<![CDATA[Fiber Bragg grating (FBG) is a passive optical sensor that detects strain through Bragg wavelength shifts. This study designed and simulated an FBG-based pulse-strain monitoring system using uniform and Gaussian apodization at 1310 nm and 1550 nm. The system was designed using OptiGrating 4.2.2.69 and OptiSystem 11.1.0.53 with a single circuit comprising four parallel FBGs. Optical fiber parameters included a core diameter of 2 microstrain, a cladding diameter of 8 microstrain, core refractive indices of 1.4600 and 1.4605, and a grating length of 0.01 m. OptiGrating simulations showed that Gaussian apodization produced a cleaner reflection spectrum with lower sidelobes (around -60 dB) than uniform apodization, which exhibited higher, broader sidelobes (around -40 dB). OptiSystem analysis using an optical spectrum analyzer (OSA) at 1310 nm showed initial and final powers of 24.920 dBm and 24.934 dBm for Gaussian apodization, and 25.000 dBm and 24.997 dBm for uniform apodization. At 1550 nm, the corresponding values were 24.725 and 24.780 dBm for Gaussian, and 24.998 dBm and 24.992 dBm for uniform apodization. Strain calculations using the Bragg wavelength shift equation yielded sensitivities of approximately 1.21 pm/microstrain at 1550 nm and 1.02 pm/microstrain at 1310 nm for both profiles, consistent with theoretical FBG sensitivity. Optical power meter (OPM) measurements supported the OSA results, while oscilloscope analysis showed stable signals for both profiles, with uniform apodization displaying slightly higher and more consistent amplitude. Uniform apodization excels in reflectance and amplitude stability, while Gaussian apodization provides better spectral quality with lower sidelobes. The system targets the normal physiological pulse-strain range (10 – 50 microstrain). Apodization selection therefore depends on the strain-sensing application's priorities.]]>
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