We have presented an analytical model of splitters based on Fiber Bragg grating used to detect a Bragg wavelength from the number of wavelengths which are traveling in an optical fiber. The number of grids and grating length can be used as a wavelength shifter.This paper presents experimental results that are used to show the effect of number of grids and the length of the grating on the Bragg wavelength and reflectivity of Fiber Bragg Grating (FBG). The pitch of grating is directly proportional to the grating length and inversely proportional to number of grids. When the grating length is fixed and the number of grids is increased, the Bragg wavelength decreases and reflectivity increases. This increase in reflectivity is very small. Further when the number of grids was kept constant and the grating length was increased the Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. In our model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.
Bending losses of power in a single mode step index optical fiber due to macro bending has been
investigated for a wavelength of 1550nm. The effects of bending radius (4-15mm, with steps of 1mm), and
wrapping turn (up to 40 turns) on loss have been studied. Twisting the optical fiber and its influence on power
loss also has been investigated. Variations of macro bending loss with these two parameters have been
measured, loss with number of turns and radius of curvature have been measured.
This work founds that the Macro bending and wrapping turn loss increases as the bending radius and wrapping
turn increases.
Core-cladding mode resonances of long period fiber grating in concentration s...IOSR Journals
Long period fiber grating (LPFG) is photoinduced fiber device that facilitates the coupling of core
mode to different cladding modes resulting into series of transmission dips in the transmission spectrum. Here
we present LPFG chemical sensor to determine the concentration of Manganese in water at ppm level. We
fabricated LPFG of period 600μm in single mode communication fiber using 12W carbon dioxide laser
applying point by point method. The fabricated LPFG is directly used as chemical sensor since cladding modes
coupled to core mode directly come in contact with surrounding chemicals. Concentration of manganese in our
collected sample is found to be 0.0329ppm. The result is verified with sophisticated Atomic Absorption
Spectrometer (AAS).
Analysis on The Impact of Reflectance in Optical Fiber Linksijtsrd
An optical fiber link is a part of an optic fiber communication system. Other components of the optic fiber link include the transmitter, connectors, and the receiver. The optical fiber could be single-mode (for long distance transmission) or multi-mode (for short distance transmission). This paper however, majors on the impact of reflectance in the single-mode optical fiber. Reflectance is a hidden threat that increases Bit Error Rate, BER, (rate at which errors occur in transmission system) and reduces system performance if not monitored or controlled. Optical Time Domain Reflectometer (OTDR) was used to measure the reflectance in single-mode fiber. Events measurements in OTDR heavily depend on good reflectance. The OTDR was able to establish the reflectance in every portion of the fiber under test. An average reflectance level of -14.9275 dB of 1550 nm signal over the span length of 20.422 km was achieved which is within the acceptable standard range. Hence, good quality performance transmissions can be achieved along these routes. J. Ilouno | M. Awoji | J. Sani"Analysis on The Impact of Reflectance in Optical Fiber Links" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14378.pdf http://www.ijtsrd.com/physics/other/14378/analysis-on-the-impact-of-reflectance-in-optical-fiber-links/j-ilouno
In an optical communications system, information from the source is encoded into electrical signals that can drive the transmitter. The transmitter consists of an LED or laser and is pulsed at the incoming frequency. The transmitter performs an EO conversion.
Bending losses of power in a single mode step index optical fiber due to macro bending has been
investigated for a wavelength of 1550nm. The effects of bending radius (4-15mm, with steps of 1mm), and
wrapping turn (up to 40 turns) on loss have been studied. Twisting the optical fiber and its influence on power
loss also has been investigated. Variations of macro bending loss with these two parameters have been
measured, loss with number of turns and radius of curvature have been measured.
This work founds that the Macro bending and wrapping turn loss increases as the bending radius and wrapping
turn increases.
Core-cladding mode resonances of long period fiber grating in concentration s...IOSR Journals
Long period fiber grating (LPFG) is photoinduced fiber device that facilitates the coupling of core
mode to different cladding modes resulting into series of transmission dips in the transmission spectrum. Here
we present LPFG chemical sensor to determine the concentration of Manganese in water at ppm level. We
fabricated LPFG of period 600μm in single mode communication fiber using 12W carbon dioxide laser
applying point by point method. The fabricated LPFG is directly used as chemical sensor since cladding modes
coupled to core mode directly come in contact with surrounding chemicals. Concentration of manganese in our
collected sample is found to be 0.0329ppm. The result is verified with sophisticated Atomic Absorption
Spectrometer (AAS).
Analysis on The Impact of Reflectance in Optical Fiber Linksijtsrd
An optical fiber link is a part of an optic fiber communication system. Other components of the optic fiber link include the transmitter, connectors, and the receiver. The optical fiber could be single-mode (for long distance transmission) or multi-mode (for short distance transmission). This paper however, majors on the impact of reflectance in the single-mode optical fiber. Reflectance is a hidden threat that increases Bit Error Rate, BER, (rate at which errors occur in transmission system) and reduces system performance if not monitored or controlled. Optical Time Domain Reflectometer (OTDR) was used to measure the reflectance in single-mode fiber. Events measurements in OTDR heavily depend on good reflectance. The OTDR was able to establish the reflectance in every portion of the fiber under test. An average reflectance level of -14.9275 dB of 1550 nm signal over the span length of 20.422 km was achieved which is within the acceptable standard range. Hence, good quality performance transmissions can be achieved along these routes. J. Ilouno | M. Awoji | J. Sani"Analysis on The Impact of Reflectance in Optical Fiber Links" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14378.pdf http://www.ijtsrd.com/physics/other/14378/analysis-on-the-impact-of-reflectance-in-optical-fiber-links/j-ilouno
In an optical communications system, information from the source is encoded into electrical signals that can drive the transmitter. The transmitter consists of an LED or laser and is pulsed at the incoming frequency. The transmitter performs an EO conversion.
Analysis of Circular Patch Antenna Embeded on Silicon Substrateijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
An optical fiber is a glass or plastic fiber that carries light along its length. They are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles to carry images. Specially designed fibers are used for other applications, including sensors and fiber lasers.
Fluorescence technique involves the optical detection and spectral analysis of light emitted by a substance undergoing a transition from an excited electronic state to a lower electronic state. The aim of this study is to assess the -amino levulinic acid (-ALA) uptake. Based on image processing technique, Matlab was used to analyze the fluorescence images resulted from activation of (-ALA) and follow its uptake along one week. Analyzing the RGB colours pixel profile from obtained results showed different profiles for malignant tissues, normal tissues, treated just after PDT and finally at one week post PDT. The treated tissues fluorescence profile showed changes from closer to malignant tissue profile till been closed to normal one.
Fibre Optic Systems(FOS) is a fibre optic supplier & manufacturer in Australia, specialising in fibre optic cords, cables & fibre optic test equipment.
Analysis of Circular Patch Antenna Embeded on Silicon Substrateijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
An optical fiber is a glass or plastic fiber that carries light along its length. They are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles to carry images. Specially designed fibers are used for other applications, including sensors and fiber lasers.
Fluorescence technique involves the optical detection and spectral analysis of light emitted by a substance undergoing a transition from an excited electronic state to a lower electronic state. The aim of this study is to assess the -amino levulinic acid (-ALA) uptake. Based on image processing technique, Matlab was used to analyze the fluorescence images resulted from activation of (-ALA) and follow its uptake along one week. Analyzing the RGB colours pixel profile from obtained results showed different profiles for malignant tissues, normal tissues, treated just after PDT and finally at one week post PDT. The treated tissues fluorescence profile showed changes from closer to malignant tissue profile till been closed to normal one.
Fibre Optic Systems(FOS) is a fibre optic supplier & manufacturer in Australia, specialising in fibre optic cords, cables & fibre optic test equipment.
STUDY ON FIBER GRATINGS AND ITS CHARACTERIZATIONDr. Ved Nath Jha
Good potential uses in fiber and fiber lasers have been seen through Random Fiber Gratings (RFGs). However, a quantitative link has never been studied between the RFG's randomness and spectral reaction. This paper first experimentally characterizes two RFGs of varying degrees of randomness by optical frequency reflectometry (OFDR). The high degree of randomness indicates that the grating intensity is limited and the strength variations in spatial domain are large. The experimental findings show. Study establishes the theoretical basis for the optimization configuration and implementation of the long-term fiber grating in the area of fiber optics sensing and communication.
Optimization of Uniform Fiber Bragg Grating Reflection Spectra for Maximum Re...ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Profile of Single Mode Fiber Coupler Combining with Bragg GratingTELKOMNIKA JOURNAL
This paper describes a numerical experiment of design and operation of a fiber coupler between
single mode fiber and fiber Bragg grating (FBG). Both components are coupled depending with optical
waveguide and source parameters. A characterization of fiber coupler is simulated by varying long grating
of 10 mm to 60 mm using transfer matrix method based on coupled mode equation. The wave peak,
transmission, and dispersion parameters are analyzed to determine the performance of the fiber coupler.
The transmission spectrum showed the wave peaks rise to any increase in the grating length on channel
1 and channel 2. Transmission on channel 1 and channel 2 decreased from the wavelength range of
1.45μm–1.55μm and rised in the range of 1,55μm–1,65μm for each increment in length of grating. The
dispersion showed the zero dispersion at specific wavelength for each increase in length of grating. This
component can be applied for controlling information signal in wide range communication.
Performance Investigation and Enhancement of Fiber Bragg Gratingfor Efficient...IOSRJECE
In this paper, the performance of various windowfunctions for Fiber Bragg Grating Sensor (FBGS)is investigated and evaluated in order to get optimized reflection spectrum with high reflectivity and an efficient side lobe suppression for efficient sensing measurement applications.For this purpose, a wide range of design parameters which include grating length and refractive index modulation amplitudehas been chosen to evaluate the sensor design. The performances of the different windowfunctions have been then compared in terms of reflectivity, full width half maximum bandwidth (FWHM), and sidelobe level(SLL) so as to get the most suitable design parametersto be used for sensing measurement.The simulation results presented in this paper show the effectiveness of the optimizedFBG sensor, which can be further implemented for high performance sensing applications.
NOVEL BAND-REJECT FILTER DESIGN USING MULTILAYER BRAGG MIRROR AT 1550 NMcscpconf
Novel band-reject filter is proposed using multilayer Bragg mirror structure by computing reflection coefficient at 1550 nm wavelength for optical communication. Dimension of different
layers and material composition are modified to study the effect on rejection bandwidth, and no of layers is also varied for analyzing passband characteristics. GaN/AlxGa1-xN composiiton is taken as the choice for simulation purpose, carried out using propagation matrix method. Refractive indices of the materials are considered as function of bandgap, perating wavelength and material composition following Adachi’s model. One interesting result arises from the computation that band-reject filter may be converted into band-pass one by suitably varying ratio of thicknesses of unit cell, or by varying Al mole fraction. Simulated results can be utilised to design VCSEL mirror as optical transmitter.
Signal Degradation In Optical Fiber
Losses in an optical fibre:-
The types of losses in a optical fibre are
Attenuation loss
Absorption
Scattering
Bending loss
Dispersion loss
Coupling loss
Performance Analysis of Apodized Fiber Bragg Gratings Formats in Optical Comm...theijes
This paper presents the performance analysis of apodized fiber bragg an optical communication system. The effected fiber bragg for capacities uniform, Gaussian and tanh capacity has been implemented and investigated. The variable file of FBG performance is talented for the distinctive apodized capacity, including utilization in the RZ beat generator. The corresponding framework throughout the fiber mode channel is simulated using optisystem version 9 programs. Results show a fit correlation for the range, eye diagram and Q-variable figure
Enhancing the Data Transmission Capability on Optical Fiber Communication Lin...IOSRJECE
Explosive growth of broadband multimedia applications, such as high-definition television (HDTV), video on demand (VOD) and interactive games imposed a huge demand for bandwidth on the access network. The potential bandwidth of optical communication system is driving force behind the worldwide development and deployment of light wave system but dispersion limits the system performance in terms of high speed optical communication. In this paper different dispersion compensation methods are discussed, which are based on Chirped Fiber Grating (CFG), Dispersion Compensation Fibers (DCF), Self Phase Modulation (SPM ) resulting from Kerr nonlinearity to overcome pulse broadening effect of Group Velocity Dispersion (GVD), which eventually have direct implication on the data transmission capability on optical fiber communication link.
Performance Analysis of Dispersion Compensation in Long Haul Optical Fiber wi...IOSR Journals
Abstract : In this paper, We investigate post, pre and symmetrical/mix dispersion compensation methods for 40
Gb/s non-return to zero link using standard and dispersion compensated fiber through FBG compensator to
optimize high data rate optical transmission. The influence of dispersion of FBG compensator and increases in
the power of CW laser has been studied to evaluate the performance of optical communication systems. The
simulation model of the WDM based on the Optisystem 11.0 is presented according to the above principle. The
simulation results are validated by analysing the Q-factor and Bit error rate (BER) in the numerical simulator.
It is found that post compensation performance is best and the input fiber power is taken as 5-10dB, the
corresponding BER performance is better.
Keywords - BER, Dispersion compensation, Q-factor, WDM.
Temperature and strain sensitivity of long period grating fiber sensor revieweSAT Journals
Abstract
Long period grating fibers are special class of fibers which are produced by periodic modulation of the refractive index of the core. This perturbation leads to forward guiding mode to couple with co propagating cladding modes depending on the phase matching condition. This coupling causes the cladding modes to attenuate during propagation in the fiber and leads to dips in the attenuation bands at discrete wavelengths in the transmission spectrum. These bands are shifted when the LPG is exposed to temperature, strain, refractive index changes in surrounding environment etc. This forms the basis of LPG sensor. The properties of LPG are modified in order to achieve the required sensitivity towards any measurands as per the applications. The performance of LPG by modifying the properties of LPG is reviewed.
Keywords: Optical fiber, Optical fiber sensor, Fiber Bragg, Long period grating, Strain, Temperature
Coupled Line Band Pass Filter with Defected Ground Structure for Wide Band Ap...IJERA Editor
In this paper a novel wideband microstrip band pass filter is proposed. The band pass filter is designed with coupling between two L-shaped microstriplines and is terminated with a high impedance line. The three circle shapes are etched out at the ground plane and is called defected ground structure (DGS), which provides better return loss as well as it reduces harmonics. Simulated and measured results both are in true agreement with each other. Results show that the defected microstrip filter has a good performance, including a wide pass band of 3.0 GHz to 5.6 GHz at 3dB cut off frequencies with bandwidth of 2.6 GHz, and a small insertion loss. The return loss is found to be higher than 15 dB.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
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We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
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Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
How to Split Bills in the Odoo 17 POS ModuleCeline George
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Reverse Pharmacology.
1. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
341International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
Reflectivity and Braggs Wavelength in FBG
Dinesh Arora ecedinesh@rediffmail.com
Research Scholar (ECE), Singhania University,
Jhunjhunu, Rajasthan-333515, INDIA
Dr. Jai Prakash ecedinesh@rediffmail.com
Professor in Department of Applied Physics,
Indo Global College of Engineering,
Mohali, Punjab-140109, INDIA
Hardeep Singh*
hardeep_saini17@yahoo.co.in
Associate Professor in Department of ECE,
Indo Global College of Engineering,
Mohali, Punjab-140109, INDIA
Dr.Amit Wason wasonamit13@gmail.com
Professor in Department of ECE,
Rayat & Bahra Institute of Engineering & Bio-Technology,
Mohali, Punjab-140104, INDIA
Abstract
We have presented an analytical model of splitters based on Fiber Bragg Grating used to detect a Bragg
wavelength from the number of wavelengths which are traveling in an optical fiber. The number of grids
and grating length can be used as a wavelength shifter. This paper presents experimental results that are
used to show the effect of number of grids, the length of the grating on the Bragg wavelength and
reflectivity of Fiber Bragg Grating (FBG). The pitch of grating is directly proportional to the grating length
and inversely proportional to number of grids. When the grating length is fixed and the number of grids is
increased, the Bragg wavelength decreases resulting in increased reflectivity. This increased reflectivity is
very small. Further when the number of grids is kept constant and the grating length is increased the
Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a very small. In
our model, the effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.
Keywords- Fiber Bragg Grating, Bragg Wavelength, Reflection, Number of Grids, Grating length, Pitch
1. INTRODUCTION
With the rapid growth of the Internet, capacity requirement is increasing day by day. This increase in the
requirement of capacity can be easily met by the existing optical fiber communication technology. The
transmission properties of an optical wave-guide are dictated by its structural characteristics, which have
a major effect in determining how an optical signal is affected as it propagates along the fiber [1]. Light
propagation occurs in the guiding region of waveguide on principle of total internal reflection at the
material interfaces. For this to occur, the guiding region must have a refractive index of greater value
than the materials surrounding it.
1.1 Fiber Bragg Grating
The Fiber Bragg Grating (FBG) was initially demonstrated by Ken Hill., K.O. [2]. FBG is a periodic
perturbation of the refractive index along the fiber length in the fiber’s core which is formed by exposure of
the core to an intense optical interference pattern. Germanium, a dopant used in many optical fiber cores,
is photosensitive to Ultraviolet (UV) light. A grating is a selective wavelength filter in the core of an optical
fiber. It is made by exposing a section of the fiber to UV light through a phase mask. An interference
pattern of maxima and minima is formed causing a permanent periodic change to the index of the core. A
2. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
342International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
small amount of light is reflected at each index variation. At the "center wavelength” or “Bragg
wavelength,” all the reflections add coherently. The grating reflects light in a narrow wavelength range,
centred at the so-called Bragg wavelength.
1.1.1 Grating Fabrication Technique
Many techniques have been developed for the fabrication of FBG i.e. transverse holographic (G.Meltz,
1989), phase mask (K.O.Hill, 1993) and point-by-point techniques [3]. When UV light radiates on an
optical fiber, the refractive index is changed permanently; this effect is known as ‘photosensitivity.’ Out of
these three, the phase mask is the most common technique due to its simple manufacturing process,
great flexibility and high performance.
Transverse holographic technique: The light from an UV source is split into two beams that are brought
together so that they intersect; the intersecting light beams form an interference pattern that is focused
using cylindrical lenses on to the core of optical fiber [3]. The fiber cladding is transparent to UV light,
whereas the core absorbs the light strongly. Due to this light beam the core is irradiated from the side,
thus giving rise to its name transverse holographic techniques. The holographic technique for grating
fabrication has two principal advantages.
• Bragg gratings could be photo imprinted in the core without removing the glass cladding.
• The period of the induced grating depends on the angle between the two interfering coherent UV
light beams.
Phase Mask Technique: In this technique the phase mask is placed between the UV light source and the
optical fiber. The shadow of the phase mask then determines the grating structure based on the
transmitted intensity of light striking the fiber [4] & [5].
FIGURE1: Phase mask fabrication techniques of Grating
Point-by-Point technique: In this technique each index perturbation is written point by point. Here, the
laser has a narrow beam that is equal to the grating period. This method of FBG inscription deep gratings
have been written in a range of optical fibers at arbitrary wavelengths. It can be used to write gratings with
periods of approximately 1 µm and above in a range of optical fibers [5]. In point by point technique, a
step change of refractive index is induced along the core of the fiber at a time. A single pulse of the UV
light passes through a mask to the core of the fiber containing a slit and thus the refractive index ( ) of the
corresponding core section increases locally. The fiber is then translated through a distance
corresponding to the grating pitch ( ) in parallel direction to the fiber axis, this process is repeated to form
the grating structure in the fiber core.
1.1.2 Grating Structure
3. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
343International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
The structure of the FBG can vary via the refractive index, or the grating period. The grating period can
be either uniform or graded or localized and distributed in a superstructure. The refractive index profile in
FBG can be uniform or apodized, and the refractive index offset is positive or zero. There are six common
structures for FBGs;
•Uniform positive-only index change,
•Gaussian apodized,
•Raised-cosine apodized,
•Chirped,
•Discrete phase shift, and
•Superstructure.
1.1.3 Grating Principle
When light passes through the FBG, the narrowband spectral component at the Bragg wavelength is
reflected by the FBG. The Bragg wavelength is given by the Equation (1) [6].
(1)
Where and Λ are the effective refractive index of the fiber and the pitch of the grating respectively.
Parameters of FBG, such as period of refractive index perturbation, magnitude of refractive index, grating
length and numbers of grids, give optical properties of FBG.
2. LITERATURE SURVEY
M.S. Ab-Rahman, et al. [7], investigated the effect of the refractive index of cladding ( ) to the Bragg
wavelength and reflectivity of the grating. They found that the effect of the was not linear. The Bragg
wavelength shifted periodically with the change of . The power also varied in a quadratic manner with
a change of . D.W. Huang, et al. [8], worked on reflectivity-tunable FBG reflector with acoustically
excited transverse vibration of the fiber. They observed that when the transverse vibration induced the
coupling between the core and cladding, the Bragg reflectivity varied from its original value to zero. With
this technique, they varied the Bragg reflectivity after a fiber grating was fabricated. C.Caucheteur,
et al. [9], investigated the polarization properties of Bragg grating. They concluded that FBGs prepared by
high-intensity laser pulse were characterized by high value polarization-dependent loss (PDL) and
differential group delay (DGD). F.Z.Zhang, et al. [10], examined the effect of the zero
th
-order diffraction of
the phase masks on FBG in polymer optical fiber by observing and analysing the micrographs of the
grating. When the strain was larger than 2%, the viscoelasticity of the polymer fiber was noticed. The 60
nm Bragg wavelength shift was observed when they investigated the strain response by stretching the
polymer optical fiber up to 6.5%.of the polymer optical fiber. B.A.Tahir, et al. [11], described the FBG
sensing system for strain measurement. They calculated the reflectivity by keeping the grating length
constant and varying the index modulation amplitude of the Grating. In their model, the average
reflectivity was 96% and negligible change in reflectivity was observed by variation in index modulation.
Also, if applied strain was uniform then Bragg wavelength shift occurred without modification of initial
spectrum shape. Good linear response was observed between applied strain and Bragg wavelength shift.
F.Zeng, et al. [12], proposed an approach to implement optical microwave filters using an FBGS with
identical reflectivity. The spectrum profile of the broadband light source can be controlled using an optical
filter, which could be used to control the filter coefficients to suppress the filters side-lobes. M.ANDO,
et al. [13], 2004, investigated the dependence of FBG characteristics on grating length. They concluded
that under the standard FBG fabrication condition, the exposure time of the FBG to excimer laser
irradiation for a given transmission time was inversely proportional to the length of the grating. During
their investigation, they fixed the value of amplitude of refractive index modulation of the grating even
when the length was varied. S.Ugale, et al. [14], found that the reflectivity increases with increase in
grating length as well as index difference.
4. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
344International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
3. ANALYTICAL MODEL
In this paper, we have investigated the effect of number of grids and grating length which will be useful in
designing the wavelength splitter with the help of FBG. The Analytical model has been proposed for the
reflectivity of grating which is given by Equation (2).
(2)
Where ‘l’ is the length of the grating, ‘k’ is the coupling coefficient; δ is detuning factor and is the
detuning ratio. The detuning parameter for FBG of period is , is known as pitch or grating
period as in Equation (3).
(3)
N is number of grids or number of grating periods. Pitch of grating also depends upon the value of
effective refractive index and Brag wavelength as shown in Equation (4).
(4)
For sinusoidal variation in index perturbation, the coupling co-efficient for 1st order Bragg grating is
where is overlap integral between forward and reverse propagating mode. V is normalized frequency as
given in Equation (5).
(5)
Where
• is effective refractive index
• is radius of core
• is index difference
4. SIMULATION, RESULT & DISCUSSION
The work was carried out on Software MATLAB 7.2 of Mathworks. The analytical model thus constructed
has investigated with variation of some of the design parameters of FBG. We have fixed some of the
parameters i.e. index difference between core and cladding, radius of core and index amplitude of the
grating. As per Equation (5), the pitch of grating is inversely proportional to the number of grids and
directly proportional to grating length. Moreover, the number of grids also affects the reflectivity of grating.
Table1. shows the relation between the number of grids and Braggs wavelength. Moreover, with the
increase in number of grids, there is a negligible increase in reflectivity.
5. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
345International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
1.549 1.55 1.551 1.552 1.553 1.554
x 10
-6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength
Reflectivity
Bragg Wavelength varying with number of Grids
N=5605
N=5608
N=5612
FIGURE 2: Bragg wavelength varying with number of grids of Grating N=5605, 5608 and 5612
1.542 1.544 1.546 1.548 1.55 1.552 1.554
x 10
-6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength
Reflectivity
Bragg Wavelength varying with number of Grids
N=5615
N=5620
N=5625
FIGURE 3: Bragg wavelength varying with number of grids of Grating N=5615, 5620 and 5625
6. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
346International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
1.54 1.545 1.55 1.555 1.56 1.565
x 10
-6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength
Reflectivity
Bragg Wavelength varying with FBG length
l=2.99mm
l=3.0mm
l=3.02mm
FIGURE 4: Bragg wavelength varying with Grating length =2.99mm, 3.00mm and 3.02mm
1.56 1.565 1.57 1.575 1.58 1.585 1.59
x 10
-6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength
Reflectivity
Bragg Wavelength varying with FBG length
l=3.03mm
l=3.04mm
l=3.06mm
FIGURE 5: Bragg wavelength varying with Grating length =3.03mm, 3.04mm and 3.06mm
The results shown in Figure 2 and Figure 3 depict the reflectivity and Bragg wavelength variation with the
number of grids. It has been shown in Figure 2 also, that the Bragg wavelength varies with the number of
7. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
347International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
grids and it decreases with the increase in number of grids. Bragg wavelength was calculated to be
1552nm for 5605 number of grids, when grating length was fixed at 3mm. It was found that the Braggs
wavelength decreased with the increase in number of grids. It decreased to 1551nm and 1550nm when
the effective number of grids was increased to 5608 and 5612. For a fix value of grating, there is no
change in Reflectivity with the increase in the number of grids. In Figure 3 the results show that Bragg
wavelength of the grating was calculated to be 1549 for the number of grids as 5615, which was
decreased to 1548, 1547, when the number of grids of grating was increased to 5620 and 5625
respectively. Moreover, with the increase in the number of grids, there was a little increase in the
reflectivity of FBG. The reflectivity was increased to 99.65% with 5650 grids when the grating length was
3mm and to 99.61% for number of grids up to 5612.
N(Number of Grids) Bragg Wavelength(nm) Reflectivity (%)
5605 1552 99.61
5608 1551 99.61
5612 1550 99.61
5615 1549 99.62
5620 1548 99.62
5625 1547 99.63
5640 1545 99.63
5650 1540 99.65
TABLE 1: Characteristics of FBG with the Variation of number of Grids
Now, on same model of FBG splitter, we have fixed the number of grids (N) and studied the effect of
varying grating length on Bragg wavelength and reflectivity. As per Equation (3), the pitch of
grating is directly to the grating length. In this section, the number of Grids (N) is fixed at 5605 and the
grating length is varied to observe the effect on Bragg wavelength and reflectivity of the grating.
Grating length(mm) Bragg Wavelength(nm) Reflectivity (%)
2.99 1547 99.6
3.00 1552 99.6
3.02 1563 99.59
3.03 1568 99.58
3.04 1573 99.58
3.05 1583 99.56
3.06 1599 99.52
3.07 1630 99.45
TABLE 2: Characteristics of FBG with the Variation of Grating length
In Figure 5, the Bragg wavelength calculated was 1568 nm for 3.03mm grating length. With increase in
the grating length, the pitch of grating increased but the Bragg wavelength of the FBG decreased and at
the same time the reflectivity of the FBG also decreased. For the grating length of 3.04mm and 3.06mm,
the Bragg wavelength noted was 1573 nm and 1583nm respectively. The Table 2 also showed that for
8. Dinesh Arora, Dr.Jai Prakash, Hardeep Singh & Dr.Amit Wason
348International Journal of Engineering (IJE), Volume (5) : Issue (5) : 2011
increase of 0.02mm in the grating length, the Bragg wavelength shifted from 1573nm to 1583nm. The
reflectivity also decreased with the increase in grating length. It was 99.60 % for 2.99mm grating length
and 99.45% for 3.15mm grating length.
The experimental results show the effect of number of grids, the length of the grating on the Bragg
wavelength and reflectivity of FBG. It is clear that the pitch of grating is directly proportional to the grating
length and inversely proportional to number of grids. When the grating length is fixed and the number of
grids is increased, the Bragg wavelength decreases resulting in increased reflectivity. This increased
reflectivity is very small. Further when the number of grids is kept constant and the grating length is
increased the Bragg wavelength increases. The effect of this increase in grating length on reflectivity is a
very small. The effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.
6. CONCLUSION
In our work, we have analyzed the effect of number of grids and grating length of FBG on reflectivity and
Bragg wavelength by keeping other parameters constant. The pitch of grating is directly proportional to
grating length and inversely proportional to number of grids. On increasing the number of grids, keeping
the grating length as fixed, the Bragg wavelength decreases and at the same time, the reflectivity
increases. The reflectivity increases by 0.02% with increase in the number of grids by 25 and at the same
time, Bragg wavelength shifted by 7nm. Also, when the grating length is varied by 0.02mm, keeping the
number of grid constant, the Bragg wavelength shifts by 10nm and reflectivity decreases by 0.02%. The
effectiveness of the grating in extracting the Braggs wavelength is nearly 100%.
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