Wyniki wyszukiwania - Biblioteka Nauki

1

Hybrid technique based on chirp effect and phase shifts for spectral Talbot effect in sampled fiber Bragg gratings (FBGs)

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Deng G. , Pan W.

Optica Applicata

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2011

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tom Vol. 41, nr 1

225--233

EN

To implement the spectral Talbot effect in sampled fiber Bragg gratings (SFBGs), a hybrid technique based on a chirp effect and phase shifts is proposed. Firstly, the general phase condition is derived as the principle of this hybrid technique, and it also can be used to demonstrate other reported techniques, including the linear chirp, the periodical chirp, and the multiple phase shift technique. According to the general phase condition and the equivalent chirp coefficient in the Talbot effect, multi-channel dispersion compensators are designed with different arrangements of chirp coefficient and phase shifts. Moreover, the dispersion value can be tuned in these devices by dynamically adjusting the phase shifts of the hybrid technique. Numerical simulations are carried out to confirm the performance of such devices realized by using the hybrid technique.

2

All optical method to achieve gain-clamping in broadband distributed fiber Raman amplifiers

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Wei H. , Tong Z. , Wang M. , Jian S.

Optica Applicata

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2004

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tom Vol. 34, nr 3

365-372

EN

In this paper, we proposed that using a pair of fiber gratings in a section of the transmission fiber, a gain clamped broadband distributed fiber Raman amplifiers (DRA) can easily be made based on the utilization of the pumps’ interactions and uneven gain property along the fiber in the amplifier

3

Analysis and application of phase shift for identical multiple wavelength sampled fiber Bragg grating

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Guodan S. , Rong W. , Tao P. , Zhihu W. , Jintian X.

Optica Applicata

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2012

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tom Vol. 42, nr 4

751--759

EN

A novel identical multiple wavelength sampled fiber Bragg grating (FBG) is proposed. A phase shift between the two adjacent FBG units is achieved by increasing the direct current (DC) refractive index of the FBG. The FBG with identical reflective spectrum is optimized with a designed sampling function. DC phase shift FBGs are analyzed and fabricated, which shows a good agreement with a discrete phase shift method. A dual-wavelength (DW) filter with channel spacing 0.16 nm is fabricated, and the experiment results verified the feasibility of this proposed method. A four-wavelength filter with channel spacing 0.16 nm is then proposed and demonstrated. This method has the following advantages: wavelength design is flexible, fabrication precision and costs are low.

4

Dispersion-compensating en/decoder for a time-spreading/wavelength-hopping optical code-division multiplexing (OCDM) system

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Zheng J. , Wang R. , Pu T. , Lu L. , Fang T. , Su Y. , Li L. , Yang Q. , Chen X.

Optica Applicata

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2013

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tom Vol. 43, nr 3

485--495

EN

A novel dispersion-compensating fiber Bragg grating (FBG)-based en/decoder is proposed to compensate both the out-band and in-band dispersion in a time-spreading/wavelength-hopping (TS/WH) optical code-division multiplexing (OCDM) system. The experimental realization of such en/decoders only needs a uniform-pitch phase mask and a sub-micrometer precision moving stage. Such an en/decoder pair with the ability of compensating the dispersion of transmission in 20-km single mode fiber (SMF) is simulated and experimentally fabricated. Both the simulation and experimental results show that the decoded pulse can be recovered without any distortion owing to the elimination of dispersion.

5

Application of fiber Bragg gratings for strain measurement in historic textiles and paintings on canvas

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Zawadzki W. , Bartosik M. , Dzierzega K. , Bratasz L. , Lukomski M. , Peacock E.

Optica Applicata

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2012

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tom Vol. 42, nr 3

503-517

EN

The aim of this work was to evaluate the applicability of optical fiber Bragg grating (FBG) sensors to the monitoring of deformation in historical textiles and paintings on canvas. Fibers with a ceramic coating were selected for strain investigation in textiles due to both their almost perfect strain transfer and much shorter relaxation times compared to fibers with an acrylate coating. FBG sensors were attached to fabrics in a non-destructive manner using specially designed magnetic clamps. Local strain measurements using these sensors were consistent with general strains measured using either a universal testing machine (UTM) or a laser triangulator when varying external load or relative humidity. However, strain magnitudes measured by the different methods were comparable only after correction for the influence of the fiber on the textile under study. Strain measurements in model paintings on canvas were carried out using uncoated fibers embedded in the gesso layers on the canvas. Despite some drawbacks, the FBG sensors were found to be useful in monitoring strain in historic textiles and consequently, for the assessment of environmental risk of these works-of-art.

6

Fiber Bragg grating-based high temperature sensor and its low cost interrogation system with enhanced resolution

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Mamidi V. R. , Kamineni S. , Ravinuthala L. N. S. P. , Madhuvarasu S. S. , Thumu V. R. , Pachava V. R. , Putha K.

Optica Applicata

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2014

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tom Vol. 44, nr 2

299--308

EN

A fiber Brag grating-based high temperature sensor together with a low cost, high speed and compact size interrogation system using a long period grating was designed, developed and tested. The designed sensor measures the temperature from room temperature to 550 °C. The sensor head was configured by encapsulating an fiber Brag grating (type-I) of Bragg resonance wavelength at 1552.88 nm in a capillary tube made of copper. Long period grating with peak transmission loss at 1550 nm was employed to convert the wavelength information from fiber Brag grating into an intensity modulated signal. Temperature related optical intensity information was again converted into its equivalent electrical signal by using a photodiode. The achieved resolution of the sensor was found to be 0.5 °C.

7

A high sensitivity vector accelerometer based on tri-axial fiber Bragg grating

100%

Jiang Q. , Yang M.

Optica Applicata

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2012

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tom Vol. 42, nr 4

901--912

EN

Firstly, a single-axis FBG accelerometer with intensity modulation-direct detection interrogation system was put forward and designed in the paper. Experiments with different excitation frequencies were implemented, which demonstrate its good mechanical structure and fabrication technology. Accordingly, a novel tri-axis FBG accelerometer based on the single-axis FBG accelerometer was proposed and a series of periodic vibration tests were finished to prove its performance at different excitation frequencies. The response of the tri-axis vector FBG accelerometer can keep up with the increasing excitation frequency with good signal-to-noise ratio (SNR) within 160 Hz. The suitable measurement frequency range of the accelerator is between 0 and 500 Hz. The cross-axis response among three axes is analyzed. These experiments indicate that horizontal axes have less influence on the vertical axis vibration of FBG.

8

Distributed strain reconstruction based on a fiber Bragg grating reflection spectrum

100%

Detka M. , Kaczmarek Z.

Metrology and Measurement Systems

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2013

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tom Vol. 20, nr 1

53-64

EN

In this paper, we present a synthesis of the parameters of the fiber Bragg grating (FBG) and the reconstruction of the distributed strain affecting the grating, performed by means of its reflection spectrum. For this purpose, we applied the transition matrix method and the Nelder-Mead nonlinear optimization method. Reconstruction results of the strain profile carried out on the basis of a simulated reflection spectrum as well as measured reflection spectrum of the FBG indicate good agreement with the original strain profile; the profile reconstruction errors are within the single digit percentage range. We can conclude that the Nelder-Mead optimization method combined with the transition matrix method can be used for distributed sensing problems.

9

Optimization of a FBG-based filtering module for a 40 Gb/s OSSB transmission system

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Drummond M. V. , Silveira T. , Silveira T. , Ferreira A. , Fonseca D. , Nogueira R. N. , Monteiro P.

Optica Applicata

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2010

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tom Vol. 40, nr 2

511--520

EN

We present the optimization of an optical filtering module (OFM) of a single-channel 40 Gb/s transmission system with optical single-sideband modulation and alternate mark inversion signaling. Sideband suppression and dispersion compensation are simultaneously performed by the fiber Bragg grating (FBG) optical filtering through amplitude and phase response, respectively. Different amounts of accumulated dispersion are compensated using an OFM based on optical switches and chirped FBGs with different accumulated dispersion. Linear transmission simulations to assess the OFM effectiveness yield a Q-factor penalty variation lower than 1 dB relative to back-to-back considering a maximum accumulated dispersion of 20400 ps/nm. A transmission distance of 1040 km of nonlinear standard single mode fiber is achieved with a Q-factor higher than 7.

10

Fiber Bragg grating and long period grating sensor for simultaneous measurement and discrimination of strain and temperature effects

100%

Srimannarayana K. , Sai Shankar M. , Sai Prasad R. L. N. , Krishna Mohan T. K. , Ramakrishna S. , Srikanth G. , Ravi Prasad Rao S.

Optica Applicata

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2008

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tom Vol. 38, nr 3

601-608

EN

Fiber Bragg grating sensors are novel in the determination of various physical parameters. In the case of fiber Bragg grating, on a single measurement of wavelength shift, it is impossible to differentiate between the effects of changes in strain and temperature. The simulation of fiber Bragg grating, long period grating characteristics and use of the different strain-temperature response of combined sensor for the simultaneous measurement and discrimination of strain and temperature in C band are demonstrated.

11

Pure rotational Raman lidar with fiber Bragg grating for temperature profiling of the atmospheric boundary layer

100%

Mao J. , Hu L. , Hua D. , Gao F. , Wu M.

Optica Applicata

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2008

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tom Vol. 38, nr 4

715-726

EN

A new pure rotational Raman lidar (PRRL) system at a wavelength of 532.25 nm has been designed for profiling the atmospheric temperature of the planetary boundary layer. A newly compact spectroscope structured with three fiber Bragg gratings (FBG) is designed to separate two pure rotational Raman signals for atmospheric temperature retrieval, and to simultaneously block the Mieand Rayleigh-scattering signals with a rejection rate of 107. A numerical simulation shows that the PRRL is capable of profiling the atmospheric temperature and a statistical temperature error less than 1 K is achieved up to a height of 2.0 km and 2.2 km for daytime and nighttime measurement, respectively.

12

Package for fiber Bragg gratings (FBG) and a comparative study on their polarization mode dispersion (PMD) at varying temperature

88%

Ning T. , Pei L. , Liu Y. , Tan Z. , Wang Q. , Zheng J. , Jian S.

Optica Applicata

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2005

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tom Vol. 35, nr 2

277-282

EN

A temperature-compensated material of fiber Bragg grating (FBG), which has negative thermal -expansion coefficient has been presented. The temperature coefficient of FBGs' center wavelength is less than 0.0005 nm/°C after three-layer-structure temperature-compensated package under tension. For the first time, PMD of FBG with and without temperature compensation has been detailedly studied and measured from -20 to 60°C. The measured result shows that the PMD changes a little at varying temperature, which means that the package did not affect the PMD characteristic of FBG.

13

Multichannel comb filter based on linearly chirped fiber Bragg grating and DC phase shift

88%

Sun G. , Wang R. , Pu T. , Wang H. , Wei Z.

Optica Applicata

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2011

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tom Vol. 41, nr 4

791--797

EN

A novel approach to implement high channel-count comb filters based on a DC phase shift is proposed. Various channel spacings can be achieved by a single chirped phase mask and a submicrometer-precision translation stage. Simulation and experiment show that arbitrary phase shifts introduced by DC refractive index modulation can be achieved. An multichannel comb filter with channel spacing of 100 GHz, 50 GHz and 40 GHz is implemented with the same phase mask. A comparison between the proposed DC phase shift and traditional discrete phase shift is made.

14

Analiza charakteru zmian parametrów apodyzowanych siatek Bragga spowodowanych zmiennym rozkładem wiązki laserowej

75%

Dziubiński G. , Kisała P.

Przegląd Elektrotechniczny

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2016

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tom R. 92, nr 10

214--217

PL

Artykuł dotyczy analizy możliwości wpływania na kluczowe parametry siatek Bragga jeszcze na etapie ich projektowania przed procesem zapisu. Zaproponowano i zdefiniowano parametry siatek, które są kluczowe przy ich wykorzystaniu w układach czujnikowych oraz systemach telekomunikacyjnych. W artykule zaprezentowano sposób modelowania siatek Bragga metodą macierzy przejścia (ang. Transfer Matrix Method). Przedstawiono funkcje apodyzacyjne, które mogą zostać opcjonalnie zastosowane podczas zapisu siatki. Zbadane zostały one pod kątem ich wpływu na charakterystyki widmowe, a także podstawowe parametry modelowanej siatki.

EN

This article concerns the analysis of Bragg grating key parameters and their influence on final gratings spectral characteristic. It proposed and defined the gratings parameters that are critical to their use in sensor systems and telecommunication systems. This article presents a simulation of fiber Bragg gratings using transfer matrix method. Apodization profiles have been discussed according to their function parameter. Different fiber gratings lengths were analyzed according to their reflection and transmission spectra.

15

Optymalizacja parametrów światłowodowych czujników do pomiaru temperatury

75%

Dziubiński G. , Harasim D. , Skorupski K. , Mussabekov K. , Kalizhanova A. , Toigozhinova A.

Rocznik Ochrona Środowiska

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2016

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tom Tom 18, cz. 2

309--324

EN

Nowadays, there are many devices the failure of which could not only lead to huge financial losses but also wreak havoc in the natural environment. Such circumstances require us to analyze the electrical components before something dangerous happens. Early reaction gives an opportunity to implement prevention measures and avoid serious consequences. Optical fiber sensors have a number of advantages, the most important of which include immunity to electromagnetic interference, low weight and the ability to incorporate them within the measured structure. Fiber Bragg gratings have other special advantages; for instance, they enable the creation of distributed sensing arrays, which contain multiple sensors. They are also insensitive to optical power source fluctuations. The multitude of FBG sensors applications extorted fabrication of gratings with different spectral shapes. Uniform gratings have spectra with strong side lobes which could affect the processing characteristics of temperature sensor. Apodization is one of ways for affecting the gratings spectral shape. This article concerns simulations based on an original computer application, which is numerical model implementation of Transfer Matrix Method. It allows to determine the spectral characteristic of optical components on the basis of the theory of coupled modes and matrix description of electromagnetic wave that passes through optical fiber. Different fiber gratings lengths were analyzed according to their reflection and transmission spectra. In the beginning, the impact of various parameters on the Bragg grating spectral characteristics was checked. Results of those simulations have been attached. The article covers measurement of real optic elements put in climatic chamber and Bragg gratings, produced under very strict conditions. The profile of the laser beam was approximated by Gaussian function using MatLab software and additional tools from package. Function matching has been defined as statistical parameters and evaluated later. The comparison of mathematical model and physical optical system, based on previously designated function apodization, has been covered. The results of these two visualizations have been summarized to better exemplify the differences and similarities. The previously measured fiber Bragg grating has been proposed as temperature sensor and parameters which may be used to construct an optical fiber temperature sensor were established. Temperature sensitivity was determined in the end.

16

Odtwarzanie rozkładu odkształcenia przy pomocy światłowodowej siatki Bragga

75%

Detka M. , Kaczmarek Z.

Przegląd Elektrotechniczny

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2013

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tom R. 89, nr 4

84-88

PL

W artykule przedstawiono rekonstrukcję rozłożonego odkształcenia działającego na światłowodową siatkę Bragga na podstawie jej widma odbitego. Wykorzystano do tego celu metodę macierzy przejścia oraz nieliniową metodę optymalizacji Neldera-Meada. Wyniki przeprowadzonych symulacji i odtwarzania profili odkształcenia wskazują na dobrą ich zgodność z oryginalnymi profilami odkształcenie; błędy rekonstrukcji tych profili nie przekraczają pojedynczych procentów.

EN

In this paper, we present a reconstruction of the distributed strain affecting the fiber Bragg grating performed by means of its reflection spectrum. For this purpose, we applied the transfer matrix method and the Nelder-Mead nonlinear optimization method. Reconstruction results of the strain profile carried out on the basis of a simulated reflection spectrum as well as measured reflection spectrum of the FBG indicate good agreement with the original strain profile; the profile reconstruction errors are within the single digit percentage range.

17

A novel method for high temperature measurements using fiber Bragg grating sensor

75%

Reddy P. S. , Sai Prasad R. L. N. , Srimannarayana K. , Sai Shankar M. , Sen Gupta D.

Optica Applicata

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2010

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tom Vol. 40, nr 3

685--692

EN

This paper reports the simulation, design and experimental analysis of a fiber Bragg grating (FBG) temperature sensor, making use of chemical composition grating (CCG), which ranges from room temperature to over 900 °C. The interrogation system of the sensor proposed is simple, effective and of low cost. The sensor head comprises FBG attached to a metal plate that will be strained due to change in the length of the plate with increase in temperature. The temperature is measured on the basis of the reflected Bragg wavelength shifts from the FBG. The dynamic range of the sensor is about 30 °C to 900 °C. The proposed sensor can be employed for monitoring the health of structural members at elevated temperatures. The dynamic range of the sensor can be increased to beyond 1500 °C by making use of FBG made up of sapphire instead of silicon fiber.

18

Metody optyczne pomiaru odkształceń i diagnostyki elementów maszyn

75%

Szumski M. , Szczerba P. , Żyłka W.

Obróbka Metalu

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2017

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tom nr 1

23--26

EN

Last years constant and consequent development of optical method on the field of processes: measuring, diagnostic an control is observed. Greater micro-processors capacity, improvement of image converter parameters, and source of light make possible to use in mentioned domains techniques applying light as a measuring medium. In this paper practical example of glider wing measurements, using fiber Bragg grating was presented. On this ground positive and negative sides of described method were discussed.

PL

W ostatnim okresie obserwowany jest stały i konsekwentny rozwój metod optycznych w miernictwie, diagnostyce i sterowaniu. Wzrost mocy obliczeniowych mikroprocesorów, stała poprawa parametrów przetworników obrazu, źródeł światła pozwala na zastosowanie technik wykorzystujących światło, jako medium pomiarowe i kontrolne. Niezaprzeczalnymi zaletami tej drogi zdobywania informacji pomiarowych są: odporność na zakłócenia zewnętrzne, szczególnie elektrostatyczne i elektromagnetyczne, duża rozdzielczość uzyskanych wyników widoczna szczególnie w przypadku zastosowania matrycowych przetworników obrazu, możliwość wykonywania pomiarów bezstykowych, niewprowadzających zmian w charakterystykach mechanicznych badanych struktur, mała wrażliwość na charakterystyki materiałowe badanych elementów.

19

Apodyzowane siatki Bragga o stałym okresie jako przetworniki odkształceń impulsowych. Analiza numeryczna

75%

Sikora A.

Pomiary Automatyka Kontrola

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2010

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tom R. 56, nr 12

1436-1438

PL

Artykuł dotyczy analizy wpływu długości apodyzowanych siatek równomiernych na dokładność przetwarzania odkształceń impulsowych o kształcie połowy sinusoidy. Nowością jest wykonanie tej analizy z jednoczesnym porównaniem wpływu wybranych profili apodyzacyjnych siatki równomiernej na dokładność tego przetwarzania. Przedstawiono wyniki obliczeń wybranych miar błędów dynamicznych. Na ich podstawie można stwierdzić, że wpływ profili apodyzacyjnych (w modelowanym zakresie) jest widoczny dla błędów czasu narastania i amplitudy, dla błędu średniokwadratowego jest nieznaczny.

EN

The fibre Bragg gratings (FBG) are used in measurements as optical transducers which can also be used in high-frequency strain measurements [1, 2]. In such applications the output signal is distorted mainly due to the grating length [3, 4]. In order to select the proper grating length, the rise-time error (RTE, Fig. 2, Eq. 3), the amplitude error of the frequency change (AFCE, Fig. 2, Eq. 4) and the mean square error (MSE, Fig. 3, Eq. 5) were calculated. The calculations were carried out in several steps. In order to model the reflected grating power, the transfer matrix description [5] was used when taking into account the individual changes of parameters of each section of the grating (Eq. 1) [6]. The effective central fre-quency was assumed to be the grating output signal (Eq. 2)[7]. The dynamic errors were calculated [8] for a half sinusoidal (Eq. 8) impulsive strain waveform, and different apodization functions (raised-cosine profile Eq. 6, sinc Eq. 7) (Fig. 1) [9]. The results can be summarized in a conclusion: the calculated errors allow selecting the proper length of the fibre grating if the errors are established, and the waveform of the pulse is identified. The influence of the apodization function is observable for the RTE and AFCE, while for the MSE it is insignifi-cant.

20

Wpływ gradientu odkształcenia światłowodowej siatki Bragga o stałym okresie na jej charakterystyki spektralne

75%

Kaczmarek Z. , Detka M.

Pomiary Automatyka Kontrola

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2010

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tom R. 56, nr 12

1439-1441

PL

W artykule przedstawiono wyniki badań eksperymentalnych i symulacji wpływu gradientu odkształcenia siatki Bragga o stałym okresie na jej charakterystyki widmowe: pasmo 3 decybelowe i współczynnik odbicia mocy. Zakres zmian gradientu odkształcenia wynosił od 0 do š27 žε/mm. Wyniki pomiarów wskazują na liniową zależność pasma 3 dB siatki od stałego gradientu odkształcenia oraz brak jego wpływu na współczynnik odbicia mocy siatki w badanym zakresie jego zmian. Wyniki tych badań mogą być przydatne przy konstrukcji czujników wielkości mechanicznych z siatkami Bragga, w których elementem sprężystym jest belka zginana oraz w pomiarach odkształceń.

EN

Experimental and simulation results of the influence of the strain gradient of a uniform fiber Bragg grating on its spectral characteristics, the 3-dB bandwidth and reflectivity, are presented in the paper. For experiments a 10 mm long grating embedded in a bended cantilever (Fig. 1) was used. The strain and the strain gradient of the cantilever were caused by a concentrated force acting on the cantilever free end. A change of the kind of strain (stretching or compression) and the strain gradient sign was achieved by reversing the cantilever in the holder. The range of the strain gradient equals 0š27 žε/mm. The measurements were taken in a setup shown in Fig. 2. Using the transfer matrix method derived from the coupled mode theory, the changes of the grating reflected spectrum caused by the strain and the strain gradient in it were simulated [5]. The obtained results of measurements and simulations show that increase in the strain gradient causes increase in the 3-dB bandwidth of the grating reflected beam both for a positive and negative strain gradient (Figs. 3-5). The dependence of the 3-dB bandwidth on the strain gradient is linear and symmetric with respected to the y-axis. The measurement results confirm this feature in the range š 8,5 žε/mm. Outside this range, increase in the 3-dB bandwidth for a negative strain gradient is smaller than for a positive one. For the investigated range of the grating strain gradient, its influence on the grating reflectivity was not observed (Fig. 6).This last feature is important in detection of the grating signals by means of optical wavelength discriminators.