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The spectrum shift of erbium-doped magneto-optic fiber Bragg grating (Er-MFBG) induced by external magnetic fields is, for the first time, directly measured by the method of the "direct edge detection," and then the effective Verdet constant of −12.42 rad∕ðT · mÞ is determined. The theoretical results are in agreement with the experimental data. Our analysis shows the transfer characteristics of the spectrum shift to the transmission power are dependent on the state of polarization and wavelength position of probe light for a given Er-MFBG.

According to the symmetry of transmission matrix for non-uniform magneto-optic fiber Bragg gratings (MFBGs), the simulation model of the non-uniform MFBGs with bidirectional injection of light has been presented for the Optisystem software. The simulation model is verified by comparing with the Matlab numeric results using the piecewise-uniform MFBG model. As an example, the polarization-dependent loss (PDL) of an MFBG-based Sagnac interferometer (MSI) is analyzed in detail. Simulation results indicate that the magnetic field sensitivity of the MSI system can be improved by optimizing the coupling coefficient of the coupler, and the maximum of peak PDL is up to three times that of the single MFBG structure. The simulation model proposed in the paper is useful for the design of MFBG-based optical information devices.

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In this paper, the performances of a wavelength interrogation-based optical fiber surface plasmon resonance sensor for hemoglobin (Hb) concentration is investigated by theoretical simulation. The proposed configuration incorporates optical fiber, 70 nm silver, 18 nm barium titanate (BaTiO3), and 2 nm zinc oxide. Simulation results show the sensor exhibits refractive index sensitivity of 4023 nm/RIU and concentration sensitivity of 10.0873 nm/(g·dL), along with Hb concentration varying from 0 to 14 g/dL. This paper especially focuses on the influence of BaTiO3 on the performances of the proposed sensor with light wavelength ranging from 350 to 1000 nm. Comparison analysis indicates sandwiching 18 nm BaTiO3 between sensing layers not only enhances the concentration sensitivity by 30.14% but also decreases the nonlinear error of the sensor from 0.68% to 0.63%. For a wavelength accuracy of 0.1 nm, the proposed sensor can provide a resolution of 0.0099 g/dL for Hb concentration detection.