The paper is devoted to the simulation and reflectance performance of the cascaded non-uniform fiber Bragg gratings
(FBG). In a FBG, periodically spaced regions in the fiber core are varied. FBGs are key enabling technologies for fiber
optical sensing for their high sensitivity and potentially low cost. Uniform, chirped, phase-shifted and sampled FBGs can
be used in the sensing systems. The cascaded FBG configuration is created by several sections where each section has a
specific number of segments. In our simulations the transfer matrix method has been used assuming the entire grating
made up of sections. Using this method the FBG reflectance spectra have been simulated in MATLAB. The simulated
reflectances of FBGs with several sections alternating along the length of the FBG have been described. The simulation
results show that the FGB reflectance at the Bragg wavelength and the reflectance bandwidth depend on the Bragg
grating periodicity that means on the periodicity in the sections. The bandwidth and the amplitude reflectance at the
Bragg wavelength for the length grating of 10 mm with several sections have been studied. The effects of sections of
different Bragg grating periods and refractive index profiles (the Gaussian profile or the sinc profile) have been
numerically investigated. From the simulations one can see that the maxima of the energy of FBGs reflected by several
apodized sections depend on the grating length. Moreover, it has been found out that the undesirable sidelobes between
main reflectance maxima can be partly suppressed by using an appropriately designed cascaded grating.
In this paper, the simulations of the reflectance of the apodized and chirped Fiber Bragg gratings (FBGs) are presented.
The reflectances of apodized FBGs with different modulations of the refractive index were simulated. The results show
that reflected light is concentrated to the main reflectance line with negligible sidelobes. Simulations of linearly chirped
FBGs show that sharp reflectance lines can be achieved which makes this kind of FBGs suitable candidates for
wavelength multiplexing/demultiplexing.
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