A discussion was held at the Institute of laser for Postgraduate Studies at the University of Baghdad to discuss the doctoral dissertation titled “multi-parameter optical fiber sensor based on graduated and tapered fibers with a hybrid core structure” by doctoral student Sura Hussein Mahmoud. The dissertation was conducted under the supervision of Professor Dr. Abdul Hadi Mutshar Abd and Assistant Professor Dr. Sarah Kazem Al-Hayal.
The objective of the research was to develop and investigate a fiber optic sensor utilizing top-down (UDT) heterogeneous fiber structures to enable simultaneous parameter measurements at spatially coupled locations. This involved the fabrication of two heterogeneous fiber structures, denoted as sensing structures A and B, by incorporating a section of non-core fiber (NCF) with lengths of 45 and 60 mm between two standard single-mode fibers (SMF). The UDT heterogeneous fiber structure was created by introducing a bottom taper between two adjacent tapers in the NCF section using the over-splicing method. The upper double tapers served as a fiber splitter/collector, while the lower double tapers acted as an optical attenuator.
The proposed dual point sensing head, comprising sensing points A and B, was designed by cascading the two sensor structures A and B to generate two separate interference drops and achieve wavelength division multiplexing. Experimental results demonstrated that the dual-point sensing structure enabled independent and simultaneous sensitivity to different parameters at sensing points A and B. The fabricated sensor was utilized to measure parameters such as paracetamol concentration, pH, and refractive index, showcasing its capability to monitor multiple parameters concurrently at separate locations. Overall, the study highlighted the potential of these cost-effective sensors in achieving high-performance measurements of diverse properties.

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