Advanced Optical Fiber Sensors for Linear and Angular Displacement
Creators: name: Zubia, Gorka
name: Zubia, Joseba
name: Durana, Gaizka
name: AMOREBIETA HERRERO, JOSU
Publisher: name: University of the Basque Country UPV/EHU
Year: 2025
Subjects: subject: Optics and Photonics
subject: Optics and Photonics/instrumentation
subject: Photons
subject: Optics
subject: Fibre optics
subject: Fiber Optic Technology
subject: Optical Fibers
subject: Sensors
subject: Optical sensors
subject: Optical Rotation
subject: photonic devices
subject: Mathematical physics
subject: Mathematical model
subject: Mathematical analysis
subject: Mathematical Computing
subject: Structural engineering
subject: Structural health monitoring
subject: Instrumentation
subject: Aerospace engineering
subject: Aircraft/instrumentation
subject: Aeronautical engineering
subject: Control measure
subject: Control engineering
subject: Sensor
subject: tip clearance
subject: tip timing
subject: photonics

description: A thesis submitted in partial fulfillment for the degree of 

Doctor of Philosophy 

in the Bilbao School of Engineering UPV/EHU. 

Applied Photonics Group. February 2025.

Industry 5.0 calls for photonic solutions that gather precise, real-time measurements under intense heat, vibration, and electromagnetic fields. Conventional electronics struggle here, often succumbing to interference or limited durability. This dissertation overcomes that gap by developing intensity-based optical fiber displacement sensors (OFDS) that measure linear and angular displacements with high accuracy, extended range, and minimal dead zones.

This research closes the loop on OFDS design by uniting theoretical modeling, simulation, and hands-on fabrication. First, a brute-force methodology mapped a broad range of geometries, revealing surprising flexibility even under tight manufacturing tolerances. Next, a concise toy model distilled complex photonic interactions into three key equations—greatly reducing computational overhead while preserving sub-1% agreement with experiments. Building on these insights, we engineered tetra- and pentafurcated OFDS prototypes with extended linear ranges (up to 10.49 mm) minimal dead zones (2.50 mm) and high sensitivity (2.20 mm−1), validated experimentally at a mean square error of 0.25%.

Finally, we introduced a heptafurcated optical fiber displacement angular and linear sensor (OFLADS), integrating concentric fiber rings for linear sensing with cross-arranged fibers for angular detection. This single, compact bundle simultaneously measures distance and tilt angles (±15º) without bulky optics or intricate alignment. Prototypes confirmed theoretical predictions, underscoring the viability of the sensor for demanding aero-engine applications.

By merging rigorous modeling, efficient design strategies, and empirical testing, this dissertation surpasses state-of-the-art OFDS limitations and completes the circle from conceptual frameworks to fully operational, multi-parameter photonic sensors. The path ahead includes further miniaturization, broader angular detection, and integration with cutting-edge photonic platforms—solidifying OFDS as a key enabler of next-generation aerospace and industrial systems.