Self-Assembling Vectorial Curvature Sensing System Based on a Single Helix of Polarization-Maintaining Fiber

• Published in: IEEE transactions on instrumentation and measurement Vol. 73; pp. 1 - 11
• Main Authors: Han, Xiaopeng, Hasi, Wuliji, Yao, Yicun, Guo, Ying, Wang, Fan, Lin, Siyu, Zhang, Yundong
• Format: Journal Article
• Language: English
• Published: New York IEEE 2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bending; Composite system; Construction industry; Crosstalk; Curvature; Gas pipelines; harmonic vernier effect; Interference fringes; Low temperature; Mach-Zehnder interferometers; Mach–Zehnder interferometer (MZI); Medical devices; Monitoring; Natural gas; Optical fiber polarization; Optical fiber sensors; Optical fibers; Optical interferometry; Periodic structures; Polarization; Polarized light; Refractivity; Self-assembly; Sensitivity; Sensors; Structural safety; twist; vector curvature sensing; Vectors (mathematics); Wavelength modulation
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2023.3324688

This article presents a novel composite vector bending sensing system capable of switching freely between wavelength and intensity modulation. The fundamental sensing unit of the system depends on an offset rotation twisted Mach-Zehnder interferometer (TW-MZI) with unique refractive index (RI) distribution characteristics proven through experiments. The sensing unit delivers remarkable performance in intensity modulation, reaching a maximum of 18.74 ± 0.01 dB/<inline-formula> <tex-math notation="LaTeX">\text{m}^{-1} </tex-math></inline-formula>. The sensing unit features a nonuniform geometric distribution and utilizes polarization-maintaining optical fibers as its structural material, enabling it to detect the correlation of polarized light and recognize the bending direction. With these advantages, a quasi-parallel distributed curvature sensing system is constructed, integrating a Sagnac interferometer (SI) as the sensing reference arm combined with the TW-MZI sensing unit. Adjusting the interference length and optical power can obtain a first-order harmonic vernier spectrum. Additionally, the envelope differencing technique enhances the interference fringe contrast, reducing the reliance on the monitoring wavelength domain. This combination highlights the composite system's wavelength modulation-based vector curvature sensing capability, achieving a maximum value of 15.59 ± 0.01 nm/<inline-formula> <tex-math notation="LaTeX">\text{m}^{-1} </tex-math></inline-formula>. Moreover, this system exhibits characteristics such as low-temperature crosstalk, high stability, and rapid responsiveness, making it well suited for applications in medical device diagnostics, oil and gas pipeline inspection, and structural safety monitoring within the construction industry.