Open Access
Narrow-linewidth multi-wavelength random distributed feedback laser
(IEEE / OSA, 2015) Leandro González, Daniel; Rota Rodrigo, Sergio; Ardanaz, Diego; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, narrow-band emission lines are generated by means of two random distributed feedback fiber laser schemes. Spectral line-widths as narrow as 3.2 pm have been measured, which significantly improves previous reported results. The laser is analyzed with the aim of obtaining a spectral line-width as narrow as possible. Additionally a variation of this setup for multi-wavelength operation is also validated. Both schemes present a simple topology that use a combination of phase-shifted fiber Bragg gratings and regular fiber Bragg gratings as filtering elements.
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
Single-longitudinal mode laser structure based on a very narrow filtering technique
(Optical Society of America, 2013) Rodríguez Cobo, Luis; Quintela, M. A.; Rota Rodrigo, Sergio; López-Amo Sáinz, Manuel; López Higuera, José Miguel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A narrow filtering technique based on the spectral overlapping of two uniform FBGs and applied to obtain a Single Longitudinal Mode (SLM) laser is proposed and demonstrated in this work. The two FBGs are spectrally detuned to reduce their coincident reflection response narrowing the equivalent filter bandwidth. A proof-of-concept linear laser has been built and tested exhibiting SLM operation even with temperature and strain variations.
Open Access
Simultaneous measurement of humidity and vibration based on a microwire sensor system using Fast Fourier Transform technique
(IEEE, 2016) Rota Rodrigo, Sergio; López Aldaba, Aitor; Pérez Herrera, Rosa Ana; López Bautista, María del Carmen; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The point sensor is able to measure a wide humidity range (20%-70% relative humidity) with a maximum sensitivity reached of 0.14πrad/% relative humidity. This microwire sensor is also operated within a frequency range from 320 to 1300 Hz with a sensitivity of around 0.0051 nm -1 /Hz. Finally, due to the system uses an optical interrogator as unique active element, the system presents a cost-effective feature.
Open Access
Optical fiber sensors for asphalt structures monitoring
(Optica Publishing Group, 2016) Bravo Acha, Mikel; Rota Rodrigo, Sergio; Leandro González, Daniel; Loayssa Lara, Alayn; Urricelqui Polvorinos, Javier; Bravo Acha, A.; Bravo Navas, M.; Mitxelena, J. R.; Martínez Mazo, J. J.; López-Amo Sáinz, Manuel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A novel optical fiber installation method was explored for asphalt monitoring. Glassfiber polymer encapsulated SMF was installed in the intermediate and surface layers in order to study the strain sensitivity with a distributed strain interrogator.
Open Access
Watt-level green random laser at 532 nm by SHG of Yb-doped fiber laser
(Optical Society of America, 2018) Rota Rodrigo, Sergio; Gouhier, B.; Dixneuf, C.; Antoni Micollier, L.; Guiraud, G.; Leandro González, Daniel; López-Amo Sáinz, Manuel; Traynor, N.; Santarelli, Giorgio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
We have developed a Watt-level random laser at 532 nm. The laser is based on a 1064 nm random distributed ytterbium-gain assisted fiber laser seed with a 0.35 nm line-width and 900 mW polarized output power. A study for the optimal length of the random distributed mirror was carried out. An ytterbium-doped fiber master oscillator power amplifier architecture is used to amplify the random seeder laser without additional spectral broadening up to 20 W. By using a periodically poled lithium niobate(PPLN) crystal in a single pass configuration we generate in excess of 1 W random laser at 532 nm by second harmonic generation with an efficiency of 9%. The green random laser exhibits an instability <1%, optical signal to noise ratio >70 dB, 0.1 nm linewidth and excellent beam quality.
Open Access
Compound lasing fiber optic ring resonators for sensing
(SPIE, 2014-06-02) Rota Rodrigo, Sergio; González Herráez, Miguel; López-Amo Sáinz, Manuel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
In this work, we present a new method for increasing simultaneously the sensitivity and interrogation stability of fiberoptic intensity sensors. The configuration is based on a double-coupler ring resonator. On one side, the attenuation sensitivity of the sensor is enhanced by placing it inside a ring resonator. On the other side, the stability of the interrogation method is rendered close to perfect by creating an external lasing ring resonator with matched spectral response. The resulting lasers allow the stable interrogation of the sensors with an impressive sensitivity enhancement. In our experiments, the dynamic range of the intensity sensor (and consequently its sensitivity) is increased 15 dB by using this laser-based interrogation system. Simultaneously, the instability of the system is reduced to ±0.05 dB. In comparison with systems based on external interrogation, our method is >100 times more stable and also simpler, as no wavelength tunable elements are required.
Open Access
Control of the strain sensitivity using a suspended core photonic crystal fiber sensing head
(SPIE, 2014-06-02) Rota Rodrigo, Sergio; López-Amo Sáinz, Manuel; Kobelke, J.; Schuster, K.; Santos, José Luís; Frazão, Orlando; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work a strain sensor based on a suspended core fiber is proposed. The sensor comprises a suspended core PCF between SMFs and is based on the multimode interference generated in these transitions. A strain sensitivity study for different sensing heads and stage separation lengths was carried out showing a sensitivity of -2.42 pm/με for the best case. Also the sensing head was tested for curvature and temperature, showing in the first case that it is insensitive to curvature effects, and secondly, that for small sensor lengths it was insensitive to temperature variations.
Open Access
An in-reflection strain sensing head based on a Hi-Bi photonic crystal fiber
(MDPI, 2013) Rota Rodrigo, Sergio; Rodrigues Pinto, Ana Margarida; Bravo Acha, Mikel; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A photonic crystal fiber-based sensing head is proposed for strain measurements. The sensor comprises a Hi-Bi PCF sensing head to measure interferometric signals in-reflection. An experimental background study of the sensing head is conducted through an optical backscatter reflectometer confirming the theoretical predictions, also included. A cost effective setup is proposed where a laser is used as illumination source, which allows accurate high precision strain measurements. Thus, a sensitivity of ~7.96 dB/me was achieved in a linear region of 1,200 μe.
Open Access
Simultaneous measurement of humidity and vibration based on a nanowire sensor system using Fast Fourier Transform technique
(IEEE, 2016) Rota Rodrigo, Sergio; López Aldaba, Aitor; Pérez Herrera, Rosa Ana; López Bautista, María del Carmen; Esteban, Óscar; López-Amo Sáinz, Manuel; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency ...