Photonic Millimeter Wave Signal Generation and Transmission Over Hybrid Links in 5G Communication Networks

[ES] El estándar de quinta generación (5G) es la clave potencial para satisfacer el aumento exponencial en la demanda de nuevas aplicaciones, servicios y usuarios. La tecnología 5G ofrecerá una latencia extremadamente baja de 1 ms, una velocidad máxima de datos de 10 Gbit/s, una alta densidad de conexión de hasta 106 dispositivos/km2 y permitirá una alta movilidad de los dispositivos de hasta 500 km/h. En esta Tesis se proponen varias soluciones basadas en tecnologías habilitadoras para el despliegue de redes 5G. La arquitectura de la red de acceso de radio en la nube (C-RAN) se emplea junto con las técnicas de Fotónica de Microondas como una solución prometedora para generar y transmitir señales de ondas milimétricas (mmW) en la próxima generación de comunicaciones móviles. La tecnología radio sobre fibra (RoF) ha demostrado ser una buena opción para enfrentarse al desafío de la distribución inalámbrica mmW debido a la gran distancia de transmisión, el gran ancho de banda y la inmunidad a las interferencias electromagnéticas, entre algunas de las principales ventajas. Además, esta tecnología se puede ampliar con comunicaciones ópticas de espacio libre (FSO) en sistemas de radio sobre FSO (RoFSO) en las redes inalámbricas. En esta Tesis, las señales mmW se generan fotónicamente mediante modulación externa de doble banda lateral con supresión de portadora (CS-DSB) y se distribuyen a través de enlaces fronthaul híbridos RoF/FSO. Además, la generación múltiple de señales permite la distribución reconfigurable en canales multiplexados por división de longitud de onda (WDM) desde una oficina central hasta las estaciones base, y se ha evaluado el impacto de las turbulencias producidas en los canales FSO sobre las señales mmW generadas fotónicamente en términos de fluctuaciones de potencia y ruido de fase de la señal. Se propone la técnica de modulación directa de un láser (DML) como solución principal para la transmisión de datos a través de enlaces ópticos híbridos que emplean un esquema de multiplicación de frecuencias ópticas, es decir, CS-DSB, para la generación de señales de mmW. En concreto, se evalúan teórica y experimentalmente los esquemas de generación fotónica local y remoto de señales mmW y se comparan para su implementación práctica en la red frontal de la C-RAN y, además, se estudia experimentalmente el impacto de la distorsión armónica y de la intermodulación en la transmisión de datos. Igualmente, con el fin de obtener la capacidad que ofrece el DML en términos de ancho de banda, también se presenta una evaluación teórica y experimental del efecto de la dispersión de la fibra y el chirp sobre diferentes anchos de banda de señales de M-modulación de amplitud en cuadratura (QAM). No obstante, la Tesis también incluye otro enfoque para la transmisión de datos basado en el uso de otro modulador externo. En este caso, la demostración experimental de la generación de señales ópticas empleando CS-DSB y la transmisión de señales a través de fibra híbrida y red frontal FSO se completa con un enlace de antena que permite transmitir señales 5G 64/256-QAM. La investigación realizada con los sistemas CS-DSB y DSB también permiten comparar la robustez frente al desvanecimiento inducido por la dispersión cromática de la fibra. Además, se ha realizado una evaluación experimental impacto las turbulencias producidas en los canales FSO sobre las señales mmW generadas fotónicamente con diferentes distribuciones térmicas y se ha cuantificado la degradación de la señal de datos de acuerdo con las condiciones de la turbulencia. Como demostradores finales, esta Tesis incluye un sistema de transmisión full-dúplex que emplea señales 5G en enlace descendente (DL) a 39 GHz y en enlace ascendente (UL) a 37 GHz; y la transmisión de señales OFDM LTE de 60 GHz (DL) y 25 GHz (UL) sobre una infraestructura heterogénea de frontal óptico que consiste en fibra óptica de 10 km, un canal FSO de 100 m y un enlace de radio inalámbrico de 2 m.[CA] L'estàndard de quinta generació (5G) és la clau potencial per a satisfer l'augment exponencial en la demanda de noves aplicacions, serveis i usuaris. La tecnologia 5G oferirà una latència extremadament baixa d'1 ms, una velocitat màxima de dades de 10 Gbit/s, una alta densitat de connexió de fins a 106 dispositius/km2 i permetrà una alta mobilitat dels dispositius de fins a 500 km/h. En aquesta tesi es proposen diverses solucions basades en tecnologies habilitadores per al desplegament de xarxes 5G. L'arquitectura de la xarxa d'accés de ràdio en el núvol (CRAN) s'empra junt amb les tècniques de Fotònica de Microones com una solució prometedora per a generar i transmetre senyals d'ones mil·limètriques (mmW) en la pròxima generació de comunicacions mòbils. La tecnologia ràdio sobre fibra ( RoF) ha demostrat ser una bona opció per a enfrontar-se al desafiament de la distribució sense fil mmW a causa de la gran distància de transmissió, el gran ample de banda i la immunitat a les interferències electromagnètiques, entre alguns dels principals avantatges. A més, aquesta tecnologia es pot ampliar amb comunicacions òptiques d'espai lliure (FSO) en sistemes de ràdio sobre FSO (RoFSO) en les xarxes sense fil. En aquesta Tesi, els senyals mmW es generen fotònicament per mitjà de modulació externa de doble banda lateral amb supressió de portadora (CS-DSB) i es distribueixen a través d'enllaços frontals híbrids RoF/FSO.. A més, la generació múltiple de senyals permet la distribució reconfigurable en canals multiplexats per divisió de longitud d'ona ( WDM) des d'una oficina central fins a les estacions base, i s'ha avaluat l'impacte de les turbulències produïdes en els canals FSO sobre els senyals mmW generades fotònicament en termes de fluctuacions de potència i soroll de fase del senyal. Aquest treball proposa la tècnica de modulació directa d'un làser (DML) com solució principal per a la transmissió de dades a través d'enllaços òptics híbrids que fan servir un esquema de multiplicació de freqüències òptiques, és a dir, CS-DSB, per a la generació de senyals de mmW. En concret, s'avalua teòric i experimentalment els esquemes de generació fotònica local i remota de senyals mmW i es comparen per a la seua implementació pràctica a la xarxa frontal de la C-RAN i a més, s'estudia experimentalment l'impacte de la distorsió harmònica i de la intermodulació en la transmissió de dades. Igualment, amb el fi d'obtindre la capacitat que ofereix el DML en termes d'amplada de banda, també es presenta una avaluació teòrica i experimental de l'efecte de la dispersió de la fibra i el chirp sobre diferents amples de banda de senyals de M-modulació d'amplitud en quadratura (QAM). No obstant això, la Tesis també inclou altre enfocament per a la transmissió de dades basat amb l¿ús d'altre modulador extern. En aquest cas, la demostració experimental de la generació de senyals òptics emprant CS-DSB i la transmissió de senyals a través de fibra híbrida i xarxa frontal FSO es completa com un enllaç d'antena que permet transmetre senyals 5G 64/256-QAM. La investigació realitzada amb els sistemes CS-DSB i DSB també permet comparar la seua robustesa davant l¿esvaïment induït per la dispersió cromàtica. A més, s'ha avaluat experimentalment l'impacte de les turbulències produïdes en els canals FSO sobre els senyals mmW generades fotònicament amb diferents distribucions tèrmiques i s'ha quantificat la degradació del senyal de dades d'acord amb les condicions de la turbulència. Com a demostradors finals, aquesta Tesi inclou un sistema de transmissió full-dúplex que empra senyals 5G en enllaç descendent (DL) a 39 GHz i en enllaç ascendent (UL) a 37 GHz; i la transmissió de senyals OFDM LTE de 60 GHz (DL) i 25 GHz (UL) sobre una infraestructura heterogènia de frontal òptic que consisteix en fibra òptica de 10 km, un canal FSO de 100 m i un enllaç de ràdio sense fil de 2 m.[EN] The fifth generation (5G) standard is the potential key to meet the exponentially increasing demand of the emerging applications, services and mobile end users. 5G technology will offer an extremely low latency of 1 ms, peak data rate of 10 Gbit/s, high contention density up to 106 devices/km2 and enable high mobility up to 500 km/h. This Thesis proposes several solutions based on enabling technologies for deploying 5G networks. Cloud-radio access network (C-RAN) architecture is employed in conjunction with microwave photonics techniques as a promising solution to generate and transmit millimeter wave (mmW) signals in the next generation of mobile communications. Radio over fiber (RoF) has been demonstrated as a good option to face the challenge of mmW wireless distribution, due to long transmission distance, large bandwidth and immunity to electromagnetic interference, as some of the main advantages. Moreover, this technology can be extended with free-space optical (FSO) communications in Radio over FSO systems (RoFSO) as wireless networks. In this Thesis, mmW signals are photonically generated by carrier suppressed double sideband (CS-DSB) external modulation and distributed over hybrid RoF/FSO fronthaul links. Moreover, multiple generated signals allow reconfigurable distribution in wavelength-division multiplexed (WDM) channels from a central office to the base stations, and the impact of turbulent FSO channels on photonically generated mmW signals has been evaluated in terms of power signal fluctuations and phase noise. A directly modulated laser (DML) is proposed as a major solution for signal transmission over hybrid optical links employing optical frequency multiplication scheme, i.e. CS-DSB, for mmW signal generation. Moreover, local and remote photonic mmW signal generation schemes are theoretically and experimentally evaluated and compared for practical deployment in C-RAN fronthaul network while the impact of harmonic and intermodulation distortion on data transmission is also experimentally studied. Furthermore, for the sake of obtaining the DML usability in terms of bandwidth, theoretical and experimental evaluation of the effect of fiber dispersion and chirp over different M-quadrature amplitude modulation (QAM) signals bandwidth is also presented. Another data transmission approach based on the cascade of two external modulators is also employed in the Thesis. In this case, the experimental demonstration of optical signal generation employing CS-DSB and signal transmission over hybrid fiber and FSO fronthaul network is completed with a seamless antenna link leading to successful transmission of 64/256-QAM 5G signals. The CS-DSB and DSB schemes are also investigated for the sake of comparison in terms of robustness against fiber chromatic dispersion-induced fading. Furthermore, experimental evaluation of the impact of turbulent FSO links on photonically generated mmW signals with different thermal distributions has been performed and data signal degradation has been quantified according to the turbulence conditions. As final demonstrators, the Thesis includes a full-duplex transmission system employing 39 GHz downlink (DL) and 37 GHz uplink (UL) 5G signals over hybrid links; and 60 GHz (DL) and 25 GHz (UL) OFDM LTE signal transmission over an heterogeneous optical fronthaul infrastructure consisting of 10 km optical fiber, 100 m FSO channel and 2 m wireless radio link.I would like to acknowledge the financial support given by Research Excellence Award Programme GVA PROMETEO 2017/103 Future Microwave Photonics and European Network for High Performance Integrated Microwave Photonics (EUIMWP) CA16220.Vallejo Castro, L. (2022). Photonic Millimeter Wave Signal Generation and Transmission Over Hybrid Links in 5G Communication Networks [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/19025

Optical CS-DSB Schemes for 5G mmW Fronthaul Seamless Transmission

[EN] This paper describes the experimental demonstration of the hybrid optical/millimeter wave signal generation and transmission over combined optical fiber and free space optics fronthaul network with a seamless antenna link. An electrical bandpass filter is used to filter out the spectrum after photodetection in order to realize the seamless antenna transmission. The successful transmission of 64/256-quadrature amplitude modulation (QAM) 5G signal with up to 200 MHz bandwidth is presented by using two different setups: one is based on two Mach-Zehnder modulators (MZM) and the other employs a directly modulated laser (DML) to provide more cost efficient fronthaul solution. The DML based approach reveals mildly better performance in comparison to the MZMs in terms of higher achieved signal-to-noise ratio and lower error vector magnitude (EVM). More specifically, the best signal-to-noise ratio and EVM achieved with the DML based setup has been 31.5 dB and 3. 3%, respectively, compared to 30.3 dB and 3.8% with the MZMs based setup while transmitting 256-QAM signal with 100 MHz bandwidth. However, both setups kept the EVM well below the given 9% and 4.5% limit for 64- and 256-QAM, respectively.This work was supported in part by the Ministry of Industry and Trade in Czech Republic under Grant FV40089, in part by EU COST Action NEWFOCUS under Grant CA19111, and in part by the Ministerio de Ciencia, Innovacion y Universidades under Grant FOCAL RTI2018-101658-B-I00.Bohata, J.; Vallejo-Castro, L.; Ortega Tamarit, B.; Zvanovec, S. (2022). Optical CS-DSB Schemes for 5G mmW Fronthaul Seamless Transmission. IEEE Photonics Journal. 14(2):1-7. https://doi.org/10.1109/JPHOT.2022.31610871714

M-QAM signal transmission at the photonically generated K-band over thermal-induced turbulent FSO links with different turbulence distributions

[EN] We present a theoretical and experimental study on the impact of different thermal-induced free-space turbulence distributions on the M-quadrature amplitude modulation (M-QAM) signal transmission in radio frequency K-band over hybrid optical links of standard single mode fiber (SSMF) and free-space optics (FSO). Frequency multiplication using an external intensity modulator biased at the null transmission point has been employed to photonically generate radio signals at a frequency of 25 GHz, included for the frequency bands for fifth-generation (5G) mobile networks. Moreover, extensive simulations have been performed for 10 Gb/s with 4-, 16-, and 64-QAM over 5 km of SSMF and 500 m long FSO channels under scenarios with different turbulence levels and distributions. Proof-of-concept experiments have been conducted for 20 MHz with 4- and 64-QAM over 5 km of SSMF and 2 m long FSO channels under turbulence conditions. Both theoretical and experimental systems have been analyzed in terms of error vector magnitude (EVM) performance showing feasible transmission over the hybrid links in the received optical power range. Non-uniform turbulence distributions are shown to have a different impact on M-QAM modulation formats, i.e., turbulence distributions with higher strength in the middle of the FSO link reveal a 1.9 dB penalty when using 64-QAM signals compared to a 1.3 dB penalty using 4-QAM signals, whereas higher penalties have been measured when 4-QAM format is transmitted over turbulence distributions with larger magnitude in the second half of the FSO link. The results have been validated by theoretical predictions and lead to practical consequences on future networks' deployment.Generalitat Valenciana (PROMETEO 2017/103); Ministerio de Ciencia, Innovacion y Universidades (FOCAL RTI2018-101658-B-I00); Ministerstvo Prumyslu a Obchodu (FV30427) and within European Cooperation in Science andTechnology (CA16220).Vallejo-Castro, L.; Nguyen, D.; Bohata, J.; Ortega Tamarit, B.; Zvanovec, S. (2020). M-QAM signal transmission at the photonically generated K-band over thermal-induced turbulent FSO links with different turbulence distributions. Applied Optics. 59(16):4997-5005. https://doi.org/10.1364/AO.390103S499750055916Zhang, R., Lu, F., Xu, M., Liu, S., Peng, P.-C., Shen, S., … Chang, G.-K. (2018). An Ultra-Reliable MMW/FSO A-RoF System Based on Coordinated Mapping and Combining Technique for 5G and Beyond Mobile Fronthaul. Journal of Lightwave Technology, 36(20), 4952-4959. doi:10.1109/jlt.2018.2866767Lee, C. H. (Ed.). (2017). 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A Novel Radio-Over-Fiber System Based on Carrier Suppressed Frequency Eightfold Millimeter Wave Generation. IEEE Photonics Journal, 9(5), 1-6. doi:10.1109/jphot.2017.2731620Khalighi, M. A., & Uysal, M. (2014). Survey on Free Space Optical Communication: A Communication Theory Perspective. IEEE Communications Surveys & Tutorials, 16(4), 2231-2258. doi:10.1109/comst.2014.2329501Bloom, S., Korevaar, E., Schuster, J., & Willebrand, H. (2003). Understanding the performance of free-space optics [Invited]. Journal of Optical Networking, 2(6), 178. doi:10.1364/jon.2.000178Anderson, H. R. (2003). Fixed Broadband Wireless System Design. doi:10.1002/0470861290Ghassemlooy, Z., Popoola, W., & Rajbhandari, S. (2019). Optical Wireless Communications. doi:10.1201/9781315151724Borah, D. K., & Voelz, D. G. (2009). Pointing Error Effects on Free-Space Optical Communication Links in the Presence of Atmospheric Turbulence. Journal of Lightwave Technology, 27(18), 3965-3973. doi:10.1109/jlt.2009.2022771Esmail, M. A., Ragheb, A., Fathallah, H., & Alouini, M.-S. (2017). Investigation and Demonstration of High Speed Full-Optical Hybrid FSO/Fiber Communication System Under Light Sand Storm Condition. IEEE Photonics Journal, 9(1), 1-12. doi:10.1109/jphot.2016.2641741Libich, J., & Zvanovec, S. (2011). Influences of turbulences in near vicinity of buildings on free-space optical links. IET Microwaves, Antennas & Propagation, 5(9), 1039. doi:10.1049/iet-map.2010.0630Niachou, K., Livada, I., & Santamouris, M. (2008). Experimental study of temperature and airflow distribution inside an urban street canyon during hot summer weather conditions. Part II: Airflow analysis. Building and Environment, 43(8), 1393-1403. doi:10.1016/j.buildenv.2007.01.040Nguyen, D.-N., Bohata, J., Spacil, J., Dousek, D., Komanec, M., Zvanovec, S., … Ortega, B. (2019). M-QAM transmission over hybrid microwave photonic links at the K-band. Optics Express, 27(23), 33745. doi:10.1364/oe.27.033745Nguyen, D.-N., Bohata, J., Komanec, M., Zvanovec, S., Ortega, B., & Ghassemlooy, Z. (2019). Seamless 25 GHz Transmission of LTE 4/16/64-QAM Signals Over Hybrid SMF/FSO and Wireless Link. Journal of Lightwave Technology, 37(24), 6040-6047. doi:10.1109/jlt.2019.2945588Vallejo, L., Komanec, M., Ortega, B., Bohata, J., Nguyen, D.-N., Zvanovec, S., & Almenar, V. (2020). Impact of Thermal-Induced Turbulent Distribution Along FSO Link on Transmission of Photonically Generated mmW Signals in the Frequency Range 26–40 GHz. IEEE Photonics Journal, 12(1), 1-9. doi:10.1109/jphot.2019.2959227Qi, G., Yao, J., Seregelyi, J., Paquet, S., Belisle, C., Zhang, X., … Kashyap, R. (2006). Phase-Noise Analysis of Optically Generated Millimeter-Wave Signals With External Optical Modulation Techniques. Journal of Lightwave Technology, 24(12), 4861-4875. doi:10.1109/jlt.2006.884990Ma, J., Yu, J., Yu, C., Xin, X., Zeng, J., & Chen, L. (2007). Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation. Journal of Lightwave Technology, 25(11), 3244-3256. doi:10.1109/jlt.2007.907794Andrews, L. C., & Phillips, R. L. (2005). Laser Beam Propagation through Random Media. doi:10.1117/3.626196Chen, X., & Yao, J. (2015). A High Spectral Efficiency Coherent Microwave Photonic Link Employing Both Amplitude and Phase Modulation With Digital Phase Noise Cancellation. Journal of Lightwave Technology, 1-1. doi:10.1109/jlt.2015.241945

Usability of a 5G fronthaul based on a DML and external modulation for M-QAM transmission over photonically generated 40 GHz

[EN] In this paper, we numerically and experimentally present the bandwidth constraints of a cost-effective 5G mobile fronthaul based on a directly-modulated laser for data modulation and a Mach-Zehnder modulator-based optical double sideband with carrier suppression scheme for optical millimeter wave (mmW) signal generation. The effect of chirp, fiber dispersion and a combination of both on different bandwidth M-Quadrature Amplitude Modulation (M-QAM) signals, i.e. M = 4, 16 and 64, at 40 GHz has also been investigated. Simulation results are firrst carried out to evaluate the impact of higher chirp of the directly-modulated laser on the link performance as a function of modulation format and signal bandwidth. We then experimentally demonstrate the same scheme transmitting M-QAM signals with bandwidths ranging from 50 to 1000 MHz over a 10 km long single mode fiber. Both experimental and simulation results show that larger signal bandwidths lead to higher optical power penalties due to the combined effect with the error vector magnitudes (EVMs), however still satisfying the required limits of 3GPP standard for allQAMsignals. Experimental measurements also showthe feasibility of including free space optics links in the optical distribution network with no further signi cant penalties. Finally, a multiband signal (three-band) transmission is demonstrated leading to an increase of the total bitrate with the measured EVMs are well below the EVM requirement.This work was supported in part by the Generalitat Valenciana under Grant PROMETEO 2017/103, in part by the Ministerio de Ciencia, Innovacion y Universidades under Grant FOCAL RTI2018-101658-B-I00, in part by the Ministerstvo Prumyslu a Obchodu under Grant FV40089, and in part by the European Cooperation in Science and Technology under Grant CA16220.Vallejo-Castro, L.; Ortega Tamarit, B.; Nguyen, D.; Bohata, J.; Almenar Terre, V.; Zvanovec, S. (2020). Usability of a 5G fronthaul based on a DML and external modulation for M-QAM transmission over photonically generated 40 GHz. IEEE Access. 8:223730-223742. https://doi.org/10.1109/ACCESS.2020.3042756S223730223742

Tratamiento de Elección entre Inyecciones Infiltrativas y Artrocentesis para el Manejo de Dolor y Limitaciones de Apertura Bucal en Trastornos de la Articulación Temporomandibular: una Revisión de Literatura

Introduction: When the functionality of the temporomandibular joint is affected, susceptibility to inflammatory dysfunctions arises, resulting in pain and reduced mandibular mobility. The objective of this article is to assess the available scientific evidence in the literature regarding the benefits of intra-articular injections of hyaluronic acid, corticosteroids, and blood derivatives, with or without arthrocentesis. Materials and Methods: A literature review was conducted on publications between September 2018 and July 2023, using search strategies with key terms and a filter for articles within the last 5 years. Only systematic reviews and/or meta-analyses were considered. A total of 46 results were obtained from PubMed, and 65 results from Google Scholar. Results: A total of 111 articles were obtained, with 98 being excluded due to not meeting all search criteria, duplicates, or unrelated articles. This left 13 selected articles. The reviewed literature demonstrates that all injections in conjunction with arthrocentesis were able to reduce pain and improve maximum mouth opening in patients with temporomandibular disorders. Conclusions: The application of hyaluronic acid injections via arthrocentesis has proven to be effective in improving maximum mouth opening. Additionally, plasma with growth factors and platelet-rich plasma in combination with arthrocentesis show promising results in terms of pain reduction and rapid healing. Lastly, corticosteroids directly affect the articular cartilage and can, in the long term, lead to harmful effects, triggering a phenomenon known as chondrotoxicity.Introducción: Al verse afectada la función de la articulación temporomandibular se genera una susceptibilidad a disfunciones inflamatorias, que generan dolor y reducción de la movilidad mandibular. El objetivo de este artículo es evaluar la evidencia científica disponible en la literatura, sobre los beneficios del ácido hialurónico, corticosteroides y hemoderivados combinados mediante inyecciones intraarticulares con o sin artrocentesis. Materiales y métodos: Se realizó una revisión de la literatura publicada entre septiembre de 2018 y julio del 2023, utilizando estrategias de búsqueda con los términos clave y filtros de 5 años de antigüedad y únicamente revisiones sistemáticas y/o meta-análisis, en PubMed se obtuvieron 46 resultados y en Google Académico se obtuvieron 65 resultados. Resultados: Se obtuvieron un total de 111 artículos, se excluyeron 98, siendo estos todos aquellos que no cubrieron todos los elementos de búsqueda, los duplicados y artículos sin relación, quedando seleccionados 13 artículos. La literatura revisada muestra que todas las inyecciones junto con la artrocentesis lograron reducir el dolor y mejorar la apertura máxima en pacientes con trastornos temporomandibulares. Conclusiones: La aplicación de inyecciones de ácido hialurónico mediante artrocentesis ha demostrado ser efectiva en la mejoría de apertura bucal máxima, también resalta el plasma con factores de crecimiento en el manejo de dolor y plasma rico en plaquetas en conjunto con la artrocentesis generan resultados prometedores en cuanto a la reducción de dolor y rápida cicatrización; por ultimo los corticosteroides afectan directamente al cartílago articular y a largo plazo pueden desencadenar efectos nocivos desencadenando un fenómeno conocido como condrotoxicidad

Impact of Thermal-Induced Turbulent Distribution Along FSO Link on Transmission of Photonically Generated mmW Signals in the Frequency Range 26¿40 GHz

[EN] Microwave photonics is a promising solution to transmit millimeter wave (mmW) signals for the 5th generation (5G) mobile communications as part of a centralized radio access network (C-RAN). In this paper, we experimentally evaluate the impact of turbulent free space optics links on photonically generated mmW signals in the frequency range of 26¿40 GHz . We analyze the remote generation of mmW signals over hybrid links based on free-space optics (FSO) and standard single mode optical fiber (SSMF) with ¿39.97dBm received electrical power and phase noise level at 100kHz as low as ¿95.92dBcHz at 26GHz . Different thermal distributions along the FSO link have been implemented and Gamma-Gamma model has been employed to estimate the thermally induced turbulence. The results show high electrical power decrease and fluctuation of the generated mmW signal according to the particular level of the turbulence in terms of refractive index structure parameter and thermal distribution along the FSO link. 8Gb/s 16-quadrature amplitude modulation (QAM) data transmission at 42GHz has been demonstrated over the hybrid link with minimal error vector magnitude (EVM) value of 5% whereas turbulent FSO link introduced up to 5dB power penalty.This work was supported in part by the Research Excellence Award Programme GVA under Grant PROMETEO 2017/103 and in part by the Spanish Ministerio de Ciencia, Innovacion y Universidades, under RTI2018-101658-B-I00 FOCAL Project and MEYS Project LTC18008 within COST CA16220.Vallejo-Castro, L.; Komanec, M.; Ortega Tamarit, B.; Bohata, J.; Nguyen, D.; Zvanovec, S.; Almenar Terre, V. (2020). Impact of Thermal-Induced Turbulent Distribution Along FSO Link on Transmission of Photonically Generated mmW Signals in the Frequency Range 26¿40 GHz. IEEE Photonics Journal. 12(1):1-9. https://doi.org/10.1109/JPHOT.2019.2959227S1912

Evaluación de la Influencia de pH en la Interfase de Restauraciones Posteriores Utilizando la Técnica de Estampa, Mediante Pruebas de Microfiltración. Estudio in vitro

Objective: To evaluate the effect that acid and alkaline pH produces at the interfase of posterior restorations using the stamp technique, through microleakage tests. Introduction: Caries is a lesion or demineralization of the enamel that can have several causes, including xerostomia, excessive intake of sugars, poor oral hygiene, and an imbalance in salivary pH. A pH lower or higher than 7 can cause clinical signs such as enamel demineralization, abrasion, and caries. There are restoration techniques such as the occlusal stamp technique is an option for restoring these pieces and preserving the natural anatomy of the tooth, achieving aesthetics and functionality. Materials and Methods: 80 posterior teeth without restorations or fractures on their occlusal face were restored using the stamping technique and divided into two groups, exposed to acid and alkaline media for 7 days. Subsequently, methylene blue was applied to them for 3 additional days, cuts were made in two halves of the samples, and they were analyzed using a stereomicroscope, control photographs and a millimeter rule. Results: They were statistically analyzed using the chi square test. Of the 80 total samples, it was found that 40 of them presented microleakages in different degrees 1, 2 or 3. In the acid medium, 23 samples with microleakages (28.75%) were observed, while in the alkaline medium 17 samples (21.25%) were found. Conclusion: The acid and alkaline pH presented microleakages using the stamp technique, however, there was a significant difference between the samples that presented microleakages and those that did not in the different media.Objetivo: Evaluar el efecto que el pH ácido y alcalino produce en la interfase de restauraciones posteriores utilizando la técnica de estampa, mediante pruebas de microfiltración. Introducción: La caries es una lesión o desmineralización del esmalte que puede tener varias causas, entre ellas, xerostomía, ingesta excesiva de azúcares, deficiente higiene bucal y un desequilibrio en el pH salival. Un pH inferior o superior a 7 puede provocar signos clínicos como desmineralización del esmalte, abrasión y caries. Existen técnicas de restauración como la técnica de estampa oclusal es una opción para la restauración de estas piezas y conservación de la anatomía natural del diente, logrando estética y funcionalidad. Materiales y métodos: Se seleccionaron 80 dientes posteriores sin restauraciones, ni fracturas en su cara oclusal, se restauraron utilizando la técnica de estampa y se dividieron en dos grupos, expuestos a medios ácido y alcalino durante 7 días. Posteriormente, se les aplicó azul de metileno durante 3 días adicionales, se realizaron cortes en dos mitades de las muestras y se analizaron utilizando un estereomicroscopio, fotografías de control y una regla milimétrica. Resultados: Fueron analizados estadísticamente utilizando la prueba de chi cuadrado. De las 80 muestras totales, se encontró que 40 de ellas presentaron microfiltraciones en diferentes grados 1,2 y 3. En el medio ácido, se observaron 23 muestras con microfiltraciones (28,75%), mientras que en el medio alcalino se encontraron 17 muestras (21,25%). Conclusión: El pH ácido como alcalino presentaron microfiltraciones utilizando la técnica de estampa, sin embargo, hubo una diferencia significativa entre las muestras que presentaron microfiltraciones y las que no en los distintos medios

On the 40 GHz Remote Versus Local Photonic Generation for DML-Based C-RAN Optical Fronthaul

[EN] Local and remote photonic millimeter wave (mmW) signal generation schemes are theoretically and experimentally evaluated in order to compare both approaches for practical deployment in a cloud radio access network (C-RAN) fronthaul network. The paper presents a full comprehensive formulation of the frequency response of a system based on a directly modulated laser transmitting data over 40 GHz signal which is generated by external carrier suppressed modulation and optical frequency multiplication. Theoretical and experimental characterization of the system response at baseband and mmW band for local and remote generation setups show very good agreement. The remote configuration leads to a higher electrical output power (i.e., 15 dB higher in 25 km fiber links) than the local generation setup in the mmW band due to the combined effect of chirp and fiber dispersion, although intermodulation distortion is higher in the former case. Transmission experiments using quadrature phase-shift keying (QPSK) signals with 250 MHz bandwidth centered at 0.5 GHz over 10 and 25 km fiber links also confirm the superior performance of the remote setup, whereas the local setup leads to similar results to optical back-to-back (OB2B) measurements, which is also validated with data signals centered at different frequencies within the laser bandwidth frequency range. Finally, experimental results show the quality of the recovered signals in terms of error vector magnitude (EVM) as a function of the received electrical power and demonstrate that no further penalties are introduced by photonic mmW signal generation with respect to electrical back-to-back (EB2B) levels.This work was supported in part by Generalitat Valenciana through PROMETEO2017/103, in part by Ministerio de Ciencia, Innovacion y Universidades through FOCAL RTI2018-101658-B-I00, in part by MEYES under Grant LTC18008, in part by the Ministry of Industry and Trade in Czech Republic under Grant FV40089, and in part by European Cooperation in Science and Technology under Grants CA16220 and CA19111.Vallejo-Castro, L.; Mora Almerich, J.; Nguyen, D.; Bohata, J.; Almenar Terre, V.; Zvanovec, S.; Ortega Tamarit, B. (2021). On the 40 GHz Remote Versus Local Photonic Generation for DML-Based C-RAN Optical Fronthaul. Journal of Lightwave Technology. 39(21):6712-6723. https://doi.org/10.1109/JLT.2021.3102818S67126723392

Full-duplex transmission of multi-Gb/s subcarrier multiplexing and 5G NR signals in 39 GHz band over fiber and space

[EN] We propose a stable full-duplex transmission of millimeter-wave signals over a hybrid single-mode fiber (SMF) and free-space optics (FSO) link for the fifth-generation (5G) radio access networks to accelerate the Industry 4.0 transformation. For the downlink (DL), we transmit 39 GHz subcarrier multiplexing (SCM) signals using variable quadrature amplitude modulation (QAM) allocations for multi-user services. As a proof of operation, we experimentally demonstrate the transmission of 3 Gb/s SCM signals (1 Gb/s per user) over a hybrid system consisting of a 10 km SMF and 1.2 m FSO link. For the uplink (UL), satisfactory performance for the transmission of 2.4 Gb/s 5G new radio (NR) signal at 37 GHz over the hybrid system is experimentally confirmed for the first time, to the best of our knowledge. The measured error vector magnitudes for both DL and UL signals using 4/16/64-QAM formats are well below the third generation partnership project (3GPP) requirements. We also further evaluate by simulation the full-duplex transmission over the system in terms of received optical and RF powers and bit error rate performance. A wireless radio distance of approximately 200 m, which is sufficient for 5G small-cell networks, is estimated for both DL and UL direction under the heavy rain condition, based on the available data from Spain. Furthermore, simulation for the DL direction is conducted to verify the superior performance of the system using variable QAM allocation over uniform QAM allocation. Using a variable modulation allocation, up to five users (2 Gb/s per user) can be transmitted over a hybrid 10 km SMF and 150 m FSO link.Ceske Vysoke Uceni Technicke v Praze (SGS20/166/OHK3/3T/13); European Cooperation in Science and Technology (CA19111 NEWFOCUS).Nguyen, D.; Vallejo-Castro, L.; Almenar Terre, V.; Ortega Tamarit, B.; Dat, PT.; Le, ST.; Bohata, J.... (2022). Full-duplex transmission of multi-Gb/s subcarrier multiplexing and 5G NR signals in 39 GHz band over fiber and space. Applied Optics. 61(5):1183-1193. https://doi.org/10.1364/AO.4475291183119361