In this paper we present the design of a layered technical textile blocks for measuring temperature and strain using FBG gratings. In addition to research into individual layers of technical textiles, we also deal with joining methods to ensure sufficient strength while maintaining the flexibility of the created textile block. The textile with dimensions of 1x1 meter is designed for use in critical infrastructure security, such as a protection of secured area. A unique, robust connector using GRIN lenses was designed to connect the individual blocks. This special connector has dimensions 30x10x4.5mm and insertion loss of about 5dB.
In the paper we present smart textiles for application in critical infrastructures based on fiber Bragg grating sensors. The suitability of the selected polyester fabric was evaluated by experimental measurement. Low elasticity caused an irreversible deformation of the fabric and thus change of the reference value when stretching the textile. With a 4.5 Newton tensile, the reference value change was up to 0.14 pm. Therefore, a combination of two layers of different textiles was tested. The second layer caused less deformation of the first layer by up to 50 percent.
We present system of structure health measurement by optical fiber sensors based on fiber Bragg gratings. Our system is focused to additionally install to existing buildings. We prepared first set-up of the system to monitoring of the nuclear power plant containment shape deformation. The presented system can measure up to several tens of sensors simultaneously. Each sensor contains optical fiber grating to measurement of change of length and the other independed fiber grating to monitor the temperature and the other ineligible effects.
We present optical fiber sensors to measurement strain and vibration. The sensors are based on fiber Bragg gratings (FBG). We prepared construction of strain sensors with respect to its implementation on the outer surface of concrete structures and with compensation of potential temperature drifts. These sensors are projected with look forward to maximal elongation and strength which can be applied to the sensor. Each sensor contains two optical fibers with FBGs. One FBG is glued into the sensor in points of fixation which are in the line with mounting holes. This FBG is prestressed to half of measurement range, than the stretching and pressing can be measured simultaneously by one FBG. The second FBG is placed inside the sensor without fixation to measure temperature drifts. The sensor can be used to structure health monitoring. The sensors to measurement vibration are based on tilted fiber Bragg grating (TFBG) with fiber taper. The sensor uses the TFBG as a cladding modes reflector and fiber taper as a bend-sensitive recoupling member. The lower cladding modes (ghost), reflected from TFBG, is recoupled back into the fiber core via tapered fiber section. We focused on optimization of TFBG tilt angle to reach maximum reflection of the ghost and taper parameters. In this article we present complete set-up, optical and mechanical parameters of both types of sensors.
We present vibration fiber sensor set up based on tilted fiber Bragg grating (TFBG) and fiber taper. The sensor uses the TFBG as a cladding modes reflector and fiber taper as a bend-sensitive recoupling member. The lower cladding modes (ghost), reflected from TFBG, is recoupled back into the fiber core via tapered fiber section. We focused on optimization of TFBG tilt angle to reach maximum reflection of the ghost and taper parameters. Comparative measurements were made using optical spectrum analyzer and superluminiscent diode as broadband light source. We present dependence between intensity of recoupled ghost mode and sensor deflection.
We present system of structure health measurement by optical fiber sensors based on fiber Bragg gratings. Our system is focused to additionally install to existing buildings. We prepared first set-up of the system to monitoring of the nuclear power plant containment shape deformation. The presented system can measure up to several tens of sensors simultaneously. Each sensor contains optical fiber grating to measurement of change of length and the other independed fiber grating to monitor the temperature and the other ineligible effects.
We present the simulation method to calculation of arbitrary fiber grating (apodized, chirp etc.) with high precision by
combination of methods based on layered dielectric media (LDM) and transfer matrix. On the contrary to the other
calculation techniques the LDM method is based on sequence of thin films of dielectric media assembled in the direction
of wave propagation. The critical parameter of fiber gratings, the bandwidth can be narrowed by higher refractive index
change, longer gratings or by multiplying fiber gratings. On the basis of our simulations and measurements of the
commercially available fiber gratings we designed a special 100 mm long fiber Bragg grating with apodization. Finally,
we simulated parameters of fiber gratings arrays-multiple fiber gratings. We expect the application of FBGs to
improvement of the linewidth and mode-hop free tuning range of semiconductor lasers at the wavelength 760 nm to
increase resolution of fiber laser interferometer based on these laser diodes.
We present methods of improvement of wavelength stability and tuneability of semiconductor laser diodes in fiber laser interferometers by fiber Bragg gratings (FBGs). We developed simulation method to calculation of arbitrary fiber grating (apodized, chirp etc.) with high precision by combination of methods based on layered dielectric media (LDM) and transfer matrix. On the basis of our simulations and measurements of the commercially available fiber gratings we designed a special 100 mm long fiber Bragg grating with apodization. We expect the application of the FBG to improvement of the linewidth and mode-hop free tuning range of semiconductor lasers at the wavelength 760 nm to increase resolution of fiber laser interferometer based on these diodes. We built the absolute fiber laser interferometer with Vertical Cavity Surface Emitting Laser (VCSEL) to easy employ FBG to stabilize wavelength and control the tuning range. First set up is presented.
Improvement of the linewidth and the mode-hop free tuning range of the Vertical Cavity Surface Emitting Laser
(VCSEL) diode is the main goal of our upcoming Fiber Bragg Gratings (FBGs). The VCSEL with the fiber grating will
be very suitable laser source for new generation of the absolute and the incremental laser interferometers based on our
published VCSEL interferometer.
The linewidth of the emission spectrum and the mode-hop free tuning range of the wavelength are critical in laser
interferometry. The full width in half maximum (FWHM) linewidth of VCSEL at 760 nm wavelength is 100 MHz
approximately. Tuning range up to 1 nm was measured by a highly precise commercial lambdameter with 0.1 pm
resolution. To improve such a characteristic a high precise FBG must be selected.
On the basis of our simulations and measurements of the commercially available fiber gratings we designed a special
100 mm long fiber Bragg grating with apodization. We expect the application of the FBG to improvement of the
linewidth and mode-hop free tuning range of VCSEL at the wavelength 760 nm to increase resolution of laser
interferometer based on VCSEL diode.
We simulated chirped and apodized fiber Bragg gratings (fiber gratings with modulation of the amplitude and with
modulation of the spacing) the same as uniform fiber gratings. Results of our simulations are presented. Apodization of
fiber Bragg gratings (FBG) has many advantages in comparison to other types of FBGs. Main improvement is
suppressing of the side lobes in the grating spectral properties. The difference of side lobes suppression for uniform and
Gaussian apodized grating is more than 110dB. On the basis of these results we designed a special fiber Bragg grating
with apodization especially for using to stabilize semiconductor lasers for high precision laser applications with central
wavelength 760nm.
We present application of methods for calculation of parameters of apodized fiber Bragg gratings (FBG). We used
combination of methods based on layered dielectric media (LDM) and the transfer matrix. On the contrary to the other
calculation techniques the LDM method is based on sequence of thin films of dielectric media assembled in the direction
of wave propagation. The combination of the LDM method and the transfer matrix method can be used to the calculation
of arbitrary fiber gratings with high precision.
For this designed apodized FBG we calculated the phase mask to manufacture by interference patterns. The phase mask
and the fixation bottom of the fiber were made by e-beam lithography to achieve highly precise stability during
manufacturing. We present the set-up of this system for writing FBG by pulsed UV laser with wavelength 266nm.
Measurement of commercially available FBG with comparison to our calculated FBG is presented.
This paper discusses methods for calculation properties of apodized fiber Bragg gratings (FBGs). These are one of the most enveloping optical devices in telecommunications and sensor systems. Work is aimed to simulation of FBGs, with utilization especially in sensor systems and laser interferometry for semiconductor laser stabilization at wavelength about 760nm. Program for FBG properties calculation was written in Matlab software. At first, FBG is divided into several uniform sections. To calculate properties of each uniform section is used coupled-mode theory. Coupled-mode theory is ordinary used for electromagnetic field specification in waveguides with periodic perturbations in the propagation direction. Next the transfer matrix method is used for overall properties calculation. The main point of simulation is reflectivity spectrum calculation in dependence of fiber dimensions and material properties. These FBGs have wide range of use in optical systems as band filters, in-fiber sensors or fiber grating lasers and amplifiers for their unique properties.
We present application of methods for calculation of parameters of apodized fiber Bragg gratings (FBG). We used combination of methods based on layered dielectric media (LDM) and the transfer matrix. On the contrary to the other calculation techniques the LDM method is based on sequence of thin films of dielectric media assembled in the direction of wave propagation. The combination of the LDM method and the transfer matrix method can be used to the calculation of arbitrary fiber gratings with high precision. For this designed apodized FBG we calculated the phase mask to manufacture by interference patterns. The phase mask and the fixation bottom of the fiber were made by e-beam lithography to achieve highly precise stability during manufacturing. We present the set-up of this system for writing FBG by pulsed UV laser with wavelength 266nm. Measurement of commercially available FBG with comparison to our calculated FBG is presented. We put together the absolute fiber laser interferometer where Vertical Cavity Surface Emitting Laser (VCSEL) is used to easy employment of FBG to stabilization and control the tuning range of the wavelength. The first set-up is presented.
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