Gotzon Aldabaldetreku

University of the Basque Country | UPV/EHU · Departamento de Ingeniería de Comunicaciones

Power electronics systems represent a fundamental technology in modern electric vehicles and also in many industrial applications. In this context, the presence of high electromagnetic interferences due to high dv/dt variations make it preferable to use polymer optical fibers (POFs) to connect the controller-to-converter digital signals, thus minim...

Raman scattering is the inelastic process where photons bounce off molecules, losing energy and becoming red-shifted. This weak effect is unique to each molecular species, making it an essential tool in, e.g., spectroscopy and label-free microscopy. The invention of the laser enabled a regime of stimulated Raman scattering (SRS), where the efficien...

Distance measurement is an essential issue in modern industry. Differential intensity sensors based on optical fibers have been very successful. Nevertheless, an inefficient fiber bundle design limits their ultimate range and sensitivity. This paper presents a method and a framework that allows researchers to find the best design for a sensor opera...

Raman scattering is the inelastic process where photons bounce off molecules, losing energy and becoming red-shifted. This weak effect is unique to each molecular species, making it an essential tool in e.g. spectroscopy and label-free microscopy. The invention of the laser enabled a regime of stimulated Raman scattering (SRS), where the efficiency...

This work introduces a mathematical model for designing optical fiber linear and angular displacement sensors (OFLADS) capable of simultaneously measuring the distance and angle of a finite reflective target such as a mirror. Recently, fiber optical sensors have found applications across industries like medical, military, or aerospace. The advantag...

Optical fiber displacement sensors (OFDS) offer several advantages over conventional sensors due to their compact size and immunity to electromagnetic interference. These are particularly useful for applications in confined spaces, including aeronautical turbines. The critical component of OFDS is the fiber bundle, whose response depends on the arr...

Trifurcated optical fiber displacement sensors (OFDS) are increasingly used in industrial and aerospace applications. The critical element of the sensor is the fiber bundle. However, there is no straightforward method to calculate it from the working specifications of the sensor, the number of fibers needed, their size, and arrangement. This work p...

Este trabajo presenta un método teórico para mejorar el diseño de sensores de desplazamiento basados en racimos de fibras ópticas bifurcados. Concretamente, el modelo permite calcular, a partir de unas especificaciones dadas de trabajo del sensor, la geometría de la agrupación de fibras. Si fijamos el punto de trabajo del sensor, su rango y/o la se...

We derive a general solution based on geometric optics that describes the light propagation properties in multimode optical fibers with inverted refractive index profiles. Using this general solution, we classify rays according to their propagation properties and calculate the analytical expressions of the ray trajectories inside these fibers under...

We report on recent advances in the use of inexpensive polymer optical fibres (POFs) for sensing applications in avionics. The sensors analysed in this manuscript take advantage of the unique properties of polymers, such as high flexibility, elasticity, and sensitivity, and they range from strain, elongation, and vibration interrogators to level an...

Fibre bundle-based reflective optical sensors are good candidates for parameter monitorisation in aero engines. Tip clearance is one of those parameters of great concern that is necessary to monitor. Within this optical technology, the evolution experienced by a custom-designed optical sensor is presented from its first configuration up to the fift...

Among the different available optical technologies, fibre bundle-based reflective optical sensors represent an interesting alternative for parameter monitorization in aero engines. Tip clearance is one of the parameters of great concern for engine designers and engineers. In the framework of this optical technology, three fibre-based reflective opt...

This work reports the development and application of two liquid-core microstructured polymer optical fibers (LC-mPOF) with different microstructure sizes. They are used in a Fiber Enhanced Raman Spectroscopy (FERS) sensing platform, with the aim of detecting glucose in aqueous solutions in the clinically relevant range for sodium-glucose co-transpo...

The cover image, by Eneko Arrospide et al., is based on the Review Polymers beyond standard optical fibres ‐ fabrication of microstructured polymer optical fibres, DOI: 10.1002/pi.5602.

This paper reports the overall fabrication process of microstructured polymer optical fibres (mPOFs). The mPOF fabrication involves a two‐step process: on the one hand, the design and creation of a preform containing a large‐scale version of the desired fibre and, on the other, the precise heating and drawing of the preform to the final fibre. The...

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing...

In contrast to conventional polymer optical fibres (POFs), single-mode microstructured POFs (SM mPOF) exhibit polarization properties that make them potentially interesting for their use in the design and development of polarimetric fibre optic systems. In spite of the theoretical six-fold symmetry of the microstructure that yields zero linear bire...

An experimental investigation on the vibrational behavior of a rotating disk by means of three optical fiber sensors is presented. The disk, which is a scale model of the real disk of an aircraft engine, was assembled in a wind tunnel in order to simulate real operation conditions. The pressure difference between the upstream and downstream sides o...

This chapter describes the mechanical properties of POFs, such as Young's modulus, strain, stress, or strength, which result relevant in the performance of POFs, as well as in the aging and in the fabrication of new POF designs. All these physical properties vary drastically depending on the designed POF type, going from conventional step-index POF...

Tip timing is a well-known technique to evaluate the amplitude and frequency of blade vibrations in turbomachinery. This technique makes use of the differences between the theoretical and the real arrival times of the blades. These time differences are converted into vibration amplitudes providing useful information about the turbine operation and...

An experimental study about the vibrational behaviour of two prototypes of a rotating disk by means of three optical sensors is presented. Both prototypes were assembled in a wind tunnel in order to reproduce real operation conditions. The optical sensors identified the vibration frequency and the nodal diameter of the first prototype by measuring...

Based on the attractive elasto-optic properties of single-mode microstructured polymer optical fibres (SM mPOFs) reported elsewhere,10 mode polarisation may be used as sensing probe for several parameters of interest like mechanical pressure. We report on a simplified detection scheme that does not require measuring the actual polarisation state of...

One of the issues that affects the performance of plastic optical fibers (POFs) is the light scattering caused by the presence of inhomogeneities in the polymer, which is responsible for the optical energy loss and for the mode coupling in POFs. The aim of this work is to compare two different methods for measuring light scattered in step index pol...

In this study, we investigate the spectral distribution of the light scattered in step-index polymer optical fibers by illuminating the fibers transversely to their symmetry axis. For that purpose, we have performed wavelength-dependent scattering measurements over the spectral range 400–750 nm in three different commercial step-index polymer optic...

We discuss the design of a simple experiment that reproduces the operation of the Michelson stellar interferometer. The emission of stellar sources has been simulated using light emerging from circular end-faces of step-index polymer optical fibers and from diffuse reflections of laser beams. Interference fringes have been acquired using a digital...

The polarisation state of light may be exploited in single-mode polymer mPOFs for sensing purposes. The bend-induced birefringence varies linearly with the inverse square of the bend radius, whereas the twist-induced polarisation rotation varies linearly with the fibre twist angle. Both effects are highly reproducible and show higher sensitivity th...

We demonstrate the influence of the relative humidity (RH) on the wavelength of fiber Bragg grating sensors (FBGS), performing tests with five FBGS at different humidity and temperature conditions. These tests were performed in a climate chamber whose RH changes according to a scheduled profile from 30% to 90%, in steps of 10%. These profiles were...

A single-mode microstructured POF (mPOF) pressed into a V-groove by a vertical force is suggested as a proof of concept for mass sensing. The working mechanism is based on the stress-induced birefringence in the mPOF that depends on several parameters such as the length of the pressed fibre section or its rotational orientation relative to the indu...

We demonstrate the feasibility of microstructured polymer optical fibers (mPOFs) for detecting and measuring the strain rate, pressure, bending and twist of engineering structures. The encouraging results open the way to the use of Long Period Grating (LPG) mPOF sensors in structural health monitoring applications.

In this paper we demonstrate the design of a low-cost optical current sensor. The sensor principle is the Faraday rotation of a light beam through a magneto-optical material, SF2, when a magnetic field is present. The prototype has a high sensitivity and a high linearity for currents ranging from 0 up to 800 A. The error of the optical fibre sensor...

We analyze the extrinsic coupling losses due to misalignments in three different SI-MCPOFs. Four kinds of misalignments are analyzed: longitudinal separation, transversal offset angular misalignment and rotational misalignment. We have performed experimental measurements and complementary computational simulations to assess the effect of misalignme...

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a...

Structural health monitoring (SHM) is a cost-effective approach to meet operational requirements, and to reduce maintenance costs in aircrafts. Besides, fiber optic sensor technology is a mature technology which can be used to monitor physical parameters of wing leading-edge surfaces and fuselage sections made of composites carbon fiber-reinforced...

Traditional limitations of capacitive, inductive or discharging probe sensor for tip timing and tip clearance measurements are overcome by reflective intensity modulated optical fiber sensors. This paper presents the signals and results corresponding to a one stage turbine rig which rotor has 146 blades, obtained from a transonic wind-tunnel test....

The first sensor we present is a low-cost current sensor, whose operational principle is Faraday rotation of a light beam through a magneto-optical material under the influence of a magnetic field. The results show that the sensor presents high sensitivity and a linear response in the range from 0 to 800A. The second sensor measures tip clearance (...

In the above paper (ibid., vol. 12, no. 8, pp. 2668-2673, Aug. 2012), the financial support for the authors was omitted. The information is presented here.

We demonstrate the feasibility of long-period gratings (LPGs) written in microstructured polymer optical fibers (mPOFs) for detecting and measuring the strain rate and magnitude of engineering structures. We validate and compare the results of our experimental tests to a commercial fiber Bragg grating sensor. The encouraging results open the way to...

In this paper we present a detailed theoretical study that describes the generation of scattered light in step-index polymer optical fibers by using the side-illumination scattering measurement technique. A detailed analysis of the variation of the maximum angle of acceptance within the fiber has been carried out in order to calculate the scattered...

Berry's phase is a quantum effect where every system transported adiabatically around a closed loop in momentum space suffers a topological phase change. The evidence of this effect at classical level has been explored analyzing the optical activity in a helically wound single-mode optical fiber. In this article we report for the first time this ge...

Multi-Core Plastic Optical Fibers (MCPOFs) are, in general, composed of plastic optical cores arranged in concentric rings around a central core. Due to this geometry, a new kind of misalignment appears when connecting these fibers: the rotational misalignment, which accounts for the coupling losses produced when the cross sections of two connected...

We study the influence of the source configuration and the fiber length on the light coherence in highly multimode step-index polymer optical fibers. We perform several computer simulations and analyze the spatial coherence properties of the output surface of the fiber. By calculating the complex coherence factor of the output surface of the fiber,...

The effect of the cladding on the emission properties of doped plastic optical fibres has been analyzed by using the side-illumination technique. For that purpose, the photoluminescence spectra of cladded and uncladed plastic optical fibres, both with the same doped core material, have been compared. In particular, we study the dependence of the em...

In this article we analyze the extrinsic coupling losses in step-index multicore polymer optical fibers (SI-MCPOFs) of different number of cores. We study the coupling losses caused by three different types of misalignments: transversal, longitudinal and angular. We have performed several experimental measurements in order to determine the coupling...

This paper demonstrates both the feasibility of long-period gratings (LPGs) written in microstructured polymer optical fibres (mPOFs) for detecting and measuring the strain rate and magnitude of engineering structures as well as its practical realization on a steel plate. The results of the experimental tests were validated and compared to a commer...

The aim of this paper is to investigate the properties of the inhomogeneities that give rise to light scattering in polymer optical fibers (POFs). We perform several measurements in two commercial POFs of identical characteristics: these measurements, based on the side-illumination technique, consist in the detection of the total amount of scattere...

The aim of this paper is to present a new ray-tracing model which describes the propagation of light in multi-core polymer optical fibers (MCPOFs), taking into account the crosstalk among their cores. The new model overcomes many of the limitations of previous approaches allowing us to simulate MCPOFs of arbitrary designs. Additionally, it provides...

The optical properties of four fluorene oligomers embedded in plastic optical fiber have been investigated by using steady-state luminescence technique. In particular, we study the dependence of the optical spectra with dopant oligofluorene, emission wavelength, excitation wavelength, and light propagation distance through the fiber. Using this inf...

The relations between radiometric magnitudes and quantities associated to optical properties of materials (processes of reflection, transmission and emission of radiant flux by or through material media) have been analyzed. By studying some particular examples, we illustrate the dependence of optical properties of materials on the radiometric magni...

We present in this paper the detailed design, development, and implementation of two optical measurement systems that serve as teaching devices for undergraduate students. The building of both prototypes has been carried out by several students for their undergraduate thesis project. Both systems are highly modular and each of their functional bloc...

The behavior of tapered graded-index polymer optical fibers is analyzed computationally for different refractive indices of the surrounding medium. This serves to clarify the main parameters affecting their possible performance as refractive-index sensors and extends an existing study of similar structures in glass fibers. The ray-tracing method is...

This paper reviews the theoretical analysis of light propagation we have carried out on multimode multi-step index (MSI) optical fibres. Starting from the Eikonal equation, we derive the analytical expressions that allow calculating the ray trajectories inside these fibres. We also analyse the effects of leaky rays on the transmission properties of...

The aim of the present paper is to provide a comprehensive analysis of coupling losses in perfluorinated (PF) multi-core polymer optical fibers (MC-POFs), which consist of groups of 127 graded-index cores. In our analysis we take into account geometrical, longitudinal, transverse, and angular misalignments. We perform several experimental measureme...

An easy-to-manufacture setup for a displacement sensor based on plastic optical fiber (POF) is analyzed, showing computational and experimental results. If the displacement is the consequence of force or pressure applied to the device, this can be used as a force or pressure transducer. Its principle of operation consists of bending a POF section a...

A comprehensive analysis of the various ray propagation mechanisms that take place between the different layers of highly multimode multistep index (MSI) fibers is presented. A suitable analytical expression that allows the evaluation of the power fraction transferred from a certain layer to another one from rays undergoing either refraction or fru...

The aim of this paper is to obtain an analytical expression for intrinsic coupling losses in multistep index (MSI) fibers. For this purpose, a uniform power distribution is assumed. In order to validate the theoretical expression, the obtained results were compared with computer simulations using the ray-tracing method as well as with results obtai...

The aim of the present paper is to provide a single analytical expression of the power transmission coefficient for leaky rays in multi-step index (MSI) fibres. This expression is valid for all tunnelling and refracting rays and allows us to evaluate numerically the power attenuation along an MSI fibre of an arbitrary number of layers. We validate...

The aim of the present paper is to provide a comprehensive analysis of the coupling losses in multi-step index (MSI) fibres. Their light power acceptance properties are investigated to obtain the corresponding analytical expressions taking into account longitudinal, transverse, and angular misalignments. For this purpose, a uniform power distributi...