&lt;title&gt;Recent advances in fiber-grating sensors for utility industry applications&lt;/title&gt;

Morey, W. W.; Meltz, G.; Weiss, Joseph M.

doi:10.1117/12.229250

Cited by 15 publications

(10 citation statements)

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“…are also given in Figures 8-12 due to various kinds of refractive index profile discussed in the beginning of Section 4. Figures 13-15 show the comparison between peaky reflectivity and group velocity dispersion D due to various kinds of refractive index profile [14,15]. It is apparent from Figure 13 that the bandwidth of reflectivity has been enhanced for the second order function which is a more complicated profile than other two cases.…”

Section: Controlling the Dispersion And Peak Reflectivity Due To An Amentioning

confidence: 91%

Dispersion and Peak Reflectivity Analysis in a Non-Uniform FBG Based Sensors Due to Arbitrary Refractive Index Profile

Raghuwanshi¹,

Kumar²,

Srinivas³

2012

PIER B

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Abstract-This paper deals with a group velocity dispersion issue and a peak reflectivity issue in a non-uniform fiber Bragg gratings (FBG) due to an arbitrary refractive index profile along the length of grating. The paper shows that by using more complicated refractive index profile one can significantly reduce the group velocity dispersion and side lobes intensity and that in main lobe the bandwidth of reflectivity would also increase substantially due to a complicated refractive index profile. To the authors' knowledge, there has not been any work reported in this direction. Generally, coupled mode theory is used to analyze the uniform fiber Bragg grating (UFBG). The analysis results in two coupled first order ordinary differential equations with constant coefficients for which closed form solutions can be found for appropriate boundary conditions. Most fiber gratings designed for practical applications however are non uniform. The main reason for using non uniform grating is that it reduces the side lobes in the reflectivity spectrum. Due to the complexity of analysis, no particular method for an analysis of the non-uniform fiber Bragg grating would be found. The two standard approaches for calculating the reflection and transmission spectra of a non uniform FBG are direct numerical integration of coupled mode equations and piecewise uniform approximation approach. The former is more accurate but computationally intensive. In this paper, piecewise uniform approximation approach is used to study a dispersion characteristic due to an arbitrary refractive index profile. The usefulness in FBG based sensors has been demonstrated.

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Section: Controlling the Dispersion And Peak Reflectivity Due To An Amentioning

confidence: 91%

Dispersion and Peak Reflectivity Analysis in a Non-Uniform FBG Based Sensors Due to Arbitrary Refractive Index Profile

Raghuwanshi¹,

Kumar²,

Srinivas³

2012

PIER B

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“…Typical values for the sensitivity to an applied axial strain are 1 nm /millistrain at 1300 urn and 0.64 nm /millistrain at 820 nm. The strain response is linear with no evidence of hysteresis at temperatures as high as 37Ø0 C [4].…”

Section: Strain and Temperature Changesmentioning

confidence: 96%

“…It is given by B I 2B = [ a; + 1/n (dnldT) I 6.7 x 1O I°C (4) up to 85°C. A typical value for the thermal response at 1550 nm is 0.01 nni/ °C .…”

Section: Strain and Temperature Changesmentioning

confidence: 99%

“…Each reflection from a crest in the index perturbation is in phase with the next one at AB. Any change in fiber properties, such as strain, temperature, or polarization which varies the modal index or grating pitch will change the Bragg wavelength [3,4]. The grating is an intrinsic sensor which changes the spectrum of an incident signal by coupling energy to other fiber modes.…”

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confidence: 99%

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<title>Overview of fiber grating-based sensors</title>

Meltz

1996

SPIE Proceedings

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OYI'ASSOCJATES, A VON, CONNECTICUT 0600] 1.0 iNTRODUCTION Optical fiber sensor technology based on intra-core Bragg gratings has been used in a number of important application areas ranging from structural monitoring to chemical sensing. Practical and cost effective systems are not far in the future judging from advances in grating manufacture and sensor readout instrumentation. Fiber grating technology is not driven by its use in sensors but rather by valuable applications in dense, broadband WDM telecommunications.In this paper, we review the fundamentals of Bragg grating sensors and discuss various means for wavelength-shift demodulation, separation of temperature and strain responses and new directions that will offer additional capabilities. FUNDAMENTALS OF BRAGG GRATING SENSORSA fiber Bragg grating is a periodic, refractive index perturbation which is formed in the core of an optical fiber by exposure to an intense IN interference pattern. The grating can be made by using a split-beam mterferometer [1] or a phase mask to form the fringes [2]. The latter technique is sometimes preferred because of the greatly relaxed requirements on the UV laser coherence and stability; although the mterferometer technique is more flexible, since the grating period can be adjusted by simply changing the angle between beams. A uniform pattern phase mask will form a grating with a pitch that is one-half the period of the etch pattern. Each separate wavelength requires a different etch pattern, although some tuning is possible by stretching or bending the fiber in the fringe pattern.A typical interferometer setup for fabricating a grating is shown in Figure 1 . UV laser radiation, usually at 248 or 1 93 urn , is split into two beams, with an odd number of reflections to preserve beam parity, focused, and recombined to form a high contrast fringe pattern within the core of the fiber. The grating formation can be observed by monitoring the reflection or transmission of a broadband source, typically an ELED, SLED or a superlumenscent rare-earth doped fiber, which is launched into the fiber from one end. After a short time, usually within minutes or less, a notch appears in the transmitted spectrum, as shown in the optical spectrum analyzer trace in the upper left-hand corner of the figure. The exposure is stopped when the desired reflectivity is reached and then the grating is annealed to avoid any variations in wavelength due to thermal deactivation of low-energy color centers [3]. 2 ISPIE Vol. 2838 O-8194-2226-6/96/$6.QQ Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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“…Nevertheless, for a Bragg grating at 1550 nm the following values of sensitivities can be obtained [17][18][19][20][21][22][23][24][25]. …”

Section: Fbg Sensitivitymentioning

confidence: 99%

Analysis and Development of a Tunable Fiber Bragg Grating Filter Based on Axial Tension/Compression

Mohammad

Szyszkowski

Zhang

et al. 2004

J. Lightwave Technol.

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Fiber Bragg gratings (FBGs) are key elements in modern telecommunication and sensing applications. In optical communication, with the advancement of the Erbium doped fiber amplifier (EDFA), there is a great demand for devices with wavelength tunability over the Erbium gain bandwidth (in particular, for wavelength division multiplexing (WDM) networks). The center wavelength of a FBG can be shifted by means of change of temperature, pressure or mechanical axial strain. The axial strain approach is the best method among all other techniques because it allows relatively large wavelength shifts with high speed. Axial strain of up to 4% will be required to cover the whole EDFA region (more than 40 nm of central wavelength shift). The formation of Bragg grating results in significant reduction in mechanical strength of optical fibers especially in tension. As a result, axial strain of only about 1% can be achieved by mechanical stretching of FBGs. In order to achieve the remaining 3% strain compression of FBGs has to be applied.In this thesis, the design and analysis of a novel device for achieving central wavelength shift are presented. In particular, the device has achieved, for a fiber with Further, using the piezoelectric transducer (PZT) actuator as a driver, tuning speed of around 1.5nm/ms was achieved.-iii - ACKNOWLEDGMENTSUpon the completion of this thesis, I would like to express my sincere gratitude and appreciation to my supervisors Professor Chris W.

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<title>Recent advances in fiber-grating sensors for utility industry applications</title>

Cited by 15 publications

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Dispersion and Peak Reflectivity Analysis in a Non-Uniform FBG Based Sensors Due to Arbitrary Refractive Index Profile

Dispersion and Peak Reflectivity Analysis in a Non-Uniform FBG Based Sensors Due to Arbitrary Refractive Index Profile

<title>Overview of fiber grating-based sensors</title>

Analysis and Development of a Tunable Fiber Bragg Grating Filter Based on Axial Tension/Compression

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