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. ; The authors are grateful to the Spanish Government project TEC2010-20224-C02-01.
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. ; The authors are grateful to the Spanish Government project TEC2010-20224-C02-01.
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. ; This work was supported in part by the Spanish Government project TEC2007-67987-C02 and in part by the European project COST-299.
This work presents an experimental demonstration of a scheme based on an internally modulated fiber ring laser for high-sensitivity temperature sensing. The attained temperature resolution has been as low as ± 2pm even when a commercial FBG with a sensitivity of 10 pm/°C was used. Thus, a fivefold improvement in the temperature sensor resolution can be achieved when compared to a simple FBG interrogation scheme. In addition to this, the measuring range could be selected only by changing the frequency modulation of the fiber ring laser. This technology also allows to triple the photodiode bandwidth unambiguously when temperature or strain measurements are carried out, which is a remarkable achievement in term of cost reduction. ; This work was supported by the Spanish Government projects TEC2013-47264-C2-2-R and TEC2014-58048-C2-1-P.
In the present work, the effect of gamma radiation on the performance of different types of erbium-doped fibers (EDFs) when they are used in a fiber ring cavity (FRC) configuration is studied. Several pieces of commercial EDF are gamma-ray irradiated with different doses to evaluate the output power variations over time. The influence of different doses, from 150 Gy to 1000 Gy, over the output power level measurement and their amplified spontaneous emission (ASE) are experimentally evaluated both in the C and L bands. By using an FRC configuration we can detect the presence of gamma radiation. We can also estimate the irradiation doses applied to EDFs by measuring the slope of the short-term emission power. ; This work was supported in part from the Spanish AEI within project TEC2016-76021-C2-1-R, Innocampus, Projects for young researchers UPNA 2019 and FEDER funds from the European Union are acknowledged. The reported investigations were performed in the frame of the COST Action MP 1401. The Romanian authors acknowledge the financial support of the Romanian Ministry of Education and Research, under Romanian National Nucleu Program LAPLAS VI—Contract n. 16N/2019. ; This work was supported in part from the Spanish AEI within project TEC2016-76021-C2-1-R, Innocampus, Projects for young researchers UPNA 2019 and FEDER funds from the European Union are acknowledged. The reported investigations were performed in the frame of the COST Action MP 1401. The Romanian authors acknowledge the financial support of the Romanian Ministry of Education and Research, under Romanian National Nucleu Program LAPLAS VI—Contract n. 16N/2019.
In this paper, a random distributed feedback fiber laser is proposed as a multiplexing scheme for ultralong range measurements (up to 200 km). Optical fiber sensors are time and wavelength multiplexed overcoming one of the main limitations of long-range sensing setups, which is their limited multiplexing capability. The direct modulation of the laser's cavity allows the interrogation of sensors by measuring the reflected power for different wavelengths and distances. Fiber Bragg gratings placed at different fiber locations and wavelengths have been interrogated in two different sensor networks. In addition, in order to improve the performance of the system, some features have been analyzed. ; This work was supported by the Spanish Government project TEC2013-47264-C2-2-R and the FEDER funds.
Trabajo presentado a la 26th International Conference on Optical Fiber Sensors. Suiza, 2020 ; A fiber ring laser cavity configuration was used to analyze the effect of gamma-irradiation over the performance of different types of erbium doped fibers. Preliminary results validates this method to monitor gamma-radiation in real time. ; Financial support from the Spanish Comisión Interministerial de Ciencia y Tecnología within project TEC2016- 76021-C2-1-R and FEDER funds from the European Union are acknowledged. The reported investigations were performed in the frame of the COST Action MP 1401.
In this work, a multi-parameter point sensor based on the combination of Fabry-Perot (FP) and the anti-resonant (AR) reflecting guidance in cascade configuration is proposed and experimentally demonstrated. This structure, based on FP interference and AR reflecting guidance, was fabricated with two different air micro-cavities. The attained experimental results showed different strain and temperature sensitivities for the antiresonance contribution. However, when analyzing the FP interference, only strain sensitivity was observed, demonstrating that this air micro-cavity was also insensitive to temperature variations. ; This work was supported by the Spanish AEI projects TEC2016-76021-C2 and PID2019-107270RB-C22, FEDER Funds, the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 838143, Projects for young researches UPNA 2019, "Caja Navarra" and "la Caixa" foundations under agreement LCF/PR/PR13/51080004 and the grant BGP18/00180 of the "Beatriz Galindo" programme from the Spanish Ministry of Science, Innovation and Universities.
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. ; This work was supported in part by the Spanish Comision Interministerial de Ciencia y Tecnología within project TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union.
An experimental comparison of stability between two different fiber laser topologies is carried out. The lasers are based on ring resonators that include highly-doped Er-fibers. Both topologies use fiber Bragg grating reflectors in order to select the emission wavelengths. The experimental results confirms that the novel topology based on fiber optic circulators arranged in an hybrid serial-parallel configuration offers a better stability and higher optical signal to noise ratios (OSNR) than the simpler based on a parallel configuration. ; This work was supported in part by the Spanish Government TEC2007-67987-C02, European COST-299.
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. ; The authors would like to thank the financial support from Spanish Comisión Interministerial de Ciencia y Tecnología within projects TEC2016-76021-C2-1-R and TEC2013-47264-C2-2-R, Campus Iberus and FEDER funds from the European Union.
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 . ; This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within project TEC2013-47264-C2-2-R and SUDOE ECOAL-MGT and FEDER funds from the European Union.
In this work, a fiber ring laser sensor has been employed to analyze the influence of passive Er-doped fiber acting as saturable absorber. Lasing modes of fiber ring lasers can be reduced by properly locating a saturable absorber that narrows the spectral width of the FBG that selects the lasing wavelength. Employing commercial Er-doped fiber, different configurations have been evaluated, reaching the SLM regime on a ring cavity of several meters. Thus, the achieved strain response of the whole sensor behaves at its mirror FBG, exhibiting linear response to strain. ; This work has been supported by the project TEC2013-47264-C2 and TEC2016-76021-C2, of the Spanish government and by a Parliament of Cantabria postdoc grant.
In this work, an experimental analysis of the performance of different types of quasi-randomly distributed reflectors inscribed into a single-mode fiber as a sensing mirror is presented. These artificially-controlled backscattering fiber reflectors are used in short linear cavity fiber lasers. In particular, laser emission and sensor application features are analyzed when employing optical tapered fibers, micro-drilled optical fibers and 50 μm-waist or 100 μm-waist micro-drilled tapered fibers (MDTF). Single-wavelength laser with an output power level of about 8.2 dBm and an optical signal-to-noise ratio of 45 dB were measured when employing a 50 μm-waist micro-drilled tapered optical fiber. The achieved temperature sensitivities were similar to those of FBGs; however, the strain sensitivity improved more than one order of magnitude in comparison with FBG sensors, attaining slope sensitivities as good as 18.1 pm/με when using a 50 μm-waist MDTF as distributed reflector. ; This work is part of the project PID2019-107270RB, funded by MCIN/ AEI/10.13039/501100011033 and FEDER "A way to make Europe", the Ministerio de Educación, Cultura y Deporte of Spain (PhD grant FPU2018/02797), the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 838143, the Beatriz Galindo BEAGAL18/00116 fellowship, the "Fundación Caja Navarra" and "Fundación la Caixa" with the proyect LCF/PR/PR13/51080004 and Projects for young researches UPNA 2019
In this work, we present an experimental measurement of temperature and strain sensitivities of a micro-drilled optical fiber (MDOF). The MDOF consisted of a quasi-randomly distributed reflector along a single mode fiber (SMF). A fiber cavity laser based on MDOF was experimentally studied, attaining a single-wavelength laser emission centered at 1568.6nm. The output power level obtained from this single-laser oscillation when pumped at 140mW was around - 9.6dBm, and an optical signal to noise ratio (OSNR) of around 45dB was measured. Although temperature sensitivities of fiber Bragg gratings used as sensors are similar to our MDOF, strain sensitivity is enhanced around one order of magnitude when the MDOF was used. ; This work was supported by the Spanish AEI TEC2016-76021-C2, FEDER Funds, and the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 838143.
