Fotonika eta argiaren nazioarteko urtea

Lección inaugural del curso académico 2015-2016Enlace a la versión en euskera: https://hdl.handle.net/2454/28896El autor analiza la importancia de la luz en nuestra sociedad

La fotónica y el año internacional de la luz

Lección inaugural del curso académico 2015-2016Enlace a la versión en castellano: https://hdl.handle.net/2454/2397

Dual-wavelength single-longitudinal-mode erbium fiber laser for temperature measurements

A dual-wavelength erbium fiber laser with single-longitudinal-mode characteristic is proposed and demonstrated. The system uses a 7-m-long highly doped erbium-doped fiber as the primary gain medium while two fiber Bragg gratings (FBGs) act as a wavelength selection mechanism. The sensing capability of the FBGs gives this source the possibility to be also used in a dual-sensor multiplexing scheme. The system is very stable and suitable for sensor multiplexing.Financial support from the Spanish Ministerio de Educación y Ciencia, project TEC2010-20224-C02-01, ECOAL-MGT Project corresponding to the E.U. SUDOE Program and to Liekki for the highly Er-doped fiber is acknowledged

All-PM fiber loop mirror interferometer analysis and simultaneous measurement of temperature and mechanical vibration

In this work, a new all-polarization maintaining (PM) fiber loop mirror interferometer is proposed and validated as temperature and mechanical vibration sensor. The scheme employs the arms of a PM coupler as communication fibers, fused with a relative angle of 45° to the sensing fiber. The length of the arms is equal so their contribution in canceled, obtaining a total transfer function exclusively defined by the sensing fiber. The capabilities of the system as sensor are tested, achieving mechanical vibration and temperature sensing without crosstalk between measurands. In this manner, vibration frequencies up to 1.5 kHz have been monitored using a commercial interrogator with a scan rate of 1 Hz and a technique based on the fast Fourier transform. Additionally, the immunity of the setup to external perturbations in the communication fibers is studied and compared to the conventional approach.This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2013-47264-C2-2-R and TEC2016-76021-C2-1-R and in part by the Institute of Smart Cities by means of a postdoctoral fellowship

Simultaneous temperature and vibration monitoring using an all-PM fiber loop mirror interferometer

In this work, an all-polarization maintaining fiber loop mirror interferometer is presented and validated as vibration and temperature sensor without crosstalk between measurands. The system is entirely built using polarization-maintaining (PM) fiber and a PM optical coupler. As a consequence, no polarization controllers are needed in the cavity, significantly simplifying the operation of the system and improving the stability and accuracy of the measurements. The loop comprises three PM fiber sections appropriately fused with an angle offset between them. In this manner, the interference is maximized and the sensing contributions of the two PM fibers used as communications channels are suppressed. The third PM fiber is used as the sensor itself, simultaneously monitoring temperature and mechanical vibration up to 1.2 kHz by means of an interrogation technique based on fast Fourier transform.Financial support from the Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2013-47264- C2-2-R and TEC2016-76021-C2-1-R

All-fiber lasers through photonic crystal fibers

A review on all-fiber lasers based on photonic crystal fibers is presented. Photonic crystal fibers present improved features beyond what conventional optical fibers can offer. Due to their geometric versatility, photonic crystal fibers can present special properties and abilities which can lead to enhanced lasing structures. A brief description of photonic crystal fibers and fiber laser’s properties is presented. All-fiber laser structures developed using photonic crystal fibers are described and divided in two groups, depending on the cavity topology: ring cavity fiber lasers and linear cavity fiber lasers. All-fiber lasers applications in the photonic crystal fiber related sensing field are described.The authors are grateful to the Spanish government project TEC2010-20224-C02-01 and the European project ECOAL-MGT – SUDOE Program

Optimization of the available spectrum of a WDM sensors network using a mode locked laser

This work experimentally proposes a new interrogation method which consists on the combination of the information given by both domains: time and frequency. On the one hand, the sensor information is obtained in the frequency domain as usual and, on the other hand, the detection of the different pulses generated through mode locking allows the identification of each FBG. It has been proved that FBGs spaced less than 0.15 nm can be interrogated. The sensor network based on simple ring Erbium doped fiber laser using the FBGs, located in a serial configuration, as wavelength selective reflectors for the lasing structure, acting them also as the sensing transducers elements.This work was supported in part by the Spanish Government projects TEC2013-47264-C2-2-R, innocampus and FEDER funds

Comparative study of ring and random cavities for fiber lasers

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.The authors would like to acknowledge the financial support from the Spanish Ministerio de Educación y Ciencia through project TEC2010-20224-C02-01

Stable multi-wavelength erbium fiber ring laser with optical feedback for remote sensing

In this work, we demonstrate a stable fiber sensing system for remote temperature measurements, where the sensing element is an array of four fiber Bragg gratings (FBGs) and sensor interrogation is achieved with a multi-wavelength erbium fiber ring laser. By introducing a feedback fiber loop in a fiber ring cavity, four laser emission lines were obtained simultaneously in single-longitudinal mode operation (SLM). The power instability obtained was lower than 0.5 dB with an optical signal-to-noise ratio (OSNR) higher than 50 dB for all the emitted wavelengths. The application of this system for remote temperature measurements has been demonstrated even though the SLM regime cannot be preserved.This work was supported by the Spanish Ministerio de Ciencia y Tecnologia through project TEC2013-47264-C2-2-R and the INTERREG SUDOE Project “ECOAL-MGT-Ecological Management of Coal Waste Piles, SOE3/P2/P714”

Internal modulation of a Random fiber laser

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.This work was supported by the Spanish Government project TEC2010-20224-C02-01