Fernández Vallejo, Montserrat

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https://academica-e.unavarra.es/handle/2454/49024

Last Name

Fernández Vallejo

First Name

Montserrat

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Ingeniería Eléctrica y Electrónica

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750618

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8522

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Now showing 1 - 10 of 18

Open Access
Low noise dual-wavelength erbium fiber laser in single-longitudinal-mode operation
(Springer, 2012) Rota Rodrigo, Sergio; Pérez Herrera, Rosa Ana; Fernández Vallejo, Montserrat; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A new stable dual-wavelength fiber-ring laser based on erbium-doped fiber amplification is reported. The laser is based on ring resonators and employs fiber Bragg gratings to select the operation wavelengths. The topology of the laser has a significant influence in its performance: allowing an independent control of the losses for both lasing wavelengths and achieving a low noise configuration. As a result, it is experimentally demonstrated that both emission lines work in single-longitudinal-mode operation and the topology offers a better stability and higher optical signalto-noise ratios than similar configurations.
Open Access
Stabilization of dual-wavelength erbium doped ring fiber lasers by single-mode operation
(IEEE, 2010) Quintela, M. A.; Pérez Herrera, Rosa Ana; Canales, Irene; Fernández Vallejo, Montserrat; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, a novel single-longitudinal-mode (SLM) dual-wavelength laser configuration is proposed and demonstrated. This laser is based on ring resonators, and employs fiber Bragg gratings to select the operation wavelengths. It includes a short piece of highly doped Er-fiber that acts as the active medium. The stable SLM operation is guaranteed when the two lasing channels present similar output powers. This behavior is shown for different pump powers.
Open Access
L-band multiwavelength single-longitudinal mode fiber laser for sensing applications
(IEEE / OSA, 2012) Pérez Herrera, Rosa Ana; Ullán Nieto, Ángel; Leandro González, Daniel; Fernández Vallejo, Montserrat; Quintela, M. A.; Loayssa Lara, Alayn; López Higuera, José Miguel; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, a novel single-longitudinal-mode (SLM) four-wavelength laser configuration for sensing applications in the L-band is proposed and experimentally demonstrated. The sensor system presented here is based on ring resonators, and employs fiber Bragg gratings to select the operation wavelengths. The stable SLM operation is guaranteed when all the lasing channels present similar output powers. It is also experimentally demonstrated that when a SLMbehavior is achieved, lower output power fluctuations are obtained. Characterization of the lasing structure for temperature sensing is also shown.
Open Access
Dual stage ytterbium doped fiber laser in MOPA configuration
(Bentham Open, 2012) Fernández Vallejo, Montserrat; Monelli, D.; Passaro, D.; Cucinotta, A.; Selleri, S.; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We report the experimental demonstration of an Ytterbium doped fiber laser (YDFL) composed by two stages in cascade. Two sorts of Ytterbium doped fiber (YDF) with different concentration have been used. A proper characterization of the YDFs has been performed in order to find the optimum YDF length. To this end, the output power and the slope-efficiency have been calculated and the signal amplification and the amplified spontaneous emission (ASE) spectra have been analyzed, which are strictly related to the absorption and emission cross-section of the YDF. The first stage has been studied for both continuous wave (CW) and pulsed regime. The results show that by using an YDF with a high slope-efficiency, up to 66%, it is possible to reach an emitted peak power of 30 W in a pulsed regime.
Open Access
Random fiber lasers: application to fiber optic sensors networks
(IEEE, 2017) López-Amo Sáinz, Manuel; Leandro González, Daniel; Miguel Soto, Verónica de; Bravo Acha, Mikel; Fernández Vallejo, Montserrat; Pérez Herrera, Rosa Ana; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
Recently, random mirrors have been proposed as a method to create fiber laser cavities. This kind of cavity is based on cooperative Rayleigh scattering, which is generated along a fiber due to the material inhomogeneities presented in that fiber. In this work, basics of Random fiber lasers and different demonstrated lasing sensors systems for interrogating arrays of optical fiber sensors are shown. These systems use different kinds of amplification and cavities schemes and can interrogate optical fiber sensors located up to 225 km away.
Open Access
Comparative study of ring and random cavities for fiber lasers
(Optical Society of America, 2014) Fernández Vallejo, Montserrat; Rota Rodrigo, Sergio; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
An experimental comparison of three fiber laser structures with the same Raman gain medium is presented in order to establish the main pros and cons of each basic scheme. The first fiber laser is based on a hybrid ring–random fiber laser, the second one is a pure ring fiber laser, and the last one is a random fiber laser. Several aspects have been taken into account in the study. First, from the optical point of view, the parameters of interest compared are output power, lasing threshold, slope efficiency, power fluctuations, and the longitudinal modes have been analyzed. Second, the possible utilization of fiber lasers in digital modulated optical communication systems is also studied.
Open Access
Internal modulation of a Random fiber laser
(Optical Society of America, 2013) Bravo Acha, Mikel; Fernández Vallejo, Montserrat; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A characterization of a modulated random mirror laser has been experimentally carried out. Unlike conventional internally modulated fiber lasers, no distortion of the modulating frequency or self-mode-locking effects were measured. The behavior of the laser using pulsed and analog modulation up to 12 GHz is shown.
Open Access
Resilient amplified double ring optical networks to multiplex optical fibre sensors
(IEEE / OSA, 2009) Fernández Vallejo, Montserrat; Pérez Herrera, Rosa Ana; Elosúa Aguado, César; Díaz Lucas, Silvia; Urquhart, Paul; Bariáin Aisa, Cándido; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We report the experimental demonstration of two configurations of an amplified optical fibre double ring network for the multiplexing of sensors. The networks are designed to be inherently resilient to fibre failures because they enable simultaneous interrogation of all the optical fibre sensors using both rings. The first design demonstrates the feasibility of the so called 'dedicated protection' and the second one 'shared protection' for fibre optic intensity sensors. Raman amplification is used to overcome the losses of the couplers used in the rings, providing power transparency. The first network uses Raman amplification in both constituent rings but in the second one Raman pumping is activated only when a fibre failure occurs. We demonstrate how the topology allows the received powers from the sensors to be equalized.
Open Access
Advanced graphene-based transparent conductive electrodes for photovoltaic applications
(MDPI, 2019) Fernández, Susana; Boscá, Alberto; Pedrós, Jorge; Inés Ortigosa, Andrea; Fernández Vallejo, Montserrat; Arnedo Gil, Israel; González, José Pablo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
New architectures of transparent conductive electrodes (TCEs) incorporating graphene monolayers in different configurations have been explored with the aim to improve the performance of silicon-heterojunction (SHJ) cell front transparent contacts. In SHJ technology, front electrodes play an important additional role as anti-reflectance (AR) coatings. In this work, different transparent-conductive-oxide (TCO) thin films have been combined with graphene monolayers in different configurations, yielding advanced transparent electrodes specifically designed to minimize surface reflection over a wide range of wavelengths and angles of incidence and to improve electrical performance. A preliminary analysis reveals a strong dependence of the optoelectronic properties of the TCEs on (i) the order in which the different thin films are deposited or the graphene is transferred and (ii) the specific TCO material used. The results shows a clear electrical improvement when three graphene monolayers are placed on top on 80-nm-thick ITO thin film. This optimum TCE presents sheet resistances as low as 55 Ω/sq and an average conductance as high as 13.12 mS. In addition, the spectral reflectance of this TCE also shows an important reduction in its weighted reflectance value of 2-3%. Hence, the work undergone so far clearly suggests the possibility to noticeably improve transparent electrodes with this approach and therefore to further enhance silicon-heterojunction cell performance. These results achieved so far clearly open the possibility to noticeably improve TCEs and therefore to further enhance SHJ contact-technology performance.
Open Access
Robust fiber-optic sensor networks
(Springer, 2012) Pérez Herrera, Rosa Ana; Fernández Vallejo, Montserrat; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The ability to operate despite failure will become increasingly important as the use of optical sensor networks grows, and the amount of sensing information to be handled by a sensor network is increasing, especially for safety and security applications. In this review, the four categories of protection to allow service to be reestablished after a failure (dedicated/shared and line/path) are thoroughly discussed. This paper also presents an overview of the most representative robust fiber-optic sensor systems, discussing their schemes, pros and cons.