demonstrate that sensing capabilities equivalent to those of ECTLs can be achieved via this sequential spectral acquisition approach. To implement this methodology, the correlation of the RBS from a characteristic fiber segment (CFS) within the optical frequency overlap region of the main interferometer is used to determine the stitching positions of adjacent frequency band measurement signals, enabling precise picometer-level wavelength stitching. By adopting a commercial distributed feedback (DFB) laser array as the system’s light source and using segmented modulation with precision stitching, an RBS detection range of 35.013 nm is achieved, and has the potential for further expansion. Leveraging this architecture, an OFDR distributed optical fiber sensing system is developed, and it demonstrates an 8-mm spatial sensing resolution and a 10 000- \mu \varepsilon measurement range. This innovative approach provides a new design paradigm for OFDR systems. The proposed OFDR distributed optical fiber sensing system demonstrates performance metrics comparable to those of conventional systems while offering significant advantages in terms of SWaP-C, holding significant promise for advancing the industrialization of this technology.