Invited Speakers

Abstract of Invited Speech

Gases turn out to be a very attractive medium for optical fibre sensing, showing highly flexible possibilities though widely unexploited so far. Thanks to the advent of low-loss hollow core fibres a new era opens for fibre sensing, exploiting the unprecedented potentialities of fluidic media like gases. Unmatched Brillouin gains can be achieved, offering a dreamful platform for high performance sensing with specific response. For instance Brillouin sensing turns strain-insensitive and therefore responds only to temperature with enhanced accuracy. Other perspectives are foreseen through thermodynamic phase transitions using specially designed fibres, opening many new avenues for simple sensing schemes and offering a bright refreshed future to optical fibre sensors.

Abstract of Invited Speech

It is well known that ultrasound waves can be generated within the volume or at the surface of a 3 dimensional specimen by illuminating a light with the help of photoacoustic effect. In general, the excited ultrasound waves are detected point-by-point with a conventional acoustic transducer. However, the contact feeling of the ultrasound wave with the conventional acoustic transducer needs harsh impedance matching and laborsome mechanical scanning to get 3 dimensional information. In this work, we present the method that can see the ultrasound wave, without contacting, that reaches to the surface of the specimen. The instantaneous moments of the traveling ultrasound wave are captured in a page-by-page mode by utilizing the digital holography and a short pulse laser. By analyzing the images of digital holography, the full-field information of the ultrasound wave could be extracted, so that the original distribution of the targets, located within the specimen and generating the ultrasound wave, could be reconstructed. In a world, the traveling ultrasound wave can be captured and released on our own will. We can find its applications not only in biomedical imaging and diagnostic but also in the remote sensing in harsh environment such as high voltage or high radioactive.

Abstract of Invited Speech

Time-expanded phase-sensitive OTDR makes use of a methodology inspired in dual comb spectroscopy to implement an efficient spectral downconversion (i.e., a time expansion) of the optical traces retrieved from a Rayleigh backscattering process. This approach enables dynamic interrogation of strain or temperature in optical fibers with high spatial resolution (in the cm range) requiring low photodetection and acquisition bandwidths (in the MHz regime or below). In this communication, we review the principles of operation and our latest advances in the development and application of this recent distributed sensing technique.

Abstract of Invited Speech

Distributed acoustic sensing (DAS) is a powerful tool for monitoring environment around optical fibers. DAS based on phase OTDR has the advantages of long measurement distance and high sensitivity. For the practical application of the phase OTDR DAS, field tests using optical fibers laid for telecommunication are intensively conducted. However, because the phase OTDR suffers from problems such as the occurrence of sensitivity dead points, waveform distortion, and the tradeoff between fiber length and vibration sampling rate, countermeasures to them must be included in the implementation of the phase OTDR as needed. In this paper, we present our recently developed countermeasures based on optical frequency multiplexing — seemingly established but still improving methodology. We show the principle as well as the results of the application to field tests with the perspective of telecommunications carrier.

Abstract of Invited Speech

The resonant fiber optic gyroscope (RFOG) is a competitive candidate because of its potential in both miniaturization and high performance. In RFOG, the rotation induced Sagnac effect behaves as the resonant frequency deviation of the two counter-propagating lightwaves. Traditionally the resonant frequencies are tracked by narrow linewidth lasers with two or more feedback control loops, making the system complex and fragile. Recently we developed a white-light multi-beam interferometry technology, in which the resonant sensor is regarded as a comb filter, and a low coherence light source is employ to detect the resonant frequency deviation from the whole spectrum of the comb filter instead of tracking single resonant frequency. The readout system has ultra-simple structure by avoiding laser frequency control loops, and can achieve high resolution by effective suppression of parasitic noises. Based on the proposed technology, the first navigation-grade RFOG is realized and its performance is continuously improved. The white-light multi-beam interferometry can be adopted in other types of resonant fiber optic sensors with high resolution. As an instance, femto-strain level resolution is achieved when it is used in dynamic strain sensing.

Abstract of Invited Speech

Optical fibre sensors have demonstrated excellent potential for radiation dosimetry, due to their small size, high sensitivity, immunity to electromagnetic interference and remote sensing capability. However, there are also several challenges that need to be addressed before they can be widely adopted in radiation environments. This is particularly true for applications in radiotherapy dosimetry, where accurate and reliable measurements are essential for ensuring the quality and safety of radiotherapy. The low doses, wide ranging dose rates and varying radiation energies, associated with radiotherapy all compound the complexities of dosimetry in this application area. We will present our latest advances in optical fibre sensors for radiation dosimetry, with a particular focus on radiotherapy dosimetry, and discuss the main challenges and opportunities for improving patient outcomes.

Abstract of Invited Speech

Optical fiber shape sensing are important measurement technologies in applications such as healthcare, structural monitoring and robotics. Current state-of-the-art optical fiber shape sensing requires complex sensor structures and interrogation systems. We recently demonstrated that the multimode fiber (MMF) output speckles contain its geometric shape information of the MMF itself. In this talk, we will introduce our recently progresses made by us in this direction, including using machine learning in a proof-of-concept 3D multi-point deformation sensing via a single MMF, and soft waveguide based shape sensing. Our results show that a single MMF based deformation sensor possesses the advantage in terms of system simplicity, resolution and sensitivity, and has the potential in deformation monitoring or shape-sensing applications.

Abstract of Invited Speech

Integrated optics is raising interest in the advancement of emerging technologies, including machine learning and quantum information processing. In this regard, programmable photonic circuits and on-chip devices provide a promising tool for making these technologies viable, as they allow performing multiple functions simultaneously at high speeds and on low foot-print frameworks. In our work, we make use of integrated programmable photonic devices to implement high-speed and secure communication in both classical and quantum domains at telecom regimes.

Abstract of Invited Speech

We report a simple and reproducible method to transfer semiconductor membranes on the top of single- and multi-mode fibers, enabling a variety of temperature, refractive index and optomechanical sensors. We also describe a novel readout approach based on integrated multispectral chips.

Abstract of Invited Speech

This lecture presents an overall picture pertaining to the “Lab on Fiber Technology” vision, illustrating the main aimed to set the foundational basis towards novel fiber optic assisted optrodes integrated in the working channels of medical needles, catheters and nano-endoscopes to advance diagnostics and therapy in precision medicine. Main achievements in the identification of nano-fabrication strategies properly working onto not conventional substrates as the case of optical fibers are here collected and discussed. Novel approaches arising from the judicious synergy nanotechnology and optical fibers to push light matter interaction towards its ultimate limit are here critically reviewed. The lecture also provides an overall picture of the perspectives and the challenges that lie ahead the development of Lab on fiber assisted intelligent needles for in vivo liquid and tissue biopsy as well as loco regional drug delivery for precision medicine applications.

Abstract of Invited Speech

The brain utilizes approximately a quarter of the body’s oxygen uptake to support neural activities, and balance between oxygen supply and consumption is crucial for the brain. Therefore, cerebral oxygenation imaging is essential for assessing brain function, identifying brain injuries, and enhancing cerebral outcomes in intensive care medicine. Head-mounted microscopes are preferable for imaging cerebral processes in freely moving rodents, e.g., mice, because brain activities can vary significantly between stationary and freely-moving states. In this talk, we report the development of a head-mounted photoacoustic fiberscope for cerebral oxygenation imaging in a freely behaving mouse. The fiberscope uses a highly sensitive fiber optic ultrasonic sensor to detect ultrasound waves generated by the brain tissue excited by a rapidly scanning pulsed laser beam. The fiberscope can continuously monitor cerebral oxygenation processes at the single-vessel resolution, showing cerebrovascular responses to external stimuli. For example, it can visualize enhanced oxygenation regulated by the cerebral vessels to compensate for hypercapnia when subjected to high-concentration CO₂ respiration. The small-sized, flexible imaging modality shows promise in neuroscience studies, detecting brain injuries and quantifying microcirculation status.

Abstract of Invited Speech

In the last decades, fiber optics has significantly grown in the field of sensor applications, mainly because of maturity reached by optical fibers for telecommunications and because of Fiber Bragg gratings development. Moreover, with the introduction of time domain and frequency domain reflectometry techniques, optical fibers have become a reliable platform of distributed sensing for long-distance application such as civil and industrial structural monitoring. In contrast with long-distance applications, the fields of biomedical applications and biosensing, which need compact and spatially dense sensor network, offer a less-developed platform for exploring optical fiber sensors innovative potential. In this context, optical fibers present advantages in terms of compactness, electromagnetic compatibility, biocompatibility, sensitivity, and multiplexing capability with respect to other sensing technologies. The possibility of optical fibers to precisely measure temperature and strain, combined with the capability of millimetre scale distributing sensing and high-level of sensors multiplexing, has paved the road for innovative applications such as 3D temperature monitoring during cancer thermal ablation and precise shape sensing of medical tools, catheters, and needles. Furthermore, optical fibers, modified with simple micro-fabrication such as tapering and etching, can become powerful refractive index sensors, suitable for building highly sensitive, compact, and cost-effective biosensors. Here, we aim to explore advancements and present future developments of fiber optics applied to biomedical application and biosensors fields.