30cm of spatial resolution using pre-excitation pulse BOTDA technique

A pre-excitation pulse technique in Brillouin optical time domain analysis (PP-BOTDA) for enhancement of the spatial resolution is shown. The technique here exposed is based on the pre-excitation of the stimulated Brillouin scattering and the subtraction of the Brillouin scattering due to the intensity dc level present in the optical pulse. A main optical pulse with 3ns of duration followed by a pulse of 40ns and half the intensity of the main one are used for obtaining 30cm of spatial resolution. The spatial range is 3600m on a standard single mode optical fiber

Quasi-distributed liquid level measurement with adaptable optical fiber transducers

A level and flexible quasi-distributed liquid sensor based on the changes in the light transmittance in a plastic optical fiber cable is proposed. The measurement points are constituted by small areas created by side-polishing on a curved fiber and the removal of a portion of the core. These points are distributed and adapted on each full-turn of a spire of fiber built on a cylindrical tube vertically positioned in a tank. The changes between the refractive indexes of air and liquid generate a signal power proportional to the position and level of the liquid. The sensor system was successfully demonstrated in the laboratory and experimental results of three prototypes with 10, 8, and 5 measurement points and with bend radius of 5mm are presented in this paper

Tunable fiber laser using concatenated non-adiabatic single-mode fiber tapers

An erbium doped fiber ring laser (EDFRL) that incorporates four non-adiabatic concatenated single-mode fiber tapers (acting as tunable filter in the laser cavity) is presented. These concatenated fiber tapers integrates a filter with a narrower band-pass and a higher modulation depth than a single taper. The tuning of this filter was implemented applying a controlled perturbation in the fiber taper. The proposed laser architecture was successfully demonstrated in the laboratory in which a tuning range of 20.8nm (1544.5nm-1565.3nm) were measured

Spectral evolution of long-period fiber grating during written process and their influence in the sensitivity

The peak loss wavelength shift, attenuation and bandwidth values on a LPG during the UV multi-pass writing process can be used to estimate the LPG sensitivities in real-time during the fabrication task

Optimal design and implementation of a temperature and strain optical transducer using FBGs and fiber taper hybrid structure

A temperature and strain optical fiber transducer and its optimal design are presented. The hybrid structure is composed of two Fiber Bragg Gratings (FBG) in a fused taper. Using the same phase mask one of the FBG is written outside of the taper, and the other one in the middle of the taper, in the area with constant diameter. The taper diameter and the structure length play a key role on the transducer behaviour. Useful results to optimize the transducer structure design, from a theoretical and experimental investigation, are reported in this paper

Transductor basado en redes de difracción en fibra óptica

Un transductor que comprende: una pletina que comprende una primera red de difracción en fibra óptica situada en su superficie superior y una segunda red de difracción en fibra óptica situada en su superficie inferior, donde dichas primera y segunda redes de difracción en fibra óptica están configuradas para traducir un cambio de curvatura en dicha pletina en un desplazamiento de la longitud de onda correspondiente a cada red de difracción en fibra óptica. El transductor comprende además una primera pieza y una segunda pieza unidas entre sí a través de al menos un eje, estando dicha pletina fijada a al menos uno de los lados de una de las piezas estando el transductor configurado para cambiar la curvatura de dicha pletina mediante un cambio del ángulo que forman dichas primera pieza y segunda piezaSolicitud: 201001178 (07.09.2010)Nº Pub. de Solicitud: ES2364469A1 (05.09.2012)Nº de Patente: ES2364469B2 (03.05.2012

Angle transducer based on fiber Bragg gratings able for tunnel auscultation

In this paper an angle transducer based on Fiber Bragg Grating (FBG) is presented. Two gratings are glued to a metallic platen, one in each side. It is insensitive to temperature changes, given that the temperature shifts affect equally to both FBG. When the platen is uniformly bent an uniform strain appears in both sides of the platen. It depends on the bend angle and the platen length and thickness. The transducer has been designed to be used in the auscultation of tunnels during their construction process and during their live time. The transducer design and its characterization are presented

Mode width sensitivity with strain in index guided Photonic Crystal Fibres

RESUMEN: Se estudia el comportamiento de la anchura del modo fundamental en una Fibra de Cristal Fotónico (FCF) guiada por índice cuando se aplica un estiramiento en un rango de valores comprendido entre 0.5 y 2.5%ε. Se identifican las regiones de frecuencia normalizada (Λ/λ) y de la fracción de llenado de aire d/Λ en los que se observa la máxima influencia del estiramiento en la sensibilidad. Finalmente, se analiza y discute su evolución.ABSTRACT: The fundamental mode width behaviour is studied for an index guided Photonic Crystal Fibre (PCF) when strain is applied in a range of values between 0.5 and 2.5%ε. The regions of normalized frequency (Λ/λ) and of the filling air fraction d/Λ, in which maximum strain influence is observed, are identified. Finally, its evolution is analyzed and argued

New method for previsional design of fabrication process of LPG’s with a given sensitivity

A theoretical-experimental based method able to design in advance the fabrication process for a given sensitivity (temperature, strain, surround index, ...) is proposed. Previous and proper characterization of the LPG specific fabrication technique is required

Brillouin fiber laser for remote interrogation of multiple fiber Bragg gratings in series

RESUMEN: En este artículo se presenta un sistema sensor de temperatura basado en un láser de efecto Brillouin en fibra óptica. La onda Stokes generada tras el proceso de scattering se hace resonar en una cavidad láser que combina ganancia Brillouin y amplificación por fibra de Erbio y su potencia se analiza mediante la técnica de detección heterodina. Se consigue interrogar 3 redes de difracción situadas a 50 km de la unidad de procesado con una potencia de bombeo de 7.5 mW.ABSTRACT: A temperature sensing system based on a Brillouin fiber laser is presented. Erbium amplification and Brillouin gain are combined in order to make the Stokes radiation resonate in the cavity. The laser output is analyzed by means of heterodyne detection. 3 fiber Bragg gratings are interrogated at 50 km away from the processing unit employing 7.5 mW as pump signal