Sistemas de banda ancha sobre fibras ópticas multimodo empleando fuentes estrechas y excitación modal central

El rápido crecimiento en la demanda de capacidad de transmisión en las redes incorporadas y de acceso al usuario ha promovido la tendencia actual a valerse de la infraestructura existente de fibra óptica multimodo (MMF) para transmitir a 10 Gb/s, tal y como establece el estándar 10-Gigabit Ethernet. El principal objetivo de esta tesis doctoral consiste en la propuesta, análisis y validación experimental de técnicas que permitan capacidades de transmisión superiores a los 10 Gb/s a través de enlaces de MMF de corto y medio alcance. La MMF presenta un ancho de banda mucho menor que la fibra monomodo (SMF) como consecuencia de la dispersión en los retardos de propagación de los diversos modos guiados. En este contexto resulta indispensable disponer de modelos que ofrezcan una descripción precisa de la propagación a través de MMF y permitan estudiar diversas soluciones orientadas a limitar la dispersión intermodal. En esta tesis se ha desarrollado el primer modelo analítico basado en la propagación de campo eléctrico que permite evaluar la respuesta en banda base y radiofrecuencia de un enlace de MMF, considerando dispersión cromática de segundo y de tercer orden. Se han evaluado distintas fuentes de degradación como son la distorsión armónica y de intermodulación y el impacto del ruido modal. La búsqueda de soluciones capaces de aumentar la capacidad de transmisión nos ha llevado a establecer teórica y experimentalmente dos condiciones necesarias para la transmisión potencial de señales de banda ancha más allá del producto ancho de banda por distancia de la MMF: la implementación de esquemas de excitación selectiva central de modos y el empleo de fuentes ópticas con una anchura de línea estrecha. La combinación de ambas soluciones con la aplicación de técnicas SCM y WDM ha resultado en la transmisión de señales de banda ancha, tanto radio sobre fibra como digitales en banda base, a través de enlaces de MMF de sílice de hasta 5 km de longitud. Cabe destacar que se ha lGasulla Mestre, I. (2008). Sistemas de banda ancha sobre fibras ópticas multimodo empleando fuentes estrechas y excitación modal central [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3881Palanci

Universal Characteristic Equation for Multi-Layer Optical Fibers

[EN] Optical fibers featuring multi-layer refractive index profiles have been widely investigated and developed in a variety of scenarios, including space-division multiplexing transmission, fiber sensing, loss and dispersion management, as well as high-power amplifiers and lasers. For the first time to our knowledge, we present in this paper a general model deriving the universal characteristic equation for multi-layer optical fibers that comprise a set of concentric layers with arbitrary radial dimensions and refractive index values, considering both stepped (as step-index) or continuous (as graded-index) profiles. Expressions for the main fiber propagation parameters are also derived. We validate the model by comparing our results to the ones provided by numerical software tools with excellent matching for a series of particular optical fibers comprising step-index trench-assisted, ring-core, triangular-index and four-cladding profiles. This compact universal characteristic equation serves as a useful tool for optical fiber designers, where one can get valuable physical insights without the need to resort to numerical software tools, and even evaluate the effect of a single layer in isolation without the need to evaluate the whole refractive index structure.This work was supported in part by the European Research Council (ERC) under Consolidator Grant Project 724663, and in part by the Spanish MINECO under TEC2016-80150-R project, BES-2015-073359 scholarship for S. Garcia and Ramon y Cajal fellowship RYC-2014-16247 for I. Gasulla.García-Cortijo, S.; Gasulla Mestre, I. (2020). Universal Characteristic Equation for Multi-Layer Optical Fibers. IEEE Journal of Selected Topics in Quantum Electronics. 26(4):1-11. https://doi.org/10.1109/JSTQE.2020.2996375S11126

Experimental demonstration of multi-cavity optoelectronic oscillation over a multicore fiber

[EN] We report, for the first time to our knowledge, the experimental demonstration of multi-cavity optoelectronic oscillators where the cavities are provided by the different cores of a multicore fiber. We implemented two multi-cavity architectures over a 20-m-long 7-core fiber link: unbalanced dual-cavity oscillation (the cavity lengths are a multiple of a reference value) and multi-cavity Vernier oscillation (the cavity lengths are slightly different). Since all the cavities are hosted under a single fiber cladding and are subject to the same environmental and mechanical conditions, optoelectronic oscillators built upon multicore fibers benefit from improved performance stability as compared to independent singlemode fiber cavities.H2020 European Research Council (ERC) (724663); Ministerio de Economia y Competitividad (TEC2014-60378-C2-1-R, TEC2016-80150-R, BES-2015- 073359, RYC2014-16247)García-Cortijo, S.; Gasulla Mestre, I. (2017). Experimental demonstration of multi-cavity optoelectronic oscillation over a multicore fiber. Optics Express. 25(20):23663-23668. https://doi.org/10.1364/OE.25.0236632366323668252

Dispersion-engineered multicore fibers for distributed radiofrequency signal processing

[EN] We report a trench-assisted heterogeneous multicore fiber optimized in terms of higher-order dispersion and crosstalk for radiofrequency true time delay operation. The analysis of the influence of the core refractive index profile on the dispersion slope and effective index reveals a tradeoff between the behavior of the crosstalk against fiber curvatures and the linearity of the propagation group delay. We investigate the optimization of the multicore fiber in the framework of this tradeoff and present a design that features a group delay relative error below 5% for an optical wavelength range up to 100 nm and a crosstalk level below -80 dB for bending radii larger than 103 mm. The performance of the true time delay line is validated in the context of microwave signal filtering and optical beamforming for phased array antennas. This work opens the way towards the development of compact fiber-integrated solutions that enable the implementation of a variety of distributed signal processing functionalities that will be key in future fiber-wireless communications networks and systems. (C) 2016 Optical Society of AmericaSpanish MINECO (TEC2015-62520-ERC Project); Spanish MINECO (TEC2014-60378-C2-1-R MEMES Project); Spanish MINECO (BES-2015-073359 fellowship); Spanish MINECO Ramon y Cajal Program (RYC-2014-16247).García Cortijo, S.; Gasulla Mestre, I. (2016). Dispersion-engineered multicore fibers for distributed radiofrequency signal processing. Optics Express. 24(18):20641-20654. https://doi.org/10.1364/OE.24.020641S2064120654241

Performance of Direct-Detection Mode-Group-Division Multiplexing using Fused Fiber Couplers

© 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works[EN] We present an end-to-end performance evaluation of a mode-group-division multiplexing system that uses direct detection instead of coherent detection, avoiding complex digital signal processing. The system transmits four data channels through a step-index fiber supporting six spatial modes comprising four mode groups, considering the two-fold degeneracy of the LPlm modes for l ≠ 0. Multiplexing and demultiplexing is performed using two- and three-core fused fiber couplers, each one phase-matched to a group of degenerate modes. These devices are analyzed through a field-based model that describes, for the first time to our knowledge, crosstalk between all the fiber modes. Propagation through the few-mode fiber is modeled considering differential modal attenuation, intermodal dispersion, chromatic dispersion, and both intergroup and intragroup modal coupling. The end-to-end link is described by a concatenation of matrix operators describing the optical field transfer functions for the multiplexer, fiber and demultiplexer. Error-free transmission of four 32-Gb/s OOK modulated data channels through a 1-km link proves the feasibility of the proposed direct-detection mode-group-division multiplexing approach.The work of I. Gasulla was supported by the Fulbright Commission and the Spanish Ministerio de Educacion through the Programa Nacional de Movilidad de Recursos Humanos del Plan Nacional de I-D + i2008-2011. The work of J. M. Kahn was supported by a Google Faculty Research Award.Gasulla Mestre, I.; Kahn, JM. (2015). Performance of Direct-Detection Mode-Group-Division Multiplexing using Fused Fiber Couplers. Journal of Lightwave Technology. 33(9):1748-1760. doi:10.1109/JLT.2015.2392255S1748176033

Dispersion-tailored few-mode fiber design for tunable microwave photonic signal processing

[EN] We present a novel double-clad step-index few-mode fiber that operates as a five-sampled tunable true-time delay line. The unique feature of this design lies in its particular modal chromatic dispersion behavior, which varies in constant incremental steps among adjacent groups of modes. This property, which to the best of our knowledge has not been reported in any other few-mode fiber to date, is the key to tunable operation of radiofrequency signal processing functionalities implemented in few-mode fibers. The performance of the designed true-time delay line is theoretically evaluated for two different microwave photonics applications, namely tunable signal filtering and optical beamforming networks for phased array antennas. In the 35-nm optical wavelength tuning range of the C-band, the free spectral range of the microwave filter and the beam-pointing angle in the phased array antenna can be continuously tuned from 12.4 up to 57 GHz and 12.6 degrees up to 90 degrees, respectively.European Research Council (Consolidator Grant Project 724663); Ministerio de Ciencia, Innovacion y Universidades (Ramon y Cajal fellowship RYC-2014-16247).Nazemosadat-Arsanjani, SB.; Gasulla Mestre, I. (2020). Dispersion-tailored few-mode fiber design for tunable microwave photonic signal processing. Optics Express. 28(24):37015-37025. https://doi.org/10.1364/OE.412830S3701537025282

Tunable True-Time Delay Operation in A Dispersion-Engineered Few-Mode Fiber

[EN] We present a simple few-mode fiber design as a promising platform to implement tunable sampled true-time delay lines for radiofrequency signal processing. To the best of our knowledge, this is the first few-mode fiber ever reported featuring evenly spaced incremental dispersion values, which is an essential characteristic required for tunable operation of microwave photonics applications. The performance of the designed five-sample true-time delay line is theoretically validated in the context of microwave signal filtering, demonstrating free spectral range continuous tunability from 12.4 up to 57 GHz.This work is supported by the European Research Council (ERC) under Consolidator Grant Project 724663, and Ramon y Cajal fellowship RYC-2014-16247 for I. Gasulla.Nazemosadat-Arsanjani, SB.; Gasulla Mestre, I. (2020). Tunable True-Time Delay Operation in A Dispersion-Engineered Few-Mode Fiber. IEEE. 203-206. https://doi.org/10.23919/MWP48676.2020.9314392S20320

Mode-division multiplexing for microwave signal processing

[EN] We present an overview of different mode-division multiplexing fiber technologies engineered to provide tunable microwave signal processing, including signal filtering and optical beamforming for phased-array antennas. The exploitation of both the space and wavelength dimensions brings advantages in terms of increased compactness, flexibility and versatility.This research was supported by the ERC Consolidator Grant ERC-COG-2016 InnoSpace 724663 and the Spanish MINECO fellowship RYC-2014- 16247 for I. Gasulla.Nazemosadat-Arsanjani, SB.; Gasulla Mestre, I. (2021). Mode-division multiplexing for microwave signal processing. IEEE. 1-2. https://doi.org/10.1109/SUM48717.2021.95058021

Photonic crystal fibers for microwave signal processing

[EN] We present a novel design of an optical True Time Delay Line based on a 19-core Photonic Crystal Fiber that operates in a broad radiofrequency signal processing range from 1 to 67 GHz on a 10-km link, thus enabling simultaneous microwave signal distribution and processing.This work was supported by the European Research Council (ERC) under Project 724663, the Spanish MINECO under BES-2017-079682 scholarship for S. Shaheen and Ramon y Cajal fellowship RYC-2014-16247 for I. Gasulla.Shaheen, S.; Gris-Sánchez, I.; Gasulla Mestre, I. (2021). Photonic crystal fibers for microwave signal processing. IEEE. 1-2. https://doi.org/10.1109/IPC48725.2021.95929341

Design of Heterogeneous Multicore fibers as sampled True Time Delay Lines

[EN] This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.40.000621. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under lawWe present a novel procedure for designing a sampled discrete true-time delay line (TTDL) for Microwave Photonics applications based on a heterogeneous MCF. Both simple step-index (SI) and trench-assisted SI profiles are numerically evaluated in terms of physical dimensions and material dopant concentrations in order to individually tailor the group delay and chromatic dispersion of each core. The proposed TTDL features unique properties beyond the current state of the art in terms of record bandwidth, compactness, flexibility, and versatility.The authors wish to acknowledge the financial support given by the Research Excellency Award Program GVA PROMETEO II/2013/012.Garcia, A.; Gasulla Mestre, I. (2015). Design of Heterogeneous Multicore fibers as sampled True Time Delay Lines. Optics Letters. 40(4):621-624. https://doi.org/10.1364/OL.40.000621S621624404Capmany, J., Mora, J., Gasulla, I., Sancho, J., Lloret, J., & Sales, S. (2013). Microwave Photonic Signal Processing. Journal of Lightwave Technology, 31(4), 571-586. doi:10.1109/jlt.2012.2222348Sancho, J., Bourderionnet, J., Lloret, J., Combrié, S., Gasulla, I., Xavier, S., … De Rossi, A. (2012). Integrable microwave filter based on a photonic crystal delay line. Nature Communications, 3(1). doi:10.1038/ncomms2092Ohman, F., Yvind, K., & Mork, J. (2007). Slow Light in a Semiconductor Waveguide for True-Time Delay Applications in Microwave Photonics. IEEE Photonics Technology Letters, 19(15), 1145-1147. doi:10.1109/lpt.2007.901435Morton, P. A., & Khurgin, J. B. (2009). Microwave Photonic Delay Line With Separate Tuning of the Optical Carrier. IEEE Photonics Technology Letters, 21(22), 1686-1688. doi:10.1109/lpt.2009.2031500Gasulla, I., & Capmany, J. (2012). Microwave Photonics Applications of Multicore Fibers. IEEE Photonics Journal, 4(3), 877-888. doi:10.1109/jphot.2012.2199101Koshiba, M., Saitoh, K., & Kokubun, Y. (2009). Heterogeneous multi-core fibers: proposal and design principle. IEICE Electronics Express, 6(2), 98-103. doi:10.1587/elex.6.98Tu, J., Saitoh, K., Koshiba, M., Takenaga, K., & Matsuo, S. (2012). Design and analysis of large-effective-area heterogeneous trench-assisted multi-core fiber. Optics Express, 20(14), 15157. doi:10.1364/oe.20.015157Watekar, P. R., Ju, S., & Han, W.-T. (2009). Design and development of a trenched optical fiber with ultra-low bending loss. Optics Express, 17(12), 10350. doi:10.1364/oe.17.01035