We present distributed Brillouin measurements realized in a commercially available graded-index few mode optical fiber. The measurements were performed using a Brillouin Optical Time Domain Reflectometer instrument coupled with an industrial multiplexer designed for the multimode fiber, enabling the characterization of 15 Hermite-Gaussian modes of the multimode fiber. The low intermodal crosstalk observed allowed for reliable measurements even in the absence of the multiplexer. Preliminary results of temperature Brillouin frequency coefficient are also presented.

Ubiquitously used for monitoring pipelines and infrastructures, distributed fibre-optic acoustic sensing is becoming an emerging technology for earthquake monitoring thanks to the possibility to interrogate a large vast of distances with a dense number of sensing points in which an optical fiber cable can be retrofitted. Moreover, it can also be used as a tool by geophysicists for the characterization of subsurface elements, such as rocks, faults, and geological structures before excavation work. In this work, we present two applications where DAS technology can contribute to assess rock properties during passive (in a mining site) and active (in a lake) seismic surveys. In both cases, seismograms generated from DAS measurements were comparable to those measured by traditional receivers, paving the way towards their use for assessing rock quality during surveys.

Functional coatings on optical fibers enable selective detection of environmental and chemical parameters, but their use is typically limited to point or quasi-distributed sensing due to localized deposition techniques. In this work, we demonstrate a possible transition towards full-length functional coatings on optical fibers using a draw tower process, enabling their potential use in distributed sensor technology. An optical fiber with Pt:WO<inf>3</inf> nanocomposite polymer functional coating is employed as a proof of concept. The results demonstrate the successful application of this functional coating along hundreds of meters of fibers using a draw tower. When integrated into a distributed sensing configuration, the Pt:WO<inf>3</inf> fiber exhibited a clear change in response with varying hydrogen concentrations from 1% to 4% H<inf>2</inf>, with a temperature increase of 2.5 °C at 4 vol.% indicating a promising performance for distributed hydrogen leak detection. This approach opens new opportunities for applying other functional coatings over extended fiber lengths using draw towers, which could be exploited for novel distributed sensing applications

The paper describes the fabrication of two nanocomposite (NC) coated optical fibers, and their use to enhance the capabilities of distributed fiber sensing. The fibers are produced in a conventional optical fiber draw tower. NC coated fibers with reduced graphene oxide were shown to have enhanced mechanical durability at elevated temperatures and have a low humidity sensitivity compared to standard polyimide coated fibers. NC coated fibers with hydrogen-sensitive materials were shown to enable distributed hydrogen leak detection, in a configuration that is scalable to long lengths.

A new, modular approach to fibre-optic sensing is presented, where different types of optical fibres and other wires are combined to compact, hybrid cable assemblies, customized for each application. These fibre-optic assemblies can be embedded or integrated in various settings, enabling multi-parameter sensing and the measurement of new parameters. In this work, we describe the fabrication process of these miniature, multi-functional cables and how it can be directly used for sensing purposes in 3 end-user inspired applications.

Fiber Bragg Gratings (FBGs) were used to monitor the manufacturing process and the operation of high voltage bushings. During operation, temperatures at several points inside the bushing were monitored. In another test, during bushing manufacturing, FBGs monitored the filling and curing process of the epoxy in Resin Impregnated Paper (RIP) bushings. Traditionally, temperature measurements inside the bushing core have been performed using thermocouple probes and only in bushings for research, not final products. The use of appropriate FBGs was successfully tested in the harsh environments of operation (under high voltage) as well as in manufacturing (high curing temperature and stress). The results demonstrate the potential of fiber optics to study and improve production methods. The study also shows that fiber optics are suitable for long-term monitoring during bushing operation.

Polymer coating layers are essential for the handling and proper function of optical fibers in their service environment. The analysis and monitoring of the elastic characteristics of coating layers are important for materials research and development, quality assurance, and maintenance. Most measurement protocols are destructive, require specialty samples, and may only be carried out offline. In this work, we monitor the velocities of dilatational acoustic waves in several coating layers of standard fibers, using forward Brillouin scattering processes. The measurements are non-destructive and performed over working fiber. Velocities are measured in three polyimide-based coating layers as functions of temperature up to 220 °C. Thermal changes in velocity are identified with 1% precision. The results suggest that the incorporation of nanoparticles within the polymer coating matrix improves its thermal stability.

Dynamic storage of qubits is crucial for quantum communication networks. Here we present an adjustable buffer capable of storing photonic polarization quantum states in a fiber loop controllable by a poled fiber modulator

Dynamic storage of qubits is crucial for quantum communication networks. Here we present an adjustable buffer capable of storing photonic polarization quantum states in a fiber loop controllable by a poled fiber modulator.

An all-fiber setup to store and retrieve light pulses using electric control is presented. The experiment is based on a Sagnac interferometer with a phase modulator fabricated using a poled fiber with internal electrodes.