Since the 1970s, when successful fiber manufacturing started, the scope of utilizing fiber optic technology had expanded, and the infrastructure for optical fiber communications was repurposed for wide-area monitoring, as sensing [1,2]. Fiber optic sensing technology has progressed substantially for decades [3,4]. The possibilities of optical sensing systems have proven themselves in the field starting from structural health monitoring to biomedical areas, owing to their small size, lightweight, electrical insulation, simple embedding technique, and ability to operate in harsh environments and inaccessible locations [2,3,5].

The beneficial properties of fiber optic sensors (FOSs) have long been acknowledged by the biomedical societies and improve their integration to medical fields [6]. Flexibility and high sensitivity make FOSs perfect for robotic manipulators [7,8], tissue palpation during minimally invasive surgery [9], and strain measurements [10]. Portability and immunity to electric and magnetic fields of optical fibers can be advantageous for monitoring physiological activity and treatment procedures during MRI scanning [[11], [12], [13]]. In addition, the ability of fiber sensor to embed into composites allows the monitoring of human activities [14] and the measurement of pressure during the prosthetic treatment [15]. Multiplexing and the possibilities of enhancing the performance of FOSs expand their application for biomedical purposes [16,17]. Providing noninvasiv…

2.1. Distributed fiber sensing

Distributed optical fiber sensing (DOFS) is an optical fiber technology that enables discrete and continuous sensing of measured parameters. It has benefits such as cost reduction by combining a large number of sensing points in one sensor, possibilities of obtaining the profile of physical characteristics, and the ability to obtain real-time measurements [39]. DFOS exhibit numerous benefits when employed in biomedical contexts. Peterson et al. presented on the progression of fiber-optic sensors in the biomedical domain and emphasized the potential utilization of FOS as physical indicators of temperature, pressure, and radiation, as well as chemical indicators of pH, partial pressure of blood gases, and glucose [40]. Tosi et al. accentuates the primary fiber optic sensing technologies that attain a limited spatial resolution and their impact on biomedical applications [37]. These applications include monitoring of thermo-therapies, diagnostics highly concentrated sensing points, needle and catheter monitoring, smart textiles, and other emerging fields of application. The papers collectively prove the beneficial characteristics of DFOS for biomedical purposes. These benefits include exceptional sensitivity, compact, minimally invasive design, the capacity for achieving high spatial measurements, remarkable flexibility, immunity to electromagnetic interference and possibiliti…

3.1. Thermal mapping in thermal ablation applications

Minimally invasive thermal ablation procedures are required for both precise temperature distribution and measurement over a specific length in real-time. The objective is to remove solid tumors by changing the localized temperature propagation, while not affecting the surrounding healthy biological tissues. Both temperature and exposure duration are the characteristics that directly affect the mortality rate of target tissues. Protein coagulation, which indicates the instantaneous death of target cancer cells, occurs either at cytotoxic temperatures of 43-45 °C in under 30-60 min, at 52 °C in 60 s, or at above 60 °C in few seconds. This shows there is steep reduction of time required to ablate target cells, thus maintaining the exact values is vital [[74], [75], [76]]. There are many thermal treatment procedures, as invasive thermal processes, hyperthermal planning. Although thermocouples are common invasive sensors, they are not reliable due to the slow response time, insufficient density of measurements, and limitation to the peripheral readings [77]. These tools have a low standard accuracy of about 1 °C, which may still be degraded with the occurrence of temperature overestimation or underestimation caused by the physical properties [78]. The advancements of computer-aided technology, Hyperthermal Treatment Planning (HTP) tools, has been towards improving e…