Dear Colleagues,

Optical fiber sensors (OFSs) are sensors that uses optical fibers for the purpose of detecting and measuring physical parameters. They have become attractive after decades of development due to their unique immunity to the electromagnetic field, the fact that they can be easily multiplexed on a large scale, their high sensitivity, their fine and soft geometric structure, etc. OFSs and related sensing techniques play an important role in the age of data-driven artificial intelligence (AI) and the Internet of Things. Market demand and advances in techniques such as light manipulating, fiber fabricating, and signal processing have driven the development of OFSs and related sensing techniques.  This Special Issue aims to present the emerging trends regarding OFSs and sensing techniques in terms of both fundamental research and field applications. In this Special Issue, original research articles on theoretical and experimental advances in OFSs and related sensing techniques are welcome. Review articles summarizing advancements in the field are also welcome. We are pleased to invite researchers to submit their publications to this Special Issue. The topics of interest for this Special Issue include (but are not limited to) the following topics:

• Distributed acoustic/vibration sensing;
• Distributed temperature/strain sensing;
• Hybrid distributed fiber-optic sensing;
• The applications of distributed fiber-optic sensing;
• The application of artificial intelligence to distributed fiber-optic sensing;
• Resonant fiber-optic biochemical sensors;
• Fiber-optic displacement sensors;
• Fiber-optic gas sensors;
• Lossy fiber-optic sensors;
• Fiber-optic point sensor applications.

Dr. Yang Lu
Dr. Qi Wang
Guest Editors

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• distributed acoustic/vibration sensing
• distributed temperature/strain sensing
• hybrid distributed fiber-optic sensing
• applications of distributed fiber-optic sensing
• application of AI to distributed fiber-optic sensing
• resonant fiber-optic biochemical sensors
• fiber-optic displacement sensors
• fiber-optic gas sensors
• lossy fiber-optic sensors
• fiber-optic point sensor applications

Title: Azobenzene Fiber Optics-Based Polarization Control Devices
Authors: Beatriz G. Soares; Susana Silva; Maria Raposo*; Paulo A. Ribeiro; Orlando Frazão
Affiliation: /
Abstract: Currently, optical fiber polarization control devices require the use of bulk components, which often see the light leaving the fiber into air, leading to high recoupling losses. On the other hand, more modular solutions using dedicated high birefringence fibers of the spun Hi-Bi type are of high cost and non-trivial application. Accordingly, the project proposes new optical fiber devicescapable of controlling the polarization state based on thin films of azobenzene compounds. The underlying idea to the project is to make use of the isomerization properties, sensitive to light, around the N=N bond of azobenzene molecules, inducing, thusly, birefringence in the medium. In this way, it is intended to incorporate films of these compounds in optical fiber devices, presenting a new solution for polarization control, which can be utilized in the development of sensors and optical filters.

Title: Polymers Enabling Biomedical Optical Guided-Wave Sensing: From Material Selection to Application
Authors: Nagar Malhar, Davide Janner
Affiliation: Politecnico di Torino
Abstract: Polymer-based optical sensors represent a transformative advancement in biomedical diagnostics and monitoring, owing to their unique properties of flexibility, biocompatibility, and selective responsiveness. This review provides a thorough examination of polymer-based optical sensors, with a prime focus on polymer-coated optical fiber sensors, emphasizing their pivotal role in enhancing the performance and applicability of optical sensing technologies in the biomedical field. Initially, we outline the fundamental operational principles of optical sensors and the significant impact of polymer integration on their functional capabilities. Specific attention is given to the various classes of polymers used, such as biocompatible, hydrophilic, and stimuli-responsive polymers, which impart selectivity, sensitivity, and stability to the sensors. It then discusses various fabrication techniques of polymer coatings and recent innovations in sensor design, including the development of nanostructured polymer coatings that further enhance the interaction between the sensor surface and biological analytes. Applications of these sensors in clinical diagnostics, real-time health monitoring, and minimally invasive surgery are examined, highlighting key studies that demonstrate their effectiveness in real-world medical settings. Challenges such as biocompatibility, sterilization, and integration with existing medical infrastructure are addressed, along with the future outlook of polymer-coated OFS in personalized medicine and wearable technology. By synthesizing the latest research, this review aims to provide insights into the current capabilities and future potential of polymer-coated optical fiber sensors in improving diagnostic and therapeutic outcomes in the biomedical field.