Fiber metrology and point sensing based on forward-stimulated Brillouin scattering Miguel V. Andrés Bou, Antonio Díez Cremades, Luis A. Sánchez, Carlos Álvarez-Ocampo, Martina Delgado-Pinar, José Luis Cruz Muñoz Proceedings of SPIE the International Society for Optical Engineering, 2025 Coupling between mechanical oscillations and optical resonances has demonstrated to be a powerful approach to investigate forward-stimulated Brillouin scattering (FSBS) in optical fibers leading to new applications. Long-period fiber gratings and whispering-gallery mode resonances permit to probe acoustic modes with high sensitivity, enabling the development of point sensors based on FSBS. Applying these concepts, Poisson’s ratio of the optical fiber and fiber diameter were measured with unprecedented precision. Simultaneous and discriminative measurements of strain and temperature were carried out with a single FSBS point sensor. The potential of FSBS as the physical mechanism to develop sensors based on the concept of mass-microbalance, suitable for bio-sensing applications, is explored.
Microsphere-Augmented PDMS integration in tapered FBG small-scale sensors for enhanced temperature sensitivity Bryan Sanipatin, Luis A. Sánchez, Lucía Arqués, Salvador Sales Scientific Reports, 2024 This work presents a novel high-sensitivity temperature sensor based on a fiber Bragg grating inscribed on a tapered optical fiber which terminates in a microsphere, all embedded within a PDMS-filled silica capillary. The fabricated microsphere at the taper’s end enhances PDMS traction, improving strain transfer between the polymer and the fiber during temperature changes. Different waist diameters for the tapered fiber were considered for the design of the sensor. The sensor’s response was analyzed over a temperature range of 20 °C to 90 °C for taper waist diameters ranging from 60 μm to 20 μm. Experimental results demonstrate a wavelength temperature sensitivity of 47.19 pm °C⁻ 1 for a 60 μm waist diameter and 221.2 pm °C⁻ 1 for a 20 μm waist diameter, achieving up to 22 times the sensitivity of a bare FBG. The experimental results were supported by finite element analysis simulations, which showed a clear correlation between the enhanced sensitivity and the increase in axial strain applied by the PDMS on the embedded fiber. This enhancement in sensitivity was demonstrated by housing the fiber in a capillary, integrating the microsphere at the end of the fiber, and diminishing the fiber taper’s diameter. Moreover, unlike traditional techniques aimed at enhancing the thermal sensitivity of fiber Bragg gratings, the sensor developed through this innovative approach exhibits enhanced performance regarding both dimensions and sensitivity.
Customized femtosecond laser-inscribed superstructure fiber Bragg grating: A novel approach to decoupling temperature and strain. Bryan Sanipatin, Luis A. Sánchez, Daniel Maldonado-Hurtado, Javier Madrigal, David Barrera, Salvador Sales Optics and Laser Technology, 2024 This paper introduces a novel technique to simultaneously measure temperature and strain using a single 5 mm femtosecond laser-inscribed superstructure fiber Bragg grating (SFBG). This SFBG enables improved spectral capabilities, resulting in side-resonances within the optical spectrum. The characteristics of the device depend on three key factors: the length of the SFBG, the inscribed FBG’s periodic perturbations, and the length of the uninscribed sections that compose the entire structure. Initially, mathematical expressions were derived to calculate the separation between the central peak and a resonance on each side, which plays a crucial role in determining the sensor’s response. Then, a series of complete simulations using OptiGrating software, and a theoretical analysis were performed to comprehend the functioning of this superstructure. Subsequently, the fabrication process employed a femtosecond laser following a point-by-point inscription. Finally obtaining a comprehensive study on the principle, design, simulation, and implementation of the proposed SFBG. The sensitivities of the central Bragg wavelength and the distance between central peak and first-order resonance when applying temperature and strain were calibrated. The results yielded sensitivities for the central Bragg peak of 10.58 pm/°C and 1.1598 pm/µɛ, while the peak-to-resonance distance had sensitivities of 0.3495 pm/°C and 0.03052 pm/µɛ. The different response of both magnitudes makes it possible to distinguish the contributions of strain and temperature within short distances, having the possibility to improve measurements in sensing applications. This study finally provides a critical insight into the design process, as it aligns with the theoretical expectations.
Forward Brillouin Scattering Spectroscopy in Optical Fibers with Whispering-Gallery Modes Luís A. Sánchez, Martina Delgado‐Pinar, Antonio Díez, Miguel V. Andrés Advanced Optical Materials, 2024 Opto‐mechanical interactions in different photonic platforms as optical fibers and optical microresonators are raising great attention, and new exciting achievements have been reported in the last few years. Transverse acoustic mode resonances (TAMRs) in optical fibers –which can be excited optically via electrostriction and generate forward Brillouin scattering (FBS)– are being promoted as the physical mechanism for new fiber‐sensing concepts. Here, the study reports a novel approach to detect and characterize opto‐excited TAMRs of an optical fiber based on the interplay with optical surface wave resonances, i.e., optical whispering‐gallery mode (WGM) resonances. TAMRs induce perturbations in the geometry and the dielectric permittivity of the fiber over the entire cross‐section. It is shown that these perturbations couple the acoustic with the optical resonances and affect WGMs in a noticeable way. The study proposes and demonstrates the use of WGMs for probing opto‐excited TAMRs in optical fibers. This probing technique provides the narrowest linewidths ever reported for the TAMRs and demonstrates an optimum efficiency for the detection of low‐order TAMRs. The interplay between sensitivity, bandwidth, and Q factor of the WGM resonance is discussed.
Optical Vernier Effect-Based DC Piezoelectric Sensor for Low Voltage Applications. Bryan Sanipatin, Luis A. Sánchez, Salvador Sales International Conference on Transparent Optical Networks, 2024 In this paper, the deflection behaviour of a customized cantilever under low voltage conditions was experimentally studied and used as a sensor, taking advantage of their physical and optical properties. When voltage is applied, the bottom layer of the cantilever expands while the top layer does not, which causes the structure to bend due to strain mismatch. Intrinsic mechanical properties of the cantilever were characterized with an additional top layer of reflective material, to create a Fabry-Pérot structure that can respond to voltage changes. The importance of this sensor lies in their potential applications in various fields, such as renewable energy and batteries monitoring. Furthermore, depending on the application, the optical Vernier effect can increase and tune the sensor’s sensitivity. In summary, the significance of this optical Vernier effect-based direct-current sensor lie in their unique combination of piezoelectric and optical sensing capabilities using a high precision and adjustable interrogation method. Thus, allowing to measure changes in voltage below 100 mV in the Fabry-Pérot scenario and around 4 mV using the optical Vernier configuration.
Small-Scale Optrode Based on PDMS for Improved Temperature Measurement Bragg Gratings Photosensitivity and Poling in Glass Waveguides Bgpp 2024 in Proceedings Advanced Photonics Congress 2024 Part of Optica Advanced Photonics Congress, 2024
Innovative Approaches for Organizing an Inclusive Optics and Photonics Conference in Virtual Format Alba de las Heras, Ana I. Gómez-Varela, María-Baralida Tomás, Rosa Ana Perez-Herrera, Luis Alberto Sánchez, Francesca Gallazzi, Beatriz Santamaría Fernández, Mario Garcia-Lechuga, Maria Vinas-Pena, Martina Delgado-Pinar, Verónica González-Fernández Optics, 2023 The COVID pandemic is forcing the renewal of scientific conferences, offering opportunities to introduce technological and inclusive developments. Our analysis focuses on the implementation of inclusive practices for female and early-career researchers in a virtual scientific conference. This organization approach was applied in the XIII Spanish Optical Meeting (RNO2021), which was also characterized by avatars interacting in an online metaverse. The effectiveness of inclusive policies and novel technological tools was evaluated using the participation data and a post-conference survey. Our study reveals the high impact of inclusive actions and a strong interest in the scientific community to explore conference advances.
Recent Advances in Forward Brillouin Scattering: Sensor Applications Luis A. Sánchez, Antonio Díez, José Luis Cruz, Miguel V. Andrés Sensors, 2023 In-fiber opto-mechanics based on forward Brillouin scattering has received increasing attention because it enables sensing the surrounding of the optical fiber. Optical fiber transverse acoustic resonances are sensitive to both the inner properties of the optical fiber and the external medium. A particularly efficient pump and probe technique—assisted by a fiber grating—can be exploited for the development of point sensors of only a few centimeters in length. When measuring the acoustic resonances, this technique provides the narrowest reported linewidths and a signal-to-noise ratio better than 40 dB. The longitudinal and transverse acoustic velocities—normalized with the fiber radius—can be determined with a relative error lower than 10−4, exploiting the derivation of accurate asymptotic expressions for the resonant frequencies. Using this technique, the Poisson’s ratio of an optical fiber and its temperature dependence have been measured, reducing the relative error by a factor of 100 with respect to previously reported values. Using a single-point sensor, discriminative measurements of strain and temperature can be performed, achieving detection limits of ±25 με and ±0.2 °C. These results show the potential of this approach for the development of point sensors, which can be easily wavelength-multiplexed.
